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1

MEG (Magnetoencephalography) multipolar modeling of distributed sources using RAP-MUSIC (Recursively Applied and Projected Multiple Signal Characterization)  

Energy Technology Data Exchange (ETDEWEB)

We describe the use of truncated multipolar expansions for producing dynamic images of cortical neural activation from measurements of the magnetoencephalogram. We use a signal-subspace method to find the locations of a set of multipolar sources, each of which represents a region of activity in the cerebral cortex. Our method builds up an estimate of the sources in a recursive manner, i.e. we first search for point current dipoles, then magnetic dipoles, and finally first order multipoles. The dynamic behavior of these sources is then computed using a linear fit to the spatiotemporal data. The final step in the procedure is to map each of the multipolar sources into an equivalent distributed source on the cortical surface. The method is illustrated through an application to epileptic interictal MEG data.

Mosher, J. C. (John C.); Baillet, S. (Sylvain); Jerbi, K. (Karim); Leahy, R. M. (Richard M.)

2001-01-01

2

Magnetoencephalography  

International Nuclear Information System (INIS)

Although magnetoencephalography (MEG) may not be familiar to many pediatric radiologists, it is an increasingly available neuroimaging technique both for evaluating normal and abnormal intracranial neural activity and for functional mapping. By providing spatial, temporal, and time-frequency spectral information, MEG affords patients with epilepsy, intracranial neoplasia, and vascular malformations an opportunity for a sensitive and accurate non-invasive preoperative evaluation. This technique can optimize selection of surgical candidates as well as increase confidence in preoperative counseling and prognosis. Research applications that appear promising for near-future clinical translation include the evaluation of children with autism spectrum disorder, traumatic brain injury, and schizophrenia. (orig.)

3

Magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Although magnetoencephalography (MEG) may not be familiar to many pediatric radiologists, it is an increasingly available neuroimaging technique both for evaluating normal and abnormal intracranial neural activity and for functional mapping. By providing spatial, temporal, and time-frequency spectral information, MEG affords patients with epilepsy, intracranial neoplasia, and vascular malformations an opportunity for a sensitive and accurate non-invasive preoperative evaluation. This technique can optimize selection of surgical candidates as well as increase confidence in preoperative counseling and prognosis. Research applications that appear promising for near-future clinical translation include the evaluation of children with autism spectrum disorder, traumatic brain injury, and schizophrenia. (orig.)

Schwartz, Erin Simon [Children' s Hospital of Philadelphia, Lurie Family Foundations MEG Imaging Center, Department of Radiology, Philadelphia, PA (United States); Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States); Edgar, J.C.; Gaetz, William C.; Roberts, Timothy P.L. [Children' s Hospital of Philadelphia, Lurie Family Foundations MEG Imaging Center, Department of Radiology, Philadelphia, PA (United States)

2010-01-15

4

Multipolar model of bremsstrahlung accompanying proton-decay of nuclei  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Emission of bremsstrahlung photons accompanying proton decay of nuclei is studied. The new improved multipolar model describing such a process is presented. The angular formalism of calculations of the matrix elements is stated in details. The bremsstrahlung probabilities for the $^{157}{\\rm Ta}$, $^{161}{\\rm Re}$, $^{167}{\\rm Ir}$ and $^{185}{\\rm Bi}$ nuclei decaying from the $2s_{1/2}$ state, the $^{109}_{53}{\\rm I}_{56}$ and $^{112}_{55}{\\rm Cs}_{57}$ nuclei decaying from...

Maydanyuk, Sergei P.

2011-01-01

5

Multipolar model of bremsstrahlung accompanying proton-decay of nuclei  

CERN Document Server

Emission of bremsstrahlung photons accompanying proton decay of nuclei is studied. The new improved multipolar model describing such a process is presented. The angular formalism of calculations of the matrix elements is stated in details. The bremsstrahlung probabilities for the $^{157}{\\rm Ta}$, $^{161}{\\rm Re}$, $^{167}{\\rm Ir}$ and $^{185}{\\rm Bi}$ nuclei decaying from the $2s_{1/2}$ state, the $^{109}_{53}{\\rm I}_{56}$ and $^{112}_{55}{\\rm Cs}_{57}$ nuclei decaying from the $1d_{5/2}$ state, the $^{146}_{69}{\\rm Tm}_{77}$ and $^{151}_{71}{\\rm Lu}_{80}$ nuclei decaying from the $0h_{11/2}$ state are predicted. Such spectra have orders of values similar to the experimental data for the bremsstrahlung photons emitted during the $\\alpha$-decay. This indicates on real possibility to study bremsstrahlung photons during proton decay experimentally and perform further measurements.

Maydanyuk, Sergei P

2011-01-01

6

A wind-shell interaction model for multipolar planetary nebulae  

CERN Document Server

We explore the formation of multipolar structures in planetary and pre-planetary nebulae from the interaction of a fast post-AGB wind with a highly inhomogeneous and filamentary shell structure assumed to form during the final phase of the high density wind. The simulations were performed with a new hydrodynamics code integrated in the interactive framework of the astrophysical modeling package SHAPE. In contrast to conventional astrophysical hydrodynamics software, the new code does not require any programming intervention by the user for setting up or controlling the code. Visualization and analysis of the simulation data has been done in SHAPE without external software. The key conclusion from the simulations is that secondary lobes in planetary nebulae, such as Hubble 5 and K3-17, can be formed through the interaction of a fast low-density wind with a complex high density environment, such as a filamentary circumstellar shell. The more complicated alternative explanation of intermittent collimated outflow...

Steffen, W; Esquivel, A; Garcia-Segura, G; Garcia-Diaz, Ma T; Lopez, J A; Magnor, M

2013-01-01

7

Analytic and numerical models of the 3D multipolar magnetospheres of pre-main sequence stars  

CERN Document Server

Traditionally models of accretion of gas on to T Tauri stars have assumed a dipole stellar magnetosphere, partly for simplicity, but also due to the lack of information about their true magnetic field topologies. Before and since the first magnetic maps of an accreting T Tauri star were published in 2007 a new generation of magnetospheric accretion models have been developed that incorporate multipole magnetic fields. Three-dimensional models of the large-scale stellar magnetosphere with an observed degree of complexity have been produced via numerical field extrapolation from observationally derived T Tauri magnetic maps. Likewise, analytic and magnetohydrodynamic models with multipolar stellar magnetic fields have been produced. In this conference review article we compare and contrast the numerical field extrapolation and analytic approaches, and argue that the large-scale magnetospheres of some (but not all) accreting T Tauri stars can be well described by tilted dipole plus tilted octupole field componen...

Gregory, S G

2011-01-01

8

Recovering experimental and theoretical electron densities in corundum using the multipolar model: IUCr Multipole Refinement Project.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This electron-density study on corundum (alpha-Al2O3) is part of the Multipole Refinement Project supported by the IUCr Commission on Charge, Spin and Momentum Densities. For this purpose, eight different data sets (two experimental and six theoretical) were chosen from which the electron density was derived by multipolar refinement (using the MOLLY program). The two experimental data sets were collected on a conventional CAD4 and at ESRF, ID11 with a CCD detector, respectively. The theoretic...

Pillet, S.; Souhassou, M.; Lecomte, C.; Schwarz, K.; Blaha, P.; Re?rat, M.; Lichanot, A.; Roversi, P.

2001-01-01

9

Magnetoencephalography recording and analysis.  

Science.gov (United States)

Magnetoencephalography (MEG) non-invasively measures the magnetic field generated due to the excitatory postsynaptic electrical activity of the apical dendritic pyramidal cells. Such a tiny magnetic field is measured with the help of the biomagnetometer sensors coupled with the Super Conducting Quantum Interference Device (SQUID) inside the magnetically shielded room (MSR). The subjects are usually screened for the presence of ferromagnetic materials, and then the head position indicator coils, electroencephalography (EEG) electrodes (if measured simultaneously), and fiducials are digitized using a 3D digitizer, which aids in movement correction and also in transferring the MEG data from the head coordinates to the device and voxel coordinates, thereby enabling more accurate co-registration and localization. MEG data pre-processing involves filtering the data for environmental and subject interferences, artefact identification, and rejection. Magnetic resonance Imaging (MRI) is processed for correction and identifying fiducials. After choosing and computing for the appropriate head models (spherical or realistic; boundary/finite element model), the interictal/ictal epileptiform discharges are selected and modeled by an appropriate source modeling technique (clinically and commonly used - single equivalent current dipole - ECD model). The equivalent current dipole (ECD) source localization of the modeled interictal epileptiform discharge (IED) is considered physiologically valid or acceptable based on waveform morphology, isofield pattern, and dipole parameters (localization, dipole moment, confidence volume, goodness of fit). Thus, MEG source localization can aid clinicians in sublobar localization, lateralization, and grid placement, by evoking the irritative/seizure onset zone. It also accurately localizes the eloquent cortex-like visual, language areas. MEG also aids in diagnosing and delineating multiple novel findings in other neuropsychiatric disorders, including Alzheimer's disease, Parkinsonism, Traumatic brain injury, autistic disorders, and so oon. PMID:24791077

Velmurugan, Jayabal; Sinha, Sanjib; Satishchandra, Parthasarathy

2014-03-01

10

Magnetoencephalography in pediatric epilepsy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetoencephalography (MEG) records the magnetic field generated by electrical activity of cortical neurons. The signal is not distorted or attenuated, and it is contactless recording that can be performed comfortably even for longer than an hour. It has excellent and decent temporal resolution, especially when it is combined with the patient’s own brain magnetic resonance imaging (magnetic source imaging). Data of MEG and electroencephalography are not mutually exclusive and it is recorde...

Hunmin Kim; Chun Kee Chung; Hee Hwang

2013-01-01

11

Magnetoencephalography recording and analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetoencephalography (MEG) non-invasively measures the magnetic field generated due to the excitatory postsynaptic electrical activity of the apical dendritic pyramidal cells. Such a tiny magnetic field is measured with the help of the biomagnetometer sensors coupled with the Super Conducting Quantum Interference Device (SQUID) inside the magnetically shielded room (MSR). The subjects are usually screened for the presence of ferromagnetic materials, and then the head position indicator coil...

Velmurugan, Jayabal; Sinha, Sanjib; Satishchandra, Parthasarathy

2014-01-01

12

Comparison of three-shell and simplified volume conductor models in magnetoencephalography.  

Science.gov (United States)

Experimental MEG source imaging studies have typically been carried out with either a spherically symmetric head model or a single-shell boundary-element (BEM) model that is shaped according to the inner skull surface. The concepts and comparisons behind these simplified models have led to misunderstandings regarding the role of skull and scalp in MEG. In this work, we assess the forward-model errors due to different skull/scalp approximations and due to differences and errors in model geometries. We built five anatomical models of a volunteer using a set of T1-weighted MR scans and three common toolboxes. Three of the models represented typical models in experimental MEG, one was manually constructed, and one contained a major segmentation error at the skull base. For these anatomical models, we built forward models using four simplified approaches and a three-shell BEM approach that has been used as reference in previous studies. Our reference model contained in addition the skull fine-structure (spongy bone). We computed signal topographies for cortically constrained sources in the left hemisphere and compared the topographies using relative error and correlation metrics. The results show that the spongy bone has a minimal effect on MEG topographies, and thus the skull approximation of the three-shell model is justified. The three-shell model performed best, followed by the corrected-sphere and single-shell models, whereas the local-spheres and single-sphere models were clearly worse. The three-shell model was the most robust against the introduced segmentation error. In contrast to earlier claims, there was no noteworthy difference in the computation times between the realistically-shaped and sphere-based models, and the manual effort of building a three-shell model and a simplified model is comparable. We thus recommend the realistically-shaped three-shell model for experimental MEG work. In cases where this is not possible, we recommend a realistically-shaped corrected-sphere or single-shell model. PMID:24434678

Stenroos, Matti; Hunold, Alexander; Haueisen, Jens

2014-07-01

13

The international arena is increasingly heading towards a multipolar model in which US hegemony is challenged by the EU and China  

Digital Repository Infrastructure Vision for European Research (DRIVER)

China has emerged as a growing power in the international arena. Hanne Cuyckens assesses the EU’s relationship with the country and the potential for both actors to challenge the United States as the dominant global power. While China and the EU have both advocated a multipolar model, in which US hegemony is balanced by other powers, the two actors have very different conceptions of how this model should be realised.

Cuyckens, Hanne

2013-01-01

14

Interictal networks in magnetoencephalography.  

Science.gov (United States)

Epileptic networks involve complex relationships across several brain areas. Such networks have been shown on intracerebral EEG (stereotaxic EEG, SEEG), an invasive technique. Magnetoencephalography (MEG) is a noninvasive tool, which was recently proven to be efficient for localizing the generators of epileptiform discharges. However, despite the importance of characterizing non-invasively network aspects in partial epilepsies, only few studies have attempted to retrieve fine spatiotemporal dynamics of interictal discharges with MEG. Our goal was to assess the relevance of magnetoencephalography for detecting and characterizing the brain networks involved in interictal epileptic discharges. We propose here a semi-automatic method based on independent component analysis (ICA) and on co-occurrence of events across components. The method was evaluated in a series of seven patients by comparing its results with networks identified in SEEG. On both MEG and SEEG, we found that interictal discharges can involve remote regions which are acting in synchrony. More regions were identified in SEEG (38 in total) than in MEG (20). All MEG regions were confirmed by SEEG when an electrode was present in the vicinity. In all patients, at least one region could be identified as leading according to our criteria. A majority (71%) of MEG leaders were confirmed by SEEG. We have therefore shown that MEG measurements can extract a significant proportion of the networks visible in SEEG. This suggests that MEG can be a useful tool for defining noninvasively interictal epileptic networks, in terms of regions and patterns of connectivity, in search for a "primary irritative zone". PMID:24105895

Malinowska, Urszula; Badier, Jean-Michel; Gavaret, Martine; Bartolomei, Fabrice; Chauvel, Patrick; Bénar, Christian-George

2014-06-01

15

The scalar magnetic potential in magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Two results on Magnetoencephalography (MEG) are reported in this presentation. First, we present an integral formula connecting the scalar magnetic potential with the values of the electric potential on the boundary of a conductive region. This formula provides the magnetic potential analogue of the well known Geselowitz formula. Second, we construct the scalar magnetic potential for the realistic ellipsoidal model of the brain, as an eigenfunction expansion in terms of surface ellipsoidal harmonics.

Dassios, G [Department of Applied Mathematics and Theoretical Physics University of Cambridge, Cambridge (United Kingdom)], E-mail: G.Dassios@damtp.cam.ac.uk

2008-07-15

16

Magnetoencephalography in pediatric epilepsy  

Directory of Open Access Journals (Sweden)

Full Text Available Magnetoencephalography (MEG records the magnetic field generated by electrical activity of cortical neurons. The signal is not distorted or attenuated, and it is contactless recording that can be performed comfortably even for longer than an hour. It has excellent and decent temporal resolution, especially when it is combined with the patient’s own brain magnetic resonance imaging (magnetic source imaging. Data of MEG and electroencephalography are not mutually exclusive and it is recorded simultaneously and interpreted together. MEG has been shown to be useful in detecting the irritative zone in both lesional and nonlesional epilepsy surgery. It has provided valuable and additive information regarding the lesion that should be resected in epilepsy surgery. Better outcomes in epilepsy surgery were related to the localization of the irritative zone with MEG. The value of MEG in epilepsy surgery is recruiting more patients to epilepsy surgery and providing critical information for surgical planning. MEG cortical mapping is helpful in younger pediatric patients, especially when the epileptogenic zone is close to the eloquent cortex. MEG is also used in both basic and clinical research of epilepsy other than surgery. MEG is a valuable diagnostic modality for diagnosis and treatment, as well as research in epilepsy.

Hunmin Kim

2013-10-01

17

Spin-Orbital Wave Excitations in Orbitally Degenerate Exchange Model with Multipolar Interactions  

CERN Document Server

Elementary excitations in the multipole ordered state, which models the phase III in CeB6, are investigated by means of a generalized Holstein-Primakoff formalism. When different kinds of nearest-neighbor exchange interactions between multipoles are comparable to each other, orbital-flip excitations exhibit almost one-dimensional dispersion along the z axis. With high symmetry of the interactions, zero modes appear due to the macroscopic degeneracy of the ground state. The next-nearest-neighbor dipole-dipole interaction, which stabilizes the magnetic order of the phase III in CeB6, lifts the degeneracy and leads to gapfull excitation spectrum. When the octupole-octupole next-nearest-neighbor interaction exists simultaneously, the spectrum shows softening at \\Gamma and Z points. These excitations may be probed by neutron scattering and ultrasonic measurements.

Kusunose, H; Kusunose, Hiroaki; Kuramoto, Yoshio

2001-01-01

18

A DETAILED SPATIOKINEMATIC MODEL OF THE CONICAL OUTFLOW OF THE MULTIPOLAR PLANETARY NEBULA NGC 7026  

Energy Technology Data Exchange (ETDEWEB)

We present extensive, long-slit, high-resolution coverage of the complex planetary nebula (PN) NGC 7026. We acquired 10 spectra using the Manchester Echelle Spectrometer at San Pedro Martir Observatory in Baja California, Mexico, and each shows exquisite detail, revealing the intricate structure of this object. Incorporating these spectra into the three-dimensional visualization and kinematic program SHAPE and using Hubble Space Telescope images of NGC 7026, we have produced a detailed structural and kinematic model of this PN. NGC 7026 exhibits remarkable symmetry consisting of three lobe pairs and four sets of knots, all symmetrical about the nucleus and displaying a conical outflow. Comparing the three-dimensional structure of this nebula to recent XMM-Newton X-ray observations, we investigate the extended X-ray emission in relation to the nebular structure. We find that the X-ray emission, while confined to the closed, northern lobes of this PN, shows an abrupt termination in the middle of the southeast lobe, which our long slit data show to be open. This is where the shocked fast wind seems to be escaping the interior of the nebula and the X-ray emission rapidly cools in this region.

Clark, D. M.; Lopez, J. A.; Steffen, W.; Richer, M. G., E-mail: dmclark@astro.unam.mx [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Ensenada, Baja California, CA 22860 (United States)

2013-03-15

19

MULTIPOLAR PLANETARY NEBULAE: NOT AS GEOMETRICALLY DIVERSIFIED AS THOUGHT  

Energy Technology Data Exchange (ETDEWEB)

Planetary nebulae (PNe) have diverse morphological shapes, including point-symmetric and multipolar structures. Many PNe also have complicated internal structures such as tori, lobes, knots, and ansae. A complete accounting of all the morphological structures through physical models is difficult. A first step toward such an understanding is to derive the true three-dimensional structure of the nebulae. In this paper, we show that a multipolar nebula with three pairs of lobes can explain many such features, if orientation and sensitivity effects are taken into account. Using only six parameters-the inclination and position angles of each pair-we are able to simulate the observed images of 20 PNe with complex structures. We suggest that multipolar structure is an intrinsic structure of PNe and the statistics of multipolar PNe have been severely underestimated in the past.

Chong, S.-N.; Imai, H.; Chibueze, J. [Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Kwok, Sun [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Tafoya, D., E-mail: chongsnco@gmail.com, E-mail: sunkwok@hku.hk [Onsala Space Observatory, SE-439 92 Onsala (Sweden)

2012-12-01

20

Multipolar Planetary Nebulae: Not as Geometrically Diversified as Thought  

CERN Document Server

Planetary nebulae (PNe) have diverse morphological shapes, including point-symmetric and multipolar structures. Many PNe also have complicated internal structures such as torus, lobes, knots, and ansae. A complete accounting of all the morphological structures through physical models is difficult. A first step toward such an understanding is to derive the true three-dimensional structure of the nebulae. In this paper, we show that a multipolar nebula with three pairs of lobes can explain many of such features, if orientation and sensitivity effects are taken into account. Using only six parameters - the inclination and position angles of each pair - we are able to simulate the observed images of 20 PNe with complex structures. We suggest that the multipolar structure is an intrinsic structure of PNe and the statistics of multipolar PNe has been severely underestimated in the past.

Chong, Sze-Ning; Imai, Hiroshi; Tafoya, Daniel; Chibueze, James; 10.1088/0004-637X/760/2/115

2012-01-01

 
 
 
 
21

Direct reconstruction algorithm of current dipoles for vector magnetoencephalography and electroencephalography  

International Nuclear Information System (INIS)

This paper presents a novel algorithm to reconstruct parameters of a sufficient number of current dipoles that describe data (equivalent current dipoles, ECDs, hereafter) from radial/vector magnetoencephalography (MEG) with and without electroencephalography (EEG). We assume a three-compartment head model and arbitrary surfaces on which the MEG sensors and EEG electrodes are placed. Via the multipole expansion of the magnetic field, we obtain algebraic equations relating the dipole parameters to the vector MEG/EEG data. By solving them directly, without providing initial parameter guesses and computing forward solutions iteratively, the dipole positions and moments projected onto the xy-plane (equatorial plane) are reconstructed from a single time shot of the data. In addition, when the head layers and the sensor surfaces are spherically symmetric, we show that the required data reduce to radial MEG only. This clarifies the advantage of vector MEG/EEG measurements and algorithms for a generally-shaped head and sensor surfaces. In the numerical simulations, the centroids of the patch sources are well localized using vector/radial MEG measured on the upper hemisphere. By assuming the model order to be larger than the actual dipole number, the resultant spurious dipole is shown to have a much smaller strength magnetic moment (about 0.05 times smaller when the SNR = 16 dB), so that the number of ECDs is reasonably estimated. We consider that our direct method with greatlynsider that our direct method with greatly reduced computational cost can also be used to provide a good initial guess for conventional dipolar/multipolar fitting algorithms

22

Direct reconstruction algorithm of current dipoles for vector magnetoencephalography and electroencephalography  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a novel algorithm to reconstruct parameters of a sufficient number of current dipoles that describe data (equivalent current dipoles, ECDs, hereafter) from radial/vector magnetoencephalography (MEG) with and without electroencephalography (EEG). We assume a three-compartment head model and arbitrary surfaces on which the MEG sensors and EEG electrodes are placed. Via the multipole expansion of the magnetic field, we obtain algebraic equations relating the dipole parameters to the vector MEG/EEG data. By solving them directly, without providing initial parameter guesses and computing forward solutions iteratively, the dipole positions and moments projected onto the xy-plane (equatorial plane) are reconstructed from a single time shot of the data. In addition, when the head layers and the sensor surfaces are spherically symmetric, we show that the required data reduce to radial MEG only. This clarifies the advantage of vector MEG/EEG measurements and algorithms for a generally-shaped head and sensor surfaces. In the numerical simulations, the centroids of the patch sources are well localized using vector/radial MEG measured on the upper hemisphere. By assuming the model order to be larger than the actual dipole number, the resultant spurious dipole is shown to have a much smaller strength magnetic moment (about 0.05 times smaller when the SNR = 16 dB), so that the number of ECDs is reasonably estimated. We consider that our direct method with greatly reduced computational cost can also be used to provide a good initial guess for conventional dipolar/multipolar fitting algorithms.

Nara, Takaaki [Graduate School of Information Science and Technology, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656 (Japan); Oohama, Junji [Graduate School of Information Science and Technology, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656 (Japan); Hashimoto, Masaru [Graduate School of Information Science and Technology, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656 (Japan); Takeda, Tsunehiro [Graduate School of Frontier Science, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8561 (Japan); Ando, Shigeru [Graduate School of Information Science and Technology, University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-8656 (Japan)

2007-07-07

23

Evaluation of the solid state dipole moment and pyroelectric coefficient of phosphangulene by multipolar modeling of X-ray structure factors  

Science.gov (United States)

The electron density distribution of the molecular pyroelectric material phosphangulene has been studied by multipolar modeling of X-ray diffraction data. The "in-crystal" molecular dipole moment has been evaluated to 4.7 D corresponding to a 42% dipole moment enhancement compared with the dipole moment measured in a chloroform solution. It is substantiated that the estimated standard deviation of the dipole moment is about 0.8 D. The standard uncertainty (s.u.) of the derived dipole moment has been derived by splitting the dataset into three independent data-sets. A novel method for obtaining pyroelectric coefficients has been introduced by combining the derived dipole moment with temperature-dependent measurements of the unit cell volume. The derived pyroelectric coefficient of 3.8(7) x 10-6 Cm 2K-1 is in very good agreement with the measured pyroelectric coefficient of p = 3 +/- 1 x 10-6 Cm-2 K-1. This method for obtaining the pyroelectric coefficient uses information from the X-ray diffraction experiment alone and can be applied to much smaller crystals than traditional methods. PMID:10845638

Madsen; Krebs; Lebech; Larsen

2000-05-15

24

Evaluation of the solid state dipole moment and pyroelectric coefficient of phosphangulene by multipolar modeling of X-ray structure factors  

DEFF Research Database (Denmark)

The electron density distribution of the molecular pyroelectric material phosphangulene has been studied by multipolar modeling of X-ray diffraction data. The "in-crystal" molecular dipole moment has been evaluated to 4.7 D corresponding to a 42% dipole moment enhancement compared with the dipole moment measured in a chloroform solution. It is substantiated that the estimated standard deviation of the dipole moment is about 0.8 D. The standard uncertainty (s.u.) of the derived dipole moment has been derived by splitting the dataset into three independent datasets. A novel method for obtaining pyroelectric coefficients has been introduced by combining the derived dipole moment with temperature-dependent measurements of the unit cell volume. The derived pyroelectric coefficient of 3.8(7)x 10(-6) Cm-2K-1 is in very good agreement with the measured pyroelectric coefficient of p = 3 +/- 1 x 10(-6) Cm-2 K-1. This method for obtaining the pyroelectric coefficient uses information from the X-ray diffraction experiment alone and can be applied to much smaller crystals than traditional methods.

Madsen, G.K.H.; Krebs, Frederik C

2000-01-01

25

Multipolar analysis of spinning binaries  

International Nuclear Information System (INIS)

We present a preliminary study of the multipolar structure of gravitational radiation from spinning black hole binary mergers. We consider three different spinning binary configurations: (1) one 'hang-up' run, where the black holes have equal masses and large spins initially aligned with the orbital angular momentum; (2) seven 'spin-flip' runs, where the holes have a mass ratio q ? M1/M2 = 4, the spins are anti-aligned with the orbital angular momentum, and the initial Kerr parameters of the holes j1 j2 = ji (where j ? J/M2) are fine-tuned to produce a Schwarzschild remnant after merger; (3) three 'super-kick' runs where the mass ratio q = 1, 2, 4 and the spins of the two holes are initially located on the orbital plane, pointing in opposite directions. For all of these simulations we compute the multipolar energy distribution and the Kerr parameter of the final hole. For the hang-up run, we show that including leading-order spin-orbit and spin-spin terms in a multipolar decomposition of the post-Newtonian waveforms improves agreement with the numerical simulation

26

Strategies for Business Schools in a Multi-Polar World  

Science.gov (United States)

Purpose: The purpose of this paper is to examine the contours of the emerging business education and institutions in a multi-polar world and to identify the causes of the strategic convergence of management education, to explore the limitations of the dominant models of management education and to propose a range of strategic alternatives for…

Dameron, Stephanie; Durand, Thomas

2013-01-01

27

Second Language Research Using Magnetoencephalography: A Review  

Science.gov (United States)

In this review we show how magnetoencephalography (MEG) is a constructive tool for language research and review MEG findings in second language (L2) research. MEG is the magnetic analog of electroencephalography (EEG), and its primary advantage over other cross-sectional (e.g. magnetic resonance imaging, or positron emission tomography) functional…

Schmidt, Gwen L.; Roberts, Timothy P. L.

2009-01-01

28

Magnetoencephalography in Pediatric Lesional Epilepsy Surgery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This study was performed to assess the usefulness of magnetoencephalography (MEG) as a presurgical evaluation modality in Korean pediatric patients with lesional localization-related epilepsy. The medical records and MEG findings of 13 pediatric patients (6 boys and 7 girls) with localization-related epilepsy, who underwent epilepsy surgery at Seoul National University Children's Hospital, were retrospectively reviewed. The hemispheric concordance rate was 100% (13/13 patients). The lobar or ...

Kim, Hunmin; Lim, Byung Chan; Jeong, Woorim; Kim, June Sic; Chae, Jong-hee; Kim, Ki Joong; Chung, Chun Kee; Hwang, Yong Seung; Hwang, Hee

2012-01-01

29

Multipolar representation of protein structure  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background That the structure determines the function of proteins is a central paradigm in biology. However, protein functions are more directly related to cooperative effects at the residue and multi-residue scales. As such, current representations based on atomic coordinates can be considered inadequate. Bridging the gap between atomic-level structure and overall protein-level functionality requires parameterizations of the protein structure (and other physicochemical properties in a quasi-continuous range, from a simple collection of unrelated amino acids coordinates to the highly synergistic organization of the whole protein entity, from a microscopic view in which each atom is completely resolved to a "macroscopic" description such as the one encoded in the three-dimensional protein shape. Results Here we propose such a parameterization and study its relationship to the standard Euclidian description based on amino acid representative coordinates. The representation uses multipoles associated with residue C? coordinates as shape descriptors. We demonstrate that the multipoles can be used for the quantitative description of the protein shape and for the comparison of protein structures at various levels of detail. Specifically, we construct a (dissimilarity measure in multipolar configuration space, and show how such a function can be used for the comparison of a pair of proteins. We then test the parameterization on a benchmark set of the protein kinase-like superfamily. We prove that, when the biologically relevant portions of the proteins are retained, it can robustly discriminate between the various families in the set in a way not possible through sequence or conventional structural representations alone. We then compare our representation with the Cartesian coordinate description and show that, as expected, the correlation with that representation increases as the level of detail, measured by the highest rank of multipoles used in the representation, approaches the dimensionality of the fold space. Conclusion The results described here demonstrate how a granular description of the protein structure can be achieved using multipolar coefficients. The description has the additional advantage of being immediately generalizable for any residue-specific property therefore providing a unitary framework for the study and comparison of the spatial profile of various protein properties.

Bourne Philip E

2006-05-01

30

Magnetoencephalography from signals to dynamic cortical networks  

CERN Document Server

"Magnetoencephalography (MEG) provides a time-accurate view into human brain function. The concerted action of neurons generates minute magnetic fields that can be detected---totally noninvasively---by sensitive multichannel magnetometers. The obtained millisecond accuracycomplements information obtained by other modern brain-imaging tools. Accurate timing is quintessential in normal brain function, often distorted in brain disorders. The noninvasiveness and time-sensitivityof MEG are great assets to developmental studies, as well. This multiauthored book covers an ambitiously wide range of MEG research from introductory to advanced level, from sensors to signals, and from focal sources to the dynamics of cortical networks. Written by active practioners of this multidisciplinary field, the book contains tutorials for newcomers and chapters of new challenging methods and emerging technologies to advanced MEG users. The reader will obtain a firm grasp of the possibilities of MEG in the study of audition, vision...

Aine, Cheryl

2014-01-01

31

SQUID-based multichannel system for Magnetoencephalography  

CERN Document Server

Here we present a multichannel system based on superconducting quantum interference devices (SQUIDs) for magnetoencephalography (MEG) measurements, developed and installed at Istituto di Cibernetica (ICIB) in Naples. This MEG system, consists of 163 full integrated SQUID magnetometers, 154 channels and 9 references, and has been designed to meet specifications concerning noise, dynamic range, slew rate and linearity through optimized design. The control electronics is located at room temperature and all the operations are performed inside a Magnetically Shielded Room (MSR). The system exhibits a magnetic white noise level of approximatively 5 fT/Hz1=2. This MEG system will be employed for both clinical and routine use. PACS numbers: 74.81.Fa, 85.25.Hv, 07.20.Mc, 85.25.Dq, 87.19.le, 87.85.Ng

Rombetto, S; Vettoliere, A; Trebeschi, A; Rossi, R; Russo, M

2013-01-01

32

An Optical-Infrared Study of the Young Multipolar Planetary Nebula NGC 6644  

CERN Document Server

High-resolution HST imaging of the compact planetary nebula NGC 6644 has revealed two pairs of bipolar lobes and a central ring lying close to the plane of the sky. From mid-infrared imaging obtained with the Gemini Telescope, we have found a dust torus which is oriented nearly perpendicular to one pair of the lobes. We suggest that NGC 6644 is a multipolar nebula and have constructed a 3-D model which allows the visualization of the object from different lines of sight. These results suggest that NGC 6644 may have similar intrinsic structures as other multipolar nebulae and the phenomenon of multipolar nebulosity may be more common than previously believed.

Hsia, Chih Hao; Zhang, Yong; Koning, Nico; Volk, Kevin

2010-01-01

33

Astronomical relativistic reference systems with multipolar expansion: the global one  

CERN Document Server

With rapid development of techniques for astronomical observations, the precision of measurements has been significantly increasing. Theories of astronomical relativistic reference systems, which are the foundation for processing and interpreting these data now and in the future, may require extensions to satisfy the needs of these trends. Besides building a framework compatible with alternative theories of gravity and the pursuit of higher order post-Newtonian approximation, it will also be necessary to make the first order post-Newtonian multipole moments of celestial bodies be explicitly expressed in the astronomical relativistic reference systems. This will bring some convenience into modeling the observations and experiments and make it easier to distinguish different contributions in measurements. As the first step, the global solar system reference system is multipolarly expanded and the post-Newtonian mass and spin moments are shown explicitly in the metric which describes the coordinates of the syste...

Xie, Yi

2014-01-01

34

Astronomical relativistic reference systems with multipolar expansion: the global one  

Science.gov (United States)

With the rapid development of techniques for astronomical observations, the precision of measurements has been significantly increasing. Theories describing astronomical relativistic reference systems, which are the foundation for processing and interpreting these data now and in the future, may require extensions to satisfy the needs of these trends. Besides building a framework compatible with alternative theories of gravity and the pursuit of higher order post-Newtonian approximation, it will also be necessary to make the first order post-Newtonian multipole moments of celestial bodies be explicitly expressed in the astronomical relativistic reference systems. This will bring some convenience into modeling the observations and experiments and make it easier to distinguish different contributions in measurements. As a first step, the global solar system reference system is expressed as a multipolar expansion and the post-Newtonian mass and spin moments are shown explicitly in the metric which describes the coordinates of the system. The full expression of the global metric is given.

Xie, Yi

2014-09-01

35

Endoscopic sphincterotomy-induced hemorrhage: treatment with multipolar electrocoagulation.  

Science.gov (United States)

Multipolar electrocoagulation is an effective therapy for patients with endoscopic evidence of active upper gastrointestinal hemorrhage or a non-bleeding visible vessel in an ulcer crater. The use of this therapy for endoscopic sphincterotomy-induced hemorrhage has not been reported previously. This prospective study attempted to assess the efficacy of multipolar electrocoagulation in patients with endoscopic sphincterotomy-induced hemorrhage not responding to conservative and/or other endoscopic measures. Nine patients with moderate or severe bleeding following endoscopic sphincterotomy (one, immediate; eight, delayed 12 to 144 hours) were treated by multipolar electrocoagulation. Prior to endoscopic therapy with multipolar electrocoagulation, the mean hematocrit drop was 14.5% and the mean number of packed red blood cells transfused was 4.8 units. Complete hemostasis was achieved in eight (89%) patients. Re-bleeding occurred in two (25%) and was controlled by a second course of multipolar electrocoagulation in one in whom it was attempted. There were no complications or deaths from multipolar electrocoagulation and surgical therapy was avoided in all nine patients. We recommend proceeding with multipolar electrocoagulation (if possible) after injection therapy and/or balloon tamponade fail to control the hemorrhage and before considering angiographic or surgical intervention. PMID:1568606

Sherman, S; Hawes, R H; Nisi, R; Lehman, G A

1992-01-01

36

THICK DISKS WITH NEWTONIAN MULTIPOLAR MOMENTS / DISCOS GRUESOS CON MOMENTOS MULTIPOLARES NEWTONIANOS  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish Se presenta una nueva familia de discos gruesos newtonianos estables a partir del método de desplazamiento, corte, llenado y reflexión construidos en (González & Letelier, 2004; Vogt & Letelier, 2005). Soluciones de la ecuación de Laplace en coordenadas cilíndricas son consideradas, éstas representa [...] rán el campo gravitacional de objetos con momentos multipolares externos solamente. Se definen y calculan las cantidades físicas en el plano del disco, tales como, la frecuencia epicíclica, kapa, la frecuencia vertical, ny, y la velocidad circular, ípsilonc de las partículas. Además, se determina la densidad superficial de masa, sigma, la densidad del disco grueso, rho, y el criterio de estabilidad de los discos gruesos a través del momentum angular o el criterio de Rayleigh (Rayleigh, 1917; Landau, 1987). Finalmente, se representan las propiedades físicas para algunos parámetros considerando sólo hasta el término cuadrupolar en la expansión multipolar del potencial gravitacional. Abstract in english We present a new family of stable thick discs from known displace, cut, fill and reflect method (González & Letelier, 2004; Vogt & Letelier, 2005) is presented. Solutions of the Laplace equation in cylindrical coordinates are considered, these one represent the gravitational field of objects with on [...] ly external multipole moments. The physical quantities in the plane of the disk, are defined and calculated such as, the epicyclic frequency, kappa, the vertical frequency, nu, and the circular velocity, upsilonc of particles. The surface density, sigma, density of thick disk, rho, and stability of thick disks through of specific angular momentum or Rayleigh criterion (Rayleigh, 1917), and (Landau, 1987) were calculated. Finally, the physical properties are shown for only some parameters considering only until quadrupolar term in the expasion gravitational potential multipolar

Framsol, López-Suspes; Guillermo A., González.

2013-09-01

37

Non-Parametric Statistical Thresholding for Sparse Magnetoencephalography Source Reconstructions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Uncovering brain activity from magnetoencephalography (MEG) data requires solving an ill-posed inverse problem, greatly confounded by noise, interference, and correlated sources. Sparse reconstruction algorithms, such as Champagne, show great promise in that they provide focal brain activations robust to these confounds. In this paper, we address the technical considerations of statistically thresholding brain images obtained from sparse reconstruction algorithms. The source power distributio...

JuliaParsonsOwen; KensukeSekihara; SrikantanS.Nagarajan

2012-01-01

38

Using variance information in magnetoencephalography measures of functional connectivity.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of magnetoencephalography (MEG) to assess long range functional connectivity across large scale distributed brain networks is gaining popularity. Recent work has shown that electrodynamic networks can be assessed using both seed based correlation or independent component analysis (ICA) applied to MEG data and further that such metrics agree with fMRI studies. To date, techniques for MEG connectivity assessment have typically used a variance normalised approach, either through the use ...

Hall, El; Woolrich, Mw; Thomaz, Ce; Morris, PG; Brookes, Mj

2013-01-01

39

Localizing evoked and induced responses to faces using magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A rich pattern of responses in frequency, time and space are known to be generated in the visual cortex in response to faces. Recently, a number of studies have used magnetoencephalography (MEG) to try to record these responses non-invasively – in many cases using source analysis techniques based on the beamforming method. Here we sought both to characterize best practice for measuring face-specific responses using MEG beamforming, and to determine whether the results produced by the beamfo...

Perry, Gavin; Singh, Krish D.

2014-01-01

40

Antiferro multipolar ordering and it's identification by NMR experiment  

International Nuclear Information System (INIS)

The antiferro-ordering of multipolar moments often plays important roles in the low temperature phase transition of f-electron systems. The splitting of NMR spectra, which is analyzed in terms of the invariant hyperfine coupling between the nuclear spin and the multipolar moments of magnetic ions, gives important information about the multipolar ordering. Experimental and theoretical studies on CeB6 and NpO2 are presented as typical examples. The study on the low temperature phase of PrFe4P12, whose nature has been controversial, are reviewed. It was concluded that it has an antiferro order with the order-parameter characterized by the identity representation of the point group. The large anisotropy of NMR splitting in the magnetic field direction dependence suggests important roles of moments with higher ranks in PrFe4P12. (author)

 
 
 
 
41

Multipolare Rhetorik vs. unilaterale Ambitionen : die Grenzen russischer Außenpolitik  

Digital Repository Infrastructure Vision for European Research (DRIVER)

"Advocating a multipolar world and against the unilateralism of the US is a constant of Russian foreign policy since the end of the East-West conflict. For Moscow, the United Nations are the most important institution to reach this goal. But Russia's declaration of a multipolar world does not lead to the consequence of multilateral action. On the contrary, Moscow pursues a clear policy which is not based on consensus and cooperation but on the so-called 'national interests' of Russia. Multipo...

Meister, Stefan

2009-01-01

42

Detection of magnetic nanoparticles with magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Superconducting quantum interference devices (SQUIDs) have been widely utilized in biomedical applications due to their extremely high sensitivity to magnetic signals. The present study explores the feasibility of a new type of nanotechnology-based imaging method using standard clinical magnetoencephalographic (MEG) systems equipped with SQUID sensors. Previous studies have shown that biological targets labeled with non-toxic, magnetized nanoparticles can be imaged by measuring the magnetic field generated by these particles. In this work, we demonstrate that (1) the magnetic signals from certain nanoparticles can be detected without magnetization using standard clinical MEG, (2) for some types of nanoparticles, only bound particles produce detectable signals, and (3) the magnetic field of particles several hours after magnetization is significantly stronger than that of un-magnetized particles. These findings hold promise in facilitating the potential application of magnetic nanoparticles to in vivo tumor imaging. The minimum amount of nanoparticles that produce detectable signals is predicted by theoretical modeling and computer simulation.

Jia Wenyan [Department of Neurosurgery, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Xu, Guizhi [Department of Neurosurgery, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Department of Biomedical Engineering, Hebei University of Technology, Tianjin, 300130 (China); Sclabassi, Robert J. [Department of Neurosurgery, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Zhu Jiangang [Department of Electrical and Computer Engineering, Carnegie Melon University, Pittsburgh, PA 15213 (United States); Bagic, Anto [Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Sun Mingui [Department of Neurosurgery, University of Pittsburgh, Pittsburgh, PA 15260 (United States)], E-mail: mrsun@neuronet.pitt.edu

2008-04-15

43

Detection of magnetic nanoparticles with magnetoencephalography  

International Nuclear Information System (INIS)

Superconducting quantum interference devices (SQUIDs) have been widely utilized in biomedical applications due to their extremely high sensitivity to magnetic signals. The present study explores the feasibility of a new type of nanotechnology-based imaging method using standard clinical magnetoencephalographic (MEG) systems equipped with SQUID sensors. Previous studies have shown that biological targets labeled with non-toxic, magnetized nanoparticles can be imaged by measuring the magnetic field generated by these particles. In this work, we demonstrate that (1) the magnetic signals from certain nanoparticles can be detected without magnetization using standard clinical MEG, (2) for some types of nanoparticles, only bound particles produce detectable signals, and (3) the magnetic field of particles several hours after magnetization is significantly stronger than that of un-magnetized particles. These findings hold promise in facilitating the potential application of magnetic nanoparticles to in vivo tumor imaging. The minimum amount of nanoparticles that produce detectable signals is predicted by theoretical modeling and computer simulation

44

Note: Optical receiver system for 152-channel magnetoencephalography  

Science.gov (United States)

An optical receiver system composing 13 serial data restore/synchronizer modules and a single module combiner converted optical 32-bit serial data into 32-bit synchronous parallel data for a computer to acquire 152-channel magnetoencephalography (MEG) signals. A serial data restore/synchronizer module identified 32-bit channel-voltage bits from 48-bit streaming serial data, and then consecutively reproduced 13 times of 32-bit serial data, acting in a synchronous clock. After selecting a single among 13 reproduced data in each module, a module combiner converted it into 32-bit parallel data, which were carried to 32-port digital input board in a computer. When the receiver system together with optical transmitters were applied to 152-channel superconducting quantum interference device sensors, this MEG system maintained a field noise level of 3 fT/?Hz @ 100 Hz at a sample rate of 1 kSample/s per channel.

Kim, Jin-Mok; Kwon, Hyukchan; Yu, Kwon-kyu; Lee, Yong-Ho; Kim, Kiwoong

2014-11-01

45

Restrictive vs. non-restrictive composition: a magnetoencephalography study.  

Science.gov (United States)

Recent research on the brain mechanisms underlying language processing has implicated the left anterior temporal lobe (LATL) as a central region for the composition of simple phrases. Because these studies typically present their critical stimuli without contextual information, the sensitivity of LATL responses to contextual factors is unknown. In this magnetoencephalography (MEG) study, we employed a simple question-answer paradigm to manipulate whether a prenominal adjective or determiner is interpreted restrictively, i.e., as limiting the set of entities under discussion. Our results show that the LATL is sensitive to restriction, with restrictive composition eliciting higher responses than non-restrictive composition. However, this effect was only observed when the restricting element was a determiner, adjectival stimuli showing the opposite pattern, which we hypothesise to be driven by the special pragmatic properties of non-restrictive adjectives. Overall, our results demonstrate a robust sensitivity of the LATL to high level contextual and potentially also pragmatic factors. PMID:25379512

Leffel, Timothy; Lauter, Miriam; Westerlund, Masha; Pylkkänen, Liina

2014-11-26

46

Optical torque from enhanced scattering by multipolar plasmonic resonance  

Science.gov (United States)

We present a theoretical study of the optical angular momentum transfer from a circularly polarized plane wave to thin metal nanoparticles of different rotational symmetries. While absorption has been regarded as the predominant mechanism of torque generation on the nanoscale, we demonstrate numerically how the contribution from scattering can be enhanced by using multipolar plasmon resonance. The multipolar modes in non-circular particles can convert the angular momentum carried by the scattered field and thereby produce scattering-dominant optical torque, while a circularly symmetric particle cannot. Our results show that the optical torque induced by resonant scattering can contribute to 80% of the total optical torque in gold particles. This scattering-dominant torque generation is extremely mode-specific, and deserves to be distinguished from the absorption-dominant mechanism. Our findings might have applications in optical manipulation on the nanoscale as well as new designs in plasmonics and metamaterials.

Lee, Yoonkyung E.; Fung, Kin Hung; Jin, Dafei; Fang, Nicholas X.

2014-12-01

47

Multipolar radiation of quantum emitters with nanowire optical antennas  

Science.gov (United States)

Multipolar transitions other than electric dipoles are generally too weak to be observed at optical frequencies in single quantum emitters. For example, fluorescent molecules and quantum dots have dimensions much smaller than the wavelength of light and therefore emit predominantly as electric dipoles. Here we demonstrate controlled emission of a quantum dot into multipolar radiation through selective coupling to a linear nanowire antenna. The antenna resonance tailors the interaction of the quantum dot with light, effectively creating a hybrid nanoscale source beyond the simple Hertz dipole. Our findings establish a basis for the controlled driving of fundamental modes in nanoantennas and metamaterials, for the understanding of the coupling of quantum emitters to nanophotonic devices such as waveguides and nanolasers, and for the development of innovative quantum nano-optics components with properties not found in nature. PMID:23612291

Curto, Alberto G.; Taminiau, Tim H.; Volpe, Giorgio; Kreuzer, Mark P.; Quidant, Romain; van Hulst, Niek F.

2013-01-01

48

Multipolar radiation of quantum emitters with nanowire optical antennas  

Science.gov (United States)

Multipolar transitions other than electric dipoles are generally too weak to be observed at optical frequencies in single quantum emitters. For example, fluorescent molecules and quantum dots have dimensions much smaller than the wavelength of light and therefore emit predominantly as electric dipoles. Here we demonstrate controlled emission of a quantum dot into multipolar radiation through selective coupling to a linear nanowire antenna. The antenna resonance tailors the interaction of the quantum dot with light, effectively creating a hybrid nanoscale source beyond the simple Hertz dipole. Our findings establish a basis for the controlled driving of fundamental modes in nanoantennas and metamaterials, for the understanding of the coupling of quantum emitters to nanophotonic devices such as waveguides and nanolasers, and for the development of innovative quantum nano-optics components with properties not found in nature.

Curto, Alberto G.; Taminiau, Tim H.; Volpe, Giorgio; Kreuzer, Mark P.; Quidant, Romain; van Hulst, Niek F.

2013-04-01

49

Multichannel System Based on a High Sensitivity Superconductive Sensor for Magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available We developed a multichannel system based on superconducting quantum interference devices (SQUIDs for magnetoencephalography measurements. Our system consists of 163 fully-integrated SQUID magnetometers, 154 channels and 9 references, and all of the operations are performed inside a magnetically-shielded room. The system exhibits a magnetic field noise spectral density of approximatively 5 fT/Hz1=2. The presented magnetoencephalography is the first system working in a clinical environment in Italy.

Sara Rombetto

2014-07-01

50

Soil moisture estimation in cereal fields using multipolarized SAR data  

Science.gov (United States)

The retrieval of soil moisture from remote sensing data is an extremely active research topic with applications on a wide range of disciplines. Microwave observations represent the most viable approach due to the influence of soils' dielectric constant (and thus soil moisture) on both the emission and backscatter of waves in this region of the spectrum. Passive observations provide higher temporal resolutions, whereas active (SAR) observations have a higher spatial detail. Even if operational moisture products, based on passive data, exist, retrieval algorithms using active observations still face several problems. Surface roughness and vegetation cover are probably the disturbing factors most affecting the accuracy of soil moisture retrievals. In this communication the influence of vegetation cover is investigated and a retrieval technique based on multipolarized C band SAR observations is proposed. With this aim a dedicated field campaign was carried out in La Tejería watershed (north of Spain) from January to August 2010. Eight RADARSAT-2 Fine-Quadpol scenes were acquired in order to investigate the role of vegetation cover on the retrieval of soil moisture, as well as the sensitivity of different polarimetric parameters to vegetation cover condition. Coinciding with image acquisitions soil moisture, plant density and crop height measurements were acquired in eight control fields (cultivated with barley and wheat crops). The sensitivity of backscatter coefficients (in HH, HV and VV polarizations) and backscatter ratios (p=HH/VV and q=HV/VV) to soil moisture and crop condition were evaluated and the semi-empirical Water Cloud Model was fitted to the observations. The results obtained showed that the contribution of the cereal vegetation cover was minimal in HH and HV polarizations, whereas the VV channel appeared to be significantly attenuated by the cereal cover, so its value decreased as the crops grew. As a result, the ratios p and q showed a very good correlation with vegetation condition and resulted to be almost insensitive to soil moisture variations. These ratios were next used to parameterize cereal vegetation cover on a retrieval scheme based on the Water Cloud Model. Results were best on VV polarization where the correlation coefficients obtained were above 0.7. The approach proposed is very promising from an operational point of view since it corrects the influence of vegetation cover in the retrieval without requiring external information to describe it. Besides, the low variability of the empirical coefficients obtained for different fields, suggests that differences in surface roughness at this stage do not significantly affect soil moisture retrievals.

Alvarez-Mozos, J.; Izagirre, A.; Larrañaga, A.

2012-04-01

51

Non-parametric statistical thresholding for sparse magnetoencephalography source reconstructions.  

Science.gov (United States)

Uncovering brain activity from magnetoencephalography (MEG) data requires solving an ill-posed inverse problem, greatly confounded by noise, interference, and correlated sources. Sparse reconstruction algorithms, such as Champagne, show great promise in that they provide focal brain activations robust to these confounds. In this paper, we address the technical considerations of statistically thresholding brain images obtained from sparse reconstruction algorithms. The source power distribution of sparse algorithms makes this class of algorithms ill-suited to "conventional" techniques. We propose two non-parametric resampling methods hypothesized to be compatible with sparse algorithms. The first adapts the maximal statistic procedure to sparse reconstruction results and the second departs from the maximal statistic, putting forth a less stringent procedure that protects against spurious peaks. Simulated MEG data and three real data sets are utilized to demonstrate the efficacy of the proposed methods. Two sparse algorithms, Champagne and generalized minimum-current estimation (G-MCE), are compared to two non-sparse algorithms, a variant of minimum-norm estimation, sLORETA, and an adaptive beamformer. The results, in general, demonstrate that the already sparse images obtained from Champagne and G-MCE are further thresholded by both proposed statistical thresholding procedures. While non-sparse algorithms are thresholded by the maximal statistic procedure, they are not made sparse. The work presented here is one of the first attempts to address the problem of statistically thresholding sparse reconstructions, and aims to improve upon this already advantageous and powerful class of algorithm. PMID:23271990

Owen, Julia P; Sekihara, Kensuke; Nagarajan, Srikantan S

2012-01-01

52

Design and performance of the LANL 158-channel magnetoencephalography system  

Energy Technology Data Exchange (ETDEWEB)

Design and performance for a recently completed whole-head magnetoencephalography (MEG) system using a superconducting imaging-surface (SIS) surrounding an array of SQUID magnetometers is reported. The helmet-like SIS is hemispherical in shape with a brim. The SIS images nearby sources while shields sensors from ambient magnetic noise. The shielding factor depends on magnetometer position and orientation. Typical shielding values of 200 in central sulcus area have been observed. Nine reference channels form three vector magnetometers, which are placed outside SIS. Signal channels consist of 149 SQUID magnetometers with 0.84nT/{Phi}{sub 0} field sensitivity and less then 3 fT/{radical}Hz noise. Typical SQUID - room temperature separations are about 20mm in the cooled state. Twelve 16-channel flux-lock loop units are connected to two 96-channel control units allowing up to 192 total SQUID channels. The control unit includes signal conditioning circuits as well as system test and control circuits. After conditioning all signals are fed to 192-channel, 24-bit data acquisition system capable of sampling up to 48kSa/sec/channel. The SIS-MEG system enables high-quality human functional brain data to be recorded in a one-layer magnetically shielded room.

Matlachov, A. N. (Andrei N.); Kraus, Robert H., Jr.; Espy, M. A. (Michelle A.); Best, E. D. (Elaine D.); Briles, M. Carolyn; Raby, E. Y. (Eric Y.); Flynn, E. R.

2002-01-01

53

Investigating the neural correlates of the stroop effect with magnetoencephalography.  

Science.gov (United States)

Reporting the ink color of a written word when it is itself a color name incongruent with the ink color (e.g. "red" printed in blue) induces a robust interference known as the Stroop effect. Although this effect has been the subject of numerous functional neuroimaging studies, its neuronal substrate is still a matter of debate. Here, we investigated the spatiotemporal dynamics of interference-related neural events using magnetoencephalography (MEG) and voxel-based analyses (SPM8). Evoked magnetic fields (EMFs) were acquired in 12 right-handed healthy subjects performing a color-word Stroop task. Behavioral results disclosed a classic interference effect with longer mean reaction times for incongruent than congruent stimuli. At the group level, EMFs' differences between incongruent and congruent trials spanned from 380 to 700 ms post-stimulus onset. Underlying neural sources were identified in the left pre-supplementary motor area (pre-SMA) and in the left posterior parietal cortex (PPC) confirming the role of these regions in conflict processing. PMID:24752907

Galer, Sophie; Op De Beeck, Marc; Urbain, Charline; Bourguignon, Mathieu; Ligot, Noémie; Wens, Vincent; Marty, Brice; Van Bogaert, Patrick; Peigneux, Philippe; De Tiège, Xavier

2015-01-01

54

Functional Connectivity Measured with Magnetoencephalography Identifies Persons with HIV Disease  

Science.gov (United States)

There is need for a valid and reliable biomarker for HIV Associated Neurocognitive Disorder (HAND). The purpose of the present study was to provide preliminary evidence of the potential utility of neuronal functional connectivity measures obtained using magnetoencephalography (MEG) to identify HIV-associated changes in brain function. Resting state, eyes closed, MEG data from 10 HIV-infected individuals and 8 seronegative controls were analyzed using mutual information (MI) between all pairs of MEG sensors to determine whether there were functional brain networks that distinguished between subject groups based on cognition (global and learning) or on serostatus. Three networks were identified across all subjects, but after permutation testing (at ? < .005) only the one related to HIV serostatus was significant. The network included MEG sensors (planar gradiometers) above the right anterior region connecting to sensors above the left posterior region. A mean MI value was calculated across all connections from the anterior to the posterior groupings; that score distinguished between the serostatus groups with only one error (sensitivity = 1.00, specificity = .88 (X2 = 15.4, df = 1, p < .01, Relative Risk = .11). There were no significant associations between the MI value and the neuropsychological Global Impairment rating, substance abuse, mood disorder, age, education, CD4+ cell counts or HIV viral load. We conclude that using a measure of functional connectivity, it may be possible to distinguish between HIV-infected and uninfected individuals, suggesting that MEG may have the potential to serve as a sensitive, non-invasive biomarker for HAND. PMID:22328062

Becker, James T.; Bajo, Ricardo; Fabrizio, Melissa; Sudre, Gustavo; Cuesta, Pablo; Aizenstein, Howard J.; Lopez, Oscar L.; Wolk, David; Parkkonen, Lauri; Maestu, Fernando; Bagic, Anto

2012-01-01

55

Wavelet-based localization of oscillatory sources from magnetoencephalography data.  

Science.gov (United States)

Transient brain oscillatory activities recorded with Eelectroencephalography (EEG) or magnetoencephalography (MEG) are characteristic features in physiological and pathological processes. This study is aimed at describing, evaluating, and illustrating with clinical data a new method for localizing the sources of oscillatory cortical activity recorded by MEG. The method combines time-frequency representation and an entropic regularization technique in a common framework, assuming that brain activity is sparse in time and space. Spatial sparsity relies on the assumption that brain activity is organized among cortical parcels. Sparsity in time is achieved by transposing the inverse problem in the wavelet representation, for both data and sources. We propose an estimator of the wavelet coefficients of the sources based on the maximum entropy on the mean (MEM) principle. The full dynamics of the sources is obtained from the inverse wavelet transform, and principal component analysis of the reconstructed time courses is applied to extract oscillatory components. This methodology is evaluated using realistic simulations of single-trial signals, combining fast and sudden discharges (spike) along with bursts of oscillating activity. The method is finally illustrated with a clinical application using MEG data acquired on a patient with a right orbitofrontal epilepsy. PMID:22410322

Lina, J M; Chowdhury, R; Lemay, E; Kobayashi, E; Grova, C

2014-08-01

56

Whole brain functional connectivity using phase locking measures of resting state magnetoencephalography.  

Science.gov (United States)

The analysis of spontaneous functional connectivity (sFC) reveals the statistical connections between regions of the brain consistent with underlying functional communication networks within the brain. In this work, we describe the implementation of a complete all-to-all network analysis of resting state neuronal activity from magnetoencephalography (MEG). Using graph theory to define networks at the dipole level, we established functionally defined regions by k-means clustering cortical surface locations using Eigenvector centrality (EVC) scores from the all-to-all adjacency model. Permutation testing was used to estimate regions with statistically significant connections compared to empty room data, which adjusts for spatial dependencies introduced by the MEG inverse problem. In order to test this model, we performed a series of numerical simulations investigating the effects of the MEG reconstruction on connectivity estimates. We subsequently applied the approach to subject data to investigate the effectiveness of our method in obtaining whole brain networks. Our findings indicated that our model provides statistically robust estimates of functional region networks. Application of our phase locking network methodology to real data produced networks with similar connectivity to previously published findings, specifically, we found connections between contralateral areas of the arcuate fasciculus that have been previously investigated. The use of data-driven methods for neuroscientific investigations provides a new tool for researchers in identifying and characterizing whole brain functional connectivity networks. PMID:25018690

Schmidt, Benjamin T; Ghuman, Avniel S; Huppert, Theodore J

2014-01-01

57

Challenges of a Multi-Polar Nuclear World  

Directory of Open Access Journals (Sweden)

Full Text Available Nuclear warfare, being calamitous, is nevertheless, unlike popular perception, far from being apocalyptic. In the article, we consider possible scenarios of nuclear war in a multi-polar nuclear world, arguing that a democratic society has good chances of victory against a totalitarian nuclear-possessing state. Afterwards, we focus on two technical issues of primary importance – targeting doctrine and civil defense. We conclude that a steadfast and determined stance together with properly conceived and well planned policies for dealing with aggression is the price democratic societies must be willing to pay in order to effectively battle aggression at all levels.

Yehoshua Socol

2012-06-01

58

BRICS and the myth of the multipolar world  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this article is to show that the BRICS countries not only don’t form part of a multi-polar world, but in reality are far from sovereign states in any sense of the word. In fact, if their real goal was indeed the creation of an alternative pole of sovereign nation-states, they should have planned at the outset to break their direct dependence on the globalized capitalist market economy, cutting their ties with global institutions controlled by the Transnational Elite (WTO, IMF and World Bank, and moving towards self-reliant economies, so that they could regain their sovereignty.

Takis Fotopoulos

2014-12-01

59

Impact of polydispersity on multipolar resonant scattering in emulsions.  

Science.gov (United States)

The influence of size polydispersity on the resonant acoustic properties of dilute emulsions, made of fluorinated-oil droplets, is quantitatively investigated. Ultrasound attenuation and dispersion measurements on various samples with controlled size polydispersities, ranging from 1% to 13%, are found to be in excellent agreement with predictions based on the independent scattering approximation. By relating the particle-size distribution of the synthesized emulsions to the quality factor of the predicted multipolar resonances, the number of observable acoustic resonances is shown to be imposed by the sample polydispersity. These results are briefly discussed into the context of metamaterials for which scattering resonances are central to their effective properties. PMID:23556570

Mascaro, Benoit; Brunet, Thomas; Poncelet, Olivier; Aristégui, Christophe; Raffy, Simon; Mondain-Monval, Olivier; Leng, Jacques

2013-04-01

60

A multipolar SR motor and its application in EV  

International Nuclear Information System (INIS)

In order to bring out the advanced features of EVs, a direct-drive (DD) with in-wheel (IW) layout has been considered, but it requires more motors than the conventional layout and the motors will be used in a hard environment. Because switched reluctance motors (SRMs) are simple and strong, we have developed a new outer-rotor-type multipolar SRM suitable for DD-IW EVs through simulations and experiments. We have implemented the developed SRMs into a prototype EV. This is the first-ever in-vehicle research to our knowledge; the developing process and the road test results will bring many useful guidelines for future developments

 
 
 
 
61

The Role of Angular Momentum in the Construction of Electromagnetic Multipolar Fields  

Science.gov (United States)

Multipolar solutions of Maxwell's equations are used in many practical applications and are essential for the understanding of light-matter interactions at the fundamental level. Unlike the set of plane wave solutions of electromagnetic fields, the multipolar solutions do not share a standard derivation or notation. As a result, expressions…

Tischler, Nora; Zambrana-Puyalto, Xavier; Molina-Terriza, Gabriel

2012-01-01

62

Localizing evoked and induced responses to faces using magnetoencephalography.  

Science.gov (United States)

A rich pattern of responses in frequency, time and space are known to be generated in the visual cortex in response to faces. Recently, a number of studies have used magnetoencephalography (MEG) to try to record these responses non-invasively - in many cases using source analysis techniques based on the beamforming method. Here we sought both to characterize best practice for measuring face-specific responses using MEG beamforming, and to determine whether the results produced by the beamformer match evidence from other modalities. We measured activity to visual presentation of face stimuli and phase-scrambled control stimuli, and performed source analyses of both induced and evoked responses using Synthetic Aperture Magnetometry. We localized the gamma-band response to bilateral lateral occipital cortex, and both the gamma-band response and the M170-evoked response to the right fusiform gyrus. Differences in the gamma-band response between faces and scrambled stimuli were confined to the frequency range 50-90 Hz; gamma-band activity at higher frequencies did not differ between the two stimulus categories. We additionally identified a component of the M220-evoked response - localized to the parieto-occipital sulcus - which was enhanced for scrambled vs. unscrambled faces. These findings help to establish that MEG beamforming can localize face-specific responses in time, frequency and space with good accuracy (when validated against established findings from functional magnetic resonance imaging and intracranial recordings), as well as contributing to the establishment of best methodological practice for the use of the beamformer method to measure face-specific responses. PMID:24617643

Perry, Gavin; Singh, Krish D

2014-05-01

63

Transition between viscous dipolar and inertial multipolar dynamos  

Science.gov (United States)

We investigate the transition from steady dipolar to reversing multipolar dynamos. The Earth has been argued to lie close to this transition, which could offer a scenario for geomagnetic reversals. We show that the transition between dipolar and multipolar dynamos is characterized by a three terms balance (as opposed to the usually assumed two terms balance), which involves the nongradient parts of inertial, viscous and Coriolis forces. We introduce from this equilibrium the sole parameter RoE-1/3?ReE2/3, which accurately describes the transition for a wide database of 132 fully three-dimensional direct numerical simulations of spherical rotating dynamos (courtesy of U. Christensen). This resolves earlier contradictions in the literature on the relevant two terms balance at the transition. Considering only a two terms balance between the nongradient part of the Coriolis force and of inertial forces provides the classical Ro/?u. This transition can be equivalently described by Re ?u2, which corresponds to the two terms balance between the nongradient part of inertial forces and viscous forces.

Oruba, Ludivine; Dormy, Emmanuel

2014-10-01

64

Anatomy of the Binary Black Hole Recoil: A Multipolar Analysis  

Science.gov (United States)

We present a multipolar analysis of the recoil velocity computed in recent numerical simulations of binary black hole coalescence, for both unequal masses and non-zero, non-precessing spins. We show that multipole moments up to and including 1 = 4 are sufficient to accurately reproduce the final recoil velocity (= 98%) and that only a few dominant modes contribute significantly to it (2 95%). We describe how the relative amplitude, and more importantly, the relative phase, of these few modes control the way in which the recoil builds up throughout the inspiral, merger, and ring-down phases. We also find that the numerical results can be reproduced, to a high level of accuracy, by an effective Newtonian formula for the multipole moments obtained by replacing in the Newtonian formula the radial separation with an effective radius computed from the numerical data. Beyond the merger, the numerical results are reproduced by a superposition of three Kerr quasi-normal modes. Analytic formulae, obtained by expressing the multipole moments in terms of the fundamental QNMs of a Kerr BH, are able to explain the onset and amount of '.anti-kick" for each of the simulations. Lastly, we apply this multipolar analysis to understand the remarkable difference between the amplitudes of planar and non-planar kicks for equal-mass spinning black holes.

Schnittman, Jeremy; Buonanno, Alessandra; vanMeter, James R.; Baker, John G.; Boggs, William D.; Centrella, Joan; Kelly, Bernard J.; McWilliams, Sean T.

2007-01-01

65

Magnetar Giant Flares --- Flux Rope Eruptions in Multipolar Magnetospheric Magnetic Fields  

CERN Document Server

We address a primary question regarding the physical mechanism that triggers the energy release and initiates the onset of eruptions in the magnetar magnetosphere. A self-consistent stationary, axisymmetric model of the magnetar magnetosphere is constructed based on a force-free magnetic field configuration which contains a helically twisted force-free flux rope. Given the complex multipolar magnetic fields at the magnetar surface, we also develop a convenient numerical scheme to solve the GS equation. Depending on the surface magnetic field polarity, there exist two kinds of magnetic field configurations, inverse and normal. For these two kinds of configurations, variations of the flux rope equilibrium height in response to gradual surface physical processes, such as flux injections and crust motions, are carefully examined. We find that equilibrium curves contain two branches, one represents a stable equilibrium branch, the other an unstable equilibrium branch. As a result, the evolution of the system shows...

Yu, Cong

2012-01-01

66

Anisotropy and kinetics of the etching of tungsten in SF6 multipolar microwave plasma  

International Nuclear Information System (INIS)

An experimental study of the etching of tungsten with SF6 has been performed in a microwave multipolar plasma using an electron cyclotron resonance excitation with an independent low dc biasing. The anisotropy and etch rate of tungsten have been measured as a function of atomic fluorine concentration in the plasma and compared with silicon characteristics. The etching mechanisms of tungsten are analyzed in light of published data on the fluorine-tungsten interaction, and the results are explained in terms of the diffusion model for plasma etching developed for the Si-F system. Atomic fluorine adsorption on tungsten appears to be monolayerlike, whereas it is of multilayer type on silicon, and associative desorption of WF6 occurs from WF3 and/or WF4 adspecies in nearest-neighbor positions

67

Binary black hole merger in the extreme-mass-ratio limit: A multipolar analysis  

International Nuclear Information System (INIS)

Building up on previous work, we present a new calculation of the gravitational wave emission generated during the transition from quasicircular inspiral to plunge, merger, and ringdown by a binary system of nonspinning black holes, of masses m1 and m2, in the extreme mass ratio limit, m1m21+m2)2. The relative dynamics of the system is computed without making any adiabatic approximation by using an effective one body (EOB) description, namely, by representing the binary by an effective particle of mass ?=m1m2/(m1+m2) moving in a (quasi-)Schwarzschild background of mass M=m1+m2 and submitted to an O(?) 5PN-resummed analytical radiation reaction force, with ?=?/M. The gravitational wave emission is calculated via a multipolar Regge-Wheeler-Zerilli-type perturbative approach (valid in the limit ?-2,10-3,10-4}, and we compute the multipolar waveform up to l=8. We estimate energy and angular momentum losses during the quasiuniversal and quasigeodesic part of the plunge phase and we analyze the structure of the ringdown. We calculate the gravitational recoil, or 'kick', imparted to the merger remnant by the gravitational wave emission and we emphasize the importance of higher multipoles to get a final value of the recoil v/(c?2)=0.0446. Wrecoil v/(c?2)=0.0446. We finally show that there is an excellent fractional agreement (?10-3) (even during the plunge) between the 5PN EOB analytically resummed radiation reaction flux and the numerically computed gravitational wave angular momentum flux. This is a further confirmation of the aptitude of the EOB formalism to accurately model extreme-mass-ratio inspirals, as needed for the future space-based LISA gravitational wave detector.

68

Simulated multipolarized MAPSAR images to distinguish agricultural crops  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Many researchers have shown the potential of Synthetic Aperture Radar (SAR) images for agricultural applications, particularly for monitoring regions with limitations in terms of acquiring cloud free optical images. Recently, Brazil and Germany began a feasibility study on the construction of an orb [...] ital L-band SAR sensor referred to as MAPSAR (Multi-Application Purpose SAR). This sensor provides L-band images in three spatial resolutions and polarimetric, interferometric and stereoscopic capabilities. Thus, studies are needed to evaluate the potential of future MAPSAR images. The objective of this study was to evaluate multipolarized MAPSAR images simulated by the airborne SAR-R99B sensor to distinguish coffee, cotton and pasture fields in Brazil. Discrimination among crops was evaluated through graphical and cluster analysis of mean backscatter values, considering single, dual and triple polarizations. Planting row direction of coffee influenced the backscatter and was divided into two classes: parallel and perpendicular to the sensor look direction. Single polarizations had poor ability to discriminate the crops. The overall accuracies were less than 59 %, but the understanding of the microwave interaction with the crops could be explored. Combinations of two polarizations could differentiate various fields of crops, highlighting the combination VV-HV that reached 78 % overall accuracy. The use of three polarizations resulted in 85.4 % overall accuracy, indicating that the classes pasture and parallel coffee were fully discriminated from the other classes. These results confirmed the potential of multipolarized MAPSAR images to distinguish the studied crops and showed considerable improvement in the accuracy of the results when the number of polarizations was increased.

Wagner Fernando, Silva; Bernardo Friedrich Theodor, Rudorff; Antonio Roberto, Formaggio; Waldir Renato, Paradella; José Claudio, Mura.

2012-06-01

69

Internal electron conversion spectra of 202Bi. Transition multipolarities of 202Pb  

International Nuclear Information System (INIS)

To refine and supplement data on multipolarity of 202Pb transitions, internal conversion electrons (ICE) spectra with 202Bi monoisotopic sources have been studied. Special attention is paid to determination of > 1000 keV transition multipolarity. Results of measurements in the energy range of 80-1700 keV are tabulated. Wei.ohted average values of ICE intensity corresponding to more than 80 transitions in 202Pb are given. Intensity values for 42 transitions were determined for the first time. Obtained refined data and new data on transition multipolarities confirm quantum characteristics suggested earlier for 202Pb levels and for some levels-refine them

70

Between thought and expression, a magnetoencephalography study of the "tip-of-the-tongue" phenomenon.  

Science.gov (United States)

"Tip-of-the-tongue" (TOT) is the phenomenon associated with the inaccessibility of a known word from memory. It is universally experienced, increases in frequency with age, and is most common for proper nouns. It is a good model for the symptom of anomia experienced much more frequently by some aphasic patients following brain injury. Here, we induced the TOT state in older participants while they underwent brain scanning with magnetoencephalography to investigate the changes in oscillatory brain activity associated with failed retrieval of known words. Using confrontation naming of pictures of celebrities, we successfully induced the TOT state in 29% of trials and contrasted it with two other states: "Know" where the participants both correctly recognized the celebrity's face and retrieved their name and "Don't Know" when the participants did not recognize the celebrity. We wished to test Levelt's influential model of speech output by carrying out two analyses, one epoching the data to the point in time when the picture was displayed and the other looking back in time from when the participants first articulated their responses. Our main findings supported the components of Levelt's model, but not their serial activation over time as both semantic and motor areas were identified in both analyses. We also found enduring decreases in the alpha frequency band in the left ventral temporal region during the TOT state, suggesting ongoing semantic search. Finally, we identified reduced beta power in classical peri-sylvian language areas for the TOT condition, suggesting that brain regions that encode linguistic memories are also involved in their attempted retrieval. PMID:24673407

Resnik, Karmen; Bradbury, David; Barnes, Gareth R; Leff, Alex P

2014-10-01

71

Semantic and Phonological Task-Set Priming and Stimulus Processing Investigated Using Magnetoencephalography (MEG)  

Science.gov (United States)

In this study the neural substrates of semantic and phonological task priming and task performance were investigated using single word task-primes. Magnetoencephalography (MEG) data were analysed using Synthetic Aperture Magnetometry (SAM) to determine the spatiotemporal and spectral characteristics of cortical responses. Comparisons were made…

McNab, F.; Rippon, G.; Hillebrand, A.; Singh, K. D.; Swithenby, S. J.

2007-01-01

72

Multitemporal Analysis of Multipolarization Synthetic Aperture Radar Images for Robust Surface Change Detection  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis addresses two approaches for change detection from multipolarization, multilooked SAR images: a post-classification comparison and a direct change detection. We consider the complete workflow associated with performing post-classification change detection from time series of multipolarization SAR (PolSAR) images acquired with different imaging geometries and polarimetric configurations. The application is connected to monitoring of changes in Arctic glaciers. The images are correc...

Akbari, Vahid

2013-01-01

73

Assessment of cortical dysfunction in human strabismic amblyopia using magnetoencephalography (MEG)  

International Nuclear Information System (INIS)

The aim of this study was to use the technique of magnetoencephalography (MEG) to determine the effects of strabismic amblyopia on the processing of spatial information within the occipital cortex of humans. We recorded evoked magnetic responses to the onset of a chromatic (red/green) sinusoidal grating of periodicity 0.5-4.0 c deg-1 using a 19-channel SQUID-based neuromagnetometer. Evoked responses were recorded monocularly on six amblyopes and six normally-sighted controls, the stimuli being positioned near the fovea in the lower right visual field of each observer. For comparison, the spatial contrast sensitivity function (CSF) for the detection of chromatic gratings was measured for one amblyope and one control using a two alternate forced-choice psychophysical procedure. We chose red/green sinusoids as our stimuli because they evoke strong magnetic responses from the occipital cortex in adult humans (Fylan, Holliday, Singh, Anderson and Harding. (1997). Neuroimage, 6, 47-57). Magnetic field strength was plotted as a function of stimulus spatial frequency for each eye of each subject. Interocular differences were only evident within the amblyopic group: for stimuli of 1-2 c deg-1, the evoked responses had significantly longer latencies and reduced amplitudes through the amblyopic eye (P<0.05). Importantly, the extent of the deficit was uncorrelated with either Snellen acuity or contrast sensitivity. Localization of the evoked responses was peocalization of the evoked responses was performed using a single equivalent current dipole model. Source localizations, for both normal and amblyopic subjects, were consistent with neural activity at the occipital pole near the V1/V2 border. We conclude that MEG is sensitive to the deficit in cortical processing associated with human amblyopia, and can be used to make quantitative neurophysiological measurements. The nature of the cortical deficit is discussed. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

74

Human visual motion areas determined individually by magnetoencephalography and 3D magnetic resonance imaging.  

Science.gov (United States)

We used magnetoencephalography to study inter-individual locational difference in the extrastriate region which responds to visual motion. Magnetic responses to visual motion onset from the right temporo-occipital area were recorded from 12 subjects. All the subjects had clear responses to apparent or random dot coherent motion. The origins of these responses was investigated by use of the single equivalent current dipole model. The nearest scalp to the origin also was identified for each subject, which may be useful in transcranial stimulation studies. Although the magnetic responses of all the subjects should have the same functional properties; be related to neural activities synchronized exclusively to the onset of motion, the estimated origins varied greatly among the subjects. The location of origin could be classified as one of three types: temporo-occipital, occipital, or parietal, according to the sulcal anatomy investigated in the individual's three-dimensional magnetic resonance image. Temporo-occipital types were found for seven subjects, and anatomically the regions were around human MT/V5. Two subjects had the occipital type, with regions posterior to the anatomical MT/V5 and corresponding to V3A anatomically. The other three subjects had origins classified as the parietal type dorso-rostral to the anatomical MT/V5, with regions around the posterior end of the superior temporal sulcus. Although all these cortical regions appear to be related to the neural process of visual motion, whether they correspond functionally to the same names or migrated MT/V5 must now be determined. PMID:10997851

Bundo, M; Kaneoke, Y; Inao, S; Yoshida, J; Nakamura, A; Kakigi, R

2000-09-01

75

Time course of early audiovisual interactions during speech and nonspeech central auditory processing: a magnetoencephalography study.  

Science.gov (United States)

Cross-modal fusion phenomena suggest specific interactions of auditory and visual sensory information both within the speech and nonspeech domains. Using whole-head magnetoencephalography, this study recorded M50 and M100 fields evoked by ambiguous acoustic stimuli that were visually disambiguated to perceived /ta/ or /pa/ syllables. As in natural speech, visual motion onset preceded the acoustic signal by 150 msec. Control conditions included visual and acoustic nonspeech signals as well as visual-only and acoustic-only stimuli. (a) Both speech and nonspeech motion yielded a consistent attenuation of the auditory M50 field, suggesting a visually induced "preparatory baseline shift" at the level of the auditory cortex. (b) Within the temporal domain of the auditory M100 field, visual speech and nonspeech motion gave rise to different response patterns (nonspeech: M100 attenuation; visual /pa/: left-hemisphere M100 enhancement; /ta/: no effect). (c) These interactions could be further decomposed using a six-dipole model. One of these three pairs of dipoles (V270) was fitted to motion-induced activity at a latency of 270 msec after motion onset, that is, the time domain of the auditory M100 field, and could be attributed to the posterior insula. This dipole source responded to nonspeech motion and visual /pa/, but was found suppressed in the case of visual /ta/. Such a nonlinear interaction might reflect the operation of a binary distinction between the marked phonological feature "labial" versus its underspecified competitor "coronal." Thus, visual processing seems to be shaped by linguistic data structures even prior to its fusion with auditory information channel. PMID:18510440

Hertrich, Ingo; Mathiak, Klaus; Lutzenberger, Werner; Ackermann, Hermann

2009-02-01

76

First-principles theory of multipolar order in actinide dioxides  

Science.gov (United States)

Magnetic phase transitions that involve multipolar degrees of freedom have been widely studied during the last couple of decades, challenging the common approximation which assumes that the physical properties of a magnetic material could be effectively described by purely dipolar degrees of freedom. Due to the complexity of the problem and to the large number of competing interactions involved, the simple (fcc) crystal structure of the actinide dioxides made them the ideal playground system for such theoretical and experimental studies. In the present paper, we summarize our recent attempts to provide an ab initio description of the ordered phases of UO2, NpO2, and AmO2 by means of state-of-the-art LDA+U first-principles calculations. This systematic analysis of the electronic structures is here naturally connected to the local crystalline fields of the 5f states in the actinide dioxide series. Related to these we find that the mechanisms which lead to the experimentally observed insulating ground states work in distinctly different ways for each compound. xml:lang="fr"

Magnani, Nicola; Suzuki, Michi-To; Oppeneer, Peter M.

2014-08-01

77

Neutron star deformation due to multipolar magnetic fields  

Science.gov (United States)

Certain multiwavelength observations of neutron stars, such as intermittent radio emissions from rotation-powered pulsars beyond the pair-cascade death line, the pulse profile of the magnetar SGR 1900+14 after its 1998 August 27 giant flare and X-ray spectral features of PSR J0821-4300 and SGR 0418+5729, suggest that the magnetic fields of non-accreting neutron stars are not purely dipolar and may contain higher order multipoles. Here, we calculate the ellipticity of a non-barotropic neutron star with (i) a quadrupole poloidal-toroidal field, and (ii) a purely poloidal field containing arbitrary multipoles, deriving the relation between the ellipticity and the multipole amplitudes. We present, as a worked example, a purely poloidal field comprising dipole, quadrupole and octupole components. We show the correlation between field energy and ellipticity for each multipole, that the l = 4 multipole has the lowest energy, and that l = 5 has the lowest ellipticity. We show how a mixed multipolar field creates an observationally testable mismatch between the principal axes of inertia (to be inferred from gravitational wave data) and the magnetic inclination angle. Strong quadrupole and octupole components (with amplitudes ˜102 times higher than the dipole) in SGR 0418+5729 still yield ellipticity ˜10-8, consistent with current gravitational wave upper limits. The existence of higher multipoles in fast-rotating objects (e.g. newborn magnetars) has interesting implications for the braking law and hence phase tracking during coherent gravitational wave searches.

Mastrano, A.; Lasky, P. D.; Melatos, A.

2013-09-01

78

Study of the multipolarity distribution in 12C and 16O nuclei up to 30MeV excitation energy by proton and alpha inelastic scattering  

International Nuclear Information System (INIS)

The high-lying states of 12C and 16O nuclei were investigated and the distribution of the different multipolarities extracted up to 30MeV excitation energy. The fine structure of the giant dipole resonance was studied and the dipole cross section compared to those expected from the model of Satchler. Other multipolarities (2+ 3- 4+ T=0) were also observed. The observed cross sections exhibit a significant fraction of the sum rule (EWSR) but never exceeds 50% (50% for 1- T=1, 20 to 40% for 2+ T=0, approximately 15% for 3- T=0 and + T=0). The distribution observed compares fairly well with the one expected from nuclear structure calculations except for 2+ T=0 in 16O where complete disagreement is observed between experiment and theory

79

Assessment of hemispheric dominance for receptive language in pediatric patients under sedation using magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Non-invasive assessment of hemispheric dominance for receptive language using Magnetoencephalography (MEG) is now a well-established procedure used across several epilepsy centers in the context of pre-surgical evaluation of children and adults while awake, alert and attentive. However, the utility of MEG for the same purpose, in cases of sedated patients, is contested. Establishment of the efficiency of MEG is especially important in the case of children who, for a number of reasons, must ...

Roozbeh Rezaie; Boop, Frederick A.

2014-01-01

80

Resting-state magnetoencephalography study of “small world” characteristics and cognitive dysfunction in patients with glioma  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Xin-Hua Hu, Ting Lei, Hua-Zhong Xu, Yuan-Jie Zou, Hong-Yi Liu Department of Neurosurgery, Brain Hospital Affiliated to Nanjing Medical University, Nanjing, People's Republic of China Background: The purpose of this study was to analyze “small world” characteristics in glioma patients in order to understand the relationship between cognitive dysfunction and brain functional connectivity network in the resting state. Methods: Resting-state magnetoencephalography was performed in...

Hu X.; Lei T; Hz, Xu; Yj, Zou; Hy, Liu

2013-01-01

 
 
 
 
81

Investigating the Neural Correlates of Percepts Using Magnetoencephalography and Magnetic Source Imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetoencephalography (MEG) has become an important tool for neuroscientists. The high temporal resolution and the low signal-to-noise ratio of MEG provide advantages that other neuroscientific methods do not. Owing to recent findings concerning the relationship between perception and neuronal oscillations, more attention is being drawn to the importance of MEG. This chapter provides an introduction to oscillatory brain dynamics and outlines the fundamental and recent research on this...

Hartmann, Thomas; Weisz, Nathan; Schlee, Winfried; Elbert, Thomas

2009-01-01

82

Magnetar Giant Flares in Multipolar Magnetic Fields --- II. Flux Rope Eruptions With Current Sheets  

CERN Document Server

We propose a physical mechanism to explain giant flares and radio afterglows in terms of a magnetospheric model containing both a helically twisted flux rope and a current sheet (CS). With the appearance of CS, we solve a mixed boundary value problem to get the magnetospheric field based on a domain decomposition method. We investigate properties of the equilibrium curve of the flux rope when the CS is present in background multipolar fields. In response to the variations at the magnetar surface, it quasi-statically evolves in stable equilibrium states. The loss of equilibrium occurs at a critical point and, beyond that point, it erupts catastrophically. New features show up when the CS is considered. Especially, we find two kinds of physical behaviors, i.e., catastrophic state transition and catastrophic escape. Magnetic energy would be released during state transitions. The released magnetic energy is sufficient to drive giant flares. The flux rope would go away from the magnetar quasi-statically, which is ...

Huang, Lei

2014-01-01

83

FMRP regulates multipolar to bipolar transition affecting neuronal migration and cortical circuitry.  

Science.gov (United States)

Deficiencies in fragile X mental retardation protein (FMRP) are the most common cause of inherited intellectual disability, fragile X syndrome (FXS), with symptoms manifesting during infancy and early childhood. Using a mouse model for FXS, we found that Fmrp regulates the positioning of neurons in the cortical plate during embryonic development, affecting their multipolar-to-bipolar transition (MBT). We identified N-cadherin, which is crucial for MBT, as an Fmrp-regulated target in embryonic brain. Furthermore, spontaneous network activity and high-resolution brain imaging revealed defects in the establishment of neuronal networks at very early developmental stages, further confirmed by an unbalanced excitatory and inhibitory network. Finally, reintroduction of Fmrp or N-cadherin in the embryo normalized early postnatal neuron activity. Our findings highlight the critical role of Fmrp in the developing cerebral cortex and might explain some of the clinical features observed in patients with FXS, such as alterations in synaptic communication and neuronal network connectivity. PMID:25402856

La Fata, Giorgio; Gärtner, Annette; Domínguez-Iturza, Nuria; Dresselaers, Tom; Dawitz, Julia; Poorthuis, Rogier B; Averna, Michele; Himmelreich, Uwe; Meredith, Rhiannon M; Achsel, Tilmann; Dotti, Carlos G; Bagni, Claudia

2014-12-01

84

Study on radiation following the 205At decay. Multipolarities of the 205Po transitions  

International Nuclear Information System (INIS)

A study is performed of spectra of #betta#-rays, conversion electrons and e#betta#-coincidences with the use of monoisotopic 205At sources. The admixture of 206At and 207At made up approximately 1%, that of 208At - about 0.3%, by activity. A study of the 205At ? 205Po decay shows 148 #betta#-transitions, 94 of them being observed for the first time. Multipolarities for 70 #betta#-transitions have been determined, for 54 of them - for the first time. For 20 #betta#-transitions the internal conversion coefficients are estimated and, respectively, probable multipolarity

85

Evidence for Early Morphological Decomposition: Combining Masked Priming with Magnetoencephalography  

Science.gov (United States)

Are words stored as morphologically structured representations? If so, when during word recognition are morphological pieces accessed? Recent masked priming studies support models that assume early decomposition of (potentially) morphologically complex words. The electrophysiological evidence, however, is inconsistent. We combined masked…

Lehtonen, Minna; Monahan, Philip J.; Poeppel, David

2011-01-01

86

Magnetoencephalography - a noninvasive brain imaging method with 1 ms time resolution  

International Nuclear Information System (INIS)

The basics of magnetoencephalography (MEG), i.e. the measurement and the analysis of the tiny magnetic fields generated outside the scalp by the working human brain, are reviewed. Three main topics are discussed: (1) the relationship between the magnetic field and its generators, including on one hand the neurophysiological basis and the physical theory of magnetic field generation, and on the other hand the techniques for the estimation of the sources from the magnetic field measurements; (2) the instrumental techniques and the laboratory practice of neuromagnetic field measurement and (3) the main applications of MEG in basic neurophysiology as well as in clinical neurology. (author)

87

A study of the multipolar composition of the electrofission cross section of 237Np  

International Nuclear Information System (INIS)

The electrofission cross section for 237Np was measured over the energy range from 0,6 to 60,0 MeV. The multipolar composition of this cross section was investigated using the virtual photons formalism with three different techniques of analysis: unfolding and two versions of multiple parameter regression. (A.C.A.S.)

88

Calculation of multipolarity mixing ratio and internal conversion coefficients for ? transition  

International Nuclear Information System (INIS)

Briefly described are the calculation methods of the multipolarity mixing ratio ?, the internal conversion coefficients ?K, ?L, ?M and ?N+O of K, L, M, N and O shell, and the total internal conversion coefficient ? for a ? transition from measured internal conversion coefficient for one of shells

89

Calculation of giant E lambda-resonances of high multipolarity in deformed nuclei  

International Nuclear Information System (INIS)

The strength functions b(E?; 0+ ? ?sup(?) for the excitation of multipole resonances with ? = 4,5,6 and 7 in doubly even deformed nuclei are investigated. The conclusions are made about possible energy regions of finding the giant electric resonances of high multipolarity

90

Connexin 43 controls the multipolar phase of neuronal migration to the cerebral cortex.  

Science.gov (United States)

The prospective pyramidal neurons, migrating from the proliferative ventricular zone to the overlaying cortical plate, assume multipolar morphology while passing through the transient subventricular zone. Here, we show that this morphogenetic transformation, from the bipolar to the mutipolar and then back to bipolar again, is associated with expression of connexin 43 (Cx43) and, that knockdown of Cx43 retards, whereas its overexpression enhances, this morphogenetic process. In addition, we have observed that knockdown of Cx43 reduces expression of p27, whereas overexpression of p27 rescues the effect of Cx43 knockdown in the multipolar neurons. Furthermore, functional gap junction/hemichannel domain, and the C-terminal domain of Cx43, independently enhance the expression of p27 and promote the morphological transformation and migration of the multipolar neurons in the SVZ/IZ. Collectively, these results indicate that Cx43 regulates the passage of migrating neurons through their multipolar stage via p27 signaling and that interference with this process, by either genetic and/or environmental factors, may cause cortical malformations. PMID:22566616

Liu, Xiuxin; Sun, Lin; Torii, Masaaki; Rakic, Pasko

2012-05-22

91

On the exterior magnetic field and silent sources in magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available Two main results are included in this paper. The first one deals with the leading asymptotic term of the magnetic field outside any conductive medium. In accord with physical reality, it is proved mathematically that the leading approximation is a quadrupole term which means that the conductive brain tissue weakens the intensity of the magnetic field outside the head. The second one concerns the orientation of the silent sources when the geometry of the brain model is not a sphere but an ellipsoid which provides the best possible mathematical approximation of the human brain. It is shown that what characterizes a dipole source as “silent” is not the collinearity of the dipole moment with its position vector, but the fact that the dipole moment lives in the Gaussian image space at the point where the position vector meets the surface of the ellipsoid. The appropriate representation for the spheroidal case is also included.

Fotini Kariotou

2004-04-01

92

Early visual processing is affected by clinical subtype in patients with unilateral spatial neglect: A magnetoencephalography study.  

Directory of Open Access Journals (Sweden)

CONCLUSIONS: These results demonstrate that early VEFs are disrupted in patients with unilateral spatial neglect and support the concept that deficits in visual processing differ according to the clinical subtype of unilateral spatial neglect and the lesion location. This study also demonstrates the feasibility of using magnetoencephalography to explore subtypes of neglect.

KatsuhiroMizuno

2013-07-01

93

Fetal Magnetoencephalography--Achievements and Challenges in the Study of Prenatal and Early Postnatal Brain Responses: A Review  

Science.gov (United States)

Fetal magnetoencephalography (fMEG) is the only non-invasive method for investigating evoked brain responses and spontaneous brain activity generated by the fetus "in utero". Fetal auditory as well as visual-evoked fields have been successfully recorded in basic stimulus-response studies. Moreover, paradigms investigating precursors for cognitive…

Sheridan, Carolin J.; Matuz, Tamara; Draganova, Rossitza; Eswaran, Hari; Preissl, Hubert

2010-01-01

94

The emerging multi-polar world and China's grand game  

Energy Technology Data Exchange (ETDEWEB)

This talk outlines a scenario describing an emerging multipolar world that is aligned with geographical regions. The stability and security of this multipolar world is examined with respect to demographics, trade (economics), resource constraints, and development. In particular I focus on Asia which has two large countries, China and India, competing for resources and markets and examine the emerging regional relations, opportunities and threats. These relationships must overcome many hurdles - the Subcontinent is in a weak position politically and strategically and faces many threats, and China's growing power could help stabilize it or create new threats. Since the fate of 1.5 billion (2.4 billion by 2050) people depends on how the Subcontinent evolves, this talk is meant to initiates a discussion of what China and India can do to help the region develop and stabilize.

Gupta, Rajan [Los Alamos National Laboratory

2011-01-19

95

Determination of the multipolarity of prompt electromagnetic transitions from angular distributions of conversion electrons. Pt. 1  

International Nuclear Information System (INIS)

The formalism for the angular distribution of conversion electrons from aligned states is described for transitions with multipole order - and #betta# angular distribution function provides an excellent method for assigning multipolarities E1, M1, E2 and (M1 + E2) to prompt decay lines. The applicability of the method is investigated for different spins, electron energies and Z-values. The influence of attenuation factors in angular distribution measurement is discussed and the effect on the multipole assignment is examined. (orig.)

96

Left atrial voltage remodeling after pulmonary venous isolation with multipolar radiofrequency ablation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: Pulmonary vein isolation (PVI) is the accepted primary endpoint for catheter ablation of atrial fibrillation (AF). The aim of this study was to evaluate the level of PVI by PVAC, a multipolar circular catheter utilizing bipolar/unipolar radiofrequency (RF) energy. Methods: Twenty patients with paroxysmal AF underwent PVAC ablation. PVI was validated by voltage reduction and pacing tests. Before and after RF ablation, left atrium (LA) ...

Francesco Laurenzi; Piergiuseppe De Girolamo; Augusto Pappalardo; Andrea Avella

2013-01-01

97

Synthetic Aperture Radar Multi-Polarization Ocean Characteristics and Ship Detection  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In our study, sea surface characteristics imaged by multi-polarization space-borne synthetic aperture radar (SAR) have been investigated. For the first time, a decomposition of different scattering mechanisms have been performed for ocean satellite SAR imagery to better understand the non-Bragg (Scalar) contribution to the total radar cross section (RCS) and Doppler measurements. Characteristics retrieval and target classification have been established, using polarimetry and Bayesian detectio...

Wang, Bo

2013-01-01

98

Equations of motion in scalar-tensor theories of gravity: A covariant multipolar approach  

Science.gov (United States)

We discuss the dynamics of extended test bodies for a large class of scalar-tensor theories of gravitation. A covariant multipolar Mathisson—Papapetrou—Dixon type of approach is used to derive the equations of motion in a systematic way for both Jordan and Einstein formulations of these theories. The results obtained provide the framework to experimentally test scalar-tensor theories by means of extended test bodies.

Obukhov, Yuri N.; Puetzfeld, Dirk

2014-11-01

99

Prefrontal Cortex Modulation during Anticipation of Working Memory Demands as Revealed by Magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available During the anticipation of task demands frontal control is involved in the assembly of stimulus-response mappings based on current goals. It is not clear whether prefrontal modulations occur in higher-order cortical regions, likely reflecting cognitive anticipation processes. The goal of this paper was to investigate prefrontal modulation during anticipation of upcoming working memory demands as revealed by magnetoencephalography (MEG. Twenty healthy volunteers underwent MEG while they performed a variation of the Sternberg Working Memory (WM task. Beta band (14–30?Hz SAM (Synthetic Aperture Magnetometry analysis was performed. During the preparatory periods there was an increase in beta power (event-related synchronization in dorsolateral prefrontal cortex (DLPFC bilaterally, left inferior prefrontal gyrus, left parietal, and temporal areas. Our results provide support for the hypothesis that, during preparatory states, the prefrontal cortex is important for biasing higher order brain regions that are going to be engaged in the upcoming task.

Richard Coppola

2010-01-01

100

Brain activity during bilateral rapid alternate finger tapping measured with magnetoencephalography  

Science.gov (United States)

Using magnetoencephalography (MEG), brain regions involved in an alternate bimanual tapping task by index fingers triggered with spontaneous timing were investigated. The tapping mode in which both index fingers moved simultaneously was interlaced during the task. The groups of the alternate tapping (AL mode) and the simultaneous tapping (SI mode) were extracted from the successive alternating taps with a histogram of intervals between the right and left index fingers. MEG signals in each mode were averaged separately before and after the tapping initiation of the dominant index finger. The activities of the contralateral sensorimotor cortex before and after the tapping initiation in the AL mode were larger than that in the SI mode. The result indicates that the activity of the contralateral sensorimotor cortex depends on the degree of achievement in the difficult motor task such as the voluntary alternate tapping movements.

Fukuda, Hiroshi; Odagaki, Masato; Hiwaki, Osamu; Kodabashi, Atsushi; Fujimoto, Toshiro

2009-04-01

 
 
 
 
101

RP58 Regulates the Multipolar-Bipolar Transition of Newborn Neurons in the Developing Cerebral Cortex  

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Full Text Available Accumulating evidence suggests that many brain diseases are associated with defects in neuronal migration, suggesting that this step of neurogenesis is critical for brain organization. However, the molecular mechanisms underlying neuronal migration remain largely unknown. Here, we identified the zinc-finger transcriptional repressor RP58 as a key regulator of neuronal migration via multipolar-to-bipolar transition. RP58?/? neurons exhibited severe defects in the formation of leading processes and never shifted to the locomotion mode. Cre-mediated deletion of RP58 using in utero electroporation in RP58flox/flox mice revealed that RP58 functions in cell-autonomous multipolar-to-bipolar transition, independent of cell-cycle exit. Finally, we found that RP58 represses Ngn2 transcription to regulate the Ngn2-Rnd2 pathway; Ngn2 knockdown rescued migration defects of the RP58?/? neurons. Our findings highlight the critical role of RP58 in multipolar-to-bipolar transition via suppression of the Ngn2-Rnd2 pathway in the developing cerebral cortex.

Chiaki Ohtaka-Maruyama

2013-02-01

102

Image-guided multipolar radiofrequency ablation of liver tumours: initial clinical results  

International Nuclear Information System (INIS)

The local effectiveness and clinical usefulness of multipolar radiofrequency (RF) ablation of liver tumours was evaluated. Sixty-eight image-guided RF sessions were performed using a multipolar device with bipolar electrodes in 53 patients. There were 45 hepatocellular carcinomas (HCC) and 42 metastases with a diameter ?3 cm (n = 55), 3.1-5 cm (n = 29) and >5 cm (n = 3); 26 nodules were within 5 mm from large vessels. Local effectiveness and complications were evaluated after RF procedures. Mean follow-up was 17 ± 10 months. Recurrence and survival rates were analysed by the Kaplan-Meier method. The primary and secondary technical effectiveness rate was 82% and 95%, respectively. The major and minor complication rate was 2.9%, respectively. The local tumour progression at 1- and 2-years was 5% and 9% for HCC nodules and 17% and 31% for metastases, respectively; four of 26 nodules (15%) close to vessels showed local progression. The survival at 1 year and 2 years was 97% and 90% for HCC and 84% and 68% for metastases, respectively. Multipolar RF technique creates ablation zones of adequate size and tailored shape and is effective to treat most liver tumours, including those close to major hepatic vessels. (orig.)

103

Cytotoxicity of paclitaxel in breast cancer is due to chromosome missegregation on multipolar spindles.  

Science.gov (United States)

The blockbuster chemotherapy drug paclitaxel is widely presumed to cause cell death in tumors as a consequence of mitotic arrest, as it does at concentrations routinely used in cell culture. However, we determine here that paclitaxel levels in primary breast tumors are well below those required to elicit sustained mitotic arrest. Instead, cells in these lower concentrations of drug proceed through mitosis without substantial delay and divide their chromosomes on multipolar spindles, resulting in chromosome missegregation and cell death. Consistent with these cell culture data, most mitotic cells in primary human breast cancers contain multipolar spindles after paclitaxel treatment. Contrary to the previous hypothesis, we find that mitotic arrest is dispensable for tumor regression in patients. These results demonstrate that mitotic arrest is not responsible for the efficacy of paclitaxel, which occurs because of chromosome missegregation on highly abnormal, multipolar spindles. This mechanistic insight may be used to improve selection of future antimitotic drugs and to identify a biomarker with which to select patients likely to benefit from paclitaxel. PMID:24670687

Zasadil, Lauren M; Andersen, Kristen A; Yeum, Dabin; Rocque, Gabrielle B; Wilke, Lee G; Tevaarwerk, Amye J; Raines, Ronald T; Burkard, Mark E; Weaver, Beth A

2014-03-26

104

Multipolar electrostatics based on the Kriging machine learning method: an application to serine.  

Science.gov (United States)

A multipolar, polarizable electrostatic method for future use in a novel force field is described. Quantum Chemical Topology (QCT) is used to partition the electron density of a chemical system into atoms, then the machine learning method Kriging is used to build models that relate the multipole moments of the atoms to the positions of their surrounding nuclei. The pilot system serine is used to study both the influence of the level of theory and the set of data generator methods used. The latter consists of: (i) sampling of protein structures deposited in the Protein Data Bank (PDB), or (ii) normal mode distortion along either (a) Cartesian coordinates, or (b) redundant internal coordinates. Wavefunctions for the sampled geometries were obtained at the HF/6-31G(d,p), B3LYP/apc-1, and MP2/cc-pVDZ levels of theory, prior to calculation of the atomic multipole moments by volume integration. The average absolute error (over an independent test set of conformations) in the total atom-atom electrostatic interaction energy of serine, using Kriging models built with the three data generator methods is 11.3 kJ mol?¹ (PDB), 8.2 kJ mol?¹ (Cartesian distortion), and 10.1 kJ mol?¹ (redundant internal distortion) at the HF/6-31G(d,p) level. At the B3LYP/apc-1 level, the respective errors are 7.7 kJ mol?¹, 6.7 kJ mol?¹, and 4.9 kJ mol?¹, while at the MP2/cc-pVDZ level they are 6.5 kJ mol?¹, 5.3 kJ mol?¹, and 4.0 kJ mol?¹. The ranges of geometries generated by the redundant internal coordinate distortion and by extraction from the PDB are much wider than the range generated by Cartesian distortion. The atomic multipole moment and electrostatic interaction energy predictions for the B3LYP/apc-1 and MP2/cc-pVDZ levels are similar, and both are better than the corresponding predictions at the HF/6-31G(d,p) level. PMID:24633774

Yuan, Yongna; Mills, Matthew J L; Popelier, Paul L A

2014-04-01

105

Investigation of cerebellar and hippocampal activation during differential eye-blink conditioning using Magnetoencephalography and functional Magnetic Resonance Imaging  

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In this investigation the response of cerebellar and hippocampal activity during differential eye-blink conditioning was studied in 60 healthy subjects. Half of the subjects received their eye-blink conditioning during Magnetoencephalography (MEG), the other half during functional Magnetic Resonance Imaging (fMRI). In each group half of the subjects received delay conditioning, while the other half received trace conditioning. For a better understanding of the learning effects, a differential...

Achenbach, Caroline

2004-01-01

106

Auditory and Cognitive Deficits Associated with Acquired Amusia after Stroke: A Magnetoencephalography and Neuropsychological Follow-Up Study  

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Acquired amusia is a common disorder after damage to the middle cerebral artery (MCA) territory. However, its neurocognitive mechanisms, especially the relative contribution of perceptual and cognitive factors, are still unclear. We studied cognitive and auditory processing in the amusic brain by performing neuropsychological testing as well as magnetoencephalography (MEG) measurements of frequency and duration discrimination using magnetic mismatch negativity (MMNm) recordings. Fifty-three p...

Sa?rka?mo?, Teppo; Tervaniemi, Mari; Soinila, Seppo; Autti, Taina; Silvennoinen, Heli M.; Laine, Matti; Hietanen, Marja; Pihko, Elina

2010-01-01

107

Magnetoencefalografía: mapeo de la dinámica espaciotemporal de la actividad neuronal / Magnetoencephalography: mapping the spatiotemporal dynamics of neuronal activity  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish La magnetoencefalografía es una técnica de neuroimagen no invasiva que mide, con gran exactitud temporal, los campos magnéticos en la superficie de la cabeza producidos por corrientes neuronales en regiones cerebrales. Esta técnica es sumamente útil en la investigación básica y clínica, porque ademá [...] s permite ubicar el origen de la actividad neural en el cerebro. En esta revisión se abordan aspectos básicos de la biofísica del método y se discuten los hallazgos sobre procesos como la percepción del habla, la atención auditiva y la integración de la información visual y auditiva, que son importantes en la investigación. Igualmente, se ilustran sus ventajas, sus limitaciones y las nuevas tendencias en la investigación con magnetoencefalografía. Abstract in english Magnetoencephalography is a noninvasive imaging technique that measures the magnetic fields on the surface of the head --produced by neuronal currents in brain regions -- and provides highly accurate temporal information. Magnetoencephalography is extremely useful in basic and clinical research as i [...] t can also locate the sources of neural activity in the brain. This review chiefly approaches biophysics-related aspects of the method; findings are also discussed on issues such as speech perception, auditory attention and integration of visual-auditory information, which are quintessential in this type of research. Lastly, this review discusses the benefits and limitations of magnetoencephalography and outlines new trends in research with this technique.

Yang, Zhang; Wenbo, Zhang; Vicenta, Reynoso Alcántara; Juan, Silva-Pereyra.

2014-01-01

108

Left atrial voltage remodeling after pulmonary venous isolation with multipolar radiofrequency ablation  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Pulmonary vein isolation (PVI is the accepted primary endpoint for catheter ablation of atrial fibrillation (AF. The aim of this study was to evaluate the level of PVI by PVAC, a multipolar circular catheter utilizing bipolar/unipolar radiofrequency (RF energy. Methods: Twenty patients with paroxysmal AF underwent PVAC ablation. PVI was validated by voltage reduction and pacing tests. Before and after RF ablation, left atrium (LA and PV electroanatomic mapping (EAM were performed by EnSite NavX system. Voltage abatement was considered for potentials 24mm: 9/20 (45% vs 11/57 (19%, p

Francesco Laurenzi

2013-11-01

109

Transformation of the multipolar components of gravitational radiation under rotations and boosts  

CERN Document Server

We study the transformation of multipolar decompositions of gravitational radiation under rotations and boosts. Rotations to the remnant black hole's frame simplify the waveforms from the merger of generic spinning black hole binaries. Boosts may be important to get an accurate gravitational-wave phasing, especially for configurations leading to large recoil velocities of the remnant. As a test of our formalism we revisit the classic problem of point particles falling into a Schwarzschild black hole. Then we highlight by specific examples the importance of choosing the right frame in numerical simulations of unequal-mass, spinning binary black-hole mergers.

Gualtieri, L; Cardoso, V; Sperhake, U

2008-01-01

110

Controlling multipolar radiation with symmetries for electromagnetic bound states in the continuum  

Science.gov (United States)

Interferences in open systems embedded in a continuum can lead to states that are bound within the continuum itself. An electromagnetic state that naturally decays becomes bound at a unique point in phase space. We demonstrate the striking occurrence of multiple such peculiar states in coupled deep subwavelength resonators. The bound states in the continuum originate from the control of multipolar radiation and their symmetries. The architectures investigated here, using all-dielectric resonators, constitute a flexible and readily achievable platform for applications requiring strong light-matter interaction and light localization.

Lepetit, Thomas; Kanté, Boubacar

2014-12-01

111

Simultaneous measurement of neuronal activity and cortical hemodynamics by unshielded magnetoencephalography and near-infrared spectroscopy.  

Science.gov (United States)

The correlation between neuronal activity and cortical hemodynamics, namely, neurovascular coupling (NVC), is important to shed light on the mechanism of a variety of brain functions or neuronal diseases. NVC can be studied by simultaneously measuring neuronal activity and cortical hemodynamics. Consequently, noninvasive measurements of the NVC have been widely studied using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). However, electromagnetic interference between EEG and fMRI is still a major problem. On the other hand, near-infrared spectroscopy (NIRS) is another promising tool for detecting cortical hemodynamics because it can be combined with EEG or magnetoencephalography (MEG) without any electromagnetic interference. Accordingly, in the present study, a simultaneous measurement system-combining an unshielded MEG using a two-dimensional gradiometer based on a low-Tc superconducting quantum interference device (SQUID) and an NIRS using nonmagnetic thin probes-was developed. This combined system was used to simultaneously measure both an auditory-evoked magnetic field and blood flow change in the auditory cortex. It was experimentally demonstrated that the combined unshielded MEG/NIRS system can simultaneously measure neuronal activity and cortical hemodynamics. PMID:23224014

Seki, Yusuke; Miyashita, Tsuyoshi; Kandori, Akihiko; Maki, Atsushi; Koizumi, Hideaki

2012-10-01

112

Magnetoencephalography based on high-Tc superconductivity: a closer look into the brain?  

CERN Document Server

Magnetoencephalography (MEG) enables the study of brain activity by recording the magnetic fields generated by neural currents and has become an important technique for neuroscientists in research and clinical settings. Unlike the liquid-helium cooled low-Tc superconducting quantum interference devices (SQUIDs) that have been at the heart of modern MEG systems since their invention, high-Tc SQUIDs can operate with liquid nitrogen cooling. The relaxation of thermal insulation requirements allows for a reduction in the stand-off distance between the sensor and the room-temperature environment from a few centimeters to less than a millimeter, where MEG signal strength is significantly higher. Despite this advantage, high-Tc SQUIDs have only been used for proof-of-principle MEG recordings of well-understood evoked activity. Here we show high-Tc SQUID-based MEG may be capable of providing novel information about brain activity due to the close proximity of the sensor to the head. We have performed single- and two-...

Öisjöen, F; Figueras, G A; Chukharkin, M L; Kalabukhov, A; Hedström, A; Elam, M; Winkler, D

2011-01-01

113

Assessment of hemispheric dominance for receptive language in pediatric patients under sedation using magnetoencephalography.  

Science.gov (United States)

Non-invasive assessment of hemispheric dominance for receptive language using magnetoencephalography (MEG) is now a well-established procedure used across several epilepsy centers in the context of pre-surgical evaluation of children and adults while awake, alert and attentive. However, the utility of MEG for the same purpose, in cases of sedated patients, is contested. Establishment of the efficiency of MEG is especially important in the case of children who, for a number of reasons, must be assessed under sedation. Here we explored the efficacy of MEG language mapping under sedation through retrospective review of 95 consecutive pediatric patients, who underwent our receptive language test as part of routine clinical evaluation. Localization of receptive language cortex and subsequent determination of laterality was successfully completed in 78% (n = 36) and 55% (n = 27) of non-sedated and sedated patients, respectively. Moreover, the proportion of patients deemed left hemisphere dominant for receptive language did not differ between non-sedated and sedated patients, exceeding 90% in both groups. Considering the challenges associated with assessing brain function in pediatric patients, the success of passive MEG in the context of the cases reviewed in this study support the utility of this method in pre-surgical receptive language mapping. PMID:25191260

Rezaie, Roozbeh; Narayana, Shalini; Schiller, Katherine; Birg, Liliya; Wheless, James W; Boop, Frederick A; Papanicolaou, Andrew C

2014-01-01

114

Assessment of hemispheric dominance for receptive language in pediatric patients under sedation using magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available Non-invasive assessment of hemispheric dominance for receptive language using Magnetoencephalography (MEG is now a well-established procedure used across several epilepsy centers in the context of pre-surgical evaluation of children and adults while awake, alert and attentive. However, the utility of MEG for the same purpose, in cases of sedated patients, is contested. Establishment of the efficiency of MEG is especially important in the case of children who, for a number of reasons, must be assessed under sedation. Here we explored the efficacy of MEG language mapping under sedation through retrospective review of 95 consecutive pediatric patients, who underwent our receptive language test as part of routine clinical evaluation. Localization of receptive language cortex and subsequent determination of laterality was successfully completed in 78% (n=36 and 55% (n=27 of non-sedated and sedated patients, respectively. Moreover, the proportion of patients deemed left hemisphere dominant for receptive language did not differ between non-sedated and sedated patients, exceeding 90% in both groups. Considering the challenges associated with assessing brain function in pediatric patients, the success of passive MEG in the context of the cases reviewed in this study support the utility of this method in pre-surgical receptive language mapping.

Roozbeh Rezaie

2014-08-01

115

Simultaneous measurement of neuronal activity and cortical hemodynamics by unshielded magnetoencephalography and near-infrared spectroscopy  

Science.gov (United States)

The correlation between neuronal activity and cortical hemodynamics, namely, neurovascular coupling (NVC), is important to shed light on the mechanism of a variety of brain functions or neuronal diseases. NVC can be studied by simultaneously measuring neuronal activity and cortical hemodynamics. Consequently, noninvasive measurements of the NVC have been widely studied using both electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). However, electromagnetic interference between EEG and fMRI is still a major problem. On the other hand, near-infrared spectroscopy (NIRS) is another promising tool for detecting cortical hemodynamics because it can be combined with EEG or magnetoencephalography (MEG) without any electromagnetic interference. Accordingly, in the present study, a simultaneous measurement system-combining an unshielded MEG using a two-dimensional gradiometer based on a low-T superconducting quantum interference device (SQUID) and an NIRS using nonmagnetic thin probes-was developed. This combined system was used to simultaneously measure both an auditory-evoked magnetic field and blood flow change in the auditory cortex. It was experimentally demonstrated that the combined unshielded MEG/NIRS system can simultaneously measure neuronal activity and cortical hemodynamics.

Seki, Yusuke; Miyashita, Tsuyoshi; Kandori, Akihiko; Maki, Atsushi; Koizumi, Hideaki

2012-10-01

116

First results for a superconducting imaging-surface sensor array for magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Magnetoencephalography (MEG) follows from the initial fundamental work of Cohen in 1968 and development by several groups, most notably at MIT and at NYU, based on the development of the Superconducting QUantum Interference Device (SQUID) using the Josephson effect. The SQUID`s incredible sensitivity to magnetic fields permits the measurement of the very weak magnetic fields emitted from the human brain due to intracellular neuronal currents. Current growth in MEG is dominated by multiple sensor arrays covering much of the head. These new large devices have primarily been developed and made commercially available by several companies including BTI in the US, CTF in Canada, and Neuromag in Finland. Large projects are also in place in Japan. These systems contain more than 100 sensors spaced at various intervals over the head using various configurations of magnetometers and gradiometers. The different designs available on the market are driven by factors such as detection efficiency, cost, and application. They now present a completely novel whole-head SQUID array system using a superconducting imaging-surface gradiometer concept derived at Los Alamos. Preliminary tests have demonstrated higher performance, lower noise, and additional shielding of background fields while using simpler fabrication techniques than existing whole-head MEG systems, which should reduce production costs.

Kraus, R.H. Jr.; Flynn, E.R.; Overton, W.; Espy, M.A.; George, J.S.; Matlachov, A.; Peters, M.V.; Ruminer, P.

1998-12-31

117

Cognitive impairments in schizophrenia as assessed through activation and connectivity measures of magnetoencephalography (MEG data  

Directory of Open Access Journals (Sweden)

Full Text Available The cognitive dysfunction present in patients with schizophrenia is thought to be driven in part by disorganized connections between higher-order cortical fields. Although studies utilizing EEG, PET and fMRI have contributed significantly to our understanding of these mechanisms, magnetoencephalography (MEG possesses great potential to answer long-standing questions linking brain interactions to cognitive operations in the disorder. Many experimental paradigms employed in EEG and fMRI are readily extendible to MEG and have expanded our understanding of the neurophysiological architecture present in schizophrenia. Source reconstruction techniques, such as adaptive spatial filtering, take advantage of the spatial localization abilities of MEG, allowing us to evaluate which specific structures contribute to atypical cognition in schizophrenia. Finally, both bivariate and multivariate functional connectivity metrics of MEG data are useful for understanding how these interactions in the brain are impaired in schizophrenia, and how cognitive and clinical outcomes are affected as a result. We also present here data from our own laboratory that illustrates how some of these novel functional connectivity measures, specifically imaginary coherence (IC, are quite powerful in relating disconnectivity in the brain to characteristic behavioral findings in the disorder.

LeightonBHinkley

2010-11-01

118

Signal Space Separation method with block matrix inversion for extraction of signals in magnetoencephalography  

Science.gov (United States)

Signal Space Separation (SSS) method is a technique utilized to eliminate the contribution of unwanted signals due to external magnetic noise that inevitably get recorded along with the actual magnetic signal due to neuronal currents in the brain. In this paper, the SSS method has been implemented using block matrix inversion. By implementing block matrix inversion along with regrouping of radial terms, it has been possible to extract the true brain signal from the measured magnetic signal which includes the contribution from an external magnetic dipole artifact for measurements from as few as 64 channels. We observe that the minimum root mean square deviation (RMSD) of the signal inferred from block matrix inversion with regrouped terms is around 6 fT when the truncation order is set at L1 = 11 for signals of interest and L2 = 2 for external noise sources and saturates to similar values for higher L1. The RMSD of extracted signal is 50% smaller than the minimum RMSD when the magnetoencephalography signal is extracted by direct pseudoinverse technique and does not have a deep minimum in the truncation order L1 as observed when direct pseudoinverse technique is used.

Baskaran, R.; Janawadkar, M. P.

2012-10-01

119

Temporal dynamics of the knowledge-mediated visual disambiguation process in humans: a magnetoencephalography study.  

Science.gov (United States)

Disambiguation of a noisy visual scene with prior knowledge is an indispensable task of the visual system. To adequately adapt to a dynamically changing visual environment full of noisy visual scenes, the implementation of knowledge-mediated disambiguation in the brain is imperative and essential for proceeding as fast as possible under the limited capacity of visual image processing. However, the temporal profile of the disambiguation process has not yet been fully elucidated in the brain. The present study attempted to determine how quickly knowledge-mediated disambiguation began to proceed along visual areas after the onset of a two-tone ambiguous image using magnetoencephalography with high temporal resolution. Using the predictive coding framework, we focused on activity reduction for the two-tone ambiguous image as an index of the implementation of disambiguation. Source analysis revealed that a significant activity reduction was observed in the lateral occipital area at approximately 120 ms after the onset of the ambiguous image, but not in preceding activity (about 115 ms) in the cuneus when participants perceptually disambiguated the ambiguous image with prior knowledge. These results suggested that knowledge-mediated disambiguation may be implemented as early as approximately 120 ms following an ambiguous visual scene, at least in the lateral occipital area, and provided an insight into the temporal profile of the disambiguation process of a noisy visual scene with prior knowledge. PMID:25363137

Urakawa, Tomokazu; Ogata, Katsuya; Kimura, Takahiro; Kume, Yuko; Tobimatsu, Shozo

2015-01-01

120

Magnetoencephalography-guided epilepsy surgery for children with intractable focal epilepsy: SickKids experience.  

Science.gov (United States)

We introduced magnetoencephalography (MEG)-guided epilepsy surgery for children with intractable focal epilepsy at The Hospital for Sick Children (SickKids) in Toronto, Canada. Surgical candidacy and decisions on surgical procedure for children with intractable focal epilepsy are based on long-term scalp video EEG (VEEG) results, magnetic resonance imaging (MRI) findings, and the distribution of MEG spike sources. After multidisciplinary discussion at the seizure conference, for the patients requiring intracranial VEEG, custom-made subdural electrode grids are designed using three-dimensional MRI superimposed with MEG spike sources to cover the area of clustered MEG spike sources. At the first surgery, neurosurgeons use the intraoperative neuronavigation system to visualize the area of clustered spike dipoles and somatosensory evoked fields on MEG to place the subdural grid and depth electrodes. At the second surgery, the area of seizure onset and active interictal spike discharges on the intracranial VEEG recording, which usually correlates with the zone of clustered MEG spike sources, is resected. This combination leads to successful surgical outcome to control seizures in these challenging paediatric patients. MEG is a useful tool in children with intractable focal epilepsy to determine the surgical candidacy and focal cortical resection to stop seizures. PMID:18313780

Ochi, Ayako; Otsubo, Hiroshi

2008-05-01

 
 
 
 
121

Differential spectral power alteration following acupuncture at different designated places revealed by magnetoencephalography  

Science.gov (United States)

As an ancient therapeutic technique in Traditional Chinese Medicine, acupuncture has been used increasingly in modern society to treat a range of clinical conditions as an alternative and complementary therapy. However, acupoint specificity, lying at the core of acupuncture, still faces many controversies. Considering previous neuroimaging studies on acupuncture have mainly employed functional magnetic resonance imaging, which only measures the secondary effect of neural activity on cerebral metabolism and hemodynamics, in the current study, we adopted an electrophysiological measurement technique named magnetoencephalography (MEG) to measure the direct neural activity. 28 healthy college students were recruited in this study. We filtered MEG data into 5 consecutive frequency bands (delta, theta, alpha, beta and gamma band) and grouped 140 sensors into 10 main brain regions (left/right frontal, central, temporal, parietal and occipital regions). Fast Fourier Transformation (FFT) based spectral analysis approach was further performed to explore the differential band-limited power change patterns of acupuncture at Stomach Meridian 36 (ST36) using a nearby nonacupoint (NAP) as control condition. Significantly increased delta power and decreased alpha as well as beta power in bilateral frontal ROIs were observed following stimulation at ST36. Compared with ST36, decreased alpha power in left and right central, right parietal as well as right temporal ROIs were detected in NAP group. Our research results may provide additional evidence for acupoint specificity.

You, Youbo; Bai, Lijun; Dai, Ruwei; Xue, Ting; Zhong, Chongguang; Liu, Zhenyu; Wang, Hu; Feng, Yuanyuan; Wei, Wenjuan; Tian, Jie

2012-03-01

122

The neural processing of musical instrument size information in the brain investigated by magnetoencephalography  

Science.gov (United States)

The specific cortical representation of size was investigated by recording auditory evoked fields (AEFs) elicited by changes of instrument size and pitch. In Experiment 1, a French horn and one scaled to double the size played a three note melody around F3 or its octave, F4. Many copies of these four melodies were played in random order and the AEF was measured continuously. A similar procedure was applied to saxophone sounds in a separate run. In Experiment 2, the size and type of instrument (French horn and saxophone) were varied without changing the octave. AEFs were recorded in five subjects using magnetoencephalography and evaluated by spatio-temporal source analysis with one equivalent dipole in each hemisphere. The morphology of the source waveforms revealed that each note within the melody elicits a well-defined P1-N1-P2 AEF-complex with adaptation for the 2nd and 3rd note. At the transition of size, pitch, or both, a larger AEF-complex was evoked. However, size changes elicited a stronger N1 than pitch changes. Furthermore, this size-related N1 enhancement was larger for French horn than saxophone. The results indicate that the N1 plays an important role in the specific representation of instrument size.

Rupp, Andre; van Dinther, Ralph; Patterson, Roy D.

2005-04-01

123

[The practical benefits of magnetoencephalography in comparison with electroencephalography in a patient with epilepsia partialis continua].  

Science.gov (United States)

A concurrent recording of electroencephalography (EEG), magnetoencephalography (MEG) and electromyography (EMG) was carried out in a patient with epilepsia partialis continua. He had continuous clonic jerks in his right hand and fingers. The EMG electrodes were placed on the thumb of his right hand. We observed numerous MEG spikes in the left central region and about half of them were accompanied by EMG potentials with a latency of about 20 msec. The EEG spikes appeared less frequently, had low amplitudes, and had unclear morphologies and further, no clear association with EMG potentials. MEG spikes were more reliably associated with individual jerks, exemplified by EMG potentials, than the EEG spikes. The MEG spikes were sharper than EEG spikes and were about 20 msec wide. The intracranial dipole localization of the MEG spikes was estimated by overlaying the calculated generator sites on magnetic resonance images. It was found that the spikes converged along a line, presumably the central sulcus. The practical benefits of the MEG as a diagnostic tool in epilepsy are illustrated. PMID:7772403

Watanabe, Y; Sato, S; Nakamura, F; Fukao, K; Yagi, K; Seino, M

1995-04-01

124

Combination of PET and magnetoencephalography in the presurgical assessment of MRI-negative epilepsy  

Directory of Open Access Journals (Sweden)

Full Text Available Despite major advances in neuroimaging, no lesion is visualized on MRI in up to a quarter of patients with drug-resistant focal epilepsy presenting for presurgical evaluation. These patients demonstrate poorer surgical outcomes than those with lesion seen on MRI. Accurate localization of the seizure onset zone is more difficult in MRI-negative patients and often requires invasive EEG recordings. Positron emission tomography (PET and magnetoencephalography (MEG have been proposed as clinically relevant tools to localize the seizure onset zone prior to intracranial EEG recordings. However, there is no consensus regarding the optimal gold standard that should be used for assessing the performance of these pre-surgical investigations. Here, we review the current knowledge concerning the usefulness of PET and MEG for presurgical assessment of MRI-negative epilepsy. Beyond the individual diagnostic performance of MEG and of different PET tracers, including [18F]-fluorodeoxyglucose, [11C]flumazenil, and markers of 5-HT1A receptors, recent data suggest that the combination of PET and MEG might provide greater sensitivity and specificity than that of each of the two individual tests in patients with normal MRI.

SylvainRheims

2013-11-01

125

A constrained ICA approach for real-time cardiac artifact rejection in magnetoencephalography.  

Science.gov (United States)

Recently, magnetoencephalography (MEG)-based real-time brain computing interfaces (BCI) have been developed to enable novel and promising methods of neuroscience research and therapy. Artifact rejection prior to source localization largely enhances the localization accuracy. However, many BCI approaches neglect real-time artifact removal due to its time consuming processing. With cardiac artifact rejection for real-time analysis (CARTA), we introduce a novel algorithm capable of real-time cardiac artifact (CA) rejection. The method is based on constrained independent component analysis (ICA), where a priori information of the underlying source signal is used to optimize and accelerate signal decomposition. In CARTA, this is performed by estimating the subject's individual density distribution of the cardiac activity, which leads to a subject-specific signal decomposition algorithm. We show that the new method is capable of effectively reducing CAs within one iteration and a time delay of 1 ms. In contrast, Infomax and Extended Infomax ICA converged not until seven iterations, while FastICA needs at least ten iterations. CARTA was tested and applied to data from three different but most common MEG systems (4-D-Neuroimaging, VSM MedTech Inc., and Elekta Neuromag). Therefore, the new method contributes to reliable signal analysis utilizing BCI approaches. PMID:24001953

Breuer, Lukas; Dammers, Jürgen; Roberts, Timothy P L; Shah, N Jon

2014-02-01

126

Dependence of the probabilities of the electric-multipole electron transitions in W24+ on multipolarity  

International Nuclear Information System (INIS)

Usually it is accepted that the probabilities of the electric-multipole electron transitions are rapidly decreasing functions of their multipolarity. Therefore while calculating the probabilities of electronic transitions between the configurations of certain chosen parities, it seems sufficient to take into account the first nonzero term, i.e., to consider the electron transitions of lowest multipolarity permitted by the exact selection rules. This paper aims at verifying this assumption on the example of electric-octupole transitions in W24+ ion. For this purpose the large-scale multiconfiguration Hartree-Fock and Dirac-Fock calculations have been performed for the configurations [Kr]4d104f4 and [Kr]4d104f35s energy levels of W24+ ion. The relativistic corrections were taken into account in the quasirelativistic Breit-Pauli and fully relativistic Breit (taking into account QED effects) approximations. The role of correlation, relativistic, and QED corrections is discussed. Line strengths, oscillator strengths, and transition probabilities in Coulomb and Babushkin gauges are presented for E1 and E3 transitions among these levels.

127

Post-Newtonian factorized multipolar waveforms for spinning, non-precessing black-hole binaries  

CERN Document Server

We generalize the factorized resummation of multipolar waveforms introduced by Damour, Iyer and Nagar to spinning black holes. For a nonspinning test-particle spiraling a Kerr black hole in the equatorial plane, we find that factorized multipolar amplitudes which replace the residual relativistic amplitude f_{l m} with its l-th root, \\rho_{l m} = f_{l m}^{1/l}, agree quite well with the numerical amplitudes up to the Kerr-spin value q \\leq 0.95 for orbital velocities v \\leq 0.4. The numerical amplitudes are computed solving the Teukolsky equation with a spectral code. The agreement for prograde orbits and large spin values of the Kerr black hole can be further improved at high velocities by properly factoring out the lower-order post-Newtonian contributions in \\rho_{l m}. The resummation procedure results in a better and systematic agreement between numerical and analytical amplitudes (and energy fluxes) than standard Taylor-expanded post-Newtonian approximants. This is particularly true for higher-order mode...

Pan, Yi; Fujita, Ryuichi; Racine, Etienne; Tagoshi, Hideyuki

2010-01-01

128

Ocean surface slick characterization by multi-polarization Radarsat-2 data  

Science.gov (United States)

Marine oil spills are an important environmental problem, and satellite SAR remote sensing have become a valuable tool for the detection and monitoring of these spills. Natural phenomena with similar appearance as oil in SAR images, producing false detections, compose a challenge for oil spill observation services. One such lookalike phenomena is biogenic slicks produced by marine organisms. In this study we evaluate multi-polarization features for oil spill characterization and oil versus biogenic slick discrimination. During large-scale oil-on-water exercises conducted in the North Sea in June 2011 and June 2012, both mineral oil and plant oil were released and imaged by Radarsat-2 in Fine Quad-polarization mode. The plant oil will form a lm resembling biogenic slicks. The mineral oil spill and simulated look-alike are in this study compared based on multi-polarization features, combining the information in HH and VV channels. The polarimetric measurements from 2011 have earlier been analysed, and a potential for discrimination between mineral oil and biogenic slicks is found. The aim of the current study is to repeat the polarimetric analysis on the new independent data set from 2012. Preliminary results of the 2012 data set reveal both internal and between slick type variations, giving support to our previous findings from 2011.

Skrunes, Stine; Brekke, Camilla; Eltoft, Torbjørn

2012-09-01

129

Improved resummation of post-Newtonian multipolar waveforms from circularized compact binaries  

CERN Document Server

We improve and generalize a resummation method of post-Newtonian multipolar waveforms from circular compact binaries introduced in Refs. \\cite{Damour:2007xr,Damour:2007yf}. One of the characteristic features of this resummation method is to replace the usual {\\it additive} decomposition of the standard post-Newtonian approach by a {\\it multiplicative} decomposition of the complex multipolar waveform $h_{\\lm}$ into several (physically motivated) factors: (i) the ``Newtonian'' waveform, (ii) a relativistic correction coming from an ``effective source'', (iii) leading-order tail effects linked to propagation on a Schwarzschild background, (iv) a residual tail dephasing, and (v) residual relativistic amplitude corrections $f_{\\lm}$. We explore here a new route for resumming $f_{\\lm}$ based on replacing it by its $\\ell$-th root: $\\rho_{\\lm}=f_{\\lm}^{1/\\ell}$. In the extreme-mass-ratio case, this resummation procedure results in a much better agreement between analytical and numerical waveforms than when using stan...

Damour, Thibault; Nagar, Alessandro

2008-01-01

130

An analysis of the electromagnetic field in multi-polar linear induction system  

International Nuclear Information System (INIS)

In this paper a new method for determination of the electromagnetic field vectors in a multi-polar linear induction system (LIS) is described. The analysis of the electromagnetic field has been done by four dimensional electromagnetic potentials in conjunction with theory of the magnetic loops . The electromagnetic field vectors are determined in the Minkovski's space as elements of the Maxwell's tensor. The results obtained are compared with those got from the analysis made by the finite elements method (FEM).With the method represented in this paper one can determine the electromagnetic field vectors in the multi-polar linear induction system using four-dimensional potential. A priority of this method is the obtaining of analytical results for the electromagnetic field vectors. These results are also valid for linear media. The dependencies are valid also at high speeds of movement. The results of the investigated linear induction system are comparable to those got by the finite elements method. The investigations may be continued in the determination of other characteristics such as drag force, levitation force, etc. The method proposed in this paper for an analysis of linear induction system can be used for optimization calculations. (Author)

131

Effects of Contralateral Noise on the 20-Hz Auditory Steady State Response - Magnetoencephalography Study  

Science.gov (United States)

The auditory steady state response (ASSR) is an oscillatory brain response, which is phase locked to the rhythm of an auditory stimulus. ASSRs have been recorded in response to a wide frequency range of modulation and/or repetition, but the physiological features of the ASSRs are somewhat different depending on the modulation frequency. Recently, the 20-Hz ASSR has been emphasized in clinical examinations, especially in the area of psychiatry. However, little is known about the physiological properties of the 20-Hz ASSR, compared to those of the 40-Hz and 80-Hz ASSRs. The effects of contralateral noise on the ASSR are known to depend on the modulation frequency to evoke ASSR. However, the effects of contralateral noise on the 20-Hz ASSR are not known. Here we assessed the effects of contralateral white noise at a level of 70 dB SPL on the 20-Hz and 40-Hz ASSRs using a helmet-shaped magnetoencephalography system in 9 healthy volunteers (8 males and 1 female, mean age 31.2 years). The ASSRs were elicited by monaural 1000-Hz 5-s tone bursts amplitude-modulated at 20 and 39 Hz and presented at 80 dB SPL. Contralateral noise caused significant suppression of both the 20-Hz and 40-Hz ASSRs, although suppression was significantly smaller for the 20-Hz ASSRs than the 40-Hz ASSRs. Moreover, the greatest suppression of both 20-Hz and 40-Hz ASSRs occurred in the right hemisphere when stimuli were presented to the right ear with contralateral noise. The present study newly showed that 20-Hz ASSRs are suppressed by contralateral noise, which may be important both for characterization of the 20-Hz ASSR and for interpretation in clinical situations. Physicians must be aware that the 20-Hz ASSR is significantly suppressed by sound (e.g. masking noise or binaural stimulation) applied to the contralateral ear. PMID:24915061

Usubuchi, Hajime; Kawase, Tetsuaki; Kanno, Akitake; Yahata, Izumi; Miyazaki, Hiromitsu; Nakasato, Nobukazu; Kawashima, Ryuta; Katori, Yukio

2014-01-01

132

Neural effects of mental fatigue caused by continuous attention load: a magnetoencephalography study.  

Science.gov (United States)

Mental fatigue can be defined as a psychobiological state caused by prolonged periods of demanding cognitive activity and manifests as a reduced efficiency in cognitive performance. Mental fatigue is one of the most significant causes of accidents in modern society. Therefore, understanding the neural mechanisms of mental fatigue is important. However, the neural mechanisms of mental fatigue are not fully understood. In this study, we investigated the neural activity that results from mental fatigue caused by a continuous attention load. We used magnetoencephalography (MEG) to evaluate the neural activities during the attention task. Ten healthy male volunteers participated in this study. They performed a continuous attention task lasting 10 min. Subjective ratings of mental fatigue, mental stress, boredom, and sleepiness were performed just after the task trial. MEG data were analyzed using narrow-band adaptive spatial filtering methods. An increase in the beta-frequency band (13-25 Hz) power in the right inferior and middle frontal gyri (Brodmann?s areas 44 and 9 respectively) was caused by the mental fatigue. The increase in the beta-frequency band power in the right middle frontal gyrus was negatively associated with the self-reported level of mental stress and was positively associated with those of boredom and sleepiness. These results demonstrate that performing a continuous mental fatigue-inducing task causes changes in the activation of the prefrontal cortex, and manifests as an increased beta-frequency power in this brain area as well as sleepiness. Our results contribute to greater understanding of the neural mechanisms of mental fatigue. PMID:24642273

Tanaka, Masaaki; Ishii, Akira; Watanabe, Yasuyoshi

2014-05-01

133

Potential Utility of Resting-State Magnetoencephalography as a Biomarker of CNS Abnormality in HIV Disease  

Science.gov (United States)

There is a lack of a neuroimaging biomarker for HIV-Associated Neurocognitive Disorder. We report magnetoencephalography (MEG) data from patients with HIV disease and risk-group appropriate controls that were collected to determine the MEG frequency profile during the resting state, and the stability of the profile over 24 weeks. 17 individuals (10 HIV+, 7 HIV?) completed detailed neurobehavioral evaluations and 10 minutes of resting-state MEG acquisition with a 306-channel whole-head system. The entire evaluation and MEG measurement were repeated 24 weeks later. Relative MEG power in the delta (0–4 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (12–30 Hz) and low gamma (30–50 Hz) bands was computed for 8 predefined sensor groups. The median stability of resting-state relative power over 24 weeks of follow-up was 0.80 with eyes closed, and 0.72 with eyes open. The relative gamma power in the right occipital (t(15) = 1.99, p < .06, r = ?.46) and right frontal (t(15t) = 2.15, p < .05, r = ?.48) regions was associated with serostatus. The effect of age on delta power was greater in the seropositive subjects (r2 = .51) than in the seronegative subjects (r2 = .11). Individuals with high theta-to-gamma ratios tended to have lower cognitive test performance, regardless of serostatus. The stability of the wide-band MEG frequency profiles over 24 weeks supports the utility of MEG as a biomarker. The links between the MEG profile, serostatus, and cognition suggest further research on its potential in HAND is needed. PMID:22414786

Becker, James T.; Fabrizio, Melissa; Sudre, Gustavo; Haridis, Anna; Ambrose, Timothy; Aizenstein, Howard J.; Eddy, William; Lopez, Oscar L.; Wolk, David; Parkkonen, Lauri; Bagic, Anto

2012-01-01

134

Plasma diffusion through a two-dimensional magnetic field. Application to multipolar discharge  

International Nuclear Information System (INIS)

In this work, a collisional plasma diffusion theory through a two dimensional magnetic field is presented. This study allows to define two types of diffusion domains: the weak field domain, where diffusion is practically isotropic, and strong field domain where diffusion is only parallel to field lines. The inversion and ion confinement by ambipolar electric field, perpendicular to line fields, is also understood. This theory is applied to a multipolar discharge. A sheath thickness can be defined, which is the width of the region in which the plasma diffusion is limited by the magnetic field. Little dependence with magnetic field is found. All these results have been observed experimentally. The diffusion equation numerical solution allows to find the density and potential profiles. The comparison of the density in the middle of the plasma with and without multicusp field is done

135

Binary black hole coalescence in the extreme-mass-ratio limit: testing and improving the effective-one-body multipolar waveform  

CERN Document Server

We discuss the properties of the effective-one-body (EOB) multipolar gravitational waveform emitted by nonspinning black-hole binaries of masses $\\mu$ and $M$ in the extreme-mass-ratio limit, $\\mu/M=\

Bernuzzi, Sebastiano; Zenginoglu, Anil

2010-01-01

136

Eficacia de los imanes permanentes multipolares en el tratamiento del dolor crónico en pacientes con osteoartrosis generalizada / Effectiveness of the multipolar permanent magnets in the treatment of chronic pain in patients with generalized osteoarthrosis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish Se efectuó un estudio longitudinal y controlado de 100 pacientes con osteoartrosis generalizada, atendidos en el Servicio de Medicina Natural y Tradicional del Hospital Provincial Docente Clinicoquirúrgico "Saturnino Lora Torres" de Santiago de Cuba, desde enero hasta diciembre del 2010, a fin de ev [...] aluar la eficacia de los imanes permanentes multipolares en el tratamiento del dolor crónico en los afectados. Estos imanes se ubicaron y fijaron en diferentes puntos de acupunturas para aliviar la dolencia. Los niveles de dolor se cuantificaron mediante la Escala Visual Análoga, por sexo y rango de edades; se evaluaron a los 0, 30, 60 y 90 días durante la terapia. Se demostró la factibilidad del uso de los imanes permanentes multipolares en el alivio del dolor de los pacientes con osteoartrosis generalizada por ser simples, seguros, eficaces y no inducir efectos adversos en el organismo. Abstract in english A longitudinal and controlled study of 100 patients with generalized osteoarthrosis, assisted in the Service of Natural and Traditional Medicine of "Saturnino Lora Torres" Clinical Surgical Teaching Provincial Hospital in Santiago de Cuba was carried out from January to December, 2010, in order to e [...] valuate the effectiveness of the multipolar permanent magnets in the treatment of the chronic pain in those affected. These magnets were placed and fixed in different acupuncture points to reduce pain. The pain levels were quantified by means of the Analogue Visual Scale, by sex and age range; they were evaluated at the 0, 30, 60 and 90 days during the therapy. The feasibility of the use of the multipolar permanent magnets was demonstrated in the relief of pain of the patients with generalized osteoarthrosis as they are simple, sure, effective and induce no adverse effects in the organism.

Mario, Hechavarría Sánchez; Mercedes, Gay Muguercia; César, Hernández Acosta; Luis Enrique, Bergues Cabrales.

2013-11-01

137

ADAM17 is critical for multipolar exit and radial migration of neuronal intermediate progenitor cells in mice cerebral cortex.  

Science.gov (United States)

The radial migration of neuronal progenitor cells is critical for the development of cerebral cortex layers. They go through a critical step transforming from multipolar to bipolar before outward migration. A Disintegrin and Metalloprotease 17 (ADAM17) is a transmembrane protease which can process many substrates involved in cell-cell interaction, including Notch, ligands of EGFR, and some cell adhesion molecules. In this study, we used in utero electroporation to knock down or overexpress ADAM17 at embryonic day 14.5 (E14.5) in neuronal progenitor cells to examine the role of ADAM17 in cortical embryonic neurogenesis. Our results showed that the radial migration of ADAM17-knocked down cells were normal till E16.5 and reached the intermediate zone (IZ). Then most transfected cells stopped migration and stayed at the IZ to inner cortical plate (CP) layer at E18.5, and there was higher percentage of multipolar cells at IZ layer in the ADAM17-knocked down group compared to the cells in control group. Marker staining revealed that those ADAM17-knocked down cells differentiated normally from neural stem cells (NSCs) to neuronal intermediate progenitor cells (nIPCs) but did not differentiate into mature neurons. The migration and multipolar exit defects caused by ADAM17 knockdown could be partially rescued by over-expressing an shRNA resistant ADAM17, while overexpressing ADAM17 alone did not affect the radial migration. Taken together, our results showed for the first time that, ADAM17 is critical in regulating the multipolar-stage exit and radial migration of the nIPCs during telencephalon cortex development in mice. PMID:23755270

Li, Qingyu; Zhang, Zhengyu; Li, Zengmin; Zhou, Mei; Liu, Bin; Pan, Le; Ma, Zhixing; Zheng, Yufang

2013-01-01

138

Hybrid ultra-low-field MRI and magnetoencephalography system based on a commercial whole-head neuromagnetometer.  

Science.gov (United States)

Ultra-low-field MRI uses microtesla fields for signal encoding and sensitive superconducting quantum interference devices for signal detection. Similarly, modern magnetoencephalography (MEG) systems use arrays comprising hundreds of superconducting quantum interference device channels to measure the magnetic field generated by neuronal activity. In this article, hybrid MEG-MRI instrumentation based on a commercial whole-head MEG device is described. The combination of ultra-low-field MRI and MEG in a single device is expected to significantly reduce coregistration errors between the two modalities, to simplify MEG analysis, and to improve MEG localization accuracy. The sensor solutions, MRI coils (including a superconducting polarizing coil), an optimized pulse sequence, and a reconstruction method suitable for hybrid MEG-MRI measurements are described. The performance of the device is demonstrated by presenting ultra-low-field-MR images and MEG recordings that are compared with data obtained with a 3T scanner and a commercial MEG device. PMID:22807201

Vesanen, Panu T; Nieminen, Jaakko O; Zevenhoven, Koos C J; Dabek, Juhani; Parkkonen, Lauri T; Zhdanov, Andrey V; Luomahaara, Juho; Hassel, Juha; Penttilä, Jari; Simola, Juha; Ahonen, Antti I; Mäkelä, Jyrki P; Ilmoniemi, Risto J

2013-06-01

139

An iterative algorithm for sparse and constrained recovery with applications to divergence-free current reconstructions in magneto-encephalography  

CERN Document Server

We propose an iterative algorithm for the minimization of a $\\ell_1$-norm penalized least squares functional, under additional linear constraints. The algorithm is fully explicit: it uses only matrix multiplications with the three matrices present in the problem (in the linear constraint, in the data misfit part and in penalty term of the functional). None of the three matrices must be invertible. Convergence is proven in a finite-dimensional setting. We apply the algorithm to a synthetic problem in magneto-encephalography where it is used for the reconstruction of divergence-free current densities subject to a sparsity promoting penalty on the wavelet coefficients of the current densities. We discuss the effects of imposing zero divergence and of imposing joint sparsity (of the vector components of the current density) on the current density reconstruction.

Loris, Ignace

2012-01-01

140

The Evolutionary Dynamics of Biofuel Value Chains : From Unipolar and Government-Driven to Multipolar Governance  

DEFF Research Database (Denmark)

In this paper I propose to push the frontier of global value chain (GVC) governance analysis through the concept of ‘polarity’. Much of the existing GVC literature has focused on ‘unipolar’ value chains, where one group of ‘lead firms’ inhabiting a specific function in a chain plays a dominant role in governing it. Some scholars have explored the dynamics of governance in GVCs characterized as ‘bipolar’, where two sets of actors in different functional positions both drive the chain. I expand this direction further to suggest conceptualizing governance within a continuum between unipolarity and multipolarity. Empirically, I do so by examining the evolutionary dynamics of governance in biofuel value chains, with specific focus on the key regulatory and institutional features that facilitated their emergence and expansion. First, I examine the formation, evolution, and governance of three national/regional value chains (in Brazil, the US, and the EU); then, I provide evidence to support a trend towards the increasing but still partial formation of a global biofuel value chain and examine its governance traits.

Ponte, Stefano

2014-01-01

 
 
 
 
141

Neutron star deformation due to arbitrary-order multipolar magnetic fields  

CERN Document Server

Certain multi-wavelength observations of neutron stars, such as intermittent radio emissions from rotation-powered pulsars beyond the pair-cascade death line, the pulse profile of the magnetar SGR 1900+14 after its 1998 August 27 giant flare, and X-ray spectral features of PSR J0821-4300 and SGR 0418+5729, suggest that the magnetic fields of non-accreting neutron stars are not purely dipolar and may contain higher-order multipoles. Here, we calculate the ellipticity of a non-barotropic neutron star with (i) a quadrupole poloidal-toroidal field, and (ii) a purely poloidal field containing arbitrary multipoles, deriving the relation between the ellipticity and the multipole amplitudes. We present, as a worked example, a purely poloidal field comprising dipole, quadrupole, and octupole components. We show the correlation between field energy and ellipticity for each multipole, that the l=4 multipole has the lowest energy, and that l=5 has the lowest ellipticity. We show how a mixed multipolar field creates an ob...

Mastrano, Alpha; Melatos, Andrew

2013-01-01

142

CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results  

Energy Technology Data Exchange (ETDEWEB)

Purpose. This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. Methods. We included 22 consecutive patients (3 women; age 74.2 {+-} 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 {+-} 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Results. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 {+-} 13.6 min and 43.7 {+-} 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 {+-} 8.8 months, local recurrence-free survival was 14.4 {+-} 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 {+-} 16.6 ml/min/1.73 m{sup 2} before RF ablation vs. 47.2 {+-} 11.9 ml/min/1.73 m{sup 2} after RF ablation; not significant). Conclusions. CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

Sommer, C. M., E-mail: christof.sommer@med.uni-heidelberg.de [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Lemm, G.; Hohenstein, E. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany); Bellemann, N.; Stampfl, U. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Goezen, A. S.; Rassweiler, J. [Clinic for Urology, SLK Kliniken Heilbronn GmbH (Germany); Kauczor, H. U.; Radeleff, B. A. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Pereira, P. L. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany)

2013-06-15

143

Invariant Form of Hyperfine Interaction with Multipolar Moments - Observation of Octupolar Moments in NpO$_{2}$ and CeB$_{6}$ by NMR -  

CERN Document Server

The invariant form of the hyperfine interaction between multipolar moments and the nuclear spin is derived, and applied to discuss possibilities to identify the antiferro-octupolar (AFO) moments by NMR experiments. The ordered phase of NpO$_{2}$ and the phase IV of Ce$_{1-x}$La$_{x}$B$_{6}$ are studied in detail. Recent $^{17}$O NMR for polycrystalline samples of NpO$_{2}$ are discussed theoretically from our formulation. The observed feature of the splitting of $^{17}$O NMR spectrum into a sharp line and a broad line, their intensity ratio, and the magnetic field dependence of the shift and of the width can be consistently explained on the basis of the triple $\\bq$ AFO ordering model proposed by Paix\\~{a}o {\\it et. al.} Thus, the present theory shows that the $^{17}$O NMR spectrum gives a strong support to the model. The 4 O sites in the fcc NpO$_2$ become inequivalent due to the secondary triple $\\bq$ ordering of AF-quadrupoles: one cubic and three non-cubic sites. It turns out that the hyperfine field due ...

Sakai, O; Shiba, H; Sakai, Osamu; Shiina, Ryousuke; Shiba, Hiroyuki

2004-01-01

144

Evaluation of focused multipolar stimulation for cochlear implants in acutely deafened cats  

Science.gov (United States)

Objective. The conductive nature of the fluids and tissues of the cochlea can lead to broad activation of spiral ganglion neurons using contemporary cochlear implant stimulation configurations such as monopolar (MP) stimulation. The relatively poor spatial selectivity is thought to limit implant performance, particularly in noisy environments. Several current focusing techniques have been proposed to reduce the spread of activation with the aim towards achieving improved clinical performance. Approach. The present research evaluated the efficacy of focused multipolar (FMP) stimulation, a relatively new focusing technique in the cochlea, and compared its efficacy to both MP stimulation and tripolar (TP) stimulation. The spread of neural activity across the inferior colliculus (IC), measured by recording the spatial tuning curve, was used as a measure of spatial selectivity. Adult cats (n = 6) were acutely deafened and implanted with an intracochlear electrode array before multi-unit responses were recorded across the cochleotopic gradient of the contralateral IC. Recordings were made in response to acoustic and electrical stimulation using the MP, TP and FMP configurations. Main results. FMP and TP stimulation resulted in greater spatial selectivity than MP stimulation. However, thresholds were significantly higher (p < 0.001) for FMP and TP stimulation compared to MP stimulation. There were no differences found in spatial selectivity and threshold between FMP and TP stimulation. Significance. The greater spatial selectivity of FMP and TP stimulation would be expected to result in improved clinical performance. However, further research will be required to demonstrate the efficacy of these modes of stimulation after longer durations of deafness.

George, Shefin S.; Wise, Andrew K.; Shivdasani, Mohit N.; Shepherd, Robert K.; Fallon, James B.

2014-12-01

145

Critical excitation-rate enhancement of a dipolar scatterer close to a plasmonic nanosphere and importance of multipolar self-coupling  

Science.gov (United States)

We develop an electrodynamic model based on dyadic Green's functions for analyzing the near-field interactions between a dipolar scatterer (DS) and a plasmonic nanosphere (PN) under external excitation, accounting for multipolar contributions in the evaluation of the scattered fields. In particular, we include all the radiative and nonradiative field interactions between the DS and the PN, particularly the physical mechanism of DS's self-coupling through the PN, which is either neglected or approximated in previous work. Our objective is to show under which conditions self-coupling is important for strong excitation-rate enhancement of the DS and provide a description of the system's properties. We analytically investigate the conditions under which the excitation rate of a DS, such as an organic dye or a quantum dot, is enhanced when located in close proximity to a PN. We show the existence of critical conditions in terms of polarizabilities and distances that lead to large enhancement based on self-coupling and how to predict it.

Tork Ladani, Faezeh; Campione, Salvatore; Guclu, Caner; Capolino, Filippo

2014-09-01

146

Multipolarity effects in ionization of the inner level of an atom by an electron impact in extended fine structures of K and L spectra of electron energy losses  

International Nuclear Information System (INIS)

The problem of multipolarity of the atom core level ionization by electron impact in extended energy loss fine structure (EELFS) spectroscopy is studied. The intensities and amplitudes of electron transitions have been calculated in the OPW approximation. The experimental K EELFS spectra of Al, Si and L EELFS spectra of Fe, Co have been obtained. Corresponding calculations have been carried out in the monopole and dipole approximations. A comparison of theoretical and experimental spectra have been made. It is shown that a good agreement between the theoretical and experimental results points to the need for taking account of multipolarity of the electron transition processes in EELFS calculations

147

Localization of interictal epileptiform activity using magnetoencephalography with synthetic aperture magnetometry in patients with a vagus nerve stimulator.  

Science.gov (United States)

Magnetoencephalography (MEG) provides useful and non-redundant information in the evaluation of patients with epilepsy, and in particular, during the pre-surgical evaluation of pharmaco-resistant epilepsy. Vagus nerve stimulation (VNS) is a common treatment for pharmaco-resistant epilepsy. However, interpretation of MEG recordings from patients with a VNS is challenging due to the severe magnetic artifacts produced by the VNS. We used synthetic aperture magnetometry (g2) [SAM(g2)], an adaptive beamformer that maps the excessive kurtosis, to map interictal spikes to the coregistered MRI image, despite the presence of contaminating VNS artifact. We present a series of eight patients with a VNS who underwent MEG recording. Localization of interictal epileptiform activity by SAM(g2) is compared to invasive electrophysiologic monitoring and other localizing approaches. While the raw MEG recordings were uninterpretable, analysis of the recordings with SAM(g2) identified foci of peak kurtosis and source signal activity that was unaffected by the VNS artifact. SAM(g2) analysis of MEG recordings in patients with a VNS produces interpretable results and expands the use of MEG for the pre-surgical evaluation of epilepsy. PMID:25505894

Stapleton-Kotloski, Jennifer R; Kotloski, Robert J; Boggs, Jane A; Popli, Gautam; O'Donovan, Cormac A; Couture, Daniel E; Cornell, Cassandra; Godwin, Dwayne W

2014-01-01

148

Does IQ affect the functional brain network involved in pseudoword reading in students with reading disability? A magnetoencephalography study  

Directory of Open Access Journals (Sweden)

Full Text Available The study examined whether individual differences in performance and verbal IQ affect the profiles of reading-related regional brain activation in 127 students experiencing reading difficulties and typical readers. Using magnetoencephalography in a pseudoword read-aloud task, we compared brain activation profiles of students experiencing word-level reading difficulties who did (n=29 or did not (n=36 meet the IQ-reading achievement discrepancy criterion. Typical readers assigned to a lower-IQ (n=18 or a higher IQ (n=44 subgroup served as controls. Minimum norm estimates of regional cortical activity revealed that the degree of hypoactivation in the left superior temporal and supramarginal gyri in both RD subgroups was not affected by IQ. Moreover, IQ did not moderate the positive association between degree of activation in the left fusiform gyrus and phonological decoding ability. We did find, however, that the hypoactivation of the left pars opercularis in RD was restricted to lower-IQ participants. In accordance with previous morphometric and fMRI studies, degree of activity in inferior frontal and inferior parietal regions correlated with IQ across reading ability subgroups. Results are consistent with current views questioning the relevance of IQ measures and IQ-discrepancy criteria in the diagnosis of dyslexia.

Panagiotis G Simos

2014-01-01

149

Comparative analysis of transverse intrafascicular multichannel, longitudinal intrafascicular and multipolar cuff electrodes for the selective stimulation of nerve fascicles  

Science.gov (United States)

The selection of a suitable nerve electrode for neuroprosthetic applications implies a trade-off between invasiveness and selectivity, wherein the ultimate goal is achieving the highest selectivity for a high number of nerve fascicles by the least invasiveness and potential damage to the nerve. The transverse intrafascicular multichannel electrode (TIME) is intended to be transversally inserted into the peripheral nerve and to be useful to selectively activate subsets of axons in different fascicles within the same nerve. We present a comparative study of TIME, LIFE and multipolar cuff electrodes for the selective stimulation of small nerves. The electrodes were implanted on the rat sciatic nerve, and the activation of gastrocnemius, plantar and tibialis anterior muscles was recorded by EMG signals. Thus, the study allowed us to ascertain the selectivity of stimulation at the interfascicular and also at the intrafascicular level. The results of this study indicate that (1) intrafascicular electrodes (LIFE and TIME) provide excitation circumscribed to the implanted fascicle, whereas extraneural electrodes (cuffs) predominantly excite nerve fascicles located superficially; (2) the minimum threshold for muscle activation with TIME and LIFE was significantly lower than with cuff electrodes; (3) TIME allowed us to selectively activate the three tested muscles when stimulating through different active sites of one device, both at inter- and intrafascicular levels, whereas selective activation using multipolar cuff (with a longitudinal tripolar stimulation configuration) was only possible for two muscles, at the interfascicular level, and LIFE did not activate selectively more than one muscle in the implanted nerve fascicle.

Badia, Jordi; Boretius, Tim; Andreu, David; Azevedo-Coste, Christine; Stieglitz, Thomas; Navarro, Xavier

2011-06-01

150

Excitatory cortical neurons with multipolar shape establish neuronal polarity by forming a tangentially oriented axon in the intermediate zone.  

Science.gov (United States)

The formation of axon-dendrite polarity is crucial for neuron to make the proper information flow within the brain. Although the processes of neuronal polarity formation have been extensively studied using neurons in dissociated culture, the corresponding developmental processes in vivo are still unclear. Here, we illuminate the initial steps of morphological polarization of excitatory cortical neurons in situ, by sparsely labeling their neuroepithelial progenitors using in utero electroporation and then examining their neuronal progeny in brain sections and in slice cultures. Morphological analysis showed that an axon-like long tangential process formed in progeny cells in the intermediate zone (IZ). Time-lapse imaging analysis using slice culture revealed that progeny cells with multipolar shape, after alternately extending and retracting their short processes for several hours, suddenly elongated a long process tangentially. These cells then transformed into a bipolar shape, extending a pia-directed leading process, and migrated radially leaving the tangential process behind, which gave rise to an "L-shaped" axon. Our findings suggest that neuronal polarity in these cells is established de novo from a nonpolarized stage in vivo and indicate that excitatory cortical neurons with multipolar shape in the IZ initiate axon outgrowth before radial migration into the cortical plate. PMID:22267309

Hatanaka, Yumiko; Yamauchi, Kenta

2013-01-01

151

Injection and Confinement of Plasma in a Stellarator with a Multipolar (? =2) Helical Field  

International Nuclear Information System (INIS)

We give the results of external injection of plasma into a closed magnetic trap and on the investigation of the effect of helical fields on the maintenance of the plasma. The ''L-I'' apparatus consists of a toroidal magnetic trap of stellarator type with a continuous ''double-thread'' multipolar (? = 2) helical field. The large diameter of the torus is 120 cm and the diameter of the vacuum chamber section 10 cm. The maximum value of the longitudinal field H is 104 Oe. The magnetic field of the stellarator is variable in time, to enable a study of adiabatic heating of the plasma in a trap of this type. The L-I stellarator and low-energy electron beams were used to investigate the structure of the magnetic surfaces. The method made it possible to determine the existence and form of closed magnetic surfaces over a wide range of the ratio of the helical and longitudinal fields. Resonance perturbations of the magnetic surfaces were detected that led to splitting of the latter and the formation of rosettes. Magnetic measurements confirmed the theoretical postulates regarding the magnetic surfaces and the effect of perturbations in resonance and non-resonance cases. Filling of the trap with plasma was effected by injecting plasma jets from spark guns into the transverse magnetic field. The total number of charged particles generated at each injection was ?5 x 1014. Injection could be made both .while the field was growing, with subsequent adiabatic compression of the plasma, and while the field was quasi-constant. Filling of the trap took place over a time of the order of tens of us. The inital density of the plasma was ?1011 cm-3, and the electron temperature ?15 eV. The density of the plasma was measured by the resonance ultra-high-frequency method and its distribution over the section was determined by twin Langmuir probes. The experiments showed the effective influence of a helical field on plasma. In the absence of a helical field, the density distribution was non-symmetrical relative to the centre of the chamber and the plasma drifted towards the external wall of the torus; its lifetime was the order of 100 to 200 ?s. When a helical field was applied then density distribution was symmetrical about the axis of the chamber and was determined by the form of the magnetic surfaces; the constant of density fall-off time was ?1 to 2 ms. The measured lifetime of the plasma when the apparatus is working as a stellarator cannot be explained by conventional diffusion. The spectrum of oscillations in the plasma electric fields was studied, and we discuss the various mechanisms capable of explaining the anomalously high plasma diffusion rates that we observed. (author)

152

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico Temporal lobe seizure recorded by magnetoencephalography: case report  

Directory of Open Access Journals (Sweden)

Full Text Available La localización del inicio de las crisis es un factor importante para la evaluación prequirúrgica de la epilepsia. En este trabajo se describe la localización del inicio de una crisis registrada mediante magnetoencefalografía (MEG en un niño de 12 años que presenta crisis parciales complejas farmacorresistentes. La RM muestra una lesión de 20mm de diámetro en el hipocampo izquierdo. EEG de superficie con ondas theta temporales izquierdas. Registro MEG interictal con punta-onda aislada posterior e inferior a la lesión de la RM. Registro MEG ictal con punta-onda (2 Hz. La localización de los dipolos indica el inicio de la crisis en la circunvolución temporal inferior en la misma localización que la actividad interictal MEG. Esta actividad ictal se propaga bilateralmente a áreas frontales. El registro corticográfico intraquirúrgico confirma los resultados de la localización interictal mediante MEG.Ictal onset localization is a important factor in presurgical evaluation of epilepsy. This paper describes the localization of a seizure onset recorded by magnetoencephalography (MEG from a 12-year-old male patient who suffered from complex partial drug-resistant seizures. MRI revealed a 20mm diameter lesion located in left hippocampus. Scalp EEG showed left temporal theta waves. Interictal MEG registrations detected isolated spike-wave activity posterior and inferior to the MRI lesion. Ictal MEG showed continuous spike-wave activity (2 Hz. Dipole localization sited seizure onset in the inferior left temporal gyrus, the same localization of the interictal MEG activity. This ictal activity spreads bilaterally to frontal areas. Intrasurgical electrocorticography recording confirmed interictal MEG results.

Carlos Amo

2004-09-01

153

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico / Temporal lobe seizure recorded by magnetoencephalography: case report  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Spanish Abstract in spanish La localización del inicio de las crisis es un factor importante para la evaluación prequirúrgica de la epilepsia. En este trabajo se describe la localización del inicio de una crisis registrada mediante magnetoencefalografía (MEG) en un niño de 12 años que presenta crisis parciales complejas farmac [...] orresistentes. La RM muestra una lesión de 20mm de diámetro en el hipocampo izquierdo. EEG de superficie con ondas theta temporales izquierdas. Registro MEG interictal con punta-onda aislada posterior e inferior a la lesión de la RM. Registro MEG ictal con punta-onda (2 Hz). La localización de los dipolos indica el inicio de la crisis en la circunvolución temporal inferior en la misma localización que la actividad interictal MEG. Esta actividad ictal se propaga bilateralmente a áreas frontales. El registro corticográfico intraquirúrgico confirma los resultados de la localización interictal mediante MEG. Abstract in english Ictal onset localization is a important factor in presurgical evaluation of epilepsy. This paper describes the localization of a seizure onset recorded by magnetoencephalography (MEG) from a 12-year-old male patient who suffered from complex partial drug-resistant seizures. MRI revealed a 20mm diame [...] ter lesion located in left hippocampus. Scalp EEG showed left temporal theta waves. Interictal MEG registrations detected isolated spike-wave activity posterior and inferior to the MRI lesion. Ictal MEG showed continuous spike-wave activity (2 Hz). Dipole localization sited seizure onset in the inferior left temporal gyrus, the same localization of the interictal MEG activity. This ictal activity spreads bilaterally to frontal areas. Intrasurgical electrocorticography recording confirmed interictal MEG results.

Carlos, Amo; Marta, Santiuste; Fernando, Maestú; Alberto, Fernández; Renata, Egatz; Mercedes, González-Hidalgo; Cristóbal, Saldaña; Antonio, Sáiz; Tomás, Ortiz.

2004-09-01

154

Impaired evoked and resting-state brain oscillations in patients with liver cirrhosis as revealed by magnetoencephalography.  

Science.gov (United States)

A number of studies suggest that the clinical manifestation of neurological deficits in hepatic encephalopathy results from pathologically synchronized neuronal oscillations and altered oscillatory coupling. In the present study spontaneous and evoked oscillatory brain activities were analyzed jointly with established behavioral measures of altered visual oscillatory processing. Critical flicker and fusion frequencies (CFF, FUF) were measured in 25 patients diagnosed with liver cirrhosis and 30 healthy controls. Magnetoencephalography (MEG) data were collected at rest and during a visual task employing repetitive stimulation. Resting MEG and evoked fields were analyzed. CFF and FUF were found to be reduced in patients, providing behavioral evidence for deficits in visual oscillatory processing. These alterations were found to be related to resting brain activity in patients, namely that the lower the dominant MEG frequency at rest, the lower the CFF and FUF. An analysis of evoked fields at sensor level indicated that in comparison to normal controls, patients were not able to dynamically adapt to flickering visual stimulation. Evoked activity was also analyzed based on independent components (ICs) derived by independent component analysis. The similarity between the shape of each IC and an artificial sine function representing the stimulation frequency was tested via magnitude squared coherence. In controls, we observed a small number of components that correlated strongly with the sine function and a high number of ICs that did not correlate with the sine function. Interestingly, patient data were characterized by a high number of moderately correlating components. Taken together, these results indicate a fundamental divergence of the cerebral resonance activity in cirrhotic patients. PMID:24179838

Götz, Theresa; Huonker, Ralph; Kranczioch, Cornelia; Reuken, Philipp; Witte, Otto W; Günther, Albrecht; Debener, Stefan

2013-01-01

155

Displacement of the central sulcus in cerebral arteriovenous malformations situated in the peri-motor cortex as assessed by magnetoencephalography  

International Nuclear Information System (INIS)

In order to determine the optimal treatment for a pen-motor cortex lesion, preoperative orientation of central sulcus (CS) is indispensable. The purpose of this study is to detect a discrepancy between ''functional'' CS and ''anatomical'' CS in cerebral lesions. Stereotactic mapping of functional'' CS was performed on 12 subjects using somatosensory evoked fields (SEFs) with MRI-linked whole head magnetoencephalography (MEG) system preoperatively. All subjects who underwent axial T1-weighted MRI scans had a left-sided lesion with diagnoses including: three arteriovenous malformations (AVM), six gliomas and three meningiomas. Two certified neurosurgeons identified the anatomical CS of the cerebral hemispheres in MRI. Right median nerves were stimulated at the wrists using the following parameters of stimulation: 1 Hz rectangular electrical wave, 0.2 msec duration, and 3 to 5 mA intensity. The sampling rate was 600 Hz and band pass filters were 0.1 to 200 Hz. One hundred epochs were averaged to determine SEFs during a 50 msec pre-stimulus to 300 msec following stimulus onset. Estimations of single dipole were corresponded with N20m of SEFs. Estimated current dipoles were superimposed on the MR images. Anatomical CS accorded with functional CS in the intracranial tumor cases. AVM cases in which the nidus was situated in the peri-motor cortex showed discrepancies between functional CS and anatomical CS marking one gyrus. AVMs situated in the peri-motor area have the abiliated in the peri-motor area have the ability to displace the CS. Preoperative consideration for AVM treatment should include functional brain mapping to decide the most suitable operative approach and avoid postoperative deficits. (author)

156

Properties of highly electronegative plasmas produced in a multipolar magnetic-confined device with a transversal magnetic filter  

DEFF Research Database (Denmark)

Highly electronegative plasmas were produced in Ar/SF6 gas mixtures in a dc discharge with multipolar magnetic confinement and transversal magnetic filter. Langmuir probe and mass spectrometry were used for plasma diagnostics. Plasma potential drift, the influence of small or large area biased electrodes on plasma parameters, the formation of the negative ion sheath and etching rates by positive and negative ions have been investigated for different experimental conditions. When the electron temperature was reduced below 1 eV the density ratio of negative ion to electron exceeded 100 even for very low amounts of SF6 gas. The plasma potential drift could be controlled by proper wall conditioning. A large electrode biased positively had no effect on plasma potential for density ratios of negative ions to electrons larger than 50. For similar electronegativities or higher a negative ion sheath could be formed by applying a positive bias of a few hundred volts.

Draghici, Mihai; Stamate, Eugen

2010-01-01

157

INTERACTIONS OF Si (III) SURFACE WITH H2, NH3, SiH4 MULTIPOLAR PLASMAS STUDIED BY IN SITU ELLIPSOMETRY  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An ultra high vacuum system consisting in a plasma chamber and an analysis chamber is used to study the interactions of various multipolar plasmas (NH3- H2SiH4) with Si surfaces. The kinetics of interaction can be followed in real time by in situ ellipsometry at 310 nm. Using the same set up the sample can be analyzed in situ by spectroscopic ellipsometry. The analysis chamber is equipped with an Auger spectrometer (CMA) and a RHEED set up.

Demay, Y.; Maurel, P.; Gourrier, S.

1983-01-01

158

A novel strategy for targeted killing of tumor cells: Induction of multipolar acentrosomal mitotic spindles with a quinazolinone derivative mdivi-1.  

Science.gov (United States)

Traditional antimitotic drugs for cancer chemotherapy often have undesired toxicities to healthy tissues, limiting their clinical application. Developing novel agents that specifically target tumor cell mitosis is needed to minimize the toxicity and improve the efficacy of this class of anticancer drugs. We discovered that mdivi-1 (mitochondrial division inhibitor-1), which was originally reported as an inhibitor of mitochondrial fission protein Drp1, specifically disrupts M phase cell cycle progression only in human tumor cells, but not in non-transformed fibroblasts or epithelial cells. The antimitotic effect of mdivi-1 is Drp1 independent, as mdivi-1 induces M phase abnormalities in both Drp1 wild-type and Drp1 knockout SV40-immortalized/transformed MEF cells. We also identified that the tumor transformation process required for the antimitotic effect of mdivi-1 is downstream of SV40 large T and small t antigens, but not hTERT-mediated immortalization. Mdivi-1 induces multipolar mitotic spindles in tumor cells regardless of their centrosome numbers. Acentrosomal spindle poles, which do not contain the bona-fide centrosome components ?-tubulin and centrin-2, were found to contribute to the spindle multipolarity induced by mdivi-1. Gene expression profiling revealed that the genes involved in oocyte meiosis and assembly of acentrosomal microtubules are highly expressed in tumor cells. We further identified that tumor cells have enhanced activity in the nucleation and assembly of acentrosomal kinetochore-attaching microtubules. Mdivi-1 inhibited the integration of acentrosomal microtubule-organizing centers into centrosomal asters, resulting in the development of acentrosomal mitotic spindles preferentially in tumor cells. The formation of multipolar acentrosomal spindles leads to gross genome instability and Bax/Bak-dependent apoptosis. Taken together, our studies indicate that inducing multipolar spindles composing of acentrosomal poles in mitosis could achieve tumor-specific antimitotic effect, and mdivi-1 thus represents a novel class of compounds as acentrosomal spindle inducers (ASI). PMID:25458053

Wang, Jingnan; Li, Jianfeng; Santana-Santos, Lucas; Shuda, Masahiro; Sobol, Robert W; Van Houten, Bennett; Qian, Wei

2014-10-17

159

Discrimination of coastal wetland environments in the Amazon region based on multi-polarized L-band airborne Synthetic Aperture Radar imagery  

Science.gov (United States)

This study assessed the use of multi-polarized L-band images for the identification of coastal wetland environments in the Amazon coast region of northern Brazil. Data were acquired with a SAR R99B sensor from the Amazon Surveillance System (SIVAM) on board a Brazilian Air Force jet. Flights took place in the framework of the 2005 MAPSAR simulation campaign, a German-Brazilian feasibility study focusing on a L-band SAR satellite. Information retrieval was based on the recognition of the interaction between a radar signal and shallow-water morphology in intertidal areas, coastal dunes, mangroves, marshes and the coastal plateau. Regarding the performance of polarizations, VV was superior for recognizing intertidal area morphology under low spring tide conditions; HH for mapping coastal environments covered with forest and scrub vegetation such as mangrove and vegetated dunes, and HV was suitable for distinguishing transition zones between mangroves and coastal plateau. The statistical results for the classification maps expressed by kappa index and general accuracy were 83.3% and 0.734 for the multi-polarized color composition (R-HH, G-HV, B-VV), 80.7% and 0.694% for HH, 79.7% and 0.673% for VV, and 77.9% and 0.645% for HV amplitude image. The results indicate that use of multi-polarized L-band SAR is a valuable source of information aiming at the identification and discrimination of distinct geomorphic targets in tropical wetlands.

Souza-Filho, Pedro Walfir M.; Paradella, Waldir R.; Rodrigues, Suzan W. P.; Costa, Francisco R.; Mura, José C.; Gonçalves, Fabrício D.

2011-11-01

160

Electroexcitation of low-multipolarity magnetic transitions in 36Ar and 38Ar  

International Nuclear Information System (INIS)

Measurements of inelastic electron scattering from 36Ar and 38Ar have been performed at low energy and backward angle to determine the distribution of M1 and M2 strength in these nuclei. The total observed M1 strength in 36Ar is approximately 93% of that predicted in the measured energy region by shell-model calculations using effective M1 operators. In 38Ar, the single strong M1 transition predicted by shell-model calculations was not observed. Instead, a number of weak transitions were observed, with total M1 strength equal to about 134% of the predicted strength

 
 
 
 
161

A Rússia na ordem mundial: com o Ocidente, com o Oriente ou um pólo autônomo em um mundo multipolar?  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O artigo persegue o objetivo de definir o lugar e o papel da Rússia nas relações internacionais contemporâneas nos últimos anos. Ao se debruçar sobre o dilema tradicional da política externa russa - Ocidentalismo versus Orientalismo - o autor analisa o cenário de multipolaridade defendido pela nova [...] concepção da política externa russa e o relaciona com a fase do pragmatismo e do multilateralismo que caracteriza a atuação internacional da Rússia de Putin, fazendo considerações, decorrentes do impacto dos ataques terroristas aos Estados Unidos em 11 de setembro de 2001 sobre a política externa russa. A atitude pragmática e a natureza multivetorial da política externa russa contribuem, segundo o autor, para o fortalecimento das posições internacionais da Rússia em comparação com a perda ou a natureza incerta das alianças e dos relacionamentos do período da transição pós-soviética. Abstract in english The article pursues the purpose to place Russia and its politics within the context of today's international relations. While discussing the traditional dilemma of the Russian foreign politics - Occidentalism versus Orientalism - the author analyses the scenario of multipolarity, backed up by the ne [...] w Russian foreign policy concept. Hence it is related to the pragmatism and the multilateralism of the international posture of Putin's Russia, the author makes several considerations, which follow from the impact of the September 11th, 2001, terrorist attacks on the United States of America with regard to Russia's foreign policy. The pragmatic attitude and the multi-axis nature of the Russian foreign policy nowadays contribute, according to the author, to strengthen Russia's international background in comparison with the loss or the uncertain nature of alliances and relationships of the post-Soviet transition period.

Alexander, Zhebit.

2003-06-01

162

A Rússia na ordem mundial: com o Ocidente, com o Oriente ou um pólo autônomo em um mundo multipolar?  

Directory of Open Access Journals (Sweden)

Full Text Available O artigo persegue o objetivo de definir o lugar e o papel da Rússia nas relações internacionais contemporâneas nos últimos anos. Ao se debruçar sobre o dilema tradicional da política externa russa - Ocidentalismo versus Orientalismo - o autor analisa o cenário de multipolaridade defendido pela nova concepção da política externa russa e o relaciona com a fase do pragmatismo e do multilateralismo que caracteriza a atuação internacional da Rússia de Putin, fazendo considerações, decorrentes do impacto dos ataques terroristas aos Estados Unidos em 11 de setembro de 2001 sobre a política externa russa. A atitude pragmática e a natureza multivetorial da política externa russa contribuem, segundo o autor, para o fortalecimento das posições internacionais da Rússia em comparação com a perda ou a natureza incerta das alianças e dos relacionamentos do período da transição pós-soviética.The article pursues the purpose to place Russia and its politics within the context of today's international relations. While discussing the traditional dilemma of the Russian foreign politics - Occidentalism versus Orientalism - the author analyses the scenario of multipolarity, backed up by the new Russian foreign policy concept. Hence it is related to the pragmatism and the multilateralism of the international posture of Putin's Russia, the author makes several considerations, which follow from the impact of the September 11th, 2001, terrorist attacks on the United States of America with regard to Russia's foreign policy. The pragmatic attitude and the multi-axis nature of the Russian foreign policy nowadays contribute, according to the author, to strengthen Russia's international background in comparison with the loss or the uncertain nature of alliances and relationships of the post-Soviet transition period.

Alexander Zhebit

2003-06-01

163

Steady-state direct-current plasma immersion ion implantation using a multipolar magnetic field electron cyclotron resonance plasma source  

International Nuclear Information System (INIS)

In semiconductor plasma immersion ion implantation (PIII) applications such as the synthesis of silicon-on-insulator by hydrogen PIII and ion cut, only ions arriving at the top surface of the sample stage are important. The ions implanted into the other surfaces of the sample chuck actually not only decrease the efficiency of the power supply and plasma source but also give rise to metallic contamination. In addition, low energy ions introduced by the initial plasma sheath propagation, pulse rise time, and pulse fall time introduce a large surface hydrogen concentration that creates surface damage and affects the wafer bonding efficacy. We have theoretically demonstrated direct-current PIII (DC-PIII) which retains the x-y immersion characteristic while simultaneously reducing this low energy ion component, obviating the need for the expensive power modulator, and extending the voltage ceiling that is no longer limited by the vacuum chamber and power modulator. In this article, we describe our hydrogen DC-PIII experiments using a conducting grid placed between the wafer stage and a multipolar electron cyclotron resonance plasma source. The grounded grid stops the propagation of the plasma sheath, thereby removing the vacuum chamber size limitation. Ions are formed in the plasma sustained by an external plasma source above the grid and accelerated through the lower zone to be implanted into the wafer biased by only a dc power supply. Atomic force microscopy, hydrogen fopply. Atomic force microscopy, hydrogen forward scattering, and secondary ion mass spectrometry analyses indicate uniform hydrogen PIII into a 100 mm silicon wafer and the surface hydrogen component is indeed reduced significantly compared to conventional pulsed PIII

164

Statistical contribution in the giant multipolar resonance decay in hevay nuclei  

International Nuclear Information System (INIS)

Statistical calculations are made for the decay in the electric monopole giant resonance in 208Pb and electric dipole giant resonance in 209Bi, using the Hauser-Feshbach formalism. Calculations are done using the experimental energy levels of the corresponding residual nuclei. The particle-vibrator model is used for those experimental levels without spin and parity determination. The influence of different parametrizations of the optical potential in the statistical calculation result is also studied. (L.C.)

165

Experimental investigation of microwave interaction with magnetoplasma in miniature multipolar configuration using impedance measurements  

Science.gov (United States)

A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance.

Dey, Indranuj; Toyoda, Yuji; Yamamoto, Naoji; Nakashima, Hideki

2014-09-01

166

Magnetar Giant Flares in Multipolar Magnetic Fields --- I. Fully and Partially Open Eruptions of Flux Ropes  

CERN Document Server

We propose a catastrophic eruption model for magnetar's enormous energy release during giant flares, in which a toroidal and helically twisted flux rope is embedded within a force-free magnetosphere. The flux rope stays in stable equilibrium states initially and evolves quasi-statically. Upon the loss of equilibrium point is reached, the flux rope cannot sustain the stable equilibrium states and erupts catastrophically. During the process, the magnetic energy stored in the magnetosphere is rapidly released as the result of destabilization of global magnetic topology. The magnetospheric energy that could be accumulated is of vital importance for the outbursts of magnetars. We carefully establish the fully open fields and partially open fields for various boundary conditions at the magnetar surface and study the relevant energy thresholds. By investigating the magnetic energy accumulated at the critical catastrophic point, we find that it is possible to drive fully open eruptions for dipole dominated background...

Huang, Lei

2014-01-01

167

Experimental investigation of microwave interaction with magnetoplasma in miniature multipolar configuration using impedance measurements  

International Nuclear Information System (INIS)

A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance

168

Experimental investigation of microwave interaction with magnetoplasma in miniature multipolar configuration using impedance measurements  

Energy Technology Data Exchange (ETDEWEB)

A miniature microwave plasma source employing both radial and axial magnetic fields for plasma confinement has been developed for micro-propulsion applications. Plasma is initiated by launching microwaves via a short monopole antenna to circumvent geometrical cutoff limitations. The amplitude and phase of the forward and reflected microwave power is measured to obtain the complex reflection coefficient from which the equivalent impedance of the plasma source is determined. Effect of critical plasma density condition is reflected in the measurements and provides insight into the working of the miniature plasma source. A basic impedance calculation model is developed to help in understanding the experimental observations. From experiment and theory, it is seen that the equivalent impedance magnitude is controlled by the coaxial discharge boundary conditions, and the phase is influenced primarily by the plasma immersed antenna impedance.

Dey, Indranuj, E-mail: indranuj@aees.kyushu-u.ac.jp; Toyoda, Yuji; Yamamoto, Naoji; Nakashima, Hideki [Department of Advanced Energy Engineering Science, Kyushu University, Kasuga 816-8580 (Japan)

2014-09-15

169

Electric and magnetic giant resonances of low multipolarity studied with inelastic electron scattering  

International Nuclear Information System (INIS)

The introduction into the field of electric and magnetic giant resonances in light and heavy nuclei is given. The recent experimental results on inelastic electron scattering obtained at the Darmstadt electron linear accelerator are used in the paper. The problem of extraction of information on electroexcitation of nuclei at low momentum transfer from the point of view of a test for nuclear models is briefly discussed. The main attention is paid to electric (E1 and E2) transitions in 11B, 28Si, 208Pb isotopes and to magnetic (M1 and M2) transitions in 12C, 16O, 28Si, sup(40, 42, 44, 48)Ca, 58Ni, 90Zr, 140Ce and 208Pb isotopes. Electric transitions are shown to have a collective nature while magnetic transitions don't show ony collectivity. The most interesting resUlt is the strong retardation of the M1 and M2 transition strengths in heavy nuclei as compared to the theoretical predictions

170

NGC 6309, a planetary nebula that shifted from round to multipolar  

Science.gov (United States)

We present new narrow-band H?, [N II], and [O III] high-resolution images of the quadrupolar planetary nebula NGC 6309 that show in great detail its bipolar lobes and reveal new morphological features. New high- and low-dispersion long-slit spectra have been obtained to help in the investigation of the new nebular components. The images and spectra unveil two diffuse blobs, one of them located ?55 arcsec from the central star along the NE direction (PA = +71°) and the other at ? 78 arcsec in the SW direction (PA = -151°). Therefore, these structures do not share the symmetry axes of the inner bipolar outflows. Their radial velocities relative to the system are quite low: +3 and -4 km s-1, respectively. Spectroscopic data confirm a high [O III] to H? ratio, indicating that the blobs are being excited by the UV flux from the central star. Our images convincingly show a spherical halo 60 arcsec in diameter encircling the quadrupolar nebula. The expansion velocity of this shell is low, ?6 km s-1. To study the formation history of NGC 6309, we have used our new images and spectra, as well as available echelle spectra of the innermost regions, to estimate the kinematical age of each structural component: the software SHAPE has been used to construct a morphokinematic model for the ring and the bipolar flows that implies an age of ˜4000 yr, the expansion of the halo sets a lower limit for its age ?46 000 yr, and the very low expansion of the blobs suggests they are part of a large structure corresponding to a mass ejection that took place ˜150 000 yr ago. In NGC 6309, we have direct evidence of a change in the geometry of mass-loss, from spherical in the halo to axially symmetric in the two pairs of bipolar lobes.

Rubio, G.; Vázquez, R.; Ramos-Larios, G.; Guerrero, M. A.; Olguín, L.; Guillén, P. F.; Mata, H.

2015-01-01

171

Brain activity is related to individual differences in the number of items stored in auditory short-term memory for pitch: evidence from magnetoencephalography.  

Science.gov (United States)

We used magnetoencephalography (MEG) to examine brain activity related to the maintenance of non-verbal pitch information in auditory short-term memory (ASTM). We focused on brain activity that increased with the number of items effectively held in memory by the participants during the retention interval of an auditory memory task. We used very simple acoustic materials (i.e., pure tones that varied in pitch) that minimized activation from non-ASTM related systems. MEG revealed neural activity in frontal, temporal, and parietal cortices that increased with a greater number of items effectively held in memory by the participants during the maintenance of pitch representations in ASTM. The present results reinforce the functional role of frontal and temporal cortices in the retention of pitch information in ASTM. This is the first MEG study to provide both fine spatial localization and temporal resolution on the neural mechanisms of non-verbal ASTM for pitch in relation to individual differences in the capacity of ASTM. This research contributes to a comprehensive understanding of the mechanisms mediating the representation and maintenance of basic non-verbal auditory features in the human brain. PMID:24642285

Grimault, Stephan; Nolden, Sophie; Lefebvre, Christine; Vachon, François; Hyde, Krista; Peretz, Isabelle; Zatorre, Robert; Robitaille, Nicolas; Jolicoeur, Pierre

2014-07-01

172

Use of multi-frequency, multi-polarization, multi-angle airborne radars for class discrimination in a southern temperature forest  

Science.gov (United States)

The utility of radar scatterometers for discrimination and characterization of natural vegetation was investigated. Backscatter measurements were acquired with airborne multi-frequency, multi-polarization, multi-angle radar scatterometers over a test site in a southern temperate forest. Separability between ground cover classes was studied using a two-class separability measure. Very good separability is achieved between most classes. Longer wavelength is useful in separating trees from non-tree classes, while shorter wavelength and cross polarization are helpful for discrimination among tree classes. Using the maximum likelihood classifier, 50% overall classification accuracy is achieved using a single, short-wavelength scatterometer channel. Addition of multiple incidence angles and another radar band improves classification accuracy by 20% and 50%, respectively, over the single channel accuracy. Incorporation of a third radar band seems redundant for vegetation classification. Vertical transmit polarization is critically important for all classes.

Mehta, N. C.

1984-01-01

173

Consistencia epistémica del síndrome de Dificultades del Aprendizaje: aportaciones de la magnetoencefalografía como técnica de neuroimagen funcional / Epistemics for Learning Disabilities: Contributions from Magnetoencephalography, a Functional Neuroimaging Tool  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish El síndrome Dificultades del Aprendizaje (DA) fue descrito en 1963 por S. Kirk. Desde entonces, diversas escuelas en EE.UU., Canadá y España han afinado su concepto y clasificación. La UCM en España ha propuesto una definición descriptiva y totalizadora, y ha estudiado empíricamente distintas manife [...] staciones, intentando descubrir sus marcadores biológicos y las características neurológicas de sus principales manifestaciones (dislexia, discalculia, disortografia, TDA, TDAH, etc.). Se describen los hallazgos en DA a partir de estudios como la magnetoencefalografía (MEG), técnica inocua que recoge campos magnéticos generados naturalmente por el cerebro y analiza su distribución espacial para localizar los generadores neuronales responsables, proporcionando información simultánea sobre la estructura y la función cerebral en patrones de normalidad en el procesamiento cognitivo y patrones aberrantes propios de las particulares manifestaciones clínicas del síndrome DA. Abstract in english The syndrome known as Learning Disabilities (LD) was described by S. Kirk in 1963. From that point on, institutions from the US, Canada and Spain have engaged in refining the concept and classification of LDs. The Complutense University in Spain, has proposed a descriptive and all-embracing definiti [...] on, and has studied the different manifestations of LD, pursuing the description of biological markers and neurological features of LD’s main expressions: dyslexia, dyscalculia, dysorthographia, Attention Deficit and Hyperactivity Disorder -ADHD, and so forth. Findings in LD using functional neuroimaging techniques, namely Magnetoencephalography (MEG), are described. MEG is a non-invasive technique, which records magnetic fields naturally generated by the brain and their spatial distribution. It allows simultaneous functional and structural information. MEG is therefore used in the study of primary and superior cognitive functions, in surveillance of patterns of normal cognitive function and those specific to the different LD clinical manifestations.

VÍCTOR, SANTIUSTE-BERMEJO; MARTA, SANTIUSTE-DÍAZ.

2008-12-01

174

Parametrized post-Newtonian theory of reference frames, multipolar expansions and equations of motion in the N-body problem  

International Nuclear Information System (INIS)

Post-Newtonian relativistic theory of astronomical reference frames based on Einstein's general theory of relativity was adopted by General Assembly of the International Astronomical Union in 2000. This theory is extended in the present paper by taking into account all relativistic effects caused by the presumable existence of a scalar field and parametrized by two parameters, ? and ?, of the parametrized post-Newtonian (PPN) formalism. We use a general class of the scalar-tensor (Brans-Dicke type) theories of gravitation to work out PPN concepts of global and local reference frames for an astronomical N-body system. The global reference frame is a standard PPN coordinate system. A local reference frame is constructed in the vicinity of a weakly self-gravitating body (a sub-system of the bodies) that is a member of the astronomical N-body system. Such local inertial frame is required for unambiguous derivation of the equations of motion of the body in the field of other members of the N-body system and for construction of adequate algorithms for data analysis of various gravitational experiments conducted in ground-based laboratories and/or on board of spacecrafts in the solar system.We assume that the bodies comprising the N-body system have weak gravitational field and move slowly. At the same time we do not impose any specific limitations on the distribution of density, velocity and the equation of state of the body's matter. Scalar-tensor equations of the gravitr. Scalar-tensor equations of the gravitational field are solved by making use of the post-Newtonian approximations so that the metric tensor and the scalar field are obtained as functions of the global and local coordinates. A correspondence between the local and global coordinate frames is found by making use of asymptotic expansion matching technique. This technique allows us to find a class of the post-Newtonian coordinate transformations between the frames as well as equations of translational motion of the origin of the local frame along with the law of relativistic precession of its spatial axes. These transformations depend on the PPN parameters ? and ?, generalize general relativistic transformations of the IAU 2000 resolutions, and should be used in the data processing of the solar system gravitational experiments aimed to detect the presence of the scalar field. These PPN transformations are also applicable in the precise time-keeping metrology, celestial mechanics, astrometry, geodesy and navigation.We consider a multipolar post-Newtonian expansion of the gravitational and scalar fields and construct a set of internal and external gravitational multipoles depending on the parameters ? and ?. These PPN multipoles generalize the Thorne-Blanchet-Damour multipoles defined in harmonic coordinates of general theory of relativity. The PPN multipoles of the scalar-tensor theory of gravity are split in three classes-active, conformal, and scalar multipoles. Only two of them are algebraically independent and we chose to work with the conformal and active multipoles. We derive the laws of conservations of the multipole moments and show that they must be formulated in terms of the conformal multipoles. We focus then on the law of conservation of body's linear momentum which is defined as a time derivative of the conformal dipole moment of the body in the local coordinates. We prove that the local force violating the law of conservation of the body's linear momentum depends exclusively on the active multipole moments of the body along with a few other terms which depend on the internal structure of the body and are responsible for the violation of the strong principle of equivalence (the Nordtvedt effect).The PPN translational equations of motion of extended bodies in the global coordinate frame and with all gravitational multipoles taken into account are derived from the law of conservation of the body's linear momentum supplemented by the law of motion of the origin of the local frame derived from the matching procedure. We use these equations to analyz

175

Binary black hole coalescence in the extreme-mass-ratio limit: Testing and improving the effective-one-body multipolar waveform  

International Nuclear Information System (INIS)

We discuss the properties of the effective-one-body (EOB) multipolar gravitational waveform emitted by nonspinning black-hole binaries of masses ? and M in the extreme-mass-ratio limit ?/M=?-4 rad and maintain then a remarkably accurate phase coherence during the long inspiral (?33 orbits), accumulating only about -2x10-3 rad until the last stable orbit, i.e. ??/??-5.95x10-6. We obtain such accuracy without calibrating the analytically resummed EOB waveform to numerical data, which indicates the aptitude of the EOB waveform for studies concerning the Laser Interferometer Space Antenna. We then improve the behavior of the EOB waveform around merger by introducing and tuning next-to-quasicircular corrections in both the gravitational wave amplitude and phase. For each multipole we tune only fr each multipole we tune only four next-to-quasicircular parameters by requiring compatibility between EOB and Regge-Wheeler-Zerilli waveforms at the light ring. The resulting phase difference around the merger time is as small as ±0.015 rad, with a fractional amplitude agreement of 2.5%. This suggest that next-to-quasicircular corrections to the phase can be a useful ingredient in comparisons between EOB and numerical-relativity waveforms.

176

The ablated volume and the thermal field distribution in swine vertebral body created by multi-polar radiofrequency ablation: an experiment in vitro  

International Nuclear Information System (INIS)

Objective: To observe the extent of bone coagulation and the thermal field distribution created in ablating the swine vertebral bodies in vitro with multi-polar radiofrequency and to discuss the correlation between the electrode position in the vertebral body and the safety of the spinal cord as well as the soft tissue injury around the vertebral body. Methods: Thirty fresh adult porcine vertebrae were randomly and equally divided into two groups. The depth of the electrode needle was 10 mm or 20 mm.When the ablation process reached to a stable state, the temperature at the scheduled spots was estimated. Twenty minutes after ablation, the vertebral body was cut along the electrode needle plane and also along the plane perpendicular to the electrode needle to observe the extent of bone coagulation. Results: The temperature at the scheduled spots reached to a stable state in 3.5 minutes. The more close to the electrode the spot was, the more quickly the temperature rose. No soft tissue injury around the vertebral body was observed in both groups and no spinal cord injury occurred when the electrode needle was 10 mm or 20 mm deep in the vertebral body. Conclusion: In treating vertebral metastases, the radiofrequency ablation is safe and reliable if the posterior wall of the vertebral body remains intact. (authors)

177

Thomas-Fermi model electron density with correct boundary conditions: Application to atoms and ions  

Energy Technology Data Exchange (ETDEWEB)

The author proposes an electron density in atoms and ions, which has the Thomas-Fermi-Dirac form in the intermediate region of r, satisfies the Kato condition for small r, and has the correct asymptotic behavior at large values of r, where r is the distance from the nucleus. He also analyzes the perturbation in the density produced by multipolar fields. He uses these densities in the Poisson equation to deduce average values of r{sup m}, multipolar polarizabilities, and dispersion coefficients of atoms and ions. The predictions are in good agreement with experimental and other theoretical values, generally within about 20%. He tabulates here the coefficient A in the asymptotic density; radial expectation values (r{sup m}) for m = 2, 4, 6; multipolar polarizabilities {alpha}{sub 1}, {alpha}{sub 2}, {alpha}{sub 3}; expectation values {l_angle}r{sup 0}{r_angle} and {l_angle}r{sup 2}{r_angle} of the asymptotic electron density; and the van der Waals coefficient C{sub 6} for atoms and ions with 2 {le} Z {le} 92. Many of the results, particularly the multipolar polarizabilities and the higher order dispersion coefficients, are the only ones available in the literature. The variation of these properties also provides interesting insight into the shell structure of atoms and ions. Overall, the Thomas-Fermi-Dirac model with the correct boundary conditions provides a good global description of atoms and ions.

Patil, S.H. [Indian Inst. of Tech., Bombay (India). Dept. of Physics

1999-01-01

178

Thomas-Fermi model electron density with correct boundary conditions: Application to atoms and ions  

International Nuclear Information System (INIS)

The author proposes an electron density in atoms and ions, which has the Thomas-Fermi-Dirac form in the intermediate region of r, satisfies the Kato condition for small r, and has the correct asymptotic behavior at large values of r, where r is the distance from the nucleus. He also analyzes the perturbation in the density produced by multipolar fields. He uses these densities in the Poisson equation to deduce average values of rm, multipolar polarizabilities, and dispersion coefficients of atoms and ions. The predictions are in good agreement with experimental and other theoretical values, generally within about 20%. He tabulates here the coefficient A in the asymptotic density; radial expectation values (rm) for m = 2, 4, 6; multipolar polarizabilities ?1, ?2, ?3; expectation values left-angle r0 right-angle and left-angle r2 right-angle of the asymptotic electron density; and the van der Waals coefficient C6 for atoms and ions with 2 ? Z ? 92. Many of the results, particularly the multipolar polarizabilities and the higher order dispersion coefficients, are the only ones available in the literature. The variation of these properties also provides interesting insight into the shell structure of atoms and ions. Overall, the Thomas-Fermi-Dirac model with the correct boundary conditions provides a good global description of atoms and ions

179

Electric Multipole Interactions in an Extended BEG Model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

General 2D dielectric phase diagrams and phase transitions for multipolar molecules adsorbed to a square ionic crystal are presented. The adsorbed molecules are modeled using a dilute spin-one Ising model in the Blume-Emery-Griffiths formalism, using a mean-field approximation. Physical constants such as the electricmultipole moments and binding energies are used to uniquely determine the interaction parameters over the full range of physically-relevant values. We find that temperature- and c...

Burns, Teresa; Dennison, Jr

2013-01-01

180

Imagens multipolarizadas do sensor Palsar/Alos na discriminação das fases fenológicas da cana?de?açúcar / Multipolarized Palsar/Alos images to discriminate sugarcane phenological phases  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O objetivo deste trabalho foi avaliar o potencial das imagens multipolarizadas do sensor?radar Palsar/Alos em diferenciar as fases fenológicas da cana?de?açúcar. Valores digitais de quatro imagens do sensor, dos meses de fevereiro, maio, agosto e outubro de 2008, com polarizações HH (emissão e receb [...] imento de onda na polarização horizontal) e HV (emissão de onda na polarização horizontal e recebimento na vertical), foram convertidos para coeficientes de retroespalhamento (?°), para a análise de dados de cana?de?açúcar, cultivadas em talhões na região nordeste do Estado de São Paulo. Foram selecionadas três variedades, em diferentes estágios fenológicos: RB85?5156, seis talhões; RB86?7515, dez talhões; e RB92?5345, dez talhões. As diferenças entre as fases fenológicas foram avaliadas para cada uma das variedades e, também, entre as variedades. A utilização simultânea ou não dos dados do sensor Palsar/Alos, obtidos em duas polarizações, foi capaz de discriminar as diferentes fases de crescimento da cana?de?açúcar, com exceção da fase de crescimento dos colmos e a fase de maturação, em que não foi observada diferença significativa. Abstract in english The objective of this work was to evaluate the potential of multipolarized Palsar/Alos satellite images to discriminate phenological phases of sugarcane. Digital values from four digital images of February, May, August, and October 2008, with HH (sending and receiving wave in horizontal polarization [...] ) and HV polarizations (sending wave in horizontal polarization and receiving in vertical polarization), were converted to backscattering coefficients (?°) for data analysis of sugarcane cultivated in the northeastern of the state of São Paulo, Brazil. Three varieties were selected at different phenological stages: RB85?5156, six stands; RB86?7515, ten stands; and RB92?5345, ten stands. The differences between the phenological phases were analyzed for each variety, and also between varieties. The single or dual?poralized Palsar/Alos data, obtained in two polarizations, were able of discriminating the different phases of sugarcane growth, except for the grand growth period and maturity phase, in which no significant difference was observed.

Michelle Cristina Araujo, Picoli; Rubens Augusto, Lamparelli; Edson Eyji, Sano; Jansle Vieira, Rocha.

1307-13-01

 
 
 
 
181

Quantifying the dynamics of water bodies, wetlands and biomass in the Poyang Lake region: A multi-polarization SAR remote sensing approach  

Science.gov (United States)

Field measurements were combined with synthetic aperture radar (SAR) images to evaluate the use of C-band multi-polarized radar remote sensing for estimating plant parameters (plant height, fresh biomass, dry biomass and vegetation water content) of wetland vegetation, and mapping the dynamics of water bodies, wetlands (natural wetlands and rice paddies) and flooding extents in the Poyang Lake region. The capacity of L-band SAR in land cover mapping was also investigated by integrating with optical imagery. Hydrological patterns in Poyang Lake are the dominant factor controlling the spatial and temporal variations of wetland species in Poyang Lake. Water levels in this region are primarily governed by five rivers (Ganjiang river, Xiushui river, Raohe river, Fuhe river, and Xinjiang river). Its northern region is also influenced by the backflow from Yangtze River. The above-ground total biomass increased steadily from March following the hydrological cycle. Wetland species colonizing at different altitudes were gradually flooded from late spring to summer. Carex spp. died during flooding periods and started another growth cycle in autumn after flooding receded. Canopy volume dominates the radar backscattering mechanism in Carex spp. wetlands during their growth period, but the temporal variation of radar backscatter from these wetlands is mainly influenced by flooding. Tall wetland species (Miscanthus sacchariflorus, Phragmites communis Trin., and others) still emerged above water surfaces during flooding peaks and started to senesce in autumn. Surface backscattering mechanism is dominant during the early growing stage and the senescent period of tall vegetation. Plant canopy variation controlled the temporal dynamics of radar backscatters from Phragmites communis Min. Radar backscattering mechanisms from Miscanthus sacchariflorus wetlands were more complicated during the flooding periods. The variations of ground water depth and plant structure of Miscanthus sacchariflorus during its growth period result in over 10 dB spatial and temporal variation in ASAR backscatter in HH- and HV-polarization. The relationship of canopy height with ASAR backscattering coefficient is the most significant among the influencing factors (plant height, fresh biomass, dry biomass, vegetation water content) on radar backscattering mechanism (R2=0.9 for HH-polarization and R2=0.59 for HV-polarization) from Phragmites cummunis Trin. HH- and HV-backscatters are more sensitive to the variation of dry biomass (R2=0.76 for HH and R2=0.56 for HV) than to that of fresh biomass (R 2=0.07 for HV and R2=0.42 for HH). Plant water content plays a negative role and attenuates the backscattering signals in both polarizations. For Phragmites communis Trin. with tall stalks (over 2m) and long, blade-like leaves, HH-polarization is more sensitive to vegetation parameters than HV-polarization for C-band SAR signals. Similar to Phragmites communis Trin., ASAR backscattering coefficient in both polarizations is more sensitive to plant height and dry biomass of non-flooded Miscanthus sacchariflorus, and their regression coefficients (R2) are over 0.5 for HH-polarization and over 0.4 for HV-polarization. Plant water content has no evident effect on the variation of ASAR backscatter. HV-polarization is more sensitive to the variation of above-water canopy parameters than HH-polarization for flooded Miscanthus saccharifiorus. HH- and HV-polarized radar backscatters from Carex spp. wetlands increased significantly with the variation of plant height, fresh biomass and dry biomass, but they reach saturated when vegetation grows up to 30cm. Compared with those tall grass with stalks and long blade-like leaves, the correlation of fresh biomass with HV-polarization is more pronounced (R 2=0.78) than that with HH-polarization (R2=0.41) for Carex spp. Vegetation structure play a more important role in radar backscattering mechanism than plant water content for these three wetland species. Temporal profiles of C-band multi-polarized backscatter coefficients for individual lan

Sang, Huiyong

182

Determination of the E1+M2+E3 multipolarity mixture for 921 keV ?-transition and analysis of the 1285 kehV, 5- level structure in 184W  

International Nuclear Information System (INIS)

Decay properties of 1285 keV, 5- level have been analysed in detail using new data on 921 and 537 keV transitions de-exciting 1285 keV, 5-184W level. 184Re and sup(184m)Re were used as 184W source. K- and L-lines of internal conversion of 921 keV gamma transition have been measured. Values of internal conversion coefficients and their ratios have been obtained. 1285 keV, 5-184 W level decay scheme is presented, as well as refined data on probabilities of transitions de-exciting it. 1285 keV, 5- level is interpreted as two-quasiparticle state with n 510 excitation - n615 excitation configuration. It is isomeric with Tsub(1/2)=8.33+-0.18 ?s. Data on transition multipolarities, impurities amplitude values of wave functions of collective excitations and matrix elements are presented as well

183

Analysis and Realization on MIMO Channel Model  

Directory of Open Access Journals (Sweden)

Full Text Available In order to build the MIMO (Multiple Input Multiple Output channel model based on IEEE 802.16, the way and analysis on how to build good MIMO channel model are described in this study. By exploiting the spatial freedom of wireless channels, MIMO systems have the potential to achieve high bandwidth efficiency, promoting MIMO to be a key technique in the next generation communication systems. As a basic researching field of MIMO technologies, MIMO channel modeling significantly serve to the performance evaluation of space-time encoding algorithms as well as system level calibration and simulation. Having the superiorities of low inner-antenna correlation and small array size, multi-polarization tends to be a promising technique in future MIMO systems. However, polarization characteristics have not yet been modeled well in current MIMO channel models, so establishing meaningful multi-polarized MIMO channel models has become a hot spot in recent channel modeling investigation. In this study, I have mainly made further research on the related theories in the channel models and channel estimation and implementation algorithms on the others’ research work.

Liu Hui

2014-04-01

184

Dynamical properties of a model for synchro-betatron coupling  

International Nuclear Information System (INIS)

The long term stability of betatron motion in presence of multipolar nonlinearities has been extensively investigated for high energy accelerators and the Henon maps has been proposed as a model. In high intensity accelerators the non linear effects due to space charge and synchro-betatron coupling are relevant. We propose a simple model to investigate the coupling between longitudinal and horizontal motion due to chromaticity. The model consists in a standard Chirikov map coupled to a Henon map. Diffusion of orbits is observed and the structure of resonances is inspected by the frequency analysis

185

Dipole models for the EEG and MEG.  

Science.gov (United States)

The current dipole is a widely used source model in forward and inverse electroencephalography and magnetoencephalography applications. Analytic solutions to the governing field equations have been developed for several approximations of the human head using ideal dipoles as the source model. Numeric approaches such as the finite-element and finite-difference methods have become popular because they allow the use of anatomically realistic head models and the increased computational power that they require has become readily available. Although numeric methods can represent more realistic domains, the sources in such models are an approximation of the ideal dipole. In this paper, we examine several methods for representing dipole sources in finite-element models and compare the resulting surface potentials and external magnetic field with those obtained from analytic solutions using ideal dipoles. PMID:12002172

Schimpf, Paul H; Ramon, Ceon; Haueisen, Jens

2002-05-01

186

Isoscalar giant resonances in a relativistic model  

International Nuclear Information System (INIS)

Isoscalar giant resonances in finite nuclei are studied in a relativistic Random Phase Approximation (RRPA) approach. The model is self-consistent in the sense that one set of coupling constants generates the Dirac-Hartree single-particle spectrum and the residual particle-hole interaction. The RRPA is used to calculate response functions of multipolarity L = 0,2,3, and 4 in light and medium nuclei. It is found that monopole and quadrupole modes exhibit a collective character. The peak energies are overestimated, but not as much as one might think if the bulk properties (compression modulus, effective mass) were the only relevant quantities

187

Clinical applications of magnetoencephalography in epilepsy  

Directory of Open Access Journals (Sweden)

Full Text Available Magnetoencehalography (MEG is being used with increased frequency in the pre-surgical evaluation of patients with epilepsy. One of the major advantages of this technique over the EEG is the lack of distortion of MEG signals by the skull and intervening soft tissue. In addition, the MEG preferentially records activity from tangential sources thus recording activity predominantly from sulci, which is not contaminated by activity from apical gyral (radial sources. While the MEG is probably more sensitive than the EEG in detecting inter-ictal spikes, especially in the some locations such as the superficial frontal cortex and the lateral temporal neocortex, both techniques are usually complementary to each other. The diagnostic accuracy of MEG source localization is usually better as compared to scalp EEG localization. Functional localization of eloquent cortex is another major application of the MEG. The combination of high spatial and temporal resolution of this technique makes it an extremely helpful tool for accurate localization of visual, somatosensory and auditory cortices as well as complex cognitive functions like language. Potential future applications include lateralization of memory function.

Ray Amit

2010-01-01

188

Internal conversion calculations in Hartree-Fock atomic model: improved agreement with experiment  

International Nuclear Information System (INIS)

Two relativistic, independent-particle atomic models are employed to calculate two sets of internal conversion coefficients, viz., the Hartree-Fock model and the Hartree-Fock-Slater model with the weighting factor C=1 in the exchange term. Eight transitions with energies of 50 to 412 keV, multipolarities, M1,E2,E3,M4, in nuclei with Z=47 to 80 are considered. The former set of the conversion coefficients is found to agree substantially better with 68 experimental data than the latter. (author)

189

Scaling laws, force balances and dynamo generation mechanisms in numerical dynamo models: influence of boundary conditions  

Science.gov (United States)

We investigate the influence of different thermal and velocity boundary conditions on numerical geodynamo models. We concentrate on the implications for magnetic field morphology, heat transport scaling laws, force balances and generation mechanisms. The field morphology most strongly depends on the local Rossby number, but there is some variation in the dipolarity of the field with boundary condition. Scaling laws also depend on the boundary conditions, but a diffusivity-free scaling is a good first order approximation for all our dipolar models. Our multipolar models, however, obey different scaling laws from dipolar models implying a different force balance in these models. We find that our dipolar models have a stronger degree of Lorentz-Coriolis balance compared to our multipolar models which have a stronger degree of Lorentz-inertial balance.The models with a stronger Lorentz-Coriolis dominance can be generated by either ??, ?2? or ?2 mechanisms whereas the models with a stronger Lorentz-inertial balance are all ?2 dynamos. These results imply that some caution is necessary when extrapolating results from dynamo models to Earth-like parameters since the choice of boundary conditions can have important effects.

Dharmaraj, G.; Stanley, S.; Qu, A. C.

2014-10-01

190

Some New Applications of Weyl's Multipolarization Operators  

CERN Document Server

In Weyl's "The Classical Groups", he introduces some some remarkable differential operators, which he calls "quasi-compositions" of the polarization operators Dij. In the present paper, an equivalent combinatorial formulation is obtained for these operators, and is then used to obtain explicit formulas for the differentials in certain complexes (constucted by Zelevinsky, and further studied by Verma, Akin et al.) which furnish higher syzygies for the Pluecker equations, and also for the defining relations for Weyl modules.

Towber, J

2001-01-01

191

Modelling Sporangiospore-yeast transformation of Dimorphomyces strain.  

Science.gov (United States)

Two types of buffered media, strictly defined-Ammonium sulphate-basal salts and complex Peptone-basal salts, were used for the cultivation of Dimorphomyces pleomorphis, one of two dimorphic fungi isolated from fermenting juice of soursop fruit, Annona muricata L. The growth count was taken every twenty-four hours. Transient morphologies were observed to change from sporangiospores through enlarged globose cells, to granular particles and eventually, polar budding yeast cells in the strictly defined medium at 15 degrees, 20 degrees, or 37 degrees C, but the complex medium casually terminally induced polar budding yeast cells and multipolar budding yeast like cells in between the growth phases, at 15 degrees and 20 degrees C, while mainly multipolar budding yeastlike morphology was observed at elevated temperature. There was obvious influence of nutritional factor or morphological expression (p < 0.01). After analysis of variance, the growth data could not fit into predictive quadratic polynomial model because the organism's response curves were incongruent with basic assumptions of the model. Furthermore, a stepwise regression analysis gave very low coefficients of determination, r2, for the interactive combinations. They were therefore, considered unfit for the data. Construction of the pII-profiles led to inference being drawn from the chemiosmotic theory, polyelectrolyte theory to account for the behaviour in the buffered multiionic media. It was also thought that inherent cellular mitotic division and glycolytic activity led to a prelogarithmic growth response. PMID:9676041

Omoifo, C O

1996-01-01

192

A sensor-weighted overlapping-sphere head model and exhaustive head model comparison for MEG  

International Nuclear Information System (INIS)

The spherical head model has been used in magnetoencephalography (MEG) as a simple forward model for calculating the external magnetic fields resulting from neural activity. For more realistic head shapes, the boundary element method (BEM) or similar numerical methods are used, but at greatly increased computational cost. We introduce a sensor-weighted overlapping-sphere (OS) head model for rapid calculation of more realistic head shapes. The volume currents associated with primary neural activity are used to fit spherical head models for each individual MEG sensor such that the head is more realistically modelled as a set of overlapping spheres, rather than a single sphere. To assist in the evaluation of this OS model with BEM and other head models, we also introduce a novel comparison technique that is based on a generalized eigenvalue decomposition and accounts for the presence of noise in the MEG data. With this technique we can examine the worst possible errors for thousands of dipole locations in a realistic brain volume. We test the traditional single-sphere model, three-shell and single-shell BEM, and the new OS model. The results show that the OS model has accuracy similar to the BEM but is orders of magnitude faster to compute. (author)

193

Dynamical modeling and the interactions with the ISM  

CERN Document Server

This paper is a review of some of the recent modeling efforts to improve our understanding of structure formation and evolution of planetary nebulae including their interaction with the interstellar medium. New propositions have been made for the formation mechanism of multi-polar PNe and PPNe. These mechanisms are based on the central engine with interacting binary stars or hole producing instabilities in expanding shock waves leading to illumination effects from the central star that change the appearance of the nebula. Furthermore, there has been a lot of progress in the observation and 3D modeling of the kinematics, which is key to the understanding of the dynamics. Extensive observational catalogs are coming online for the kinematics, as well as some very detailed proper motion measurements have been made. New techniques for morpho--kinematic 3D modeling help to make the interpretation of kinematic data more reliable and detailed. In addition to individual pointed observations, new surveys have lead to t...

Steffen, Wolfgang

2011-01-01

194

Probabilistic forward model for electroencephalography source analysis  

Energy Technology Data Exchange (ETDEWEB)

Source localization by electroencephalography (EEG) requires an accurate model of head geometry and tissue conductivity. The estimation of source time courses from EEG or from EEG in conjunction with magnetoencephalography (MEG) requires a forward model consistent with true activity for the best outcome. Although MRI provides an excellent description of soft tissue anatomy, a high resolution model of the skull (the dominant resistive component of the head) requires CT, which is not justified for routine physiological studies. Although a number of techniques have been employed to estimate tissue conductivity, no present techniques provide the noninvasive 3D tomographic mapping of conductivity that would be desirable. We introduce a formalism for probabilistic forward modeling that allows the propagation of uncertainties in model parameters into possible errors in source localization. We consider uncertainties in the conductivity profile of the skull, but the approach is general and can be extended to other kinds of uncertainties in the forward model. We and others have previously suggested the possibility of extracting conductivity of the skull from measured electroencephalography data by simultaneously optimizing over dipole parameters and the conductivity values required by the forward model. Using Cramer-Rao bounds, we demonstrate that this approach does not improve localization results nor does it produce reliable conductivity estimates. We conclude that the conductivity of the skull has to be either accurately measured by an independent technique, or that the uncertainties in the conductivity values should be reflected in uncertainty in the source location estimates.

Plis, Sergey M [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); George, John S [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Jun, Sung C [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Ranken, Doug M [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Volegov, Petr L [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Schmidt, David M [MS-D454, Applied Modern Physics Group, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2007-09-07

195

Probabilistic forward model for electroencephalography source analysis  

International Nuclear Information System (INIS)

Source localization by electroencephalography (EEG) requires an accurate model of head geometry and tissue conductivity. The estimation of source time courses from EEG or from EEG in conjunction with magnetoencephalography (MEG) requires a forward model consistent with true activity for the best outcome. Although MRI provides an excellent description of soft tissue anatomy, a high resolution model of the skull (the dominant resistive component of the head) requires CT, which is not justified for routine physiological studies. Although a number of techniques have been employed to estimate tissue conductivity, no present techniques provide the noninvasive 3D tomographic mapping of conductivity that would be desirable. We introduce a formalism for probabilistic forward modeling that allows the propagation of uncertainties in model parameters into possible errors in source localization. We consider uncertainties in the conductivity profile of the skull, but the approach is general and can be extended to other kinds of uncertainties in the forward model. We and others have previously suggested the possibility of extracting conductivity of the skull from measured electroencephalography data by simultaneously optimizing over dipole parameters and the conductivity values required by the forward model. Using Cramer-Rao bounds, we demonstrate that this approach does not improve localization results nor does it produce reliable conductivity estimates. We conclude that the conducity estimates. We conclude that the conductivity of the skull has to be either accurately measured by an independent technique, or that the uncertainties in the conductivity values should be reflected in uncertainty in the source location estimates

196

Detailed magnetic model simulations of the H- injection chicane magnets for the CERN PS Booster Upgrade, including eddy currents and influence on beam dynamics  

CERN Document Server

The CERN PS Booster will be upgraded with an H- injection system. The chicanemagnets for the injection bump ramp-down in 5 ms and generate eddy currents in the inconel vacuum chamber which perturb the homogeneity of the magnetic field. The multipolar field components are extracted from 3D OPERA simulations and are included in the lattice model. The -beating correction is computed all along the ramp and complete tracking simulations including space-charge are performed to evaluate the impact of these perturbations and correction on beam dynamics.

Benedetto, E; Borburgh, J; Carli, C; Martini, M; Forte, V

2014-01-01

197

Giant resonance of electrical multipole from droplet model  

International Nuclear Information System (INIS)

The formalism of the electrical multipole resonance developed from the Droplet nuclear model is presented. It combines the approaches of Goldhaber-Teller (GT) and Steinwedel-Jensen (SJ) and it shows the relative contribution of Coulomb, superficial and neutron excess energies. It also discusses the calculation of half-width. The model evaluates correctly the resonance energies as a function of nuclear mass and allows, through the Mixture Index, the prediction of the complementary participation of modes SJ and GT in the giant nuclear resonance. Values of the mixture index, for each multipolarity, reproduce well the form factors obtained from experiments of charged particle inelastic scattering. The formalism presented for the calculation of the half-width gives a macroscopic description of the friction mechanism. The establishment of the macroscopic structure of the Dissipation Function is used as a reference in the comparison of microscopic calculations. (Author)

198

Nonparametric Statistical Thresholding for Sparse Magnetoencephalography Source Reconstructions  

Directory of Open Access Journals (Sweden)

Full Text Available Uncovering brain activity from MEG data requires solving an ill-posed inverse problem, greatly confounded by noise, interference, and correlated sources. Sparse reconstruction algorithms, such as Champagne, show great promise in that they provide focal brain activations robust to these confounds. In this paper, we address the technical considerations of statistically thresholding brain images obtained from sparse reconstruction algorithms. The source power distribution of sparse algorithms makes this class of algorithms ill-suited to "conventional" techniques. We propose two nonparametric resampling methods hypothesized to be compatible with sparse algorithms. The first adapts the maximal statistic procedure to sparse reconstruction results and the second departs from maximal statistics, putting forth a less stringent procedure that protects against spurious peaks. Three MEG data sets are utilized to demonstrate the efficacy of the proposed methods. Two sparse algorithms, Champagne and generalized minimum current estimation (G-MCE, are compared to two non-sparse algorithms, a variant of minimum-norm estimation, sLORETA, and an adaptive beamformer. The results, in general, demonstrate that the already sparse images obtained from Champagne and G-MCE are further thresholded by both proposed statistical thresholding procedures. While non-sparse algorithms are thresholded by the maximal statistic procedure, they are not made sparse. The work presented here is one of the first attempts to address the problem of statistically thresholding sparse reconstructions, and aims to improve upon this already advantageous and powerful class of algorithm.

JuliaParsonsOwen

2012-12-01

199

Thalamocortical dysrhythmia: A neurological and neuropsychiatric syndrome characterized by magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Spontaneous magnetoencephalographic activity was recorded in awake, healthy human controls and in patients suffering from neurogenic pain, tinnitus, Parkinson's disease, or depression. Compared with controls, patients showed increased low-frequency ? rhythmicity, in conjunction with a widespread and marked increase of coherence among high- and low-frequency oscillations. These data indicate the presence of a thalamocortical dysrhythmia, which we propose is responsible for all the above menti...

Llina?s, Rodolfo R.; Ribary, Urs; Jeanmonod, Daniel; Kronberg, Eugene; Mitra, Partha P.

1999-01-01

200

Adaptive Cluster Analysis Approach for Functional Localization Using Magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper we propose an agglomerative hierarchical clustering Ward’s algorithm in tandem with the Affinity Propagation algorithm to reliably localize active brain regions from magnetorencephalography (MEG brain signals. Reliable localization of brain areas with MEG has been difficult due to variations in signal strength, and the spatial extend of the reconstructed activity. The proposed approach to resolve this difficulty is based on adaptive clustering on reconstructed beamformer images to find locations that are consistently active across different participants and experimental conditions with high spatial resolution. Using data from a human reaching task, we show that the method allows more accurate and reliable localization from MEG data alone without using functional magnetic resonance imaging (fMRI or any other imaging techniques.

HoomanAlikhanian

2013-05-01

 
 
 
 
201

Magnetoencephalography of frontotemporal dementia: spatiotemporally localized changes during semantic decisions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Behavioural variant frontotemporal dementia is a neurodegenerative disorder with dysfunction and atrophy of the frontal lobes leading to changes in personality, behaviour, empathy, social conduct and insight, with relative preservation of language and memory. As novel treatments begin to emerge, biomarkers of frontotemporal dementia will become increasingly important, including functionally relevant neuroimaging indices of the neurophysiological basis of cognition. We used magnetoencephalogra...

Hughes, Laura E.; Nestor, Peter J.; Hodges, John R.; Rowe, James B.

2011-01-01

202

Investigating neurophysiological correlates of metacontrast masking with magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available Early components of visual evoked potentials (VEP in EEG seem to be unaffected by target visibility in visual masking studies. Bridgeman's reanalysis of Jeffreys and Musselwhite's (1986 data suggests that a later visual component in the VEP, around 250 ms reflects the perceptual effect of masking. We challenge this view on the ground that temporal interactions between targets and masks unrelated to stimulus visibility could account for Bridgeman's observation of a U-shaped time course in VEP amplitudes for this later component. In an MEG experiment of metacontrast masking with variable stimulus onset asynchrony, we introduce a proper control, a pseudo mask. In contrast to an effective mask, the pseudomask should produce neither behavioral masking nor amplitude modulations of late VEPs. Our results show that effective masks produced a strong U-shaped perceptual effect of target visibility while performance remained virtually perfect when a pseudomask was used. The visual components around 250 ms after target onset did not show a distinction between mask and pseudomask conditions. The results indicate that these visual evoked potentials do not reveal neurophysiological correlates of stimulus visibility but rather reflect dynamic interactions between superimposed potentials elicited by stimuli in close temporal proximity. However, we observed a postperceptual component around 340 ms after target onset, located over temporal-parietal cortex, which shows a clear effect of visibility. Based on P300 ERP literature, this finding could indicate that working memory related processes contribute to metacontrast masking.

Jens Schwarzbach

2006-01-01

203

Distorted cortical networks in dislexia: findings using Magnetoencephalography (MEG  

Directory of Open Access Journals (Sweden)

Full Text Available In dyslexic children a functional deficit in the brain circuitry supporting some of the cognitive operations taking place while they learn how the printed words maps onto spoken language is suspected. Until recently, however, no information existed regarding the functional status of this circuit during the early stages of reading acquisition. In the context of three studies we sought to address key issues in the pathophysiology of this condition using Magnetoencephalograhy (MEG at the University of Texas-Houston. The first study, including 30 kindergarten children at risk for developing reading problems and 15 not-at-risk controls, ascertained that the aberrant neural circuit that underlies reading problems appears to be present in the initial stages of reading acquisition. A subset of these children were retested a year later using identical procedures in a second study. Children in the at-risk group showed the most prominent changes in brain activation profiles and successfully predicted individual differences in the growth of reading skill measures. The results of a third study showed clearly that the aberrant activation profile can be normalized following intensive behavioral instruction. These findings are consistent with the view that dyslexia represents a functional deficit in the neural network that mediates the conversion of print to sound, which is amenable to change given adequate instruction.

Eduardo M. Catillo

2008-04-01

204

Electro-magneto-encephalography for the three-shell model: minimal L2-norm in spherical geometry  

Science.gov (United States)

The problem of determining a continuously distributed neuronal current inside the brain within the framework of the three-shell model was analysed in Fokas (2009 J. R. Soc. Interface 6 479-88), where it was shown that the simultaneous use of electro-encephalography and magneto-encephalography yields information about two of the three scalar functions specifying the interior current. In particular, for the spherical and ellipsoidal geometries, it is possible to determine the angular parts of these two functions, as well as to obtain certain explicit constraints satisfied by their radial parts. The complete determination of the radial parts of these two functions, as well as the determination of the third unknown function, requires some a priori assumption about the current. One such possible assumption is that the current minimizes the L2-norm. It is shown here that in the case of spherical geometry this assumption yields a unique and explicit formula for the current.

Fokas, A. S.; Kurylev, Y.

2012-03-01

205

Electro-magneto-encephalography for the three-shell model: numerical implementation via splines for distributed current in spherical geometry  

International Nuclear Information System (INIS)

The basic inverse problems for the functional imaging techniques of electroencephalography (EEG) and magnetoencephalography (MEG) consist in estimating the neuronal current in the brain from the measurement of the electric potential on the scalp and of the magnetic field outside the head. Here we present a rigorous derivation of the relevant formulae for a three-shell spherical model in the case of independent as well as simultaneous MEG and EEG measurements. Furthermore, we introduce an explicit and stable technique for the numerical implementation of these formulae via splines. Numerical examples are presented using the locations and the normal unit vectors of the real 102 magnetometers and 70 electrodes of the Elekta Neuromag (R) system. These results may have useful implications for the interpretation of the reconstructions obtained via the existing approaches. (paper)

206

Electro-magneto-encephalography for the three-shell model: numerical implementation via splines for distributed current in spherical geometry  

Science.gov (United States)

The basic inverse problems for the functional imaging techniques of electroencephalography (EEG) and magnetoencephalography (MEG) consist in estimating the neuronal current in the brain from the measurement of the electric potential on the scalp and of the magnetic field outside the head. Here we present a rigorous derivation of the relevant formulae for a three-shell spherical model in the case of independent as well as simultaneous MEG and EEG measurements. Furthermore, we introduce an explicit and stable technique for the numerical implementation of these formulae via splines. Numerical examples are presented using the locations and the normal unit vectors of the real 102 magnetometers and 70 electrodes of the Elekta Neuromag (R) system. These results may have useful implications for the interpretation of the reconstructions obtained via the existing approaches.

Fokas, A. S.; Hauk, O.; Michel, V.

2012-03-01

207

Electro-magneto-encephalography for the three-shell model: minimal L2-norm in spherical geometry  

International Nuclear Information System (INIS)

The problem of determining a continuously distributed neuronal current inside the brain within the framework of the three-shell model was analysed in Fokas (2009 J. R. Soc. Interface 6 479–88), where it was shown that the simultaneous use of electro-encephalography and magneto-encephalography yields information about two of the three scalar functions specifying the interior current. In particular, for the spherical and ellipsoidal geometries, it is possible to determine the angular parts of these two functions, as well as to obtain certain explicit constraints satisfied by their radial parts. The complete determination of the radial parts of these two functions, as well as the determination of the third unknown function, requires some a priori assumption about the current. One such possible assumption is that the current minimizes the L2-norm. It is shown here that in the case of spherical geometry this assumption yields a unique and explicit formula for the current. (paper)

208

Evaluation of multiple-sphere head models for MEG source localization  

Energy Technology Data Exchange (ETDEWEB)

Magnetoencephalography (MEG) source analysis has largely relied on spherical conductor models of the head to simplify forward calculations of the brain's magnetic field. Multiple- (or overlapping, local) sphere models, where an optimal sphere is selected for each sensor, are considered an improvement over single-sphere models and are computationally simpler than realistic models. However, there is limited information available regarding the different methods used to generate these models and their relative accuracy. We describe a variety of single- and multiple-sphere fitting approaches, including a novel method that attempts to minimize the field error. An accurate boundary element method simulation was used to evaluate the relative field measurement error (12% on average) and dipole fit localization bias (3.5 mm) of each model over the entire brain. All spherical models can contribute in the order of 1 cm to the localization bias in regions of the head that depart significantly from a sphere (inferior frontal and temporal). These spherical approximation errors can give rise to larger localization differences when all modeling effects are taken into account and with more complex source configurations or other inverse techniques, as shown with a beamformer example. Results differed noticeably depending on the source location, making it difficult to recommend a fitting method that performs best in general. Given these limitations, it may be advisable to expand the use of realistic head models.

Lalancette, M; Cheyne, D [Department of Diagnostic Imaging, The Hospital for Sick Children, 555 University Ave., Toronto, Ontario M5G 1X8 (Canada); Quraan, M, E-mail: marc.lalancette@sickkids.ca, E-mail: douglas.cheyne@utoronto.ca [Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, Toronto, Ontario M5T 2S8 (Canada)

2011-09-07

209

Evaluation of multiple-sphere head models for MEG source localization  

International Nuclear Information System (INIS)

Magnetoencephalography (MEG) source analysis has largely relied on spherical conductor models of the head to simplify forward calculations of the brain's magnetic field. Multiple- (or overlapping, local) sphere models, where an optimal sphere is selected for each sensor, are considered an improvement over single-sphere models and are computationally simpler than realistic models. However, there is limited information available regarding the different methods used to generate these models and their relative accuracy. We describe a variety of single- and multiple-sphere fitting approaches, including a novel method that attempts to minimize the field error. An accurate boundary element method simulation was used to evaluate the relative field measurement error (12% on average) and dipole fit localization bias (3.5 mm) of each model over the entire brain. All spherical models can contribute in the order of 1 cm to the localization bias in regions of the head that depart significantly from a sphere (inferior frontal and temporal). These spherical approximation errors can give rise to larger localization differences when all modeling effects are taken into account and with more complex source configurations or other inverse techniques, as shown with a beamformer example. Results differed noticeably depending on the source location, making it difficult to recommend a fitting method that performs best in general. Given these limitations, it may be advisable to expand the use ns, it may be advisable to expand the use of realistic head models.

210

Sustaining multilateral trade cooperation in a multipolar world economy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The deadlock in the WTO Doha Round has been accompanied by an increased focus on the negotiation of preferential trade agreements, including so-called ‘mega-regionals’. This paper discusses possible implications for—and possible responses by—excluded countries that have little prospects of participating in most of the mega-regionals. A number of complementary avenues are identified through which such countries might attenuate the potential downsides of preferential trade liberalizatio...

Hoekman, Bernard M.

2013-01-01

211

Controversies over the US Hegemony in the Multipolar World  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Since the end of the Cold War, American hegemony continues to characterize the international system. This hegemony has met with a considerably higher acceptance by other states and other actors of the international system than a world of competing superpowers and political blocs. The main argument developed in this paper is that American primacy may not last forever, but as there is no effective global security mechanism for coping with the growing threat of extremist religious and political ...

Gwiazda, Adam

2010-01-01

212

Multipolar second-harmonic generation from films of chalcogenide glasses  

Science.gov (United States)

Chalcogenide glasses are amorphous semiconductors with a number of interesting properties required for photonic devices. Particularly, their optical properties can be tuned through the change of the glass composition. We investigate second-order nonlinear optical properties of chalcogenide glass (Ge27Se64Sb9) thin films fabricated by thermal evaporation. The strong second-harmonic generation observed for the samples investigated is analyzed as a function of incident polarization. Furthermore, the role of multipole effects in second-harmonic generation is also studied by using two beams at the fundamental frequency. Our results suggest that the higher-multipole effects are present and contribute significantly to the second-harmonic response of chalcogenide the samples.

Slablab, A.; Koskinen, K.; Czaplicki, R.; Karunakaran, N. T.; Sebastian, I.; Chandran, C. Pradeep; Kailasnath, M.; Radhakrishnan, P.; Kauranen, M.

2014-05-01

213

The filamentary Multi-Polar Planetary Nebula NGC 5189  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present a set of optical and infrared images combined with long-slit, medium and high dispersion spectra of the southern planetary nebula (PN) NGC 5189. The complex morphology of this PN is puzzling and has not been studied in detail so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearanc...

Sabin, L.; Zquez, R. V. U. E.; Pez, J. A. L. U. F.; Edaz, Ma T. Garc U. Eda-d U.; Ramos-larios, G.

2012-01-01

214

The filamentary multi-polar planetary nebula NGC 5189  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish Presentamos un conjunto de imágenes ópticas e infrarrojas combinadas con espectros de rendija larga de mediana y alta dispersión de la Nebulosa Planetaria (NP) del sur NGC 5189. La compleja morfología de esta NP es desconcertante y no había sido estudiada en detalle hasta ahora. Nuestra investigació [...] n revela la presencia de un toroide denso y frío, en el infrarrojo, el cual probablemente generó uno de los dos flujos bipolares vistos en el óptico y podría, mediante un proceso de interacción, ser también responsable de la apariencia retorcida del toroide óptico. Los espectros de alta resolución del MES-AAT muestran claramente la presencia de nudos y estructuras filamentosas, así como tres burbujas en expansión. Nuestros hallazgos sugieren que NGC 5189 es una NP cuadrupolar con varios conjuntos de condensaciones simétricas en la cual la interacción de flujos determinó su compleja morfología. Abstract in english We present a set of optical and infrared images combined with long-slit, medium and high dispersion spectra of the southern planetary nebula (PN) NGC 5189. The complex morphology of this PN is puzzling and has not been studied in detailed so far. Our investigation reveals the presence of a new dense [...] and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process. The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC 5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined its complex morphology.

L., Sabin; R., Vázquez; J. A., López; Ma. T., García-Díaz; G., Ramos-Larios.

2012-10-01

215

THE FILAMENTARY MULTI-POLAR PLANETARY NEBULA NGC5189  

Directory of Open Access Journals (Sweden)

Full Text Available We present a set of optical and infrared images combined with long-slit, medium and high dispersion spectra of the southern planetary nebula (PN NGC5189. The complex morphology of this PN is puzzling and has not been studied in detailed so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process. The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined its complex morphology.

L. Sabin

2012-01-01

216

China's Soft Diplomacy in an Emerging Multi-polar World  

DEFF Research Database (Denmark)

Keynote presentation for the conference"The Growing Prominence of China on the World Stage: Exploring the Political, Economic, and Cultural Relations of China and Global Stakeholders" International Conference, Berlin, September 15th - 18th, 2011 - Held Parallel to the "Berlin - Asia Pacific Weeks Conference 2011

Schmidt, Johannes Dragsbæk

217

Bipolar and multipolar Jets in protoplanetary and planetary nebulae  

Directory of Open Access Journals (Sweden)

Full Text Available Uno de los retos m as emocionantes con que actualmente se enfrentan las teor as de evoluci on posterior a la secuencia principal, es entender c omo estrellas AGB (ingl. "Asymptotic Giant Branch" y sus envolturas cicunestelares esf ericas (siglas en ingl es: CSEs se transforman en nebulosas planetarias (NPs con su asombrosa variedad de morfolog as asf ericas. El modelo m as exitoso para dar forma a los NPs|el modelo generalizado de vientos estelares interactuantes, en el cual un viento esf erico de alta velocidad (> 1000 km s...

Sahai Raghvendra

2002-01-01

218

Probing Electronic Correlations in Actinide Materials Using Multipolar Transitions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report nonresonant inelastic x-ray scattering from the semi-core 5d levels of several actinide compounds. Dipole-forbidden, high-multipole features form a rich bound-state spectrum dependent on valence electron configuration and spin-orbit and Coulomb interactions. Cross-material comparisons, together with the anomalously high Coulomb screening required for agreement between atomic multiplet theory and experiment, demonstrate sensitivity to the neighboring electronic envi...

Bradley, J. A.; Gupta, S. Sen; Seidler, G. T.; Moore, K. T.; Haverkort, M. W.; Sawatzky, G. A.; Conradson, S. D.; Clark, D. L.; Kozimor, S. A.; Boland, K. S.

2010-01-01

219

Probing electronic correlations in actinide materials using multipolar transitions  

Science.gov (United States)

We report nonresonant inelastic x-ray scattering from the semicore 5d levels of several actinide compounds. Dipole-forbidden, high-multipole features form a rich bound-state spectrum dependent on valence electron configuration and spin-orbit and Coulomb interactions. Cross-material comparisons, together with the anomalously high Coulomb screening required for agreement between atomic-multiplet theory and experiment, demonstrate sensitivity to the neighboring electronic environment, such as is needed to address longstanding questions of electronic localization and bonding in 5f compounds.

Bradley, J. A.; Sen Gupta, S.; Seidler, G. T.; Moore, K. T.; Haverkort, M. W.; Sawatzky, G. A.; Conradson, S. D.; Clark, D. L.; Kozimor, S. A.; Boland, K. S.

2010-05-01

220

The filamentary Multi-Polar Planetary Nebula NGC 5189  

CERN Document Server

We present a set of optical and infrared images combined with long-slit, medium and high dispersion spectra of the southern planetary nebula (PN) NGC 5189. The complex morphology of this PN is puzzling and has not been studied in detail so far. Our investigation reveals the presence of a new dense and cold infrared torus (alongside the optical one) which probably generated one of the two optically seen bipolar outflows and which might be responsible for the twisted appearance of the optical torus via an interaction process. The high-resolution MES-AAT spectra clearly show the presence of filamentary and knotty structures as well as three expanding bubbles. Our findings therefore suggest that NGC 5189 is a quadrupolar nebula with multiple sets of symmetrical condensations in which the interaction of outflows has determined the complex morphology.

Sabin, L; López, J A; García-Díaz, Ma T; Ramos-Larios, G

2012-01-01

 
 
 
 
221

Using Structural Equation Modeling to Assess Functional Connectivity in the Brain: Power and Sample Size Considerations.  

Science.gov (United States)

The present study assessed the impact of sample size on the power and fit of structural equation modeling applied to functional brain connectivity hypotheses. The data consisted of time-constrained minimum norm estimates of regional brain activity during performance of a reading task obtained with magnetoencephalography. Power analysis was first conducted for an autoregressive model with 5 latent variables (brain regions), each defined by 3 indicators (successive activity time bins). A series of simulations were then run by generating data from an existing pool of 51 typical readers (aged 7.5-12.5 years). Sample sizes ranged between 20 and 1,000 participants and for each sample size 1,000 replications were run. Results were evaluated using chi-square Type I errors, model convergence, mean RMSEA (root mean square error of approximation) values, confidence intervals of the RMSEA, structural path stability, and D-Fit index values. Results suggested that 70 to 80 participants were adequate to model relationships reflecting close to not so close fit as per MacCallum et al.'s recommendations. Sample sizes of 50 participants were associated with satisfactory fit. It is concluded that structural equation modeling is a viable methodology to model complex regional interdependencies in brain activation in pediatric populations. PMID:25435589

Sideridis, Georgios; Simos, Panagiotis; Papanicolaou, Andrew; Fletcher, Jack

2014-10-01

222

Mental imagery of speech and movement implicates the dynamics of internal forward models  

Directory of Open Access Journals (Sweden)

Full Text Available The classical concept of efference copies in the context of internal forward models has stimulated productive research in cognitive science and neuroscience. There are compelling reasons to argue for such a mechanism, but finding direct evidence in the human brain remains difficult. Here we investigate the dynamics of internal forward models from an unconventional angle: mental imagery, assessed while recording high temporal resolution neuronal activity using magnetoencephalography (MEG. We compare two overt and covert tasks; our covert, mental imagery tasks are unconfounded by overt input/output demands – but in turn necessitate the development of appropriate multi-dimensional topographic analyses. Finger tapping (studies 1-2 and speech experiments (studies 3-5 provide temporally constrained results that implicate the estimation of an efference copy. We suggest that one internal forward model over parietal cortex subserves the kinesthetic feeling in motor imagery. Secondly, observed auditory neural activity ~170 ms after motor estimation in speech experiments (studies 3-5 demonstrates the anticipated auditory consequences of planned motor commands in a second internal forward model in imagery of speech production. Our results provide neurophysiological evidence from the human brain in favor of internal forward models deploying efference copies in somatosensory and auditory cortex, in finger tapping and speech production tasks, respectively, and also suggest the dynamics and sequential updating structure of internal forward models.

DavidPoeppel

2010-10-01

223

A variational Bayes spatiotemporal model for electromagnetic brain mapping.  

Science.gov (United States)

In this article, we present a new variational Bayes approach for solving the neuroelectromagnetic inverse problem arising in studies involving electroencephalography (EEG) and magnetoencephalography (MEG). This high-dimensional spatiotemporal estimation problem involves the recovery of time-varying neural activity at a large number of locations within the brain, from electromagnetic signals recorded at a relatively small number of external locations on or near the scalp. Framing this problem within the context of spatial variable selection for an underdetermined functional linear model, we propose a spatial mixture formulation where the profile of electrical activity within the brain is represented through location-specific spike-and-slab priors based on a spatial logistic specification. The prior specification accommodates spatial clustering in brain activation, while also allowing for the inclusion of auxiliary information derived from alternative imaging modalities, such as functional magnetic resonance imaging (fMRI). We develop a variational Bayes approach for computing estimates of neural source activity, and incorporate a nonparametric bootstrap for interval estimation. The proposed methodology is compared with several alternative approaches through simulation studies, and is applied to the analysis of a multimodal neuroimaging study examining the neural response to face perception using EEG, MEG, and fMRI. PMID:24354514

Nathoo, F S; Babul, A; Moiseev, A; Virji-Babul, N; Beg, M F

2014-03-01

224

Modelling  

CERN Document Server

Modeling of technical machines became a standard technique since computer became powerful enough to handle the amount of data relevant to the specific system. Simulation of an existing physical device requires the knowledge of all relevant quantities. Electric fields given by the surrounding boundary as well as magnetic fields caused by coils or permanent magnets have to be known. Internal sources for both fields are sometimes taken into account, such as space charge forces or the internal magnetic field of a moving bunch of charged particles. Used solver routines are briefly described and some bench-marking is shown to estimate necessary computing times for different problems. Different types of charged particle sources will be shown together with a suitable model to describe the physical model. Electron guns are covered as well as different ion sources (volume ion sources, laser ion sources, Penning ion sources, electron resonance ion sources, and H$^-$-sources) together with some remarks on beam transport.

Spädtke, P

2013-01-01

225

Modelling  

International Nuclear Information System (INIS)

This last volume in the series of textbooks on environmental isotopes in the hydrological cycle provides an overview of the basic principles of existing conceptual formulations of modelling approaches. While some of the concepts provided in Chapter 2 and Chapter 3 are of general validity for quantitative interpretation of isotope data; the modelling methodologies commonly employed for incorporating isotope data into evaluations specifically related to groundwater systems are given in this volume together with some illustrative examples. Development of conceptual models for quantitative interpretations of isotope data in hydrogeology and the assessment of their limitations and field verification has been given priority in the research and development efforts of the IAEA during the last decade. Several Co-ordinated Research Projects on this specific topic were implemented and results published by the IAEA. Based on these efforts and contributions made by a number of scientists involved in this specific field, the IAEA has published two Technical Documents entitled ''Mathematical models and their applications to isotope studies in groundwater studies -- IAEA TECDOC-777, 1994'' and ''Manual on Mathematical models in isotope hydrogeology -- IAEA TECDOC-910, 1996''. Results of a recently completed Co-ordinated Research Project by the IAEA entitled ''Use of isotopes for analysis of flow and transport dynamics in groundwater systems'' will also soon be published by the IAEA. will also soon be published by the IAEA. This is the reason why the IAEA was involved in the co-ordination required for preparation of this volume; the material presented is a condensed overview prepared by some of the scientists that were involved in the above cited IAEA activities. This volume VI providing such an overview was included into the series to make this series self-sufficient in its coverage of the field of Isotope Hydrology. A special chapter on the methodologies and concepts related to geochemical modelling in groundwater systems would have been most desirable to include. The reader is referred to IAEA-TECDOC-910 and other relevant publications for guidance in this specific field

226

Differences Between MEG and High-Density EEG Source Localizations Using a Distributed Source Model in Comparison to fMRI.  

Science.gov (United States)

Electroencephalography (EEG) and magnetoencephalography (MEG) are widely used to localize brain activity and their spatial resolutions have been compared in several publications. While most clinical studies demonstrated higher accuracy of MEG source localization, simulation studies suggested a more accurate EEG than MEG localization for the same number of channels. However, studies comparing real MEG and EEG data with equivalent number of channels are scarce. We investigated 14 right-handed healthy subjects performing a motor task in MEG, high-density-(hd-) EEG and fMRI as well as a somatosensory task in MEG and hd-EEG and compared source analysis results of the evoked brain activity between modalities with different head models. Using individual head models, hd-EEG localized significantly closer to the anatomical reference point obtained by fMRI than MEG. Source analysis results were least accurate for hd-EEG based on a standard head model. Further, hd-EEG and MEG localized more medially than fMRI. Localization accuracy of electric source imaging is dependent on the head model used with more accurate results obtained with individual head models. If this is taken into account, EEG localization can be more accurate than MEG localization for the same number of channels. PMID:25296614

Klamer, Silke; Elshahabi, Adham; Lerche, Holger; Braun, Christoph; Erb, Michael; Scheffler, Klaus; Focke, Niels K

2015-01-01

227

A Model for the Escape of Solar-Flare Accelerated Particles  

CERN Document Server

Impulsive solar energetic particles (SEP) bursts are frequently observed in association with so-called eruptive flares consisting of a coronal mass ejection (CME) and a flare. These highly prompt SEPs are believed to be accelerated by the flare rather than by a CME shock, but in the standard flare model the accelerated particles should remain trapped in the corona or in the ejected plas- moid. In this case, however, the particles would reach the Earth only after a delay of many hours to a few days. We present a new model that can account for the prompt injection of energetic particles onto open interplanetary magnetic flux tubes. The basic idea underlying the model is that magnetic reconnection between the ejection and external open field allows for the release of the ener- getic particles. We demonstrate the model using 2.5D MHD simulations of a CME/flare event. The model system consists of a multipolar field with a coro- nal null point and with photospheric shear imposed at a polarity inversion line, as in ...

Masson, Sophie; DeVore, C Rick

2013-01-01

228

Generalized model of interacting bosons for collective states  

International Nuclear Information System (INIS)

With the purpose of overcoming the difficulties of theoretical description of collective excitations of heavy nuclei it is suggested to expand the ineracting boson model including in it along with monopole S and quadrupole d-bosons dipole p-bosons. The SU(3)-symmetric hamiltonian and T(E2)-boson operator are considered. The results of calculations of energy spectra and probabilities of E2-transitions B(E2) are compared with experimental values for the most studied 232Th and 236U actinide nuclei. The calculated spectra reproduce the structures of levels observed in the experiment. The agreement of experimental and theoretical data for B(E2) in main band for 236U is slightly better than for 232Th. The conclusion is drawn that inclusion of dipole bosonic degrees of freedom along with bosons of other multipolarities (monopole, quadrupole, octupole, if there is octupole static deformation) is undoubtedly necessary for describing the properties of collective excitations of low energy in heavy nuclei

229

The structure of 193Au within the Interacting Boson Fermion Model  

Science.gov (United States)

A ?? angular correlation experiment investigating the nucleus 193Au is presented. In this work the level scheme of 193Au is extended by new level information on spins, multipolarities and newly observed states. The new results are compared with theoretical predictions from a general Interacting Boson Fermion Model (IBFM) calculation for the positive-parity states. The experimental data is in good agreement with an IBFM calculation using all proton orbitals between the shell closures at Z=50 and Z=126. As a dominant contribution of the d orbital to the wave function of the lowest excited states is observed, a truncated model of the IBFM using a Bose-Fermi symmetry is applied to the describe 193Au. Using the parameters of a fit performed for 193Au, the level scheme of 192Pt, the supersymmetric partner of 193Au, is predicted but shows a too small boson seniority splitting. We obtained a common fit by including states observed in 192Pt. With the new parameters a supersymmetric description of both nuclei is established.

Thomas, T.; Bernards, C.; Régis, J.-M.; Albers, M.; Fransen, C.; Jolie, J.; Heinze, S.; Radeck, D.; Warr, N.; Zell, K.-O.

2014-02-01

230

The structure of {sup 193}Au within the Interacting Boson Fermion Model  

Energy Technology Data Exchange (ETDEWEB)

A ?? angular correlation experiment investigating the nucleus {sup 193}Au is presented. In this work the level scheme of {sup 193}Au is extended by new level information on spins, multipolarities and newly observed states. The new results are compared with theoretical predictions from a general Interacting Boson Fermion Model (IBFM) calculation for the positive-parity states. The experimental data is in good agreement with an IBFM calculation using all proton orbitals between the shell closures at Z=50 and Z=126. As a dominant contribution of the d{sub 3/2} orbital to the wave function of the lowest excited states is observed, a truncated model of the IBFM using a Bose–Fermi symmetry is applied to the describe {sup 193}Au. Using the parameters of a fit performed for {sup 193}Au, the level scheme of {sup 192}Pt, the supersymmetric partner of {sup 193}Au, is predicted but shows a too small boson seniority splitting. We obtained a common fit by including states observed in {sup 192}Pt. With the new parameters a supersymmetric description of both nuclei is established.

Thomas, T., E-mail: tim.thomas@ikp.uni-koeln.de [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany); WNSL, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Bernards, C. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany); WNSL, Yale University, P.O. Box 208120, New Haven, CT 06520-8120 (United States); Régis, J.-M.; Albers, M.; Fransen, C.; Jolie, J.; Heinze, S.; Radeck, D.; Warr, N.; Zell, K.-O. [Institute for Nuclear Physics, University of Cologne, Zülpicher Straße 77, D-50937 Köln (Germany)

2014-02-15

231

GNSS-Reflectometry: Forest canopies polarization scattering properties and modeling  

Science.gov (United States)

Nowadays, GNSS-Reflectometry (GNSS-R) can be a new promising remote sensing tool in the ocean, snow/ice and land surfaces, e.g., vegetation biomass monitoring. Although GNSS-R provides a potentially special L-band multi-angular and multi-polarization measurement, the theoretical vegetation scattering properties and mechanisms for GNSS-R are not understood clearly. In this paper, the GNSS-R vegetation polarization scattering properties are studied and modeled at different incidence angles (specular direction). The bistatic scattering model Bi-mimics is employed, which is the first-order radiative transfer equation. As a kind of forest stand, the Aspen’s crown layer is composed of entire leaves, and its parameters in Mimics handbook are used as model input. The specular circular polarizations (co-polarization RR and cross-polarization LR) are simulated. For cross-polarization, the received polarization is assumed as a linear (horizontal and vertical) polarizations and ±45° linear polarizations. Therefore, the HR VR, +45R and -45R polarizations are simulated here. Contributions from different scattering components at RR, LR and VR polarization are also presented. For co-polarization, it is large in the whole specular angles (10-80°). The scattering trends of the other cross polarization (HR, LR, +45R and -45R) are a little similar when compared to the RR and RV. Therefore, the RHCP and V polarizations are more favorable to collect the reflected signals. The trunk heights and crown depths do not affect the scattering trends of RR, RV and RL, while the trunk height has some effect on the scattering amplitude of different polarizations. The azimuth angle has more effects on RR, RL and RV scattering, especially in lower than 50°. The observation angles and polarization combinations are extremely important for GNSS-R remote sensing.

Wu, Xuerui; Jin, Shuanggen

2014-09-01

232

Direction of magnetoencephalography sources associated with feedback and feedforward contributions in a visual object recognition task.  

Science.gov (United States)

Identifying inter-area communication in terms of the hierarchical organization of functional brain areas is of considerable interest in human neuroimaging. Previous studies have suggested that the direction of magneto- and electroencephalography (MEG, EEG) source currents depend on the layer-specific input patterns into a cortical area. We examined the direction in MEG source currents in a visual object recognition experiment in which there were specific expectations of activation in the fusiform region being driven by either feedforward or feedback inputs. The source for the early non-specific visual evoked response, presumably corresponding to feedforward driven activity, pointed outward, i.e., away from the white matter. In contrast, the source for the later, object-recognition related signals, expected to be driven by feedback inputs, pointed inward, toward the white matter. Associating specific features of the MEG/EEG source waveforms to feedforward and feedback inputs could provide unique information about the activation patterns within hierarchically organized cortical areas. PMID:25445356

Ahlfors, Seppo P; Jones, Stephanie R; Ahveninen, Jyrki; Hämäläinen, Matti S; Belliveau, John W; Bar, Moshe

2015-01-12

233

Use of superconducting plates and shells to deflect magnetic noise fields: Application to MEG (magnetoencephalography)  

Energy Technology Data Exchange (ETDEWEB)

Insertion of a superconducting plate or shell in a magnetic field causes a surface current distribution which opposes the applied field. Resultant fields near plate edges are higher while those near centers are much lower than applied fields. We make use of these principles in MEG by placing suitably oriented gradiometers at points where noise fields are smallest. Signals from nearby brain wave sources are enhanced because the net signal is a combination of that from the sources and that from its image. The principles of noise deflection and source imaging are applied to new concepts of gradiometry. 4 refs., 2 figs.

Overton, W.C. Jr.; van Hulsteyn, D.B.; Flynn, E.R. (Los Alamos National Lab., NM (USA))

1989-01-01

234

The influence of low-grade glioma on resting state oscillatory brain activity: a magnetoencephalography study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose: In the present MEG-study, power spectral analysis of oscillatory brain activity was used to compare resting state brain activity in both low-grade glioma (LGG) patients and healthy controls. We hypothesized that LGG patients show local as well as diffuse slowing of resting state brain activity compared to healthy controls and that particularly global slowing correlates with neurocognitive dysfunction. Patient and methods Resting state MEG recordings were obtai...

Bosma, I.; Stam, C.; Douw, L.; Bartolomei, F.; Heimans, J.; Dijk, B.; Postma, T.; Klein, M.; Reijneveld, J.

2008-01-01

235

Aberrant Neuromagnetic Activation in the Motor Cortex in Children with Acute Migraine: A Magnetoencephalography Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Migraine attacks have been shown to interfere with normal function in the brain such as motor or sensory function. However, to date, there has been no clinical neurophysiology study focusing on the motor function in children with migraine during headache attacks. To investigate the motor function in children with migraine, twenty-six children with acute migraine, meeting International Classification of Headache Disorders criteria and age- and gender-matched healthy children were studied using...

Guo, Xinyao; Xiang, Jing; Wang, Yingying; O’brien, Hope; Kabbouche, Marielle; Horn, Paul; Powers, Scott W.; Hershey, Andrew D.

2012-01-01

236

Tinnitus perception and distress is related to abnormal spontaneous brain activity as measured by magnetoencephalography.  

Directory of Open Access Journals (Sweden)

Full Text Available BACKGROUND: The neurophysiological mechanisms underlying tinnitus perception are not well understood. Surprisingly, there have been no group studies comparing abnormalities in ongoing, spontaneous neuronal activity in individuals with and without tinnitus perception. METHODS AND FINDINGS: Here, we show that the spontaneous neuronal activity of a group of individuals with tinnitus (n = 17 is characterised by a marked reduction in alpha (8-12 Hz power together with an enhancement in delta (1.5-4 Hz as compared to a normal hearing control group (n = 16. This pattern was especially pronounced for temporal regions. Moreover, correlations with tinnitus-related distress revealed strong associations with this abnormal spontaneous activity pattern, particularly in right temporal and left frontal areas. Overall, effects were stronger for the alpha than for the delta frequency band. A data stream of 5 min, recorded with a whole-head neuromagnetometer under a resting condition, was sufficient to extract the marked differences. CONCLUSIONS: Despite some limitations, there are arguments that the regional pattern of abnormal spontaneous activity we found could reflect a tinnitus-related cortical network. This finding, which suggests that a neurofeedback approach could reduce the adverse effects of this disturbing condition, could have important implications for the treatment of tinnitus.

2005-06-01

237

Epistemics for Learning Disabilities: Contributions from Magnetoencephalography, a Functional Neuroimaging Tool  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The syndrome known as Learning Disabilities (LD) was described by S. Kirk in 1963. From that point on, institutions from the US, Canada and Spain have engaged in refining the concept and classification of LDs. The Complutense University in Spain, has proposed a descriptive and all-embracing definition, and has studied the different manifestations of LD, pursuing the description of biological markers and neurological features of LD’s main expressions: dyslexia, dyscalculia, dysorthographia, ...

VÍCTOR SANTIUSTE-BERMEJO; MARTA SANTIUSTE-DÍAZ

2008-01-01

238

Alpha-band hypersynchronization in progressive mild cognitive impairment: a magnetoencephalography study.  

Science.gov (United States)

People with mild cognitive impairment (MCI) show a high risk to develop Alzheimer's disease (AD; Petersen et al., 2001). Nonetheless, there is a lack of studies about how functional connectivity patterns may distinguish between progressive (pMCI) and stable (sMCI) MCI patients. To examine whether there were differences in functional connectivity between groups, MEG eyes-closed recordings from 30 sMCI and 19 pMCI subjects were compared. The average conversion time of pMCI was 1 year, so they were considered as fast converters. To this end, functional connectivity in different frequency bands was assessed with phase locking value in source space. Then the significant differences between both groups were correlated with neuropsychological scores and entorhinal, parahippocampal, and hippocampal volumes. Both groups did not differ in age, gender, or educational level. pMCI patients obtained lower scores in episodic and semantic memory and also in executive functioning. At the structural level, there were no differences in hippocampal volume, although some were found in left entorhinal volume between both groups. Additionally, pMCI patients exhibit a higher synchronization in the alpha band between the right anterior cingulate and temporo-occipital regions than sMCI subjects. This hypersynchronization was inversely correlated with cognitive performance, both hippocampal volumes, and left entorhinal volume. The increase in phase synchronization between the right anterior cingulate and temporo-occipital areas may be predictive of conversion from MCI to AD. PMID:25355209

López, María Eugenía; Bruña, Ricardo; Aurtenetxe, Sara; Pineda-Pardo, José Ángel; Marcos, Alberto; Arrazola, Juan; Reinoso, Ana Isabel; Montejo, Pedro; Bajo, Ricardo; Maestú, Fernando

2014-10-29

239

A signal-processing pipeline for magnetoencephalography resting-state networks.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To study functional connectivity using magnetoencephalographic (MEG) data, the high-quality source-level reconstruction of brain activity constitutes a critical element. MEG resting-state networks (RSNs) have been documented by means of a dedicated processing pipeline: MEG recordings are decomposed by independent component analysis (ICA) into artifact and brain components (ICs); next, the channel maps associated with the latter ones are projected into the source space and the resulting voxel-...

Mantini, D.; Della Penna, S.; Marzetti, L.; Pasquale, F.; Pizzella, V.; Corbetta, M.; Romani, Gl

2011-01-01

240

A signal-processing pipeline for magnetoencephalography resting-state networks.  

Science.gov (United States)

To study functional connectivity using magnetoencephalographic (MEG) data, the high-quality source-level reconstruction of brain activity constitutes a critical element. MEG resting-state networks (RSNs) have been documented by means of a dedicated processing pipeline: MEG recordings are decomposed by independent component analysis (ICA) into artifact and brain components (ICs); next, the channel maps associated with the latter ones are projected into the source space and the resulting voxel-wise weights are used to linearly combine the IC time courses. An extensive description of the proposed pipeline is provided here, along with an assessment of its performances with respect to alternative approaches. The following investigations were carried out: (1) ICA decomposition algorithm. Synthetic data are used to assess the sensitivity of the ICA results to the decomposition algorithm, by testing FastICA, INFOMAX, and SOBI. FastICA with deflation approach, a standard solution, provides the best decomposition. (2) Recombination of brain ICs versus subtraction of artifactual ICs (at the channel level). Both the recombination of the brain ICs in the sensor space and the classical procedure of subtracting the artifactual ICs from the recordings provide a suitable reconstruction, with a lower distortion using the latter approach. (3) Recombination of brain ICs after localization versus localization of artifact-corrected recordings. The brain IC recombination after source localization, as implemented in the proposed pipeline, provides a lower source-level signal distortion. (4) Detection of RSNs. The accuracy in source-level reconstruction by the proposed pipeline is confirmed by an improved specificity in the retrieval of RSNs from experimental data. PMID:22432954

Mantini, Dante; Della Penna, Stefania; Marzetti, Laura; de Pasquale, Francesco; Pizzella, Vittorio; Corbetta, Maurizio; Romani, Gian Luca

2011-01-01

 
 
 
 
241

Theoretical Models and Relevant Calculations of Photon Production and Photonuclear Reaction Data  

Science.gov (United States)

Photon production and photonuclear reaction data, with emphasis on theoretical model aspects aimed at reliable evaluations, represent a challenge in many technological applications, from radiation shielding for different nuclear systems, including accelerators, to devices relevant to nuclear energy applications, particularly the ones concerning the Accelerator Driven Systems for nuclear waste transmutation. In this field of applied science, theoretical calculations complementing the existing experimental data play an essential role in performing valuable nuclear data evaluations, particularly when the measured quantities are discrepant, scarce, or even lacking. In this framework, new improved results of theoretical and evaluation activities carried out at ENEA, Division for Advanced Physics Technologies, are presented especially concerning photonuclear reaction cross sections. Relevant aspects of nuclear structure models are discussed together with a critical analysis of the related computing codes considered in the present ENEA evaluations, aimed at producing specific contributions to the above-mentioned nuclear programs and applications and at cooperating in the framework of the international initiatives and efforts on the inter-comparison of the evaluated data and of the relevant models and codes. An innovative method has been developed and utilized for microscopic and statistical models of nuclear structure, especially referring to algebraic models aimed at complementing the reaction models for the treatment of pre-equilibrium and compound-nucleus processes. The relevant microscopic algebraic model calculations are discussed, as they reasonably approximate the observed structure of photonuclear cross sections due to multi-polarity effects. Accordingly, theoretical calculation methods are presented for Ti and Mo isotopes, as materials relevant to nuclear applications, and significant results are reviewed for Ti natural isotopes and the element in comparison with the experimental data when available from the existing literature.

Menapace, E.; Maino, G.; Groppi, F.

2005-05-01

242

Prediction of vapor-liquid equilibrium and PVTx properties of geological fluid system with SAFT-LJ EOS including multi-polar contribution. Part II: Application to H2O-NaCl and CO2-H2O-NaCl System  

Science.gov (United States)

The SAFT-LJ equation of state improved by Sun and Dubessy (2010) can represent the vapor-liquid equilibrium and PVTx properties of the CO2-H2O system over a wide P-T range because it accounts for the energetic contribution of the main types of molecular interactions in terms of reliable molecular based models. Assuming that NaCl fully dissociates into individual ions (spherical Na+ and Cl-) in water and adopting the restricted primitive model of mean spherical approximation to account for the energetic contribution due to long-range electrostatic forces between ions, this study extends the improved SAFT-LJ EOS to the H2O-NaCl and the CO2-H2O-NaCl systems at temperatures below 573 K. The EOS parameters for the interactions between ion and ion and between ion and water were determined from the mean ionic activity coefficient data and the density data of the H2O-NaCl system. The parameters for the interactions between ion and CO2 were evaluated from CO2 solubility data of the CO2-H2O-NaCl system. Comparison with the experimental data shows that this model can predict the mean ionic activity coefficient, osmotic coefficient, saturation pressure, and density of aqueous NaCl solution and can predict the vapor-liquid equilibrium and PVTx properties of the CO2-H2O-NaCl system over the range from 273 to 573 K, from 0 to 1000 bar, and from 0 to 6 mol/kg NaCl with high accuracy.

Sun, Rui; Dubessy, Jean

2012-07-01

243

Joint EEG/fMRI state space model for the detection of directed interactions in human brains--a simulation study.  

Science.gov (United States)

An often addressed challenge in neuroscience research is the assignment of different tasks to specific brain regions. In many cases several brain regions are activated during a single task. Therefore, one is also interested in the temporal evolution of brain activity to infer causal relations between activated brain regions. These causal relations may be described by a directed, task specific network which consists of activated brain regions as vertices and directed edges. The edges describe the causal relations. Inference of the task specific brain network from measurements like electroencephalography (EEG) or functional magnetic resonance imaging (fMRI) is challenging, due to the low spatial resolution of the former and the low temporal resolution of the latter. Here, we present a simulation study investigating a possible combined analysis of simultaneously measured EEG and fMRI data to address the challenge specified above. A nonlinear state space model is used to distinguish between the underlying brain states and the (simulated) EEG/fMRI measurements. We make use of a modified unscented Kalman filter and a corresponding unscented smoother for the estimation of the underlying neural activity. Model parameters are estimated using an expectation-maximization algorithm, which exploits the partial linearity of our model. Inference of the brain network structure is then achieved using directed partial correlation, a measure for Granger causality. The results indicate that the convolution effect of the fMRI forward model imposes a big challenge for the parameter estimation and reduces the influence of the fMRI in combined EEG-fMRI models. It remains to be investigated whether other models or similar combinations of other modalities such as, e.g., EEG and magnetoencephalography can increase the profit of the promising idea of combining various modalities. PMID:22027197

Lenz, Michael; Musso, Mariachristina; Linke, Yannick; Tüscher, Oliver; Timmer, Jens; Weiller, Cornelius; Schelter, Björn

2011-11-01

244

CAM3 bias over the Arctic region during northern winter studied with a linear stationary model  

Energy Technology Data Exchange (ETDEWEB)

This study builds upon two prior papers, which examine Arctic region bias of CAM3 (NCAR Community Atmosphere Model version 3) simulations during winter. CAM3 output is compared with ECMWF (European Centre for Medium-Range Weather Forecasts) 40 year reanalysis (ERA-40) data. Our prior papers considered the temperature and the vorticity equation terms and demonstrated that diabatic, transient, and linear terms dominate nonlinear bias terms over most areas of interest. Accordingly, this paper uses a linearized form of the model's dynamical core equations to study aspects of the forcing that lead to the CAM3 biases. We treat the model's long term winter bias as a solution to a linear stationary wave model (LSWM). Key features of the bias in the vorticity, temperature, and ln of surface pressure (=q) fields are shown at medium resolution. The important features found at medium resolution are captured at the much lower LSWM resolution. The Arctic q bias has two key features: excess q over the Barents Sea and a missing Beaufort High (negative maximum q bias) to the north of Alaska and eastern Siberia. The forcing fields are calculated by the LSWM. Horizontal advection tends to create multi-polar combinations of negative and positive extrema in the forcing. The positive and negative areas of forcing approximately match corresponding areas in the bias. There is a broad relation between cold bias with elevated q bias, as expected from classical theory. Forcing in related quantities: near surface vorticity and surface pressure combine to produce the sea level pressure bias. (orig.)

Grotjahn, Richard [University of California, Department of Land, Air and Water Resources, Davis, CA (United States); Pan, Lin-Lin; Tribbia, Joseph [National Center for Atmospheric Research, Boulder, CO (United States)

2011-08-15

245

Distinguishing mechanisms of gamma frequency oscillations in human current source signals using a computational model of a laminar neocortical network  

Directory of Open Access Journals (Sweden)

Full Text Available Gamma frequency rhythms have been implicated in numerous studies for their role in healthy and abnormal brain function. The frequency band has been described to encompass as broad a range as 30–150 Hz. Crucial to understanding the role of gamma in brain function is an identification of the underlying neural mechanisms, which is particularly difficult in the absence of invasive recordings in macroscopic human signals such as those from magnetoencephalography (MEG and electroencephalography (EEG. Here, we studied features of current dipole (CD signals from two distinct mechanisms of gamma generation, using a computational model of a laminar cortical circuit designed specifically to simulate CDs in a biophysically principled manner (Jones et al., 2007; Jones et al., 2009. We simulated spiking pyramidal interneuronal gamma (PING whose period is regulated by the decay time constant of GABAA-mediated synaptic inhibition and also subthreshold gamma driven by gamma-periodic exogenous excitatory synaptic drive. Our model predicts distinguishable CD features created by spiking PING compared to subthreshold driven gamma that can help to disambiguate mechanisms of gamma oscillations in human signals. We found that gamma rhythms in neocortical layer 5 can obscure a simultaneous, independent gamma in layer 2/3. Further, we arrived at a novel interpretation of the origin of high gamma frequency rhythms (100–150 Hz, showing that they emerged from a specific temporal feature of CDs associated with single cycles of PING activity and did not reflect a separate rhythmic process. Last we show that the emergence of observable subthreshold gamma required highly coherent exogenous drive. Our results are the first to demonstrate features of gamma oscillations in human current source signals that distinguish cellular and circuit level mechanisms of these rhythms and may help guide understanding of their functional role.

ShaneLee

2013-12-01

246

Use of the isolated problem approach for multi-compartment BEM models of electro-magnetic source imaging  

International Nuclear Information System (INIS)

The isolated problem approach (IPA) is a method used in the boundary element method (BEM) to overcome numerical inaccuracies caused by the high-conductivity difference in the skull and the brain tissues in the head. Haemaelaeinen and Sarvas (1989 IEEE Trans. Biomed. Eng. 36 165-71) described how the source terms can be updated to overcome these inaccuracies for a three-layer head model. Meijs et al (1989 IEEE Trans. Biomed. Eng. 36 1038-49) derived the integral equations for the general case where there are an arbitrary number of layers inside the skull. However, the IPA is used in the literature only for three-layer head models. Studies that use complex boundary element head models that investigate the inhomogeneities in the brain or model the cerebrospinal fluid (CSF) do not make use of the IPA. In this study, the generalized formulation of the IPA for multi-layer models is presented in terms of integral equations. The discretized version of these equations are presented in two different forms. In a previous study (Akalin-Acar and Gencer 2004 Phys. Med. Biol. 49 5011-28), we derived formulations to calculate the electroencephalography and magnetoencephalography transfer matrices assuming a single layer in the skull. In this study, the transfer matrix formulations are updated to incorporate the generalized IPA. The effects of the IPA are investigated on the accuracy of spherical and realistic models when the CSF layer and a tumour tissue are included in the model. Itumour tissue are included in the model. It is observed that, in the spherical model, for a radial dipole 1 mm close to the brain surface, the relative difference measure (RDM*) drops from 1.88 to 0.03 when IPA is used. For the realistic model, the inclusion of the CSF layer does not change the field pattern significantly. However, the inclusion of an inhomogeneity changes the field pattern by 25% for a dipole oriented towards the inhomogeneity. The effect of the IPA is also investigated when there is an inhomogeneity in the brain. In addition to a considerable change in the scale of the potentials, the field pattern also changes by 15%. The computation times are presented for the multi-layer realistic head model

247

A modelling study to inform specification and optimal electrode placement for imaging of neuronal depolarization during visual evoked responses by electrical and magnetic detection impedance tomography  

International Nuclear Information System (INIS)

Electrical impedance tomography (EIT) has the potential to achieve non-invasive functional imaging of fast neuronal activity in the human brain due to opening of ion channels during neuronal depolarization. Local changes of resistance in the cerebral cortex are about 1%, but the size and location of changes recorded on the scalp are unknown. The purpose of this work was to develop an anatomically realistic finite element model of the adult human head and use it to predict the amplitude and topography of changes on the scalp, and so inform specification for an in vivo measuring system. A detailed anatomically realistic finite element (FE) model of the head was produced from high resolution MRI. Simulations were performed for impedance changes in the visual cortex during evoked activity with recording of scalp potentials by electrodes or magnetic flux density by magnetoencephalography (MEG) in response to current injected with electrodes. The predicted changes were validated by recordings in saline filled tanks and with boundary voltages measured on the human scalp. Peak changes were 1.03 ± 0.75 µV (0.0039 ± 0.0034%) and 27 ± 13 fT (0.2 ± 0.5%) respectively, which yielded an estimated peak signal-to-noise ratio of about 4 for in vivo averaging over 10 min and 1 mA current injection. The largest scalp changes were over the occipital cortex. This modelling suggests, for the first time, that reproducible changes could be recorded on the scalp in vivo in single channels, although a higher SNR would be desirable for accurate image production. The findings suggest that an in vivo study is warranted in order to determine signal size but methods to improve SNR, such as prolonged averaging or other signal processing may be needed for accurate image production

248

[Catheter ablation of atrial fibrillation. Pulmonary vein isolation by using a new multipolar ablation catheter].  

Science.gov (United States)

Catheter ablation of atrial fibrillation (AF) is an established therapeutical option, particularly in treatment of paroxysmal atrial fibrillation. This paper presents the results of using the PVAC multi-electrode ablation catheter (PVAC®, Medtronic Ablation Frontiers, Carlsbad, CA, USA). In 253 patients with paroxysmal or persistant AF, 1051 pulmonary veins were isolated, including ablation of 34 left common ostia and 1 right common ostium. Except one vein, all pulmonary veins in all patients were successfully isolated. In 23 patients with documented typical atrial flutter, the right atrial isthmus was additionally ablated within the same procedure. Follow-up (FU) visits were performed after 1, 3, 6 and 12 months with 12-lead-ECG, 24h-Holter-ECG and 4-days-Holter ECG. Mean FU was 11?±?7 months with 1.1 interventions per patient (24 redo cases). During FU, 122 of 181 patients with paroxysmal AF (69%) and 23 of 40 patients with persistant AF (58%) were in stable sinus rhythm (SR) after ablation. 159 (62.8%) patients wer under antiarrhythmic drugs after ablation, 214 (84.5%) patients with additional ?-blockers. Total procedure time was 71?±?19 min, and total fluoroscopy time was 16?±?6 min. In 3 cases (1.2%) procedure-related complications occured. Pulmonary vein isolation by using the PVAC-ablation catheter is a safe and effective method in treatment of paroxysmal and persistant AF. PMID:22528180

Spitzer, Stefan G; Karolyi, Laszlo

2011-05-01

249

Investigation of the Multipolarity of 169Tm 93.61 KeV ?-transition  

International Nuclear Information System (INIS)

The conversion spectrum of 169Tm 93.61 KeV ?-transition was measured by magnetic beta spectrometer with 0,04% high resolution. Forms of L1, L2, L3 lines are studied and relative amounts of their broadening are measured. Mean quantity of ? from the established internal conversion coefficients are calculated ?2=0.034±0.003. Average significance of the share of electric quadruple admixture ?=(3.3±0.3)% are found, wnich corresponds to M1+3.3%E2 mixed ?-transition. (authors)

250

Multipolarity or cosmopolitanism? A critique of Mouffe from a hegemony-theoretical perspective  

DEFF Research Database (Denmark)

In a series of publications Chantal Mouffe (2004, 2005a, 2005b, 2008, 2009, 2013) has criticized cosmopolitanism for its lack of conceptualization of power, conflict and struggle, in short of politics. Even though this critique is largely well placed, the conclusions drawn from the analysis by Mouffe are flawed. As she puts it, if a cosmopolitan democracy “was ever realized, it could only signify the world hegemony of a dominant power that would have been able to impose its conception of the world on the entire planet and which, identifying its interests with those of humanity, would treat any disagreement as an illegitimate challenge to its ‘rational’ leadership”. Mouffe, On the Political pp. 106–7. I argue that Mouffe paradoxically seems to be using a traditional 'realist' conceptualization of hegemony, signifying simply domination. Against this I argue that a post-structuralist understanding of hegemony – as developed by herself and Laclau in Hegemony and Socialist Strategy, (Laclau and Mouffe,1985), precisely allows us to see the distance between universal values, such as freedom and equality for all, and their actual interpretation and use. The fact that the West are using democracy and human rights as legitimating devises for non-democratic goals, should not make us abandon the realization of these values on the global scale as the political goal.

Hansen, Allan Dreyer

251

NGC 6309, a Planetary Nebula that Shifted from Round to Multipolar  

CERN Document Server

We present new narrow-band Ha, [N II], and [O III] high-resolution images of the quadrupolar planetary nebula (PN) NGC 6309 that show in great detail its bipolar lobes and reveal new morphological features. New high- and low-dispersion long-slit spectra have been obtained to help in the investigation of the new nebular components. The images and spectra unveil two diffuse blobs, one of them located at 55 arcsec from the central star along the NE direction (PA= +71) and the other at 78 arcsec in the SW direction (PA= -151). Therefore, these structures do not share the symmetry axes of the inner bipolar outflows. Their radial velocities relative to the system are quite low: +3 and -4 km/s, respectively. Spectroscopic data confirm a high [O III] to Ha ratio, indicating that the blobs are being excited by the UV flux from the central star. Our images convincingly show a spherical halo 60 arcsec in diameter encircling the quadrupolar nebula. The expansion velocity of this shell is low, 66 km/s. The software SHAPE ...

Rubio, Gabriel; Ramos-Larios, Gerardo; Guerrero, Martin A; Olguin, Lorenzo; Guillen, Pedro F; Mata, Hector

2014-01-01

252

Multipolar permanent-magnet synchronous generators intended for wind power plants  

Science.gov (United States)

The analytical method of calculating two-dimensional magnetic fields in the active section of permanent-magnet synchronous electrical rotating machines, as applied to their use in the wind energy industry, has been developed. The analytical relationships for calculating distribution of two-dimensional magnetic fields and determining output parameters with due regard for geometry of the active section, the number of pairs of poles, and magnetic characteristics of materials have been obtained. The criteria dependences needed for calculating the electromotive force and main inductive reactance of permanent-magnet synchronous electric machines, with consideration for the geometry of a machine and electrophysical properties of materials being used, have been derived. The procedure of evaluating parameters of permanent-magnet synchronous generators for large-size wind power plants is presented.

Kovalev, L. K.; Kovalev, K. L.; Tulinova, Ye. Ye.; Ivanov, N. S.

2012-12-01

253

Ce site substitution effects on the multipolar interactions in CeB6  

International Nuclear Information System (INIS)

Ce-site substitution effects on the quadrupolar and octupolar interactions in CeB6 were investigated for CexR1-xB6 (R=Nd, Gd) single crystals. In CexNd1-xB6 (x=0.8, 0.7), new phase V appears between phase III and I. Phase V may be the antiferro (AF) magnetic state judging from the existence of the magnetic anisotropy clearly seen for x=0.7. From the x dependence of TN and TQ, the Nd doping suppresses the AFQ and AFO interactions. In the case of Gd doping, quite unusual successive transition III-II-V-I is observed for small Gd concentration. For larger Gd concentration, phase II is pushed up to higher fields and the AF magnetic state appears at low fields, which is not dominated by the AFQ ordering. (author)

254

Ce site substitution effect on the multipolar ordering in CeB{sub 6}  

Energy Technology Data Exchange (ETDEWEB)

We have studied the Ce-cite substitution effect by R(=Pr, Nd) ion on the multipole interactions in CeB{sub 6}. We found that T{sub Q} of Ce{sub 0.9}Nd{sub 0.1}B{sub 6} in magnetic fields is higher than that of Ce{sub 0.9}Pr{sub 0.1}B{sub 6} and the magnetization is larger in the former than in the latter. The larger suppression of T{sub Q} in Ce{sub x}Pr{sub 1-x}B{sub 6} suggests the larger reduction of the T{sub xyz} antiferro-octupolar (AFO) interaction in this system considering that T{sub Q} at H=0 is nearly the same in both systems. The smaller magnetization in Ce{sub x}Pr{sub 1-x}B{sub 6} than in Ce{sub x}Nd{sub 1-x}B{sub 6} originates from the larger suppression of T{sub xyz} AFO interaction and also the larger Ce-Pr AF exchange interaction than in Ce{sub x}Nd{sub 1-x}B{sub 6}.

Sera, M. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan)]. E-mail: sera@sci.hiroshima-u.ac.jp; Kawaguchi, M. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Kishimoto, S. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Kondo, A. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Iwakubo, H. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Tou, H. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Umeo, K. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan); Iga, F. [Department of ADSM, Hiroshima University, Higashi-Hiroshima, Kagamiyama 1-3-1, 739-8530 (Japan)

2007-03-15

255

Ce site substitution effect on the multipolar ordering in CeB6  

International Nuclear Information System (INIS)

We have studied the Ce-cite substitution effect by R(=Pr, Nd) ion on the multipole interactions in CeB6. We found that TQ of Ce0.9Nd0.1B6 in magnetic fields is higher than that of Ce0.9Pr0.1B6 and the magnetization is larger in the former than in the latter. The larger suppression of TQ in CexPr1-xB6 suggests the larger reduction of the Txyz antiferro-octupolar (AFO) interaction in this system considering that TQ at H=0 is nearly the same in both systems. The smaller magnetization in CexPr1-xB6 than in CexNd1-xB6 originates from the larger suppression of Txyz AFO interaction and also the larger Ce-Pr AF exchange interaction than in CexNd1-xB6

256

Ce site substitution effect on the multipolar ordering in CeB6  

Science.gov (United States)

We have studied the Ce-cite substitution effect by R(=Pr, Nd) ion on the multipole interactions in CeB6. We found that TQ of Ce0.9Nd0.1B6 in magnetic fields is higher than that of Ce0.9Pr0.1B6 and the magnetization is larger in the former than in the latter. The larger suppression of TQ in CexPr1-xB6 suggests the larger reduction of the Txyz antiferro-octupolar (AFO) interaction in this system considering that TQ at H=0 is nearly the same in both systems. The smaller magnetization in CexPr1-xB6 than in CexNd1-xB6 originates from the larger suppression of Txyz AFO interaction and also the larger Ce-Pr AF exchange interaction than in CexNd1-xB6.

Sera, M.; Kawaguchi, M.; Kishimoto, S.; Kondo, A.; Iwakubo, H.; Tou, H.; Umeo, K.; Iga, F.

257

Treatment of atrial fibrillation with radiofrequency ablation and simultaneous multipolar mapping of the pulmonary veins  

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Full Text Available OBJECTIVE: To demonstrate the feasibility and safety of simultaneous catheterization and mapping of the 4 pulmonary veins for ablation of atrial fibrillation. METHODS: Ten patients, 8 with paroxysmal atrial fibrillation and 2 with persistent atrial fibrillation, refractory to at least 2 antiarrhythmic drugs and without structural cardiopathy, were consecutively studied. Through the transseptal insertion of 2 long sheaths, 4 pulmonary veins were simultaneously catheterized with octapolar microcatheters. After identification of arrhythmogenic foci radiofrequency was applied under angiographic or ultrasonographic control. RESULTS: During 17 procedures, 40 pulmonary veins were mapped, 16 of which had local ectopic activity, related or not with the triggering of atrial fibrillation paroxysms. At the end of each procedure, suppression of arrhythmias was obtained in 8 patients, and elimination of pulmonary vein potentials was accomplished in 4. During the clinical follow-up of 9.6±3 months, 7 patients remained in sinus rhythm, 5 of whom were using antiarrhythmic drugs that had previously been ineffective. None of the patients had pulmonary hypertension or evidence of stenosis in the pulmonary veins. CONCLUSION: Selective and simultaneous catheterization of the 4 pulmonary veins with microcatheters for simultaneous recording of their electrical activity is a feasible and safe procedure that may help ablation of atrial fibrillation.

Rocha Neto Almino C.

2001-01-01

258

Multipolar correlations and deformation effect on nuclear transition matrix elements of double-{beta} decay  

Energy Technology Data Exchange (ETDEWEB)

The two-neutrino and neutrinoless double-beta decay of {sup 94,96}Zr, {sup 98,100}Mo, {sup 104}Ru, {sup 110}Pd, {sup 128,130}Te and {sup 150}Nd isotopes for the 0{sup +} {yields} 0{sup +} transition is studied within the PHFB framework along with an effective two-body interaction consisting of pairing, quadrupole-quadrupole and hexadecapole-hexadecapole correlations. It is found that the effect of hexa-deca-polar correlations can be assimilated substantially as a renormalisation of the quadrupole-quadrupole interaction. The effect of deformation on nuclear transition matrix elements is investigated by varying the strength of quadrupolar correlations in the parent and daughter nuclei independently. The variation of the nuclear transition matrix elements as a function of the difference in deformation parameters of parent and daughter nuclei reveals that, in general, the former tend to be maximum for equal deformation and they decrease as the difference in deformation parameters increases, exhibiting a very similar trend for the ({beta}{sup -}{beta}{sup -}){sub 2{nu}} and ({beta}{sup -}{beta}{sup -}){sub 0{nu}} transition matrix elements. (authors)

Chandra, R.; Raina, P.K. [IIT Kharagpur, Dept. of Physics and Meteorology, Kharagpur (India); Chandra, R.; Rath, P.K. [Lucknow Univ., Dept. of Physics (India); Chaturvedi, K. [Bundelkhand Univ., Dept. of Physics (India); Hirsch, J.G. [Universidad Nacional Autonoma de Mexico A.P. 70-543, Instituto de Ciencias Nucleares (Mexico)

2009-05-15

259

Multipolarity or cosmopolitanism? : A critique of Mouffe from a hegemony-theoretical perspective  

DEFF Research Database (Denmark)

In a series of publications Chantal Mouffe (2004, 2005a, 2005b, 2008, 2009, 2013) has criticized cosmopolitanism for its lack of conceptualization of power, conflict and struggle, in short of politics. Even though this critique is largely well placed, the conclusions drawn from the analysis by Mouffe are flawed. As she puts it, if a cosmopolitan democracy “was ever realized, it could only signify the world hegemony of a dominant power that would have been able to impose its conception of the world on the entire planet and which, identifying its interests with those of humanity, would treat any disagreement as an illegitimate challenge to its ‘rational’ leadership”. Mouffe, On the Political pp. 106–7. I argue that Mouffe paradoxically seems to be using a traditional 'realist' conceptualization of hegemony, signifying simply domination. Against this I argue that a post-structuralist understanding of hegemony – as developed by herself and Laclau in Hegemony and Socialist Strategy, (Laclau and Mouffe,1985), precisely allows us to see the distance between universal values, such as freedom and equality for all, and their actual interpretation and use. The fact that the West are using democracy and human rights as legitimating devises for non-democratic goals, should not make us abandon the realization of these values on the global scale as the political goal.

Hansen, Allan Dreyer

260

Multipolar electrostatics for proteins: atom-atom electrostatic energies in crambin.  

Science.gov (United States)

Accurate electrostatics necessitates the use of multipole moments centered on nuclei or extra point charges centered away from the nuclei. Here, we follow the former alternative and investigate the convergence behavior of atom-atom electrostatic interactions in the pilot protein crambin. Amino acids are cut out from a Protein Data Bank structure of crambin, as single amino acids, di, or tripeptides, and are then capped with a peptide bond at each side. The atoms in the amino acids are defined through Quantum Chemical Topology (QCT) as finite volume electron density fragments. Atom-atom electrostatic energies are computed by means of a multipole expansion with regular spherical harmonics, up to a total interaction rank of L?=??A+ ?B?+?1?=?10. The minimum internuclear distance in the convergent region of all the 15 possible types of atom-atom interactions in crambin that were calculated based on single amino acids are close to the values calculated from di and tripeptides. Values obtained at B3LYP/aug-cc-pVTZ and MP2/aug-cc-pVTZ levels are only slightly larger than those calculated at HF/6-31G(d,p) level. This convergence behavior is transferable to the well-known amyloid beta polypeptide A?1-42. Moreover, for a selected central atom, the influence of its neighbors on its multipole moments is investigated, and how far away this influence can be ignored is also determined. Finally, the convergence behavior of AMBER becomes closer to that of QCT with increasing internuclear distance. PMID:24449043

Yuan, Yongna; Mills, Matthew J L; Popelier, Paul L A

2014-02-15

 
 
 
 
261

Preliminary results from the NASA/JPL multifrequency, multipolarization synthetic aperture radar  

Science.gov (United States)

A brief description is given of the three-frequency polarimetric synthetic-aperture radar built and tested at the Jet Propulsion Laboratory. The radar has the capability to simultaneously acquire fully polarimetric data at P-, L-, and C-bands from a DC-8 airborne platform. The radar has an instantaneous data rate of approximately 2.1 Gb/s and has selectable record rates between 80-240 Mb/s. The system has a wide dynamic range featuring 8-b analog-to-digital converters and full digital floating-point processing. The processing is accomplished offline on a minicomputer system assisted by an array processor. Sample images are presented.

Held, Daniel N.; Brown, Walter E.; Miller, Timothy W.

1988-01-01

262

Multipolar universal relations between f-mode frequency and tidal deformability of compact stars  

CERN Document Server

Though individual stellar parameters of compact stars usually demonstrate obvious dependence on the equation of state (EOS), EOS-insensitive universal formulas relating these parameters remarkably exist. In the present paper, we explore the inter-relationship between two such formulas, namely the f-I relation connecting the $f$-mode quadrupole oscillation frequency $\\omega_2$ and the moment of inertia $I$, and the I-Love-Q relations relating $I$, the quadrupole tidal deformability $\\lambda_2$, and the quadrupole moment $Q$, which have been proposed by Lau et al. [Astrophys. J. {\\bf 714}, 1234 (2010)], and Yagi and Yunes [Science, {\\bf 341}, 365 (2013)], respectively. A relativistic universal relation between $\\omega_l$ and $\\lambda_l$ with the same angular momentum $l=2,3,\\ldots$, the so called "diagonal f-Love relation" that holds for realistic compact stars and stiff polytropic stars, is unveiled here. An in-depth investigation in the Newtonian limit is further carried out to pinpoint its underlying physica...

Chan, T K; Leung, P T; Lin, L -M

2014-01-01

263

Multipolarities of the yrast and statistical cascades in the reactions 150Nd(20Ne,xn?)  

International Nuclear Information System (INIS)

The total conversion coefficient, ?, of the ?-ray continuum has been determined as a function of ?-ray energy fom 0.5 to 2.5 MeV. The results are consistent with a mixture of E1 and E2 for E/sub ?/ > or = 1.0 MeV, with a smooth increase of the E1 fraction with E/sub ?/ up to approx. 1.5 MeV. At lower energy, in the upper half of the yrast region, ? shows the expected dominance of E2 radiation, but for the lower half an increasing M1 contribution is found

264

Evidence for multipolarities other than E2 in the 2H(d,?)4He reaction  

International Nuclear Information System (INIS)

Angular distributions of the vector and tensor analyzing powers Asub(y)(theta) and Asub(yy)(theta) have been measured for the reaction 2H(d vector,?)4He at an incident enrgy of 10 MeV. Results are discussed in the light of recent efforts to determine the D-state amplitude in 4He. Evidence is found that the radiation contains multipoles other than E2, contrary to what has been widely assumed. (orig.)

265

Low multipolarity magnetic transitions in 90Zr excited by 1800 electron scattering  

International Nuclear Information System (INIS)

Spectra of 37.2 and 60.6 MeV electrons scattered at 1800 constitute evidence for very low M1 transition strength and significant M2 transition strength in the 9 MeV excitation energy region of 90Zr. This is consistent with recent high resolution results of other workers at more forward angles

266

Study of H- production in H2 microwave multipolar plasmas by optical and electrical diagnostics  

International Nuclear Information System (INIS)

A way to achieve heating is the injection in the plasma of highly energetic particles (? MeV) that will transfer their energy during collisions. For this purpose, energetic charged particles are independently created in D2 plasmas and then neutralized so they can penetrate into the tokamak without being sensitive to the magnetic confinement. Neutral beam injection can deliver up to 16 MW into the ITER plasma. D- beams are used rather than D+ as the neutralisation of the latter is almost zero instead of 60% for D-, at the energy of interest. In this framework, our work is devoted to the production of H- negative ions from H2 microwave multi-dipolar plasmas. Negative ions are produced inside the plasma volume by dissociative electron attachment to highly vibrationally-excited molecules H2 (step 3). They can also be produced throughout plasma-surface interactions, where H atoms created in the plasma volume stick on the material (step 1) and recombine with hydrogen present on the surface, resulting in the desorption of a vibrationally-excited H2 molecule (step 2), which reacts with a cold electron to form a negative ion (step 3). Plasma diagnostics are implemented to better understand the mechanisms involved in H production. Step 3 is studied by means of Langmuir probes for electron density and energy distribution measurements, while laser photo-detachment (Nd-YAG, 1064 nm) gives nego-detachment (Nd-YAG, 1064 nm) gives negative ion densities. H atom densities are followed by Optical Emission Spectroscopy (OES) using actinometry, as well as Laser Induced Fluorescence with one (LIF) or two (TALIF) photons. By generating H atom spatial profiles via Abel transform, we try to differentiate volume mechanisms from surface ones. This document is composed of a short paper followed by a poster

267

Understanding the electric and magnetic response of isolated metaatoms by means of a multipolar field decomposition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We introduce a technique to decompose the scattered near field of two-dimensional arbitrary metaatoms into its multipole contributions. To this end we expand the scattered field upon plane wave illumination into cylindrical harmonics as known from Mie's theory. By relating these cylindrical harmonics to the field radiated by Cartesian multipoles, the contribution of the lowest order electric and magnetic multipoles can be identified. Revealing these multipoles is essential for the design of m...

Petschulat, J.; Yang, Jianji; Menzel, C.; Rockstuhl, C.; Chipouline, A.; Lalanne, Philippe; Tu?nnermann, A.; Lederer, F.; Pertsch, T.

2010-01-01

268

Understanding the electric and magnetic response of isolated metaatoms by means of a multipolar field decomposition.  

Science.gov (United States)

We introduce a technique to decompose the scattered near field of two-dimensional arbitrary metaatoms into its multipole contributions. To this end we expand the scattered field upon plane wave illumination into cylindrical harmonics as known from Mie's theory. By relating these cylindrical harmonics to the field radiated by Cartesian multipoles, the contribution of the lowest order electric and magnetic multipoles can be identified. Revealing these multipoles is essential for the design of metamaterials because they largely determine the character of light propagation. In particular, having this information at hand it is straightforward to distinguish between effects that result either from the arrangement of the metaatoms or from their particular design. PMID:20639930

Petschulat, J; Yang, J; Menzel, C; Rockstuhl, C; Chipouline, A; Lalanne, P; Tüennermann, A; Lederer, F; Pertsch, T

2010-07-01

269

Use of the isolated problem approach for multi-compartment BEM models of electro-magnetic source imaging  

Energy Technology Data Exchange (ETDEWEB)

The isolated problem approach (IPA) is a method used in the boundary element method (BEM) to overcome numerical inaccuracies caused by the high-conductivity difference in the skull and the brain tissues in the head. Haemaelaeinen and Sarvas (1989 IEEE Trans. Biomed. Eng. 36 165-71) described how the source terms can be updated to overcome these inaccuracies for a three-layer head model. Meijs et al (1989 IEEE Trans. Biomed. Eng. 36 1038-49) derived the integral equations for the general case where there are an arbitrary number of layers inside the skull. However, the IPA is used in the literature only for three-layer head models. Studies that use complex boundary element head models that investigate the inhomogeneities in the brain or model the cerebrospinal fluid (CSF) do not make use of the IPA. In this study, the generalized formulation of the IPA for multi-layer models is presented in terms of integral equations. The discretized version of these equations are presented in two different forms. In a previous study (Akalin-Acar and Gencer 2004 Phys. Med. Biol. 49 5011-28), we derived formulations to calculate the electroencephalography and magnetoencephalography transfer matrices assuming a single layer in the skull. In this study, the transfer matrix formulations are updated to incorporate the generalized IPA. The effects of the IPA are investigated on the accuracy of spherical and realistic models when the CSF layer and a tumour tissue are included in the model. It is observed that, in the spherical model, for a radial dipole 1 mm close to the brain surface, the relative difference measure (RDM*) drops from 1.88 to 0.03 when IPA is used. For the realistic model, the inclusion of the CSF layer does not change the field pattern significantly. However, the inclusion of an inhomogeneity changes the field pattern by 25% for a dipole oriented towards the inhomogeneity. The effect of the IPA is also investigated when there is an inhomogeneity in the brain. In addition to a considerable change in the scale of the potentials, the field pattern also changes by 15%. The computation times are presented for the multi-layer realistic head model.

Gencer, Nevzat G; Akalin-Acar, Zeynep [Department of Electrical and Electronics Engineering, Brain Research Laboratory, Middle East Technical University, 06531 Ankara (Turkey)

2005-07-07

270

Damping of the giant resonances in a fluid-dynamical model  

International Nuclear Information System (INIS)

The relevance to the damping of the giant resonances, of the anharmonic coupling between the normal modes, is investigated in a fluid dynamical mode. It is found that this mechanism leads to a weak damping which, however, increases very drastically with the wavevector, implying a very short life time for high multipolarity modes. (Author)

271

Human in vitro reporter model of neuronal development and early differentiation processes  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background During developmental and adult neurogenesis, doublecortin is an early neuronal marker expressed when neural stem cells assume a neuronal cell fate. To understand mechanisms involved in early processes of neuronal fate decision, we investigated cell lines for their capacity to induce expression of doublecortin upon neuronal differentiation and develop in vitro reporter models using doublecortin promoter sequences. Results Among various cell lines investigated, the human teratocarcinoma cell line NTERA-2 was found to fulfill our criteria. Following induction of differentiation using retinoic acid treatment, we observed a 16-fold increase in doublecortin mRNA expression, as well as strong induction of doublecortin polypeptide expression. The acquisition of a neuronal precursor phenotype was also substantiated by the establishment of a multipolar neuronal morphology and expression of additional neuronal markers, such as Map2, ?III-tubulin and neuron-specific enolase. Moreover, stable transfection in NTERA-2 cells of reporter constructs encoding fluorescent or luminescent genes under the control of the doublecortin promoter allowed us to directly detect induction of neuronal differentiation in cell culture, such as following retinoic acid treatment or mouse Ngn2 transient overexpression. Conclusion Induction of doublecortin expression in differentiating NTERA-2 cells suggests that these cells accurately recapitulate some of the very early events of neuronal determination. Hence, the use of reporter genes under the control of the doublecortin promoter in NTERA-2 cells will help us to investigate factors involved early in the course of neuronal differentiation processes. Moreover the ease to detect the induction of a neuronal program in this model will permit to perform high throughput screening for compounds acting on the early neuronal differentiation mechanisms.

Bogdahn Ulrich

2008-02-01

272

How neurons migrate: a dynamic in-silico model of neuronal migration in the developing cortex  

LENUS (Irish Health Repository)

Abstract Background Neuronal migration, the process by which neurons migrate from their place of origin to their final position in the brain, is a central process for normal brain development and function. Advances in experimental techniques have revealed much about many of the molecular components involved in this process. Notwithstanding these advances, how the molecular machinery works together to govern the migration process has yet to be fully understood. Here we present a computational model of neuronal migration, in which four key molecular entities, Lis1, DCX, Reelin and GABA, form a molecular program that mediates the migration process. Results The model simulated the dynamic migration process, consistent with in-vivo observations of morphological, cellular and population-level phenomena. Specifically, the model reproduced migration phases, cellular dynamics and population distributions that concur with experimental observations in normal neuronal development. We tested the model under reduced activity of Lis1 and DCX and found an aberrant development similar to observations in Lis1 and DCX silencing expression experiments. Analysis of the model gave rise to unforeseen insights that could guide future experimental study. Specifically: (1) the model revealed the possibility that under conditions of Lis1 reduced expression, neurons experience an oscillatory neuron-glial association prior to the multipolar stage; and (2) we hypothesized that observed morphology variations in rats and mice may be explained by a single difference in the way that Lis1 and DCX stimulate bipolar motility. From this we make the following predictions: (1) under reduced Lis1 and enhanced DCX expression, we predict a reduced bipolar migration in rats, and (2) under enhanced DCX expression in mice we predict a normal or a higher bipolar migration. Conclusions We present here a system-wide computational model of neuronal migration that integrates theory and data within a precise, testable framework. Our model accounts for a range of observable behaviors and affords a computational framework to study aspects of neuronal migration as a complex process that is driven by a relatively simple molecular program. Analysis of the model generated new hypotheses and yet unobserved phenomena that may guide future experimental studies. This paper thus reports a first step toward a comprehensive in-silico model of neuronal migration.

Setty, Yaki

2011-09-30

273

Effect of nuclear deformation on the alpha-decay half-life of even-even alpha emitters  

International Nuclear Information System (INIS)

Alpha-decay half-life of even-even emitters has been calculated in terms of a tunnelling through a quantum mechanical potential barrier. A multipolar expansion of Coulomb potential has been developed taking into account the nuclear quadrupole, hexadecapole, and hexacontatetrapole deformations. We show that using a free-parameter model the calculated half-lives do not vary significantly with higher order multipolarities of the daughter nucleus deformation. (author)

274

Impaired evoked and resting-state brain oscillations in patients with liver cirrhosis as revealed by magnetoencephalography???  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A number of studies suggest that the clinical manifestation of neurological deficits in hepatic encephalopathy results from pathologically synchronized neuronal oscillations and altered oscillatory coupling. In the present study spontaneous and evoked oscillatory brain activities were analyzed jointly with established behavioral measures of altered visual oscillatory processing. Critical flicker and fusion frequencies (CFF, FUF) were measured in 25 patients diagnosed with liver cirrhosis and ...

Go?tz, Theresa; Huonker, Ralph; Kranczioch, Cornelia; Reuken, Philipp; Witte, Otto W.; Gu?nther, Albrecht; Debener, Stefan

2013-01-01

275

Frequency-pattern functional tomography of magnetoencephalography data allows new approach to the study of human brain organization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method based on a set of new theorems for the analysis of multichannel time series is described, based on precise Fourier transform and coherence analysis of the restored signals from a detailed set of frequency components. Magnetic field recordings of spontaneous and evoked activity by means of magnetic encephalography demonstrated that multichannel precise Fourier spectrum contains a very large set of harmonics with high coherence. The inverse problem can be solved with great precision ba...

Llina?s, Rodolfo R.; Ustinin, Mikhail N.

2014-01-01

276

Frequency-pattern functional tomography of magnetoencephalography data allows new approach to the study of human brain organization  

Directory of Open Access Journals (Sweden)

Full Text Available A method based on a set of new theorems for the analysis of multichannel time series is described, based on precise Fourier transform and coherence analysis of the restored signals from a detailed set of frequency components. Magnetic field recordings of spontaneous and evoked activity by means of magnetic encephalography demonstrated that multichannel precise Fourier spectrum contains a very large set of harmonics with high coherence. The inverse problem can be solved with great precision based on coherent harmonics, so the technique is a promising platform of general analysis in brain imaging. The analysis method makes it possible to reconstruct sites and timing of electrical activity generated by both spontaneous and evoked brain function at different depths in the brain in the millisecond time range.

Rodolfo R Llinás

2014-04-01

277

Frequency-pattern functional tomography of magnetoencephalography data allows new approach to the study of human brain organization.  

Science.gov (United States)

A method based on a set of new theorems for the analysis of multichannel time series is described, based on precise Fourier transform and coherence analysis of the restored signals from a detailed set of frequency components. Magnetic field recordings of spontaneous and evoked activity by means of magnetic encephalography demonstrated that multichannel precise Fourier spectrum contains a very large set of harmonics with high coherence. The inverse problem can be solved with great precision based on coherent harmonics, so the technique is a promising platform of general analysis in brain imaging. The analysis method makes it possible to reconstruct sites and timing of electrical activity generated by both spontaneous and evoked brain function at different depths in the brain in the millisecond time range. PMID:24808829

Llinás, Rodolfo R; Ustinin, Mikhail N

2014-01-01

278

On macromolecular refinement at subatomic resolution withinteratomic scatterers  

Energy Technology Data Exchange (ETDEWEB)

A study of the accurate electron density distribution in molecular crystals at subatomic resolution, better than {approx} 1.0 {angstrom}, requires more detailed models than those based on independent spherical atoms. A tool conventionally used in small-molecule crystallography is the multipolar model. Even at upper resolution limits of 0.8-1.0 {angstrom}, the number of experimental data is insufficient for the full multipolar model refinement. As an alternative, a simpler model composed of conventional independent spherical atoms augmented by additional scatterers to model bonding effects has been proposed. Refinement of these mixed models for several benchmark datasets gave results comparable in quality with results of multipolar refinement and superior of those for conventional models. Applications to several datasets of both small- and macro-molecules are shown. These refinements were performed using the general-purpose macromolecular refinement module phenix.refine of the PHENIX package.

Afonine, Pavel V.; Grosse-Kunstleve, Ralf W.; Adams, Paul D.; Lunin, Vladimir Y.; Urzhumtsev, Alexandre

2007-11-09

279

Preferred Ice Crystal Orientation Fabric Measurements within the Greenland Ice Sheet Using Multi-Polarization Radar Data  

Science.gov (United States)

Discharge of ice from the Greenland Ice Sheet to the ocean has increased significantly over the last 25 years due to the acceleration of important outlet glaciers. It was reported that the Greenland Ice Sheet contributed about 2.5 m out of about 6 m of sea-level rise during the Eemian interglacial period. The temperatures during Eemian were reported to be about 8o×4o C higher than the mean of the past millennium. Laboratory measurements have shown that glacial ice, characterized by preferred crystal orientation fabric (COF), is three times more deformable than ice with randomly oriented crystalline structures. Layers characterized by preferred ice COF can influence the flow behavior of a glacier or ice sheet. However, COF measurements are typically obtained from ice cores, and thus are very spatially limited and mostly constrained to areas with little ice flow. A more efficient technique to map the extent of ice fabric over larger regions of ice sheets is needed to better understand the effects on large scale ice flow processes. Radar measurements are capable of discriminating between reflections caused by changes in density, electrical permittivity and COF by exploiting the anisotropic and birefringent properties of ice crystals. For this investigation two radar datasets were collected during the survey of the Greenland Eemian Ice Drilling Site (77.45°N 51.06°W) in August 2008, using a ground-based and chirped-pulse Multi-Channel Radar Depth Sounder (MCRDS) developed by the Center for Remote Sensing of Ice Sheets (CReSIS). The radar used two transmit and eight receive antennas at the center frequency of 150 MHz with a bandwidth of 30 MHz. The first data set consisted of polarimatric measurements acquired in a circular pattern (radius: 35 m) with two co-polarized antenna orientations (one transmitter and four receivers oriented with 90° offsets in the directions of the incident H-Field and E-Field, respectively). Analysis of the circular data shows a periodic power variation with four distinct extinction patterns occurring at 90 degree intervals starting at approximately 700 m depth. Furthermore a 20 degree phase change is observed between the E- and H-field data. Both observations suggest that approximately 72% of the 2542m ice column exhibits birefringent anisotropy caused by preferred ice crystal orientation. The second dataset was acquired in a grid pattern consisting of twenty 10-Km 2D lines (NW to SE) spaced at 0.5-Km and three 10-Km lines (NE to SW) spaced at 2.5-Km. Both transmit and eight receive antenna were oriented parallel to the vehicle track, resulting in E-Field co-polarized data. We will determine the dominant COF relative to the ice divide for a 100 square Km region around the NEEM camp using the results from both datasets. The results of this investigation will be compared to the NEEM ice core observations to determine the accuracy of the analysis. In this investigation we will provide a brief overview of the system and experiments and present the results of data analysis.

Velez-Gonzalez, J. A.; JiLu, L.; Leuschen, C.; Gogineni, P.; Van der Veen, C. J.; Tsoflias, G. P.; Drews, R.; Harish, A. R.

2013-12-01

280

Dual-frequency and Multi-polarization Shuttle Imaging Radar for Volcano Detection in Kunlun Mountain of Western China  

Science.gov (United States)

This paper discusses the methods and mechanisms of detecting volcanoes using L.C bands and HH, HV, VV polarization imaging radar, and gives the spatial distributions of volcanoes elevated more than 5300m above the sea level, eruptive phases and analytical results of rock components.

Huadong, G.; Jingjuan, L.; Changlin, W.; Caho, W.; Farr, T. G.; Evans, D. L.

1996-01-01

 
 
 
 
281

The African Union (AU), new partnership for African Aevelopment (NEPAD) and regional integration in Africa in a multipolar word  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is trite to argue that regional integration or cooperation in Africa is deeply rooted in the historical evolution of the continent’s socio-political forces. No doubt, the trans-Atlantic slave trade created a huge social, political, economic, and cultural distortion in Africa. It was a period when millions of productive Africans were forcefully uprooted from the continent and taken to Europe and the Americas. However, the end of the slave trade opened a new vista in the efforts of peop...

Asogwa, Felix Chinwe

2014-01-01

282

Study of H{sup -} production in H{sub 2} microwave multipolar plasmas by optical and electrical diagnostics  

Energy Technology Data Exchange (ETDEWEB)

A way to achieve heating is the injection in the plasma of highly energetic particles ({approx} MeV) that will transfer their energy during collisions. For this purpose, energetic charged particles are independently created in D{sub 2} plasmas and then neutralized so they can penetrate into the tokamak without being sensitive to the magnetic confinement. Neutral beam injection can deliver up to 16 MW into the ITER plasma. D{sup -} beams are used rather than D{sup +} as the neutralisation of the latter is almost zero instead of 60% for D{sup -}, at the energy of interest. In this framework, our work is devoted to the production of H{sup -} negative ions from H{sub 2} microwave multi-dipolar plasmas. Negative ions are produced inside the plasma volume by dissociative electron attachment to highly vibrationally-excited molecules H{sub 2} (step 3). They can also be produced throughout plasma-surface interactions, where H atoms created in the plasma volume stick on the material (step 1) and recombine with hydrogen present on the surface, resulting in the desorption of a vibrationally-excited H{sub 2} molecule (step 2), which reacts with a cold electron to form a negative ion (step 3). Plasma diagnostics are implemented to better understand the mechanisms involved in H production. Step 3 is studied by means of Langmuir probes for electron density and energy distribution measurements, while laser photo-detachment (Nd-YAG, 1064 nm) gives negative ion densities. H atom densities are followed by Optical Emission Spectroscopy (OES) using actinometry, as well as Laser Induced Fluorescence with one (LIF) or two (TALIF) photons. By generating H atom spatial profiles via Abel transform, we try to differentiate volume mechanisms from surface ones. This document is composed of a short paper followed by a poster

Soum-Glaude, A.; Bechu, S. [Laboratoire de Physique Subatomique et de Cosmologie, Grenoble (France); Welzel, S.; Engeln, R. [Group Plasma and Materials Processing, Department of Applied Physics, Technische Universiteit Eindhoven, Eindhoven (Netherlands)

2011-07-01

283

Spin, parity, and multipolarity assignments and g-factor measurements using the TRISTAN superconducting magnet and four detector coincidence apparatus  

International Nuclear Information System (INIS)

The use of a multidetector ?-ray coincidence system for perturbed and unperturbed ?-ray angular correlations at the on-line mass separator TRISTAN is described. Applications of angular correlation techniques for deducing spin and parity assignments in a variety of even-even nuclides (116Ag, 142Ba, 142Ce, 144Ce), odd-odd nuclides (144La, 138Cs, 132Sb) and odd-mass nuclides (139Xe, 105Rh) are discussed. (Auth.)

284

Correction of Multipolar Field Errors in Insertion Regions for the Phase 1 LHC Upgrade and Dynamic Aperture  

CERN Document Server

The Phase 1 upgrade of the LHC interaction regions aims at increasing the machine luminosity by reducing the beam size at the interaction point. This requires an in-depth review of the full insertion region layout and a large set of options have been proposed with conceptually different designs. This paper reports on a general approach for the compensation of the non-linear eld errors of the insertion region magnets by means of dedicated correctors. The goal is to use the same correction approach for all the different layouts. The correction algorithm is based on the computation of the high orders of the polynomial transfer map using MAD-X and Polymorphic Tracking Code, while the actual performance of the method is estimated by computing the dynamic aperture of the layouts under study.

Tomás, R; de Maria, R

2008-01-01

285

Model’s comparison  

DEFF Research Database (Denmark)

Three popular disease spread simulation models were used to simulate the spread of foot-and-mouth disease (FMD) in Denmark. The models’ predictions in term of disease spread, consequence, and the ranking of the applied control strategies were compared. The original Davis Animal Disease Spread (DADS version 0.05) was adapted to DTU-DADS, and this model as well as InterSpread Plus (ISP version 2.001.11) and the North American Animal Disease Spread Model (NAADSM version 3.0.81) were all used to simulate hypothetical spread of FMD in Denmark. Data on Danish herds were used including herd type, movements, and location in the period 1st October 2006 to 30th September 2007. The three models to the highest possible extend set up to simulate the same epidemics in 3 different control scenarios: 1) A basic scenario representing EU and Danish control strategies, 2) pre-emptive depopulation of susceptible herds in a 500 meters radius around the detected herds, and 3) suppressive vaccination of susceptible herds in a 1,000 meters radius around the detected herds. Depopulation and vaccination started either 14 days following the detection of the first infected herd or following detection of 50 infected herds. Five thousand index herds were selected randomly in which there were 1,000 cattle herds located in high density cattle area and 1,000 in low density cattle area, 1,000 swine herds located in high density swine area and 1,000 in low density swine area, and 1,000 sheep herds. Generally, NAADSM predicted the largest, longest duration and costliest epidemics. DTU-DADS predicted larger, longer duration and costlier epidemics than ISP, except when epidemics started in cattle herds located in high density cattle area. ISP predicted suppressive vaccination to be less costly than depopulation, while the least costly control strategy predicted by DTU-DADS differed depending on the species and density area of the index herd. It was not possible to run the depopulation scenarios in the NAADSM due to limitations in the model. Running several models in parallel gives better insight in disease spread, limits typing and coding errors and improves understanding of modeled processes. The chosen control strategy might depend on the chosen model.

Hisham Beshara Halasa, Tariq; Boklund, Anette

2012-01-01

286

Modelling SDL, Modelling Languages  

Directory of Open Access Journals (Sweden)

Full Text Available Today's software systems are too complex to implement them and model them using only one language. As a result, modern software engineering uses different languages for different levels of abstraction and different system aspects. Thus to handle an increasing number of related or integrated languages is the most challenging task in the development of tools. We use object oriented metamodelling to describe languages. Object orientation allows us to derive abstract reusable concept definitions (concept classes from existing languages. This language definition technique concentrates on semantic abstractions rather than syntactical peculiarities. We present a set of common concept classes that describe structure, behaviour, and data aspects of high-level modelling languages. Our models contain syntax modelling using the OMG MOF as well as static semantic constraints written in OMG OCL. We derive metamodels for subsets of SDL and UML from these common concepts, and we show for parts of these languages that they can be modelled and related to each other through the same abstract concepts.

Michael Piefel

2007-02-01

287

Polarimetric SAR Data for Urban Land Cover Classification Using Finite Mixture Model  

Science.gov (United States)

Image classification techniques play an important role in automatic analysis of remote sensing data. This paper demonstrates the potential of polarimetric synthetic aperture radar (PolSAR) for urban land cover mapping using an unsupervised classification approach. Analysis of PolSAR images often shows that non-Gaussian models give better representation of the scattering vector statistics. Hence, processing algorithms based on non-Gaussian statistics should improve performance, compared to complex Gaussian distributions. Several distributions could be used to model SAR image texture with different spatial correlation properties and various degrees of inhomogeneity [1-3]. Statistical properties are widely used for image segmentation and land cover classification of PolSAR data. The pixel-based approaches cluster individual pixels through analysis of their statistical properties. Those methods work well on the relatively coarse spatial resolution images. But classification results based on pixelwise analysis demonstrate the pepper-salt effect of speckle in medium and high resolution applications such as urban area monitoring [4]. Therefore, the expected improvement of the classification results is hindered by the increase of textural differences within a class. In such situation, enhancement could be made through exploring the contextual correlation among pixels by Markov random field (MRF) models [4, 5]. The potential of MRF models to retrieve spatial contextual information is desired to improve the accuracy and reliability of image classification. Unsupervised contextual polarimetric SAR image segmentation is addressed by combining statistical modeling and spatial context within an MRF framework. We employ the stochastic expectation maximization (SEM) algorithm [6] to jointly perform clustering of the data and parameter estimation of the statistical distribution conditioned to each image cluster and the MRF model. This classification method is applied on medium resolution L-band ALOS data from Tehran, Iran. Clustering results are presented and discussed in the full paper, also comparing the classification approach with other commonly used algorithms. References: [1] J.-S. Lee, M. Grunes, and R. Kwok, "Classification of multi-look polarimetric SAR imagery based on the complex Wishart distribution," Int. J Remote Sens., vol. 15, no. 11, pp. 2299-2311, Jul. 1994. [2] C. C. Freitas, A. C. Frery, and A. H. Correia, "The polarimetric G0 distribution for SAR data analysis," Environmetrics, vol. 16, no. 1, pp. 13-31, Feb. 2005. [3] A. P. Doulgeris, S. N. Anfinsen, and T. Eltoft, "Automated non-Gaussian clustering of polarimetric synthetic aperture radar images," IEEE Trans. Geosci. Remote Sens., vol. 49, no. 10, pp. 3665-3676, Oct. 2011. [4]. V. Akbari, A. P. Doulgeris, G. Moser, S. N. Anfinsen, T. Eltoft, and S. Serpico, "A textural-contextual model for unsupervised segmentation of multi-polarization synthetic aperture radar images," IEEE Transactions on Geoscience and Remote Sensing, in press. [5] S. Li, "Markov Random Field Modeling in Image Analysis," 3rd ed. London, U.K., Springer-Verlag, 2009.

Mahdianpari, Masoud; Akbari, Vahid; Mohammadimanesh, Fariba; Alioghli Fazel, Mohammad

2013-04-01

288

Modelling Practice  

DEFF Research Database (Denmark)

This chapter deals with the practicalities of building, testing, deploying and maintaining models. It gives specific advice for each phase of the modelling cycle. To do this, a modelling framework is introduced which covers: problem and model definition; model conceptualization; model data requirements; model construction; model solution; model verification; model validation and finally model deployment and maintenance. Within the adopted methodology, each step is discussedthrough the consideration of key issues and questions relevant to the modelling activity. Practical advice, based on many years of experience is providing in directing the reader in their activities.Traps and pitfalls are discussed and strategies also given to improve model development towards “fit-for-purpose” models. The emphasis in this chapter is the adoption and exercise of a modelling methodology that has proven very successful in many model building activities. It is vital that good methodologies are adopted for both thoroughness andefficiency purposes. Asking good questions for each modelling stage can aid in getting to effective and efficient solutions in modelling practice. Modelling is very much a ‘goal oriented’ activity, under constraints of system insight, time, cost and human resources. The George Box dictum that “all models are wrong, some are useful” should be coupled with the parsimony principle to ensure optimal outcomes.

Cameron, Ian; Gani, Rafiqul

2011-01-01

289

Modeling Malaria  

Science.gov (United States)

In this module, we develop models of the effects of malaria on various populations of humans and mosquitoes. After considering differential equations to model a system, we create a model using the systems modeling tool STELLA. Projects involve various refinements of the model.

Shiflet, Angela B.; Shiflet, George W.

290

Modelling SDL, Modelling Languages  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Today’s so?ware systems are too complex to implement them and model them using only one language. As a result,modern so?ftware engineering uses different languages for different levels of abstraction and different system aspects. ?Thus to handle an increasing number of related or integrated languages is the most challenging task in the development of tools. We use object oriented metamodelling to describe languages. Object orientation allows us to derive abstract reusable concept de...

Piefel, Michael; Scheidgen, Markus

2006-01-01

291

Fair Model  

Science.gov (United States)

The Fair model web site includes a freely available United States macroeconomic econometric model and a multicounty econometric model. The models run on the Windows OS. Instructors can use the models to teach forecasting, run policy experiments, and evaluate historical episodes of macroeconomic behavior. The web site includes extensive documentation for both models. The simulation is for upper-division economics courses in macroeconomics or econometrics. The principle developer is Ray Fair at Yale University.

Blecha, Betty

292

Model theory  

CERN Document Server

Model theory deals with a branch of mathematical logic showing connections between a formal language and its interpretations or models. This is the first and most successful textbook in logical model theory. Extensively updated and corrected in 1990 to accommodate developments in model theoretic methods - including classification theory and nonstandard analysis - the third edition added entirely new sections, exercises, and references. Each chapter introduces an individual method and discusses specific applications. Basic methods of constructing models include constants, elementary chains, Sko

Chang, CC

2013-01-01

293

Animal models.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Animal models of cerebral ischaemia mimic at best less than 25% of all strokes. Compounds which prove efficacious in animal models should, therefore, only be expected to improve outcome in a quarter of all strokes. If trials for acute stroke are to succeed, stroke subgroups represented by the animal models should be targeted. For the other subgroups, e.g. lacunar stroke, appropriate animal models need to be developed. Moreover, thrombolysis should be included in animal models because it is li...

Small, Dl; Buchan, Am

2000-01-01

294

Modeling the purposes of models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Today, the purpose of a model is often kept implicit. The lack of explicit statements about a model's purpose hinders both its creation and its (re)use. In this paper, we adapt two goal modeling techniques, the Goal-Question-Metric paradigm and KAOS, an intentional modeling language, so that the purpose of a model can be explicitly stated and operationalized. Using some examples, we present how these approaches can document a model's purpose so that this model can be validated, improved and u...

Jeanneret, Ce?dric; Glinz, Martin; Baar, Thomas

2012-01-01

295

Geochemical modeling  

International Nuclear Information System (INIS)

Contributions to the workshop 'Geochemical modeling' from 19 to 20 September 1990 at the Karlsruhe Nuclear Research Centre. The report contains the programme and a selection of the lectures held at the workshop 'Geochemical modeling'. (BBR)

296

Battery Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The use of mobile devices is often limited by the capacity of the employed batteries. The battery lifetime determines how long one can use a device. Battery modeling can help to predict, and possibly extend this lifetime. Many different battery models have been developed over the years. However, with these models one can only compute lifetimes for specific discharge profiles, and not for workloads in general. In this paper, we give an overview of the different battery models that are availabl...

Jongerden, M. R.; Haverkort, B. R.

2008-01-01

297

Model Typing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Model-Driven Engineering is a discipline for the construction of systems based on the use of models. Although research is active into the use of MDE and its core technologies such as languages for storing, transforming and manipulating models, less attention has been paid to techniques for ensuring the safe reuse and composition of the elements which manipulate models. This thesis presents an approach based on ideas and formalisms from the domain of type systems for defining clear notions of ...

Steel, James

2007-01-01

298

Magnetosphere models  

International Nuclear Information System (INIS)

In this work the most recent magnetospheric models are reviewed. After a short overview of the particle environment, a synthetic survey of the problem is given. For each feature of magnetospheric modelling (boundary, current sheet, ring-current) the approaches used by different authors are described. In the second part a description is given of the magnetospheric models, divided into four groups. In the last part, the different uses of magnetospheric models are illustrated by means of examples

299

Computable models  

CERN Document Server

Computational models can be found everywhere in present day science and engineering. In providing a logical framework and foundation for the specification and design of specification languages, Raymond Turner uses this framework to introduce and study computable models. In doing so he presents the first systematic attempt to provide computational models with a logical foundation. Computable models have wide-ranging applications from programming language semantics and specification languages, through to knowledge representation languages and formalism for natural language semantics. They are al

Turner, Raymond

2009-01-01

300

Animal models.  

Science.gov (United States)

Epilepsy accounts for a significant portion of the dis-ease burden worldwide. Research in this field is fundamental and mandatory. Animal models have played, and still play, a substantial role in understanding the patho-physiology and treatment of human epilepsies. A large number and variety of approaches are available, and they have been applied to many animals. In this chapter the in vitro and in vivo animal models are discussed,with major emphasis on the in vivo studies. Models have used phylogenetically different animals - from worms to monkeys. Our attention has been dedicated mainly to rodents.In clinical practice, developmental aspects of epilepsy often differ from those in adults. Animal models have often helped to clarify these differences. In this chapter, developmental aspects have been emphasized.Electrical stimulation and chemical-induced models of seizures have been described first, as they represent the oldest and most common models. Among these models, kindling raised great interest, especially for the study of the epileptogenesis. Acquired focal models mimic seizures and occasionally epilepsies secondary to abnormal cortical development, hypoxia, trauma, and hemorrhage.Better knowledge of epileptic syndromes will help to create new animal models. To date, absence epilepsy is one of the most common and (often) benign forms of epilepsy. There are several models, including acute pharmacological models (PTZ, penicillin, THIP, GBL) and chronic models (GAERS, WAG/Rij). Although atypical absence seizures are less benign, thus needing more investigation, only two models are so far available (AY-9944,MAM-AY). Infantile spasms are an early childhood encephalopathy that is usually associated with a poor out-come. The investigation of this syndrome in animal models is recent and fascinating. Different approaches have been used including genetic (Down syndrome,ARX mutation) and acquired (multiple hit, TTX, CRH,betamethasone-NMDA) models.An entire section has been dedicated to genetic models, from the older models obtained with spontaneous mutations (GEPRs) to the new engineered knockout, knocking, and transgenic models. Some of these models have been created based on recently recognized patho-genesis such as benign familial neonatal epilepsy, early infantile encephalopathy with suppression bursts, severe myoclonic epilepsy of infancy, the tuberous sclerosis model, and the progressive myoclonic epilepsy. The contribution of animal models to epilepsy re-search is unquestionable. The development of further strategies is necessary to find novel strategies to cure epileptic patients, and optimistically to allow scientists first and clinicians subsequently to prevent epilepsy and its consequences. PMID:22938964

Coppola, Antonietta; Moshé, Solomon L

2012-01-01

 
 
 
 
301

Modeling & Simulation  

Science.gov (United States)

Modeling & Simulation is a journal published by The Society for Modeling and Simulation International. The Society has made its 2004 Modeling and Simulation Resource Guide available free to download. The directory provides descriptions and contact information for the many modeling and simulation software packages currently available, as well as listings for various modeling and simulation organizations worldwide. Two guest articles describe techniques for the application of real-time simulation in simulations that are complex. Previously published articles are also posted in the online archive.

302

Station Models  

Science.gov (United States)

This project will allow users to become acquainted with station models that are found on weather maps. Students will study the various atmospheric variables that are depicted on a station model and then practice on an interactive station model program. Part 1 - Being able to read and interpret weather maps is a very important skill in meteorology. One of the most basic skills of predicting the weather is being able to interpret a station model of a given location. A station model is a bundle of information that ...

Ertl, Mr.

2007-11-03

303

Constitutive Models  

DEFF Research Database (Denmark)

This chapter presents various types of constitutive models and their applications. There are 3 aspects dealt with in this chapter, namely: creation and solution of property models, the application of parameter estimation and finally application examples of constitutive models. A systematic procedure is introduced for the analysis and solution of property models. Models that capture and represent the temperature dependent behaviour of physical properties are introduced, as well as equation of state models (EOS) such as the SRK EOS. Modelling of liquid phase activity coefficients are also covered, illustrating several models such as the Wilson equation and NRTL equation, along with their solution strategies. A section shows how to use experimental data to regress the property model parameters using a least squares approach. A full model analysis is applied in each example that discusses the degrees of freedom, dependent and independent variables and solution strategy. Vapour-liquid and solid-liquid equilibrium is covered, and applications to droplet evaporation and kinetic models are given.

Sales-Cruz, Mauricio; Piccolo, Chiara

2011-01-01

304

ICRF modelling  

International Nuclear Information System (INIS)

This lecture provides a survey of the methods used to model fast magnetosonic wave coupling, propagation, and absorption in tokamaks. The validity and limitations of three distinct types of modelling codes, which will be contrasted, include discrete models which utilize ray tracing techniques, approximate continuous field models based on a parabolic approximation of the wave equation, and full field models derived using finite difference techniques. Inclusion of mode conversion effects in these models and modification of the minority distribution function will also be discussed. The lecture will conclude with a presentation of time-dependent global transport simulations of ICRF-heated tokamak discharges obtained in conjunction with the ICRF modelling codes. 52 refs., 15 figs

305

ICRF modelling  

Energy Technology Data Exchange (ETDEWEB)

This lecture provides a survey of the methods used to model fast magnetosonic wave coupling, propagation, and absorption in tokamaks. The validity and limitations of three distinct types of modelling codes, which will be contrasted, include discrete models which utilize ray tracing techniques, approximate continuous field models based on a parabolic approximation of the wave equation, and full field models derived using finite difference techniques. Inclusion of mode conversion effects in these models and modification of the minority distribution function will also be discussed. The lecture will conclude with a presentation of time-dependent global transport simulations of ICRF-heated tokamak discharges obtained in conjunction with the ICRF modelling codes. 52 refs., 15 figs.

Phillips, C.K.

1985-12-01

306

Functions and Models: Mathematical Models  

Science.gov (United States)

Describe the process of mathematical modeling;Name and describe some methods of modeling;Classify a symbolically represented function as one of the elementary algebraic or transcendental functions;Appraise the suitability of different models for interpreting a given set of data.

Michael Freeze

307

Inter-trial effect in luminance processing revealed by magnetoencephalography / Efecto inter-ensayo en el procesamiento de iluminación revelado por magnetoencefalografía  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish En este estudio, se examinó si el procesamiento de iluminación en el sistema visual humano exhibie algún efecto de historia (es decir, modulación inter-ensayo) en experimentos psicofísicos y de magnetoencefalografía (MEG). Un disco se presentó contra un fondo negro en varios niveles de iluminación e [...] n un orden aleatorio. Durante el registro de MEG, los participantes fueron instruidos para clasificar el brillo del disco (estimación de magnitud) y reportarlo durante el intervalo inter-ensayo. Los resultados de MEG mostraron que la activación neuromagnetica alrededor 200-220 ms después de la aparición de estímulo en las regiones occipito-temporal izquierda en un ensayo dade fue más débil cuando la iluminación de disco en el ensayo inmediatamente antes fue mayor. También se observó un efecto inverso inter-ensayo en el experimento psicofísico. Estos hallazgos sugieren que la actividad neuromagnética refleja la modulación inter-ensayo de procesamiento de iluminación que se correlaciona con la percepción subjetiva de brillo. Abstract in english In this study, we examined whether luminance processing in the human visual system would exhibit any history effect (i.e., inter-trial modulation) in psychophysical and magnetoencephalographic experiments. A disk was presented against a black background at various luminance levels in a randomized or [...] der. During the MEG recording, participants were instructed to rate the brightness of the disk (magnitude estimation) and to report it aloud during inter-stimulus interval. The MEG results showed that the neuromagnetic activation around 200-220 ms after the stimulus onset in the left occipito-temporal regions at a given trial was weaker when the disk luminance in the immediately prior trial was higher. An inverse inter-trial effect was also observed in the psychophysical experiment. These findings suggest that the neuromagnetic activity reflects the inter-trial modulation of luminance processing that correlates with the subjective perception of brightness.

Aki, Kondo; Katsumi, Watanabe.

2013-12-15

308

Experimental and database-transferred electron-density analysis and evaluation of electrostatic forces in coumarin-102 dye.  

Science.gov (United States)

The electron-density distribution of a new crystal form of coumarin-102, a laser dye, has been investigated using the Hansen-Coppens multipolar atom model. The charge density was refined versus high-resolution X-ray diffraction data collected at 100?K and was also constructed by transferring the charge density from the Experimental Library of Multipolar Atom Model (ELMAM2). The topology of the refined charge density has been analysed within the Bader `Atoms In Molecules' theory framework. Deformation electron-density peak heights and topological features indicate that the chromen-2-one ring system has a delocalized ?-electron cloud in resonance with the N (amino) atom. The molecular electrostatic potential was estimated from both experimental and transferred multipolar models; it reveals an asymmetric character of the charge distribution across the molecule. This polarization effect is due to a substantial charge delocalization within the molecule. The molecular dipole moments derived from the experimental and transferred multipolar models are also compared with the liquid and gas-phase dipole moments. The substantial molecular dipole moment enhancements observed in the crystal environment originate from the crystal field and from intermolecular charge transfer induced and controlled by C-H···O and C-H···N intermolecular hydrogen bonds. The atomic forces were integrated over the atomic basins and compared for the two electron-density models. PMID:23165601

Bibila Mayaya Bisseyou, Yvon; Bouhmaida, Nouhza; Guillot, Benoit; Lecomte, Claude; Lugan, Noel; Ghermani, Noureddine; Jelsch, Christian

2012-12-01

309

Turbulence modelling  

International Nuclear Information System (INIS)

This paper is an introduction course in modelling turbulent thermohydraulics, aimed at computational fluid dynamics users. No specific knowledge other than the Navier Stokes equations is required beforehand. Chapter I (which those who are not beginners can skip) provides basic ideas on turbulence physics and is taken up in a textbook prepared by the teaching team of the ENPC (Benque, Viollet). Chapter II describes turbulent viscosity type modelling and the 2k-? two equations model. It provides details of the channel flow case and the boundary conditions. Chapter III describes the 'standard' (Rij-?) Reynolds tensions transport model and introduces more recent models called 'feasible'. A second paper deals with heat transfer and the effects of gravity, and returns to the Reynolds stress transport model. (author)

310

Phenomenological models  

Energy Technology Data Exchange (ETDEWEB)

The biological effects of ionizing radiation exposure are the result of a complex sequence of physical, chemical, biochemical, and physiological interactions. One way to begin a search for an understanding of health effects of radiation is through the development of phenomenological models of the response. Many models have been presented and tested in the slowly evolving process of characterizing cellular response. A range of models covering different endpoints and phenomena has developed in parallel. Many of these models employ similar assumptions about some underlying processes while differing about the nature of others. An attempt is made to organize many of the models into groups with similar features and to compare the consequences of those features with the actual experimental observations. It is assumed that by showing that some assumptions are inconsistent with experimental observations, the job of devising and testing mechanistic models can be simplified. 43 refs., 13 figs.

Braby, L.A.

1990-09-01

311

Modeling Arcs  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although vacuum arcs were first identified over 110 years ago, they are not yet well understood. We have since developed a model of breakdown and gradient limits that tries to explain, in a self-consistent way: arc triggering, plasma initiation, plasma evolution, surface damage and gra- dient limits. We use simple PIC codes for modeling plasmas, molecular dynamics for modeling surface breakdown, and surface damage, and mesoscale surface thermodynamics and finite element elec...

Insepov, Zeke; Norem, Jim; Veitzer, Seth; Mahalingam, Sudhakar

2011-01-01

312

Ventilation Model  

Energy Technology Data Exchange (ETDEWEB)

The purpose of the Ventilation Model is to simulate the heat transfer processes in and around waste emplacement drifts during periods of forced ventilation. The model evaluates the effects of emplacement drift ventilation on the thermal conditions in the emplacement drifts and surrounding rock mass, and calculates the heat removal by ventilation as a measure of the viability of ventilation to delay the onset of peak repository temperature and reduce its magnitude. The heat removal by ventilation is temporally and spatially dependent, and is expressed as the fraction of heat carried away by the ventilation air compared to the fraction of heat produced by radionuclide decay. One minus the heat removal is called the wall heat fraction, or the remaining amount of heat that is transferred via conduction to the surrounding rock mass. Downstream models, such as the ''Multiscale Thermohydrologic Model'' (BSC 2001), use the wall heat fractions as outputted from the Ventilation Model to initialize their post-closure analyses. The Ventilation Model report was initially developed to analyze the effects of preclosure continuous ventilation in the Engineered Barrier System (EBS) emplacement drifts, and to provide heat removal data to support EBS design. Revision 00 of the Ventilation Model included documentation of the modeling results from the ANSYS-based heat transfer model. The purposes of Revision 01 of the Ventilation Model are: (1) To validate the conceptual model for preclosure ventilation of emplacement drifts and verify its numerical application in accordance with new procedural requirements as outlined in AP-SIII-10Q, Models (Section 7.0). (2) To satisfy technical issues posed in KTI agreement RDTME 3.14 (Reamer and Williams 2001a). Specifically to demonstrate, with respect to the ANSYS ventilation model, the adequacy of the discretization (Section 6.2.3.1), and the downstream applicability of the model results (i.e. wall heat fractions) to initialize post-closure thermal models (Section 6.6). (3) To satisfy the remainder of KTI agreement TEF 2.07 (Reamer and Williams 2001b). Specifically to provide the results of post-test ANSYS modeling of the Atlas Facility forced convection tests (Section 7.1.2). This portion of the model report also serves as a validation exercise per AP-SIII.10Q, Models, for the ANSYS ventilation model. (4) To further satisfy KTI agreements RDTME 3.01 and 3.14 (Reamer and Williams 2001a) by providing the source documentation referred to in the KTI Letter Report, ''Effect of Forced Ventilation on Thermal-Hydrologic Conditions in the Engineered Barrier System and Near Field Environment'' (Williams 2002). Specifically to provide the results of the MULTIFLUX model which simulates the coupled processes of heat and mass transfer in and around waste emplacement drifts during periods of forced ventilation. This portion of the model report is presented as an Alternative Conceptual Model with a numerical application, and also provides corroborative results used for model validation purposes (Section 6.3 and 6.4).

V. Chipman

2002-10-05

313

Ventilation Model  

International Nuclear Information System (INIS)

The purpose of the Ventilation Model is to simulate the heat transfer processes in and around waste emplacement drifts during periods of forced ventilation. The model evaluates the effects of emplacement drift ventilation on the thermal conditions in the emplacement drifts and surrounding rock mass, and calculates the heat removal by ventilation as a measure of the viability of ventilation to delay the onset of peak repository temperature and reduce its magnitude. The heat removal by ventilation is temporally and spatially dependent, and is expressed as the fraction of heat carried away by the ventilation air compared to the fraction of heat produced by radionuclide decay. One minus the heat removal is called the wall heat fraction, or the remaining amount of heat that is transferred via conduction to the surrounding rock mass. Downstream models, such as the ''Multiscale Thermohydrologic Model'' (BSC 2001), use the wall heat fractions as outputted from the Ventilation Model to initialize their post-closure analyses. The Ventilation Model report was initially developed to analyze the effects of preclosure continuous ventilation in the Engineered Barrier System (EBS) emplacement drifts, and to provide heat removal data to support EBS design. Revision 00 of the Ventilation Model included documentation of the modeling results from the ANSYS-based heat transfer model. The purposes of Revision 01 of the Ventilation Model are: (1) To validate the conceptual model for preclosure ventilation of emplacement drifts and verify its numerical application in accordance with new procedural requirements as outlined in AP-SIII-10Q, Models (Section 7.0). (2) To satisfy technical issues posed in KTI agreement RDTME 3.14 (Reamer and Williams 2001a). Specifically to demonstrate, with respect to the ANSYS ventilation model, the adequacy of the discretization (Section 6.2.3.1), and the downstream applicability of the model results (i.e. wall heat fractions) to initialize post-closure thermal models (Section 6.6). (3) To satisfy the remainder of KTI agreement TEF 2.07 (Reamer and Williams 2001b). Specifically to provide the results of post-test ANSYS modeling of the Atlas Facility forced convection tests (Section 7.1.2). This portion of the model report also serves as a validation exercise per AP-SIII.10Q, Models, for the ANSYS ventilation model. (4) To further satisfy KTI agreements RDTME 3.01 and 3.14 (Reamer and Williams 2001a) by providing the source documentation referred to in the KTI Letter Report, ''Effect of Forced Ventilation on Thermal-Hydrologic Conditions in the Engineered Barrier System and Near Field Environment'' (Williams 2002). Specifically to provide the results of the MULTIFLUX model which simulates the coupled processes of heat and mass transfer in and around waste emplacement drifts during periods of forced ventilation. This portion of the model report is presented as an Alternative Conceptual Model with a numerical application, and also provides corroborative results used for model validation purposes (Section 6.3 and 6.4)

314

Damping rates of surface plasmons for particles of size from nano- to micrometers; reduction of the nonradiative decay  

International Nuclear Information System (INIS)

Damping rates of multipolar, localized surface plasmons (SPs) of gold and silver nanospheres of radii up to 1000 nm were found with the tools of classical electrodynamics. The significant increase in damping rates followed by noteworthy decrease for larger particles takes place along with substantial red-shift of plasmon resonance frequencies as a function of particle size. We also introduced interface damping into our modeling, which substantially modifies the plasmon damping rates of smaller particles. We demonstrate unexpected reduction of the multipolar SP damping rates in certain size ranges. This effect can be explained by the suppression of the nonradiative decay channel as a result of the lost competition with the radiative channel. We show that experimental dipole damping rates [H. Baida, et al., Nano Lett. 9(10) (2009) 3463, and C. Sönnichsen, et al., Phys. Rev. Lett. 88 (2002) 077402], and the resulting resonance quality factors can be described in a consistent and straightforward way within our modeling extended to particle sizes still unavailable experimentally. -- Highlights: ? We model plasmon damping rates up to the uncommonly large particles of 1000 nm. ? We demonstrate reduction of multipolar SP damping rates below its low size limit. ? We show that the radiative decay competes with the nonradiative processes. ? We model the quality Q-factor of SP multipolar resonances as a function of size. ? We confront our size characteristics with the experimental results of other authors.

315

Model Selection for Geostatistical Models  

Energy Technology Data Exchange (ETDEWEB)

We consider the problem of model selection for geospatial data. Spatial correlation is typically ignored in the selection of explanatory variables and this can influence model selection results. For example, the inclusion or exclusion of particular explanatory variables may not be apparent when spatial correlation is ignored. To address this problem, we consider the Akaike Information Criterion (AIC) as applied to a geostatistical model. We offer a heuristic derivation of the AIC in this context and provide simulation results that show that using AIC for a geostatistical model is superior to the often used approach of ignoring spatial correlation in the selection of explanatory variables. These ideas are further demonstrated via a model for lizard abundance. We also employ the principle of minimum description length (MDL) to variable selection for the geostatistical model. The effect of sampling design on the selection of explanatory covariates is also explored.

Hoeting, Jennifer A.; Davis, Richard A.; Merton, Andrew A.; Thompson, Sandra E.

2006-02-01

316

Modeling Sunspots  

Science.gov (United States)

Modeling in science has been studied by education researchers for decades and is now being applied broadly in school. It is among the scientific practices featured in the "Next Generation Science Standards" ("NGSS") (Achieve Inc. 2013). This article describes modeling activities in an extracurricular science club in a high…

Oh, Phil Seok; Oh, Sung Jin

2013-01-01

317

OSPREY Model  

Energy Technology Data Exchange (ETDEWEB)

The absence of industrial scale nuclear fuel reprocessing in the U.S. has precluded the necessary driver for developing the advanced simulation capability now prevalent in so many other countries. Thus, it is essential to model complex series of unit operations to simulate, understand, and predict inherent transient behavior and feedback loops. A capability of accurately simulating the dynamic behavior of advanced fuel cycle separation processes will provide substantial cost savings and many technical benefits. The specific fuel cycle separation process discussed in this report is the off-gas treatment system. The off-gas separation consists of a series of scrubbers and adsorption beds to capture constituents of interest. Dynamic models are being developed to simulate each unit operation involved so each unit operation can be used as a stand-alone model and in series with multiple others. Currently, an adsorption model has been developed within Multi-physics Object Oriented Simulation Environment (MOOSE) developed at the Idaho National Laboratory (INL). Off-gas Separation and REcoverY (OSPREY) models the adsorption of off-gas constituents for dispersed plug flow in a packed bed under non-isothermal and non-isobaric conditions. Inputs to the model include gas, sorbent, and column properties, equilibrium and kinetic data, and inlet conditions. The simulation outputs component concentrations along the column length as a function of time from which breakthrough data is obtained. The breakthrough data can be used to determine bed capacity, which in turn can be used to size columns. It also outputs temperature along the column length as a function of time and pressure drop along the column length. Experimental data and parameters were input into the adsorption model to develop models specific for krypton adsorption. The same can be done for iodine, xenon, and tritium. The model will be validated with experimental breakthrough curves. Customers will be given access to OSPREY to used and evaluate the model.

Veronica J. Rutledge

2013-01-01

318

Linear Models  

CERN Document Server

This 1971 classic on linear models is once again available--as a Wiley Classics Library Edition. It features material that can be understood by any statistician who understands matrix algebra and basic statistical methods.

Searle, Shayle R

2012-01-01

319

Energy Models  

Science.gov (United States)

Energy models characterize the energy system, its evolution, and its interactions with the broader economy. The energy system consists of primary resources, including both fossil fuels and renewables; power plants, refineries, and other technologies to process and convert these r...

320

Programming models  

Energy Technology Data Exchange (ETDEWEB)

A programming model is a set of software technologies that support the expression of algorithms and provide applications with an abstract representation of the capabilities of the underlying hardware architecture. The primary goals are productivity, portability and performance.

Daniel, David J [Los Alamos National Laboratory; Mc Pherson, Allen [Los Alamos National Laboratory; Thorp, John R [Los Alamos National Laboratory; Barrett, Richard [SNL; Clay, Robert [SNL; De Supinski, Bronis [LLNL; Dube, Evi [LLNL; Heroux, Mike [SNL; Janssen, Curtis [SNL; Langer, Steve [LLNL; Laros, Jim [SNL

2011-01-14

 
 
 
 
321

Preference Modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper provides the reader with a presentation of preference modelling fundamental notions as well as some recent results in this field. Preference modelling is an inevitable step in a variety of fields: economy, sociology, psychology, mathematical programming, even medicine, archaeology, and obviously decision analysis. Our notation and some basic definitions, such as those of binary relation, properties and ordered sets, are presented at the beginning of the paper. We start by discussin...

O?ztu?rk, Meltem; Tsoukias, Alexis; Vincke, Philippe

2006-01-01

322

Modelling Constructs  

DEFF Research Database (Denmark)

There are many different notations and formalisms for modelling business processes and workflows. These notations and formalisms have been introduced with different purposes and objectives. Later, influenced by other notations, comparisons with other tools, or by standardization efforts, these notations have been extended in order to increase expressiveness and to be more competitive. This resulted in an increasing number of notations and formalisms for modelling business processes and in an increase of the different modelling constructs provided by modelling notations, which makes it difficult to compare modelling notations and to make transformations between them. One of the reasons is that, in each notation, the new concepts are introduced in a different way by extending the already existing constructs. In this chapter, we go the opposite direction: We show that it is possible to add most of the typical extensions on top of any existing notation or formalism—without changing the formalism itself. Basically, we introduce blocks with some additional attributes defining their initiation and termination behaviour. This serves two purposes: First, it gives a clearer understanding of the basic constructs and how they can be combined with more advanced constructs. Second, it will help combining different modelling notations with each other. Note that, though we introduce a notation for blocks in this chapter, we are not so much interested in promoting this notation here. The notation should just prove that it is possible to separate different issues of a modelling notation, and this way making its concepts clearer and the interchange of models easier. A fully-fledged block notation with a clear and simple interface to existing formalisms is yet to be developed.

Kindler, Ekkart

2009-01-01

323

Modeling depression in animal models.  

Science.gov (United States)

Animal models and preclinical tests have played large roles in the development of antidepressant drugs and are likely to continue to play important roles. In the present communication, the main animal models of depression have been described and reviewed. These models include the Flinders sensitive line (FSL) rat, the Wistar Kyoto (WKY) rat, the fawn-hooded (FH) rat, and the learned helpless (LH) rat. In addition, the materials used to assess the behavior of these rats, including swim tanks, drinking tubes, and an open field apparatus, have been discussed. Finally, the methods used in collecting the relevant behaviors in the animal models are described. These include the procedures used in the forced swim test and chronic mild stress protocols, including the sucrose preference test. It is concluded that the behavioral tests used to infer depressed-like behavior in rats will continue to provide useful data if the appropriate animals and proper methods are used. PMID:22231810

Overstreet, David H

2012-01-01

324

Mechanistic models  

Energy Technology Data Exchange (ETDEWEB)

Several models and theories are reviewed that incorporate the idea of radiation-induced lesions (repairable and/or irreparable) that can be related to molecular lesions in the DNA molecule. Usually the DNA double-strand or chromatin break is suggested as the critical lesion. In the models, the shoulder on the low-LET survival curve is hypothesized as being due to one (or more) of the following three mechanisms: (1) ``interaction`` of lesions produced by statistically independent particle tracks; (2) nonlinear (i.e., linear-quadratic) increase in the yield of initial lesions, and (3) saturation of repair processes at high dose. Comparisons are made between the various approaches. Several significant advances in model development are discussed; in particular, a description of the matrix formulation of the Markov versions of the RMR and LPL models is given. The more advanced theories have incorporated statistical fluctuations in various aspects of the energy-loss and lesion-formation process. An important direction is the inclusion of physical and chemical processes into the formulations by incorporating relevant track structure theory (Monte Carlo track simulations) and chemical reactions of radiation-induced radicals. At the biological end, identification of repair genes and how they operate as well as a better understanding of how DNA misjoinings lead to lethal chromosome aberrations are needed for appropriate inclusion into the theories. More effort is necessary to model the complex end point of radiation-induced carcinogenesis.

Curtis, S.B.

1990-09-01

325

Mechanistic models  

Energy Technology Data Exchange (ETDEWEB)

Several models and theories are reviewed that incorporate the idea of radiation-induced lesions (repairable and/or irreparable) that can be related to molecular lesions in the DNA molecule. Usually the DNA double-strand or chromatin break is suggested as the critical lesion. In the models, the shoulder on the low-LET survival curve is hypothesized as being due to one (or more) of the following three mechanisms: (1) interaction'' of lesions produced by statistically independent particle tracks; (2) nonlinear (i.e., linear-quadratic) increase in the yield of initial lesions, and (3) saturation of repair processes at high dose. Comparisons are made between the various approaches. Several significant advances in model development are discussed; in particular, a description of the matrix formulation of the Markov versions of the RMR and LPL models is given. The more advanced theories have incorporated statistical fluctuations in various aspects of the energy-loss and lesion-formation process. An important direction is the inclusion of physical and chemical processes into the formulations by incorporating relevant track structure theory (Monte Carlo track simulations) and chemical reactions of radiation-induced radicals. At the biological end, identification of repair genes and how they operate as well as a better understanding of how DNA misjoinings lead to lethal chromosome aberrations are needed for appropriate inclusion into the theories. More effort is necessary to model the complex end point of radiation-induced carcinogenesis.

Curtis, S.B.

1990-09-01

326

Subcomponent models  

International Nuclear Information System (INIS)

According to the instruction given by Professor Lanius and Professor Uhlman, the Conference Chairmen, and by Professor Ranft and Professor Nowak, the Chairmen of the Program Committee, I have organized the Session B04 ''Subcomponent Models'' in the following way: First, I have tried to review recent theoretical works on composite models of quarks and leptons, including twenty-six contributed papers allocated to this session, with the title of ''Composite Models''. Next, I have asked Professor Yamada from University of Tokyo to review recent experimental works related to this subject, including three contributed papers allocated to this session, with the title of ''Experimental Search for Compositeness''. After that, I have invited Professor Mohapatra from University of Maryland and Professor Nielsen from Niels Bohr Institute to give talks on their own recent works contributed to this session, with the titles of ''Fermion Generations and Compositeness'' and ''Field Theories without Fundamental (Gauge) Symmetry'', respectively. (author)

327

Application of radar polarimetry to forestry  

Science.gov (United States)

In order to understand L-band multipolarization radar measurements of forested areas, a model for the forest polarization signature was developed. The model is based on backscatter from dielectric cylinders which represent branches and trunks. In the model the Stokes matrices corresponding to several different scattering mechanisms is calculated, combining the results to get the total Stokes matrix. Comparison of model predictions with radar measurements shows that the model can accurately predict the forest polarization signature.

Durden, S. L.; Zebker, H. A.; Vanzyl, J. J.

1988-01-01

328

Environmental modeling  

CERN Document Server

The book has two aims: to introduce basic concepts of environmental modelling and to facilitate the application of the concepts using modern numerical tools such as MATLAB. It is targeted at all natural scientists dealing with the environment: process and chemical engineers, physicists, chemists, biologists, biochemists, hydrogeologists, geochemists and ecologists. MATLAB was chosen as the major computer tool for modeling, firstly because it is unique in it's capabilities, and secondly because it is available in most academic institutions, in all universities and in the research departments of

Holzbecher, Ekkehard

2012-01-01

329

Molecular modeling  

Directory of Open Access Journals (Sweden)

Full Text Available The use of computational chemistry in the development of novel pharmaceuticals is becoming an increasingly important tool. In the past, drugs were simply screened for effectiveness. The recent advances in computing power and the exponential growth of the knowledge of protein structures have made it possible for organic compounds to be tailored to decrease the harmful side effects and increase the potency. This article provides a detailed description of the techniques employed in molecular modeling. Molecular modeling is a rapidly developing discipline, and has been supported by the dramatic improvements in computer hardware and software in recent years.

Sharma Aarti

2009-01-01

330

Supernova models  

International Nuclear Information System (INIS)

Recent progress in understanding the observed properties of Type I supernovae as a consequence of the thermonuclear detonation of white dwarf stars and the ensuing decay of the 56Ni produced therein is reviewed. Within the context of this model for Type I explosions and the 1978 model for Type II explosions, the expected nucleosynthesis and gamma-line spectra from both kinds of supernovae are presented. Finally, a qualitatively new approach to the problem of massive star death and Type II supernovae based upon a combination of rotation and thermonuclear burning is discussed

331

Modeling Business  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Business concepts are studied using a metamodel-based approach, using UML 2.0. The Notation Independent Business concepts metamodel is introduced. The approach offers a mapping between different business modeling notations which could be used for bridging BM tools and boosting the MDA approach.

Vitolins, Valdis; Kalnins, Audris

2003-01-01

332

Quasimolecular modelling  

CERN Document Server

In this book the author has tried to apply "a little imagination and thinking" to modelling dynamical phenomena from a classical atomic and molecular point of view. Nonlinearity is emphasized, as are phenomena which are elusive from the continuum mechanics point of view. FORTRAN programs are provided in the Appendices.

Greenspan, Donald

1991-01-01

333

Biotran model  

International Nuclear Information System (INIS)

The BIOTRAN model was developed at Los Alamos to help predict short- and long-term consequences to man from releases of radionuclides into the environment. It is a dynamic model that simulates on a daily and yearly basis the flux of biomass, water, and radionuclides through terrestrial and aquatic ecosystems. Biomass, water, and radionuclides are driven within the ecosystems by climate variables stochastically generated by BIOTRAN each simulation day. The climate variables influence soil hydraulics, plant growth, evapotranspiration, and particle suspension and deposition. BIOTRAN has 22 different plant growth strategies for simulating various grasses, shrubs, trees, and crops. Ruminants and humans are also dynamically simulated by using the simulated crops and forage as intake for user-specified diets. BIOTRAN has been used at Los Alamos for long-term prediction of health effects to populations following potential accidental releases of uranium and plutonium. Newly developed subroutines are described: a human dynamic physiological and metabolic model; a soil hydrology and irrigation model; limnetic nutrient and radionuclide cycling in fresh-water lakes. 7 references

334

Defect modelling  

International Nuclear Information System (INIS)

Calculations, drawing principally on developments at AERE Harwell, of the relaxation about lattice defects are reviewed with emphasis on the techniques required for such calculations. The principles of defect modelling are outlined and various programs developed for defect simulations are discussed. Particular calculations for metals, ionic crystals and oxides, are considered. (UK)

335

Marshmallow Models  

Science.gov (United States)

No glue is needed for learners of any age to become marshmallow architects or engineers. Using marshmallows and water (and maybe edible decorations like peanut butter, pretzels, gumdrops, etc.), learners wet a few marshamallows at a time and stick them together bit by bit to construct whatever models they want.

Lawrence Hall of Science

2010-01-01

336

Criticality Model  

Energy Technology Data Exchange (ETDEWEB)

The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms and various in-package and external configurations. The waste forms considered in this calculation are pressurized water reactor (PWR), boiling water reactor (BWR), Fast Flux Test Facility (FFTF), Training Research Isotope General Atomic (TRIGA), Enrico Fermi, Shippingport pressurized water reactor, Shippingport light water breeder reactor (LWBR), N-Reactor, Melt and Dilute, and Fort Saint Vrain Reactor spent nuclear fuel (SNF). The scope of this analysis is to document the criticality computational method. The criticality computational method will be used for evaluating the criticality potential of configurations of fissionable materials (in-package and external to the waste package) within the repository at Yucca Mountain, Nevada for all waste packages/waste forms. The criticality computational method is also applicable to preclosure configurations. The criticality computational method is a component of the methodology presented in ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003). How the criticality computational method fits in the overall disposal criticality analysis methodology is illustrated in Figure 1 (YMP 2003, Figure 3). This calculation will not provide direct input to the total system performance assessment for license application. It is to be used as necessary to determine the criticality potential of configuration classes as determined by the configuration probability analysis of the configuration generator model (BSC 2003a).

A. Alsaed

2004-09-14

337

Criticality Model  

International Nuclear Information System (INIS)

The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms and various in-package and external configurations. The waste forms considered in this calculation are pressurized water reactor (PWR), boiling water reactor (BWR), Fast Flux Test Facility (FFTF), Training Research Isotope General Atomic (TRIGA), Enrico Fermi, Shippingport pressurized water reactor, Shippingport light water breeder reactor (LWBR), N-Reactor, Melt and Dilute, and Fort Saint Vrain Reactor spent nuclear fuel (SNF). The scope of this analysis is to document the criticality computational method. The criticality computational method will be used for evaluating the criticality potential of configurations of fissionable materials (in-package and external to the waste package) within the repository at Yucca Mountain, Nevada for all waste packages/waste forms. The criticality computational method is also applicable to preclosure configurations. The criticality computational method is a component of the methodology presented in ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003). How the criticality computational method fits in the overall disposal criticality analysis methodology is illustrated in Figure 1 (YMP 2003, Figure 3). This calculation will not provide direct input to the total system performance assessment for license application. It is to be used as necessary to determine the criticality potential of configuration classes as determined by the configuration probability analysis of the configuration generator model (BSC 2003a)

338

Molecular Modeling  

Science.gov (United States)

Molecular modeling has trickled down from the realm of pharmaceutical and research laboratories into the realm of undergraduate chemistry instruction. It has opened avenues for the visualization of chemical concepts that previously were difficult or impossible to convey. I am sure that many of you have developed exercises using the various molecular modeling tools. It is the desire of this Journal to become an avenue for you to share these exercises among your colleagues. It is to this end that Ron Starkey has agreed to edit such a column and to publish not only the description of such exercises, but also the software documents they use. The WWW is the obvious medium to distribute this combination and so accepted submissions will appear online as a feature of JCE Internet. gif" width=211 heighth=164 align=right> Typical molecular modeling exercise: finding conformation energies. Molecular Modeling Exercises and Experiments is the latest feature column of JCE Internet, joining Conceptual Questions and Challenge Problems, Hal's Picks, and Mathcad in the Chemistry Curriculum. JCE Internet continues to seek submissions in these areas of interest and submissions of general interest. If you have developed materials and would like to submit them, please see our Guide to Submissions for more information. The Chemical Education Resource Shelf, Equipment Buyers Guide, and WWW Site Review would also like to hear about chemistry textbooks and software, equipment, and WWW sites, respectively. Please consult JCE Internet Features to learn more about these resources at JCE Online. Email Announcements Would you like to be informed by email when the latest issue of the Journal is available online? when a new JCE Software title is shipping? when a new JCE Internet article has been published or is available for Open Review? when your subscription is about to expire? A new feature of JCE Online makes this possible. Visit our Guestbook to learn how. When you submit the form on this page, which includes your email address, you may choose to receive an email notice about a Journal event that interests you. Currently such events include availability of the latest issue of the Journal at JCE Online, expiration of your Journal subscription, shipment of a new JCE Software issue, publication of a new JCE Internet article or its availability for Open Review, and other announcements from the Journal. You may choose any number of these options independently. gif" width=213 heighth=226 align=right> JCE Online Guestbook. Your Privacy JCE Online promises to you that we will not use the information that you provide in our Guestbook for anything other than our own internal information. We will not provide this information to third parties. We will use the information you provide only in our effort to help make the JCE serve you better. You only need to provide your email address to take advantage of this service; the other information you provide is optional. Molecular Modeling Exercises and Experiments: Mission Statement We are seeking in this JCE Internet feature column to publish molecular modeling exercises and experiments that have been used successfully in undergraduate instruction. The exercises will be published here on JCE Internet. An abstract of published submissions will appear in print in the Journal of Chemical Education. Acceptable exercises could be used in either a chemistry laboratory or a chemistry computer laboratory. The exercise could cover any area of chemistry, but should be limited to undergraduate instructional applications. We envision that most of the exercises/experiments will utilize one of the popular instructional molecular modeling software programs (e.g. HyperChem, Spartan, CAChe, PC Model). Exercises that are specific to a particular modeling program are acceptable, but those usable with any modeling program are preferred. Ideally the exercises/experiments will be of the type where the "correct"answer is not obvious so

Holmes, Jon L.

1999-06-01

339

The electric field induced by transcranial magnetic stimulation: A comparison between analytic and fem solutions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The induced electric field profiles in a homogeneous isotropic sphere, were calculated and compared between an analytic and a finite-element method in the framework of transcranial magnetic stimulation (TMS). This model can also be applied for concentric spheres in the framework of magnetic induction tomography (MIT), non destructive testing (NDT) or to calculate the lead field in magnetoencephalography (MEG). The calculations were performed using Eaton’s...

Porzig Konstantin; Brauer Hartmut; Toepfer Hannes

2014-01-01

340

Geospace Environment Modeling  

Science.gov (United States)

... General Circulation Model (GGCM) with predictive capability. This GGCM model will be modularized and ... and full models for the GGCM. II. PROGRAM DESCRIPTION The Geospace Environment Modeling (GEM ...

 
 
 
 
341

Molecular Modelling  

Directory of Open Access Journals (Sweden)

Full Text Available

The use of computational chemistry in the development of novel pharmaceuticals is becoming an increasingly important
tool. In the past, drugs were simply screened for effectiveness. The recent advances in computing power and
the exponential growth of the knowledge of protein structures have made it possible for organic compounds to tailored to
decrease harmful side effects and increase the potency. This article provides a detailed description of the techniques
employed in molecular modeling. Molecular modelling is a rapidly developing discipline, and has been supported from
the dramatic improvements in computer hardware and software in recent years.

Aarti Sharma

2009-12-01

342

Modelling tsunamis  

International Nuclear Information System (INIS)

We doubt the relevance of soliton theory to the modelling of tsunamis, and present a case in support of an alternative view. Although the shallow-water equations do provide, we believe, an appropriate basis for this phenomenon, an asymptotic analysis of the solution for realistic variable depths, and for suitable background flows, is essential for a complete understanding of this phenomenon. In particular we explain how a number of tsunami waves can arrive at a shoreline. (letter to the editor)

343

Nuclear Models  

International Nuclear Information System (INIS)

The atomic nucleus is a typical example of a many-body problem. On the one hand, the number of nucleons (protons and neutrons) that constitute the nucleus is too large to allow for exact calculations. On the other hand, the number of constituent particles is too small for the individual nuclear excitation states to be explained by statistical methods. Another problem, particular for the atomic nucleus, is that the nucleon-nucleon (n-n) interaction is not one of the fundamental forces of Nature, and is hard to put in a single closed equation. The nucleon-nucleon interaction also behaves differently between two free nucleons (bare interaction) and between two nucleons in the nuclear medium (dressed interaction).Because of the above reasons, specific nuclear many-body models have been devised of which each one sheds light on some selected aspects of nuclear structure. Only combining the viewpoints of different models, a global insight of the atomic nucleus can be gained. In this chapter, we revise the the Nuclear Shell Model as an example of the microscopic approach, and the Collective Model as an example of the geometric approach. Finally, we study the statistical properties of nuclear spectra, basing on symmetry principles, to find out whether there is quantum chaos in the atomic nucleus. All three major approaches have been rewarded with the Nobel Prize of Physics. In the text, we will stress how each approach introduces its own series of approximations to reduce the wn series of approximations to reduce the prohibitingly large number of degrees of freedom of the full many-body problem to a smaller manageable number of effective degrees of freedom.

344

MEMRISTOR MODELLING  

Digital Repository Infrastructure Vision for European Research (DRIVER)

V diplomskem delu obravnavamo postopek modeliranja memristorja. Definiramo memristor in odkritje memristorja. Opišemo sintezo memristorja s pomo?jo M-R mutatorja, ki je osnova za postavitev modela. Osredoto?imo se na model memristorja z odsekovno linearno karakteristiko na osnovi katerega preverimo ustreznost modela s pomo?jo simulatorja SPICE. Veljavnost modela dodatno preverimo na primeru dveh vezij, ki vsebujejo memristor. V prvem primeru izvedemo simulacijo delovanja amorfnega pragov...

Skribe, Gregor

2009-01-01

345

Adsorption Modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study, adsorption was explored to remove toxic metals from wastewaters. The main focus of the research work lies on adsorption process, which is described theoretically and studied experimentally. Theoretical part involves studying of the adsorption concepts, adsorbents and adsorption process modelling. Experimental part of the work was aimed to create a condition which will allow examining the adsorption process by using adsorbents to remove toxic metal from aqueous solution. The exp...

Musin, Eduard

2013-01-01

346

Determination of Classification Accuracy for Land Use/cover Types Using Landsat-Tm Spot-Mss and Multipolarized and Multi-Channel Synthetic Aperture Radar  

Science.gov (United States)

The primary objective of this study was to determine the degree to which modern SAR systems can be used to obtain information about the Earth's vegetative resources. Information obtainable from microwave synthetic aperture radar (SAR) data was compared with that obtainable from LANDSAT-TM and SPOT data. Three hypotheses were tested: (a) Classification of land cover/use from SAR data can be accomplished on a pixel-by-pixel basis with the same overall accuracy as from LANDSAT-TM and SPOT data. (b) Classification accuracy for individual land cover/use classes will differ between sensors. (c) Combining information derived from optical and SAR data into an integrated monitoring system will improve overall and individual land cover/use class accuracies. The study was conducted with three data sets for the Sleeping Bear Dunes test site in the northwestern part of Michigan's lower peninsula, including an October 1982 LANDSAT-TM scene, a June 1989 SPOT scene and C-, L- and P-Band radar data from the Jet Propulsion Laboratory AIRSAR. Reference data were derived from the Michigan Resource Information System (MIRIS) and available color infrared aerial photos. Classification and rectification of data sets were done using ERDAS Image Processing Programs. Classification algorithms included Maximum Likelihood, Mahalanobis Distance, Minimum Spectral Distance, ISODATA, Parallelepiped, and Sequential Cluster Analysis. Classified images were rectified as necessary so that all were at the same scale and oriented north-up. Results were analyzed with contingency tables and percent correctly classified (PCC) and Cohen's Kappa (CK) as accuracy indices using CSLANT and ImagePro programs developed for this study. Accuracy analyses were based upon a 1.4 by 6.5 km area with its long axis east-west. Reference data for this subscene total 55,770 15 by 15 m pixels with sixteen cover types, including seven level III forest classes, three level III urban classes, two level II range classes, two water classes, one wetland class and one agriculture class. An initial analysis was made without correcting the 1978 MIRIS reference data to the different dates of the TM, SPOT and SAR data sets. In this analysis, highest overall classification accuracy (PCC) was 87% with the TM data set, with both SPOT and C-Band SAR at 85%, a difference statistically significant at the 0.05 level. When the reference data were corrected for land cover change between 1978 and 1991, classification accuracy with the C-Band SAR data increased to 87%. Classification accuracy differed from sensor to sensor for individual land cover classes, Combining sensors into hypothetical multi-sensor systems resulted in higher accuracies than for any single sensor. Combining LANDSAT -TM and C-Band SAR yielded an overall classification accuracy (PCC) of 92%. The results of this study indicate that C-Band SAR data provide an acceptable substitute for LANDSAT-TM or SPOT data when land cover information is desired of areas where cloud cover obscures the terrain. Even better results can be obtained by integrating TM and C-Band SAR data into a multi-sensor system.

Dondurur, Mehmet

347

Many-body theory of dilute gas condensates - derivation of a field-modified Gross-Pitaevskii equation from multipolar QED  

CERN Document Server

The Hamiltonian of a moving atom in electromagnetic fields includes velocity- dependent terms. We show that the leading velocity dependence emerges systematically in the non-relativistic limit from a scheme firmly based on the relativistic invariance of the energy-momentum stress tensor of the coupled matter-fields system. We then extend the Hamiltonian to the many-body situation suitable for describing a Bose-Einstein condensate (BEC). From first principles, we use the equation of motion for the condensate wavefunction to obtain an extended version of the Gross-Pitaevskii (GP) equation and an equation for the internal states of the atoms. It is shown that laser fields modify the GP equation by inclusion of convective terms involving a Rontgen interaction plus a term coupling the centre of mass momentum to the Poynting vector. We also obtain the modified Maxwell equations for the electromagnetic fields coupled to the BEC involving the average velocity of the atoms.

Boussiakou, L G; Babiker, M

2000-01-01

348

Students' Models of Curve Fitting: A Models and Modeling Perspective  

Science.gov (United States)

The Models and Modeling Perspectives (MMP) has evolved out of research that began 26 years ago. MMP researchers use Model Eliciting Activities (MEAs) to elicit students' mental models. In this study MMP was used as the conceptual framework to investigate the nature of students' models of curve fitting in a problem-solving environment consisting of…

Gupta, Shweta

2010-01-01

349

Ozone modeling  

International Nuclear Information System (INIS)

Exhaust gases from power plants that burn fossil fuels contain concentrations of sulfur dioxide (SO2), nitric oxide (NO), particulate matter, hydrocarbon compounds and trace metals. Estimated emissions from the operation of a hypothetical 500 MW coal-fired power plant are given. Ozone is considered a secondary pollutant, since it is not emitted directly into the atmosphere but is formed from other air pollutants, specifically, nitrogen oxides (NO), and non-methane organic compounds (NMOQ) in the presence of sunlight. (NMOC are sometimes referred to as hydrocarbons, HC, or volatile organic compounds, VOC, and they may or may not include methane). Additionally, ozone formation Alternative is a function of the ratio of NMOC concentrations to NOx concentrations. A typical ozone isopleth is shown, generated with the Empirical Kinetic Modeling Approach (EKMA) option of the Environmental Protection Agency's (EPA) Ozone Isopleth Plotting Mechanism (OZIPM-4) model. Ozone isopleth diagrams, originally generated with smog chamber data, are more commonly generated with photochemical reaction mechanisms and tested against smog chamber data. The shape of the isopleth curves is a function of the region (i.e. background conditions) where ozone concentrations are simulated. The location of an ozone concentration on the isopleth diagram is defined by the ratio of NMOC and NOx coordinates of the point, known as the NMOC/NOx ratio. Results obtained by the described model are presented

350

Modeling biomembranes.  

Energy Technology Data Exchange (ETDEWEB)

Understanding the properties and behavior of biomembranes is fundamental to many biological processes and technologies. Microdomains in biomembranes or ''lipid rafts'' are now known to be an integral part of cell signaling, vesicle formation, fusion processes, protein trafficking, and viral and toxin infection processes. Understanding how microdomains form, how they depend on membrane constituents, and how they act not only has biological implications, but also will impact Sandia's effort in development of membranes that structurally adapt to their environment in a controlled manner. To provide such understanding, we created physically-based models of biomembranes. Molecular dynamics (MD) simulations and classical density functional theory (DFT) calculations using these models were applied to phenomena such as microdomain formation, membrane fusion, pattern formation, and protein insertion. Because lipid dynamics and self-organization in membranes occur on length and time scales beyond atomistic MD, we used coarse-grained models of double tail lipid molecules that spontaneously self-assemble into bilayers. DFT provided equilibrium information on membrane structure. Experimental work was performed to further help elucidate the fundamental membrane organization principles.

Plimpton, Steven James; Heffernan, Julieanne; Sasaki, Darryl Yoshio; Frischknecht, Amalie Lucile; Stevens, Mark Jackson; Frink, Laura J. Douglas

2005-11-01

351

Document Models  

CERN Document Server

Exchanging electronic texts in different formats has been a problem for many years. For example, it is difficult to convert a TeX document into an MS Word document. Proprietary solutions exist for specific purposes, but their application is restricted to a limited community of users. A truly universal for document archival consists of the use of a number of standards for document models. This article describes the standards that have been recently adopted in that area : SGML, CALS, HTML, XML, HyTime, DSSSL, CSS, MHEG and PREMO. Together, they attempt to solve the problem of interchanging and reusing composite documents.

Van Herwijnen, Eric

1997-01-01

352

Modelling Sonoluminescence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In single-bubble sonoluminescence, a bubble trapped by a sound wave in a flask of liquid is forced to expand and contract; exactly once per cycle, the bubble emits a very sharp ($< 50 ps$) pulse of visible light. This is a robust phenomenon observable to the naked eye, yet the mechanism whereby the light is produced is not well understood. One model that has been proposed is that the light is "vacuum radiation" generated by the coupling of the electromagnetic fields to the s...

Chodos, Alan; Groff, Sarah

1998-01-01

353

Model Awal Dan Model Klasik Struktur Informasi  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper describes early models of information structure and classical models of information structure. Early models of information structure consist of (1) subject- predicate structure, (2) the early psychological model, (3) the communicative model, and (4) linguistics, psychology, and information structure. Classical models is begun from the Prague school, Halliday and the American structuralists, Chafe on givenness, and Chomsky on focus and presupposition. The most characteristic feat...

Widayati, Dwi

2010-01-01

354

Modelling Decision Rules in System Dynamics Models.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper focuses on modelling decision rules, fundamental components of simulation models and one of the most difficult tasks in modelling and analysis. Modelling decision rules in system dynamics modelsfollows the process described by the Scientific Method, by which scientists (in this case, modellers) make an effort to construct an accurate representation of the world (in this case, representations of human decisions in systems dynamics models). Consequently, the paper is organized in the...

Santiago Arango

2004-01-01

355

Towards a Multi Business Model Innovation Model  

DEFF Research Database (Denmark)

This paper studies the evolution of business model (BM) innovations related to a multi business model framework. The paper tries to answer the research questions: • What are the requirements for a multi business model innovation model (BMIM)? • How should a multi business model innovation model look like? Different generations of BMIMs are initially studied in the context of laying the baseline for how next generation multi BM Innovation model (BMIM) should look like. All generations of models are analyzed with the purpose of comparing the characteristics and challenges of previous generations of BMIMs. On behalf of these results and case analyses, the paper concludes by proposing a framework for a multi BMIM.

Lindgren, Peter; JØrgensen, Rasmus

2012-01-01

356

Modelling Sonoluminescence  

CERN Document Server

In single-bubble sonoluminescence, a bubble trapped by a sound wave in a flask of liquid is forced to expand and contract; exactly once per cycle, the bubble emits a very sharp ($< 50 ps$) pulse of visible light. This is a robust phenomenon observable to the naked eye, yet the mechanism whereby the light is produced is not well understood. One model that has been proposed is that the light is "vacuum radiation" generated by the coupling of the electromagnetic fields to the surface of the bubble. In this paper, we simulate vacuum radiation by solving Maxwell's equations with an additional term that couples the field to the bubble's motion. We show that, in the static case originally considered by Casimir, we reproduce Casimir's result. In a simple purely time-dependent example, we find that an instability occurs and the pulse of radiation grows exponentially. In the more realistic case of spherically-symmetric bubble motion, we again find exponential growth in the context of a small-radius approximation.

Chodos, A; Chodos, Alan; Groff, Sarah

1999-01-01

357

Modeling sonoluminescence  

International Nuclear Information System (INIS)

In single-bubble sonoluminescence, a bubble trapped by a sound wave in a flask of liquid is forced to expand and contract; exactly once per cycle, the bubble emits a very sharp (<50 ps) pulse of visible light. This is a robust phenomenon observable to the naked eye, yet the mechanism whereby the light is produced is not well understood. One model that has been proposed is that the light is open-quotes vacuum radiationclose quotes generated by the coupling of the electromagnetic fields to the surface of the bubble. In this paper, we simulate vacuum radiation by solving Maxwell's equations with an additional term that couples the field to the bubble's motion. We show that, in the static case originally considered by Casimir [Proc. K. Ned. Akad. Nel. 51, 783 (1948)], we reproduce Casimir's result. In a simple purely time-dependent example, we find that an instability occurs and the pulse of radiation grows exponentially. In the more realistic case of spherically symmetric bubble motion, we again find exponential growth in the context of a small-radius approximation. copyright 1999 The American Physical Society

358

Aspects of process modelling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Process modelling is a basic activity in process engineering. The process industries develop and use models for different purposes. This paper, in essence a survey, represents useful model and modelling knowledge categorisations, general requirements set on process models, common modelling paradigms used in process engineering, the phases of the process of process modelling and common modelling pitfalls. This paper clearly illustrates the manifold approaches or paradigms used ...

Jaako, Juha

1998-01-01

359

Rotating universe models  

International Nuclear Information System (INIS)

A review is made of some properties of the rotating Universe models. Godel's model is identified as a generalized filted model. Some properties of new solutions of the Einstein's equations, which are rotating non-stationary Universe models, are presented and analyzed. These models have the Godel's model as a particular case. Non-stationary cosmological models are found which are a generalization of the Godel's metrics in an analogous way in which Friedmann is to the Einstein's model. (L.C.)

360

Weibull model selection for reliability modelling  

International Nuclear Information System (INIS)

A large number of models have been derived from the two-parameter Weibull distribution and are referred to as Weibull models. They exhibit a wide range of shapes for the density and hazard functions, which makes them suitable for modelling complex failure data sets. The WPP and IWPP plot allows one to determine in a systematic manner if one or more of these models are suitable for modelling a given data set. This paper deals with this topic

 
 
 
 
361

Influence of internal structure on the motion of test bodies in extreme mass ratio situations (MG13)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present some recent results on the motion of test bodies with internal structure in General Relativity. On the basis of a multipolar approximation scheme, we study the motion of extended test bodies endowed with an explicit model for the quadrupole. The model is inspired by effective actions recently proposed in the context of the post-Newtonian approximation, including spin-squared and tidal contributions. In the equatorial plane of the Kerr geometry, the motion can be c...

Steinhoff, Jan; Puetzfeld, Dirk

2013-01-01

362

Cognitive models embedded in system simulation models  

International Nuclear Information System (INIS)

If we are to discuss and consider cognitive models, we must first come to grips with two questions: (1) What is cognition; (2) What is a model. Presumably, the answers to these questions can provide a basis for defining a cognitive model. Accordingly, this paper first places these two questions into perspective. Then, cognitive models are set within the context of computer simulation models and a number of computer simulations of cognitive processes are described. Finally, pervasive issues are discussed vis-a-vis cognitive modeling in the computer simulation context

363

Business Model Innovation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The chapter offers a broad review of the literature at the nexus between Business Models and innovation studies, and examines the notion of Business Model Innovation in three different situations: Business Model Design in newly formed organizations, Business Model Reconfiguration in incumbent firms, and Business Model Innovation in the broad context of sustainability. Tools and perspectives to make sense of Business Models and support managers and entrepreneurs in dealing with Business Model ...

Dodgson, Mark; Gann, David; Phillips, Nelson; Massa, Lorenzo; Tucci, Christopher

2010-01-01

364

Modeling, computation and optimization  

CERN Document Server

This volume provides recent developments and a state-of-the-art review in various areas of mathematical modeling, computation and optimization. It contains theory, computation as well as the applications of several mathematical models to problems in statistics, games, optimization and economics for decision making. It focuses on exciting areas like models for wireless networks, models of Nash networks, dynamic models of advertising, application of reliability models in economics, support vector machines, optimization, complementarity modeling and games.

Neogy, S K

2009-01-01

365

Orthogonal Meta-Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This article introduces meta-modeling hierarchies additional to the conventional meta-modeling hierarchy in a model-driven architecture. Additional hierarchies are introduced orthogonal to the conventional meta-modeling hierarchy for an appropriate correlation of information on combined hierarchies. In particular, orthogonal meta-modeling enables the grouping of models on the same conventional meta-modeling layer based on additional semantic dependencies. For the enhancement of conventional m...

Katharina Gorlach; Frank Leymann

2014-01-01

366

DIPOLE COLLAPSE AND DYNAMO WAVES IN GLOBAL DIRECT NUMERICAL SIMULATIONS  

International Nuclear Information System (INIS)

Magnetic fields of low-mass stars and planets are thought to originate from self-excited dynamo action in their convective interiors. Observations reveal a variety of field topologies ranging from large-scale, axial dipoles to more structured magnetic fields. In this article, we investigate more than 70 three-dimensional, self-consistent dynamo models in the Boussinesq approximation obtained by direct numerical simulations. The control parameters, the aspect ratio, and the mechanical boundary conditions have been varied to build up this sample of models. Both strongly dipolar and multipolar models have been obtained. We show that these dynamo regimes in general can be distinguished by the ratio of a typical convective length scale to the Rossby radius. Models with a predominantly dipolar magnetic field were obtained, if the convective length scale is at least an order of magnitude larger than the Rossby radius. Moreover, we highlight the role of the strong shear associated with the geostrophic zonal flow for models with stress-free boundary conditions. In this case the above transition disappears and is replaced by a region of bistability for which dipolar and multipolar dynamos coexist. We interpret our results in terms of dynamo eigenmodes using the so-called test-field method. We can thus show that models in the dipolar regime are characterized by an isolated 'single mode'. Competing overtones become significant as the boundary to multipolar dynamos is approached. dary to multipolar dynamos is approached. We discuss how these findings relate to previous models and to observations.

367

Armas estratégicas e poder no sistema internacional: o advento das armas de energia direta e seu impacto potencial sobre a guerra e a distribuição multipolar de capacidades Strategic weapons and power in international system: the arise of direct energy weapons and their potential impact over the war and multipolar distribution of capabilities  

Directory of Open Access Journals (Sweden)

Full Text Available O pós-Guerra Fria (1991-2006 apresenta uma mudança significativa no cenário estratégico: a maior acessibilidade da tecnologia militar e o surgimento de novas armas capazes de modificar o poder coercitivo dos países - como as armas de energia direta - acabam pondo em xeque a ideia de que a primazia nuclear é condição suficiente para garantir a unipolaridade. Focando-se no atual recrudescimento das tensões entre EUA e Rússia - especialmente com a proposta norte-americana de implementação do Escudo Antimíssil no Leste Europeu - e analisando as relações de poder entre os três países, procuramos revelar que tipo de competição ocorrerá no sistema internacional nas próximas décadas. O presente artigo analisa as reais possibilidades de que a primazia nuclear norte-americana se torne efetiva, uma vez que, para tanto, é necessário o desarmamento estratégico das demais potências. Como uma guerra nuclear entre os três países possui um custo político muito elevado, as disputas tendem a ser decididas na esfera das operações. Para ilustrar esta última afirmação, usamos um cenário contrafactual de guerra nuclear limitada entre Estados Unidos, Rússia e China, por meio do qual tentamos evidenciar as precondições táticas e operacionais para uma eventual vitória da coalizão sino-russa.The evolution of the Post-Cold War (1991-2006 international system shows a significant amount of change regarding the strategic capabilities of United States, Russia, and China. The rise of a new class of strategic weapons called directed energy weapons (lasers and high power microwaves, as well as the great costs associated with the quest for nuclear primacy, demand closer examination of the current assumption about the links between nuclear primacy and unipolar distribution of power in the International System. Starting with the current tensions between US and Russia, we try to reveal in this article what kind of competition might be observed in the international system over the next decade. The present work analyzes the real possibilities of the USA achieving an effective nuclear primacy condition, which requires the complete disarmament of all other powers. Since a nuclear war between the three countries has a very high political cost, disputes tend to be settled on the operational sphere. In order to demonstrate this final point, we made comparative use of two nuclear war scenarios. The article concludes by establishing the tactical and operational conditions that Russia and China seems to counting with in order to defeat United States if a shooting war comes.

Fabrício Schiavo Ávila

2009-04-01

368

Armas estratégicas e poder no sistema internacional: o advento das armas de energia direta e seu impacto potencial sobre a guerra e a distribuição multipolar de capacidades / Strategic weapons and power in international system: the arise of direct energy weapons and their potential impact over the war and multipolar distribution of capabilities  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O pós-Guerra Fria (1991-2006) apresenta uma mudança significativa no cenário estratégico: a maior acessibilidade da tecnologia militar e o surgimento de novas armas capazes de modificar o poder coercitivo dos países - como as armas de energia direta - acabam pondo em xeque a ideia de que a primazia [...] nuclear é condição suficiente para garantir a unipolaridade. Focando-se no atual recrudescimento das tensões entre EUA e Rússia - especialmente com a proposta norte-americana de implementação do Escudo Antimíssil no Leste Europeu - e analisando as relações de poder entre os três países, procuramos revelar que tipo de competição ocorrerá no sistema internacional nas próximas décadas. O presente artigo analisa as reais possibilidades de que a primazia nuclear norte-americana se torne efetiva, uma vez que, para tanto, é necessário o desarmamento estratégico das demais potências. Como uma guerra nuclear entre os três países possui um custo político muito elevado, as disputas tendem a ser decididas na esfera das operações. Para ilustrar esta última afirmação, usamos um cenário contrafactual de guerra nuclear limitada entre Estados Unidos, Rússia e China, por meio do qual tentamos evidenciar as precondições táticas e operacionais para uma eventual vitória da coalizão sino-russa. Abstract in english The evolution of the Post-Cold War (1991-2006) international system shows a significant amount of change regarding the strategic capabilities of United States, Russia, and China. The rise of a new class of strategic weapons called directed energy weapons (lasers and high power microwaves), as well a [...] s the great costs associated with the quest for nuclear primacy, demand closer examination of the current assumption about the links between nuclear primacy and unipolar distribution of power in the International System. Starting with the current tensions between US and Russia, we try to reveal in this article what kind of competition might be observed in the international system over the next decade. The present work analyzes the real possibilities of the USA achieving an effective nuclear primacy condition, which requires the complete disarmament of all other powers. Since a nuclear war between the three countries has a very high political cost, disputes tend to be settled on the operational sphere. In order to demonstrate this final point, we made comparative use of two nuclear war scenarios. The article concludes by establishing the tactical and operational conditions that Russia and China seems to counting with in order to defeat United States if a shooting war comes.

Fabrício Schiavo, Ávila; José Miguel, Martins; Marco, Cepik.

2009-04-01

369

Wake modelling combining mesoscale and microscale models  

DEFF Research Database (Denmark)

In this paper the basis for introducing thrust information from microscale wake models into mesocale model wake parameterizations will be described. A classification system for the different types of mesoscale wake parameterizations is suggested and outlined. Four different mesoscale wake parameterizations are demonstrated in theWeather Research and Forecasting mesoscale model (WRF) in an idealized atmospheric flow. The model framework is the Horns Rev I wind farm experiencing an 7.97 m/s wind from 269.4o. Three of the four parameterizations use thrust output from the CRESflow-NS microscale model. The characteristics of the mesoscale wake that developed from the four parameterizations are examined. In addition the mesoscale model wakes are compared to measurement data from Horns Rev I. Overall it is seen as an advantage to incorporate microscale model data in mesocale model wake parameterizations.

Badger, Jake; Volker, Patrick

2013-01-01

370

Comparison of laser models  

Science.gov (United States)

Progress on the comparison of laser models is reported. Equations for an oscillatory model and a nonoscillatory model for the simulation of iodine laser operation are solved. Reaction rate coefficients used in both models are listed. Currently there are four models for the simulation of iodine laser operation are solved. Reaction rate coefficients used in both models are listed. Currently there are four models for the simulation of an iodine laser. They are: (1) a time dependent model; (2) a quasi-steady state model; (3) a noncompressible model; and (4) a compressible flow laser model. Current research is being directed toward: (1) parameter studies using the compressible flow laser model; (2) development of a two-pass amplifier model; and (3) solving a system of equations describing operation of the high powered iodine MOPA (master oscillator power amplifier).

Heinbockel, John H.

1989-01-01

371

Orthogonal Meta-Modeling  

Directory of Open Access Journals (Sweden)

Full Text Available This article introduces meta-modeling hierarchies additional to the conventional meta-modeling hierarchy in a model-driven architecture. Additional hierarchies are introduced orthogonal to the conventional meta-modeling hierarchy for an appropriate correlation of information on combined hierarchies. In particular, orthogonal meta-modeling enables the grouping of models on the same conventional meta-modeling layer based on additional semantic dependencies. For the enhancement of conventional meta-modeling this paper discusses the creation of orthogonal meta-modeling hierarchies, the specification of semantic dependencies in meta-modeling hierarchies, semantic instances as well as the inheritance of semantic dependencies in meta-modeling hierarchies in general. Furthermore, the paper outlines the impact of orthogonal semantic meta-modeling on automated model transformation.

Katharina Gorlach

2014-04-01

372

Model selection for logistic regression models  

Science.gov (United States)

Model selection for logistic regression models decides which of some given potential regressors have an effect and hence should be included in the final model. The second interesting question is whether a certain factor is heterogeneous among some subsets, i.e. whether the model should include a random intercept or not. In this paper these questions will be answered with classical as well as with Bayesian methods. The application show some results of recent research projects in medicine and business administration.

Duller, Christine

2012-09-01

373

Modeling Population Growth: Exponential and Hyperbolic Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A standard part of the calculus curriculum is learning exponential growth models. This paper, designed to serve as a teaching aid, extends the standard modeling by showing that simple exponential models, relying on two points to fit parameters do not do a good job in modeling population data of the distant past. Moreover, they provide a constant doubling time. Therefore, the student is introduced to hype...

Dean Hathout

2013-01-01

374

Automated data model evaluation  

International Nuclear Information System (INIS)

Modeling process is essential phase within information systems development and implementation. This paper presents methods and techniques for analysis and evaluation of data model correctness. Recent methodologies and development results regarding automation of the process of model correctness analysis and relations with ontology tools has been presented. Key words: Database modeling, Data model correctness, Evaluation

375

Multilevel Model Prediction  

Science.gov (United States)

Multilevel models are proven tools in social research for modeling complex, hierarchical systems. In multilevel modeling, statistical inference is based largely on quantification of random variables. This paper distinguishes among three types of random variables in multilevel modeling--model disturbances, random coefficients, and future response…

Frees, Edward W.; Kim, Jee-Seon

2006-01-01

376

"Bohr's Atomic Model."  

Science.gov (United States)

"Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

Willden, Jeff

2001-01-01

377

Semantic Business Process Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This book presents a process-oriented business modeling framework based on semantic technologies. The framework consists of modeling languages, methods, and tools that allow for semantic modeling of business motivation, business policies and rules, and business processes. Quality of the proposed modeling framework is evaluated based on the modeling content of SAP Solution Composer and several real-world business scenarios.

Markovic, Ivan

2010-01-01

378

China model: Energy modeling the modern dynasty  

Energy Technology Data Exchange (ETDEWEB)

In this paper a node-based microeconomic analysis is used to model the Chinese energy system. This model is run across multiple periods employing Lagrangian Relaxation techniques to achieve general equilibrium. Later, carbon dioxide emissions are added and the model is run to answer the question, {open_quotes}How can greenhouse gas emissions be reduced{close_quotes}?

Shaw, J.

1996-05-01

379

Solicited abstract: Global hydrological modeling and models  

Science.gov (United States)

The origins of rainfall-runoff modeling in the broad sense can be found in the middle of the 19th century arising in response to three types of engineering problems: (1) urban sewer design, (2) land reclamation drainage systems design, and (3) reservoir spillway design. Since then numerous empirical, conceptual and physically-based models are developed including event based models using unit hydrograph concept, Nash's linear reservoir models, HBV model, TOPMODEL, SHE model, etc. From the late 1980s, the evolution of global and continental-scale hydrology has placed new demands on hydrologic modellers. The macro-scale hydrological (global and regional scale) models were developed on the basis of the following motivations (Arenll, 1999). First, for a variety of operational and planning purposes, water resource managers responsible for large regions need to estimate the spatial variability of resources over large areas, at a spatial resolution finer than can be provided by observed data alone. Second, hydrologists and water managers are interested in the effects of land-use and climate variability and change over a large geographic domain. Third, there is an increasing need of using hydrologic models as a base to estimate point and non-point sources of pollution loading to streams. Fourth, hydrologists and atmospheric modellers have perceived weaknesses in the representation of hydrological processes in regional and global climate models, and developed global hydrological models to overcome the weaknesses of global climate models. Considerable progress in the development and application of global hydrological models has been achieved to date, however, large uncertainties still exist considering the model structure including large scale flow routing, parameterization, input data, etc. This presentation will focus on the global hydrological models, and the discussion includes (1) types of global hydrological models, (2) procedure of global hydrological model development, (3) state-of-the-art of existing global hydrological models, and (4) challenges. Acknowledgment: Thanks to Lebing Gong, Elin Widén-Nilsson, and Sven Halldin of Uppsala University for the team work in global hydrological models.

Xu, Chong-Yu

2010-05-01

380

Model Theory and Applications  

CERN Document Server

This title includes: Lectures - G.E. Sacks - Model theory and applications, and H.J. Keisler - Constructions in model theory; and, Seminars - M. Servi - SH formulas and generalized exponential, and J.A. Makowski - Topological model theory.

Mangani, P

2011-01-01

 
 
 
 
381

Composite Linear Models  

Science.gov (United States)

Statistical Software Composite Linear Models (Written by Stuart G. Baker) The composite linear models software is a matrix approach to compute maximum likelihood estimates and asymptotic standard errors for models for incomplete multinomial data. It

382

Environmental Satellite Models for a Macroeconomic Model  

International Nuclear Information System (INIS)

To support national environmental policy, it is desirable to forecast and analyse environmental indicators consistently with economic variables. However, environmental indicators are physical measures linked to physical activities that are not specified in economic models. One way to deal with this is to develop environmental satellite models linked to economic models. The system of models presented gives a frame of reference where emissions of greenhouse gases, acid gases, and leaching of nutrients to the aquatic environment are analysed in line with - and consistently with - macroeconomic variables. This paper gives an overview of the data and the satellite models. Finally, the results of applying the model system to calculate the impacts on emissions and the economy are reviewed in a few illustrative examples. The models have been developed for Denmark; however, most of the environmental data used are from the CORINAIR system implemented in numerous countries

383

Accelerated life models modeling and statistical analysis  

CERN Document Server

The authors of this monograph have developed a large and important class of survival analysis models that generalize most of the existing models. In a unified, systematic presentation, this monograph fully details those models and explores areas of accelerated life testing usually only touched upon in the literature.Accelerated Life Models: Modeling and Statistical Analysis presents models, methods of data collection, and statistical analysis for failure-time regression data in accelerated life testing and for degradation data with explanatory variables. In addition to the classical results, the authors devote considerable attention to models with time-varying explanatory variables and to methods of semiparametric estimation. They also examine the simultaneous analysis of degradation and failure-time data when the intensities of failure in different modes depend on the level of degradation and the values of explanatory variables.The authors avoid technical details by explaining the ideas and referring to reso...

Bagdonavicius, Vilijandas

2001-01-01

384

Dynamic vector hysteresis modeling  

Energy Technology Data Exchange (ETDEWEB)

The possibility of considering dynamic effects in three vector hysteresis models is investigated. The friction model of oriented Preisach operators which rotate due to the torque exerted by the external field, the coercive spheres model, the 3D analogue of the classical Preisach model, and a further collective model based on micromagnetic analogy are considered. Furthermore, the 'external' dynamic generalization of the static hysteresis models is introduced for the vector case.

Fuezi, Janos [Neutron Spectroscopy Department, Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary) and Electrical Engineering Department, Transylvania University, Brasov (Romania)]. E-mail: fuzi@szfki.hu

2006-02-01

385

Dynamic vector hysteresis modeling  

International Nuclear Information System (INIS)

The possibility of considering dynamic effects in three vector hysteresis models is investigated. The friction model of oriented Preisach operators which rotate due to the torque exerted by the external field, the coercive spheres model, the 3D analogue of the classical Preisach model, and a further collective model based on micromagnetic analogy are considered. Furthermore, the 'external' dynamic generalization of the static hysteresis models is introduced for the vector case

386

Predictive Models for Music  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Modeling long-term dependencies in time series has proved very difficult to achieve with traditional machine learning methods. This problem occurs when considering music data. In this paper, we introduce generative models for melodies. We decompose melodic modeling into two subtasks. We first propose a rhythm model based on the distributions of distances between subsequences. Then, we define a generative model for melodies given chords and rhythms based on modeling sequences of Narmour featur...

Paiement, Jean-franc?ois; Grandvalet, Yves; Bengio, Samy

2008-01-01

387

Geologic Framework Model Analysis Model Report  

International Nuclear Information System (INIS)

The purpose of this report is to document the Geologic Framework Model (GFM), Version 3.1 (GFM3.1) with regard to data input, modeling methods, assumptions, uncertainties, limitations, and validation of the model results, qualification status of the model, and the differences between Version 3.1 and previous versions. The GFM represents a three-dimensional interpretation of the stratigraphy and structural features of the location of the potential Yucca Mountain radioactive waste repository. The GFM encompasses an area of 65 square miles (170 square kilometers) and a volume of 185 cubic miles (771 cubic kilometers). The boundaries of the GFM were chosen to encompass the most widely distributed set of exploratory boreholes (the Water Table or WT series) and to provide a geologic framework over the area of interest for hydrologic flow and radionuclide transport modeling through the unsaturated zone (UZ). The depth of the model is constrained by the inferred depth of the Tertiary-Paleozoic unconformity. The GFM was constructed from geologic map and borehole data. Additional information from measured stratigraphy sections, gravity profiles, and seismic profiles was also considered. This interim change notice (ICN) was prepared in accordance with the Technical Work Plan for the Integrated Site Model Process Model Report Revision 01 (CRWMS M and O 2000). The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. The GFM is one component of the Integrated Site Model (ISM) (Figure l), which has been developed to provide a consistent volumetric portrayal of the rock layers, rock properties, and mineralogy of the Yucca Mountain site. The ISM consists of three components: (1) Geologic Framework Model (GFM); (2) Rock Properties Model (RPM); and (3) Mineralogic Model (MM). The ISM merges the detailed project stratigraphy into model stratigraphic units that are most useful for the primary downstream models and the repository design. These downstream models include the hydrologic flow models and the radionuclide transport models. All the models and the repository design, in turn, will be incorporated into the Total System Performance Assessment (TSPA) of the potential radioactive waste repository block and vicinity to determine the suitability of Yucca Mountain as a host for the repository. The interrelationship of the three components of the ISM and their interface with downstream uses are illustrated in Figure 2

388

Geologic Framework Model Analysis Model Report  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this report is to document the Geologic Framework Model (GFM), Version 3.1 (GFM3.1) with regard to data input, modeling methods, assumptions, uncertainties, limitations, and validation of the model results, qualification status of the model, and the differences between Version 3.1 and previous versions. The GFM represents a three-dimensional interpretation of the stratigraphy and structural features of the location of the potential Yucca Mountain radioactive waste repository. The GFM encompasses an area of 65 square miles (170 square kilometers) and a volume of 185 cubic miles (771 cubic kilometers). The boundaries of the GFM were chosen to encompass the most widely distributed set of exploratory boreholes (the Water Table or WT series) and to provide a geologic framework over the area of interest for hydrologic flow and radionuclide transport modeling through the unsaturated zone (UZ). The depth of the model is constrained by the inferred depth of the Tertiary-Paleozoic unconformity. The GFM was constructed from geologic map and borehole data. Additional information from measured stratigraphy sections, gravity profiles, and seismic profiles was also considered. This interim change notice (ICN) was prepared in accordance with the Technical Work Plan for the Integrated Site Model Process Model Report Revision 01 (CRWMS M&O 2000). The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. The GFM is one component of the Integrated Site Model (ISM) (Figure l), which has been developed to provide a consistent volumetric portrayal of the rock layers, rock properties, and mineralogy of the Yucca Mountain site. The ISM consists of three components: (1) Geologic Framework Model (GFM); (2) Rock Properties Model (RPM); and (3) Mineralogic Model (MM). The ISM merges the detailed project stratigraphy into model stratigraphic units that are most useful for the primary downstream models and the repository design. These downstream models include the hydrologic flow models and the radionuclide transport models. All the models and the repository design, in turn, will be incorporated into the Total System Performance Assessment (TSPA) of the potential radioactive waste repository block and vicinity to determine the suitability of Yucca Mountain as a host for the repository. The interrelationship of the three components of the ISM and their interface with downstream uses are illustrated in Figure 2.

R. Clayton

2000-12-19

389

Cosmological models without singularities  

International Nuclear Information System (INIS)

A previously studied theory of gravitation in flat space-time is applied to homogeneous and isotropic cosmological models. There exist two different classes of models without singularities: (i) ever-expanding models, (ii) oscillating models. The first class contains models with hot big bang. For these models there exist at the beginning of the universe-in contrast to Einstein's theory-very high but finite densities of matter and radiation with a big bang of very short duration. After short time these models pass into the homogeneous and isotropic models of Einstein's theory with spatial curvature equal to zero and cosmological constant ALPHA >= O. (author)

390

Power- Supply Network Modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work deals with the extraction of ICEM parameters and its validation on the power supply network of a 8-bit microcontroller. The objective of the ICEM model [1] (Integrated Circuit Electromagnetic Model) for Components is to propose electrical modeling for conducted and radiation emission prediction [2]. The ICEM model is based on two sub-models. The first one models the power network of the I.C. and the second one models the I.C. activity as a current generator. The ICEM model can be us...

Levant, Jean-luc; Ramdani, Mohamed; Perdriau, Richard

2002-01-01

391

Simplicity, Complexity and Modelling  

CERN Document Server

Several points of disagreement exist between different modelling traditions as to whether complex models are always better than simpler models, as to how to combine results from different models and how to propagate model uncertainty into forecasts. This book represents the result of collaboration between scientists from many disciplines to show how these conflicts can be resolved. Key Features: Introduces important concepts in modelling, outlining different traditions in the use of simple and complex modelling in statistics. Provides numerous case studies on complex modelling, such as clima

Christie, Mike; Dawid, Philip; Senn, Stephen S

2011-01-01

392

Modelling Food Webs  

CERN Document Server

We review theoretical approaches to the understanding of food webs. After an overview of the available food web data, we discuss three different classes of models. The first class comprise static models, which assign links between species according to some simple rule. The second class are dynamical models, which include the population dynamics of several interacting species. We focus on the question of the stability of such webs. The third class are species assembly models and evolutionary models, which build webs starting from a few species by adding new species through a process of "invasion" (assembly models) or "speciation" (evolutionary models). Evolutionary models are found to be capable of building large stable webs.

Drossel, B

2002-01-01

393

Multilevel modeling using R  

CERN Document Server

A powerful tool for analyzing nested designs in a variety of fields, multilevel/hierarchical modeling allows researchers to account for data collected at multiple levels. Multilevel Modeling Using R provides you with a helpful guide to conducting multilevel data modeling using the R software environment.After reviewing standard linear models, the authors present the basics of multilevel models and explain how to fit these models using R. They then show how to employ multilevel modeling with longitudinal data and demonstrate the valuable graphical options in R. The book also describes models fo

Finch, W Holmes; Kelley, Ken

2014-01-01

394

Electroabsorption spectra of quadrupolar and octupolar dyes in solution: beyond the liptay formulation.  

Science.gov (United States)

We present theoretical models for electroabsorption (EA) spectra of polar and multipolar (quadrupolar and octupolar) organic chromophores in solutions. Based on essential-state models for the electronic structure, we obtain closed expressions for the EA spectra of these dyes. For polar dyes, we regain the well-known Liptay result, which relates the EA spectrum to the linear absorption spectrum and its first and second derivatives. For multipolar dyes, an additional contribution is found, which is due to the field-induced absorption toward dark states: when the dark states are close in energy to allowed states, this term leads to spurious second-derivative-like structures in the EA spectrum. This is particularly well-apparent for quadrupolar dyes where second-derivative contributions to the EA signal are symmetry-forbidden. The extension of essential-state models to account for slow degrees of freedom, including molecular vibrations and polar solvation, leads to a more-realistic description of optical spectra but hinders the analytical treatment of EA. However, numerically exact EA spectra can be obtained along the same lines that have been recently developed for linear and two-photon absorption spectra of (multi)polar organic chromophores in solution. Essential-state models offer the possibility for a joint analysis of linear and nonlinear spectra (including EA) of (multi)polar dyes: reliable information can then be extracted also on molecular properties for systems where overlapping signals from allowed and dark states would hinder the standard analysis of EA spectra. PMID:18729423

Sissa, Cristina; Terenziani, Francesca; Painelli, Anna

2008-09-18

395

Low-spin states of 14764Gd83 in the ?-decay of 147gTb  

International Nuclear Information System (INIS)

Spectra of ?-rays, internal conversion electrons and ?-?-coincidences in the ?-decay of the isomeric 1/2+, 1.6 h, 147Tb state are studied using semiconductor detectors. More than one hundred of new gamma-transitions are observed. Multipolarities of some gamma-transitions with energy up to 2 MeV are established. The proposed decay scheme of 147Tb, 1.6 h is discussed in framework of the shell model. (orig.)

396

Researches with the synchrotron Saturne I. Chapter 5  

International Nuclear Information System (INIS)

1370 MeV ?-scattering from 24Mg is studied from 40 to 80 (lab.). The angular distributions of the continuum exhibit oscillation patterns, superposed on flat background angular distributions. From a Glauber model analysis, their multipolarities are determined. The transition strength exhausts about 55% of the isoscalar E2 energy weighted sum rule. Some E4 transition strengths are found, as well as E3 or E0 strength

397

Gamov-Teller resonances relaxation influence on the ?-decay strength function and emission probability of delayed neutron  

International Nuclear Information System (INIS)

A method to calculate the ?-strength functions for neutron rich nuclei is formulated within the framework of the shell optical model. Two main effects are taken into account: the suppression of the one-particle ?-transition strength due to the coupling with the giant resonance of the appropriate multipolarity; the redistribution of the ?-transition strength due to the coupling of the particle-hole configurations (which form the ?-decay states) with many-particle ones

398

Laser-assisted nuclear [gamma] excitation by the inverse electronic-bridge process  

Energy Technology Data Exchange (ETDEWEB)

A method to generate low-energy and high-multipolarity nuclear transitions through a laser-assisted, resonant, inverse electronic-bridge process is presented. The cross section of the suggested nuclear-excitation process is calculated in a simple model. The yield is compared with the yields of ordinary [gamma]-ray absorption and Coulomb excitation. The excitation of the [sup 235[ital m

Kalman, P.; Keszthelyi, T. (Department of Experimental Physics, Institute of Physics, Technical University of Budapest, H-1521 Budapest, Budafoki ut 8. F. I. I. 10 (Hungary))

1993-02-01

399

Metallic resonant nanostructures for visible range metamaterials : contribution from generalized ellipsometry to the comprehension of their optical properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work deals with the optical properties of two types of layered composite materials containing metallic nanostructures which present multipolar plasmon resonances. Two methods were used to study the optical properties in the near IR-visible spectrum: finite elements model calculation and generalized ellipsometry. The first type of material contained an array of gold U-shaped resonators realized by e-beam lithography. Mueller-matrix measurements by ellipsometry allowed evidencing two speci...

Guth, Nicolas

2012-01-01

400

Analysis of astrometric catalogues with vector spherical harmonics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Comparison of stellar catalogues with position and proper motion components using a decomposition on a set of orthogonal vector spherical harmonics. We show the theoretical and practical advantages of this technique as a result of invariance properties and the independence of the decomposition from a prior model. We describe the mathematical principles used to perform the spectral decomposition, evaluate the level of significance of the multipolar components and examine the ...

Mignard, Francois; Klioner, Sergei

2012-01-01

 
 
 
 
401

Deviation of quadrupolar bodies from geodesic motion in a Kerr spacetime  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The deviation from geodesic motion of the world line of an extended body endowed with multipolar structure up to the mass quadrupole moment is studied in the Kerr background according to the Mathisson-Papapetrou-Dixon model. The properties of the quadrupole tensor are clarified by identifying the relevant components which enter the equations of motion, leading to the definition of an effective quadrupole tensor sharing its own algebraic symmetries, but also obeying those imp...

Bini, Donato; Geralico, Andrea

2013-01-01

402

Influence of internal structure on the motion of test bodies in extreme mass ratio situations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the motion of test bodies with internal structure in General Relativity. With the help of a multipolar approximation method for extended test bodies we derive the equations of motion up to the quadrupolar order. The motion of pole-dipole and quadrupole test bodies is studied in the context of the Kerr geometry. For an explicit quadrupole model, which includes spin and tidal interactions, the motion in the equatorial plane is characterized by an effective poten...

Steinhoff, Jan; Puetzfeld, Dirk

2012-01-01

403

Trapping ions with lasers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work theoretically addresses the trapping an ionized atom with a single valence electron by means of lasers, analyzing qualitatively and quantitatively the consequences of the net charge of the particle. In our model, the coupling between the ion and the electromagnetic field includes the charge monopole and the internal dipole, within a multipolar expansion of the interaction Hamiltonian. Specifically, we perform a Power-Zienau-Woolley transformation, taking into accou...

Cormick, Cecilia; Schaetz, Tobias; Morigi, Giovanna

2010-01-01

404

Structure studies on fp-shell nuclei  

International Nuclear Information System (INIS)

In this thesis, the structure of fp-shell nuclei is studied for the mass region 52-62. Model calculations are done to investigate excitation energies, electric quadrupole and magnetic dipole moments and transitions. Next, collective states are analyzed microscopically, single-particle transfer strength for more than twenty reactions are discussed. The next chapter deals with electron scattering form factors. Besides elastic magnetic scattering and inelastic quadrupole scattering, attention is given to excitations of high multipolarity

405

Ionic Permeation Free Energy in Gramicidin: A Semimicroscopic Perspective  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ion permeation through the gramicidin channel is studied using a model that circumvents two major difficulties inherent to standard simulational methods. It exploits the timescale separation between electronic and structural contributions to dielectric stabilization, accounting for the influence of electronic polarization by embedding the channel in a dielectric milieu that describes this polarization in a mean sense. The explicit mobile moieties are the ion, multipolar waters, and the carbon...

Dorman, Vladimir L.; Jordan, Peter C.

2004-01-01

406

ROCK PROPERTIES MODEL ANALYSIS MODEL REPORT  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this Analysis and Model Report (AMR) is to document Rock Properties Model (RPM) 3.1 with regard to input data, model methods, assumptions, uncertainties and limitations of model results, and qualification status of the model. The report also documents the differences between the current and previous versions and validation of the model. The rock properties models are intended principally for use as input to numerical physical-process modeling, such as of ground-water flow and/or radionuclide transport. The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. This work was conducted in accordance with the following planning documents: WA-0344, ''3-D Rock Properties Modeling for FY 1998'' (SNL 1997, WA-0358), ''3-D Rock Properties Modeling for FY 1999'' (SNL 1999), and the technical development plan, Rock Properties Model Version 3.1, (CRWMS M&O 1999c). The Interim Change Notice (ICNs), ICN 02 and ICN 03, of this AMR were prepared as part of activities being conducted under the Technical Work Plan, TWP-NBS-GS-000003, ''Technical Work Plan for the Integrated Site Model, Process Model Report, Revision 01'' (CRWMS M&O 2000b). The purpose of ICN 03 is to record changes in data input status due to data qualification and verification activities. These work plans describe the scope, objectives, tasks, methodology, and implementing procedures for model construction. The constraints, caveats, and limitations associated with this model are discussed in the appropriate text sections that follow. The work scope for this activity consists of the following: (1) Conversion of the input data (laboratory measured porosity data, x-ray diffraction mineralogy, petrophysical calculations of bound water, and petrophysical calculations of porosity) for each borehole into stratigraphic coordinates; (2) Re-sampling and merging of data sets; (3) Development of geostatistical simulations of porosity; (4) Generation of derivative property models via linear coregionalization with porosity; (5) Post-processing of the simulated models to impart desired secondary geologic attributes and to create summary and uncertainty models; and (6) Conversion of the models into real-world coordinates. The conversion to real world coordinates is performed as part of the integration of the RPM into the Integrated Site Model (ISM) 3.1; this activity is not part of the current analysis. The ISM provides a consistent volumetric portrayal of the rock layers, rock properties, and mineralogy of the Yucca Mountain site and consists of three components: (1) Geologic Framework Model (GFM); (2) RPM, which is the subject of this AMR; and (3) Mineralogic Model. The interrelationship of the three components of the ISM and their interface with downstream uses are illustrated in Figure 1. Figure 2 shows the geographic boundaries of the RPM and other component models of the ISM.

Clinton Lum

2002-02-04

407

Hierarchical control models for multimodal process modeling.  

Science.gov (United States)

The multimodal and hierarchical structure characteristics of a system make process modeling quite difficult. In this paper, we present a hierarchical control model (HCM) for hierarchically multimodal processing. From multiple streams, a control layer extracts the inherent group process that denotes the evolution of the system and controls the evolution of every modality. HCMs model the influences of the group on modalities and represent the hierarchical structure of the system by a multilayer network. To estimate the state order of the model, we also present a new information criterion that corrects the preference of traditional criteria for more complex models and proves the rationality of HCMs. Comparisons with other models on multiagent activity recognition show that HCMs are reliable and efficient. PMID:19342349

Zhang, Weidong; Chen, Feng; Xu, Wenli

2009-10-01

408

Integrated Site Model Process Model Report  

International Nuclear Information System (INIS)

The Integrated Site Model (ISM) provides a framework for discussing the geologic features and properties of Yucca Mountain, which is being evaluated as a potential site for a geologic repository for the disposal of nuclear waste. The ISM is important to the evaluation of the site because it provides 3-D portrayals of site geologic, rock property, and mineralogic characteristics and their spatial variabilities. The ISM is not a single discrete model; rather, it is a set of static representations that provide three-dimensional (3-D), computer representations of site geology, selected hydrologic and rock properties, and mineralogic-characteristics data. These representations are manifested in three separate model components of the ISM: the Geologic Framework Model (GFM), the Rock Properties Model (RPM), and the Mineralogic Model (MM). The GFM provides a representation of the 3-D stratigraphy and geologic structure. Based on the framework provided by the GFM, the RPM and MM provide spatial simulations of the rock and hydrologic properties, and mineralogy, respectively. Functional summaries of the component models and their respective output are provided in Section 1.4. Each of the component models of the ISM considers different specific aspects of the site geologic setting. Each model was developed using unique methodologies and inputs, and the determination of the modeled units for each of the components is dependent on the requirements of that component. Therefore, while the ISM represents the integration of the rock properties and mineralogy into a geologic framework, the discussion of ISM construction and results is most appropriately presented in terms of the three separate components. This Process Model Report (PMR) summarizes the individual component models of the ISM (the GFM, RPM, and MM) and describes how the three components are constructed and combined to form the ISM

409

Model Telekomunikasi Dan Lokasi  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Tesis ini membahas model untuk pola jaringan telekomunikasi dimana terdapat problem lokasi yang dilibatkan. Kemudian bagaimana mengklasifikasikan model ke dalam tiga klas sebagai model dinamik yang tidak berkapasitas dan berkapasitas. Pada tiap klas akan dibahas problem inti yaitu generalisasinya dan metode solusi pada literaturnya. Oleh sebab itu, dipresentasikan relaksasi Lagrange berdasarkan prosedur solusi untuk menyelesaikan formulasi nonlinier ini. Selanjutnya direpresentasikan model...

Januasi Simarmata

2009-01-01

410

Yet another hysteresis model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A hysteresis model based on the assumption of fixed order magnetization reversals is proposed. The model uses one-dimensional diagram for representing states of a system despite of two-dimensional Preisach diagram. The distinctive feature of the model is that it is applicable to any system compliant with the return-point memory and includes Preisach model as a special case.

Langvagen, Sergey

2001-01-01

411

Fire Model Matrix  

Science.gov (United States)

The Fire Model Matrix is an on-line resource that presents four fire community models in a matrix that facilitates the exploration of the characteristics of each model. As part of the Advanced Fire Weather Forecasters Course, this matrix is meant to sensitize forecasters to the use of weather data in these fire models to forecast potential fire activity.

Comet

2008-02-05

412

AIDS Epidemiological models  

Science.gov (United States)

The aim of this paper is to present mathematical modelling of the spread of infection in the context of the transmission of the human immunodeficiency virus (HIV) and the acquired immune deficiency syndrome (AIDS). These models are based in part on the models suggested in the field of th AIDS mathematical modelling as reported by ISHAM [6].

Rahmani, Fouad Lazhar

2010-11-01

413

Conceptual Model for Communication  

CERN Document Server

A variety of idealized models of communication systems exist, and all may have something in common. Starting with Shannons communication model and ending with the OSI model, this paper presents progressively more advanced forms of modeling of communication systems by tying communication models together based on the notion of flow. The basic communication process is divided into different spheres (sources, channels, and destinations), each with its own five interior stages, receiving, processing, creating, releasing, and transferring of information. The flow of information is ontologically distinguished from the flow of physical signals, accordingly, Shannons model, network based OSI models, and TCP IP are redesigned.

Fedaghi, Sabah Al; Fadel, Zahraa

2009-01-01

414

Validation of HEDR models  

International Nuclear Information System (INIS)

The Hanford Environmental Dose Reconstruction (HEDR) Project has developed a set of computer models for estimating the possible radiation doses that individuals may have received from past Hanford Site operations. This document describes the validation of these models. In the HEDR Project, the model validation exercise consisted of comparing computational model estimates with limited historical field measurements and experimental measurements that are independent of those used to develop the models. The results of any one test do not mean that a model is valid. Rather, the collection of tests together provide a level of confidence that the HEDR models are valid

415

A Model for Conversation  

DEFF Research Database (Denmark)

This essay discusses models. It examines what models are, the roles models perform and suggests various intentions that underlie their construction and use. It discusses how models act as a conversational partner, and how they support various forms of conversation within the conversati