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1

On MEG forward modelling using multipolar expansions  

International Nuclear Information System (INIS)

Magnetoencephalography (MEG) is a non-invasive functional imaging modality based on the measurement of the external magnetic field produced by neural current sources within the brain. The reconstruction of the underlying sources is a severely ill-posed inverse problem typically tackled using either low-dimensional parametric source models, such as an equivalent current dipole (ECD), or high-dimensional minimum-norm imaging techniques. The inability of the ECD to properly represent non-focal sources and the over-smoothed solutions obtained by minimum-norm methods underline the need for an alternative approach. Multipole expansion methods have the advantages of the parametric approach while at the same time adequately describing sources with significant spatial extent and arbitrary activation patterns. In this paper we first present a comparative review of spherical harmonic and Cartesian multipole expansion methods that can be used in MEG. The equations are given for the general case of arbitrary conductors and realistic sensor configurations and also for the special cases of spherically symmetric conductors and radially oriented sensors. We then report the results of computer simulations used to investigate the ability of a first-order multipole model (dipole and quadrupole) to represent spatially extended sources, which are simulated by 2D and 3D clusters of elemental dipoles. The overall field of a cluster is analysed using singular value decomposition and compared to the unit fields of a multipole, centred in the middle of the cluster, using subspace correlation metrics. Our results demonstrate the superior utility of the multipolar source model over ECD models in providing source representations of extended regions of activity. (author)

2002-02-21

2

Hubble Space Telescope Observations and Geometric Models of Compact Multipolar Planetary Nebulae  

Science.gov (United States)

We report high angular resolution Hubble Space Telescope observations of 10 compact planetary nebulae (PNs). Many interesting internal structures, including multipolar lobes, arcs, two-dimensional rings, tori, and halos, are revealed for the first time. These results suggest that multipolar structures are common among PNs, and these structures develop early in their evolution. From three-dimensional geometric models, we have determined the intrinsic dimensions of the lobes. Assuming the lobes are the result of interactions between later-developed fast winds and previously ejected asymptotic giant branch winds, the geometric structures of these PNs suggest that there are multiple phases of fast winds separated by temporal variations and/or directional changes. A scenario of evolution from lobe-dominated to cavity-dominated stages is presented. The results reported here will provide serious constraints on any dynamical models of PNs.

Hsia, Chih-Hao; Chau, Wayne; Zhang, Yong; Kwok, Sun

2014-05-01

3

Multipolar electrostatics.  

Science.gov (United States)

Atomistic simulation of chemical systems is currently limited by the elementary description of electrostatics that atomic point-charges offer. Unfortunately, a model of one point-charge for each atom fails to capture the anisotropic nature of electronic features such as lone pairs or ?-systems. Higher order electrostatic terms, such as those offered by a multipole moment expansion, naturally recover these important electronic features. The question remains as to why such a description has not yet been widely adopted by popular molecular mechanics force fields. There are two widely-held misconceptions about the more rigorous formalism of multipolar electrostatics: (1) Accuracy: the implementation of multipole moments, compared to point-charges, offers little to no advantage in terms of an accurate representation of a system's energetics, structure and dynamics. (2) Efficiency: atomistic simulation using multipole moments is computationally prohibitive compared to simulation using point-charges. Whilst the second of these may have found some basis when computational power was a limiting factor, the first has no theoretical grounding. In the current work, we disprove the two statements above and systematically demonstrate that multipole moments are not discredited by either. We hope that this perspective will help in catalysing the transition to more realistic electrostatic modelling, to be adopted by popular molecular simulation software. PMID:24741671

Cardamone, Salvatore; Hughes, Timothy J; Popelier, Paul L A

2014-05-14

4

Optical Photometry of BY Cam Modeled Using a Multipolar Magnetic Field Structure  

Science.gov (United States)

We present new high-speed broad-band optical photometry of the asynchronous polar (magnetic cataclysmic variable) BY Cam. Observations were obtained at the 2.1-m Otto Struve Telescope of McDonald observatory with 3s integration times. In an attempt to understand the complex changes in accretion flow geometry, we performed full 3D MHD simulations assuming a variety of white dwarf magnetic field structures including both aligned and non-aligned dipole plus quadrupole field components. We compare model predictions with photometry and various phases of the beat cycle and find that synthetic light curves derived from a multipolar field structure are consistent with the optical photometry.

Morales, John; Mason, P. A.; Zhilkin, A.; Bisikalo, D. V.; Robinson, E. L.

2014-01-01

5

Hybrid MEG (Magnetoencephalography) source characterization by cortical remapping and imaging of parametric source models  

Energy Technology Data Exchange (ETDEWEB)

Reliable estimation of the local spatial extent of neural activity is a key to the quantitative analysis of MEG sources across subjects and conditions. In association with an understanding of the temporal dynamics among multiple areas, this would represent a major advance in electrophysiological source imaging. Parametric current dipole approaches to MEG (and EEG) source localization can rapidly generate a physical model of neural current generators using a limited number of parameters. However, physiological interpretation of these models is often difficult, especially in terms of the spatial extent of the true cortical activity. In new approaches using multipolar source models [3, 5], similar problems remain in the analysis of the higher-order source moments as parameters of cortical extent. Image-based approaches to the inverse problem provide a direct estimate of cortical current generators, but computationally expensive nonlinear methods are required to produce focal sources [1,4]. Recent efforts describe how a cortical patch can be grown until a best fit to the data is reached in the least-squares sense [6], but computational considerations necessitate that the growth be seeded in predefined regions of interest. In a previous study [2], a source obtained using a parametric model was remapped onto the cortex by growing a patch of cortical dipoles in the vicinity of the parametric source until the forward MEG or EEG fields of the parametric and cortical sources matched. The source models were dipoles and first-order multipoles. We propose to combine the parametric and imaging methods for MEG source characterization to take advantage of (i) the parsimonious and computationally efficient nature of parametric source localization methods and (ii) the anatomical and physiological consistency of imaging techniques that use relevant a priori information. By performing the cortical remapping imaging step by matching the multipole expansions of the original parametric source and the equivalent cortical patch, rather than their forward fields, we achieve significant reductions in computational complexity.

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

2001-01-01

6

Libration driven multipolar instabilities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider rotating flows in non-axisymmetric enclosures that are driven by libration, i.e. by a small periodic modulation of the rotation rate. Thanks to its simplicity, this model is relevant to various contexts, from industrial containers (with small oscillations of the rotation rate) to fluid layers of terrestial planets (with length-of-day variations). Assuming a multipolar $n$-fold boundary deformation, we first obtain the two-dimensional basic flow. We then perform a short-wavelength ...

2014-01-01

7

Modeling temporal variations in multipolarized radar scattering from intertidal coastal wetlands  

Science.gov (United States)

Coastal wetlands form critical ecosystems that are very sensitive to natural and anthropogenic environmental factors. These dynamic environments can exhibit both seasonal and year-to-year variability causing significant temporal variations in remotely sensed data. Understanding these variations is necessary if time series of remotely sensed data are to be used to monitor and manage coastal environments. Coastal areas can also experience persistent cloud cover, thereby making the use of microwave sensors, such as radar, potentially attractive for monitoring. Data acquired by polarimetric Synthetic Aperture Radar (SAR) and Laser Altimeter (LIDAR) sensors are analyzed to evaluate the response of a coastal marsh complex to climatic and tidal processes. The utility of L-band SAR data is investigated for detecting the presence of inundation and quantifying seasonal variations in plant phenology in several wetland environments. A coherent microwave scattering model is used to simulate radar backscatter from the marsh under different phenological and inundation conditions. Coastal marshes can exhibit scattering behavior that is different from other environments, such as forests and inland grasslands, for which scattering phenomena have been more thoroughly studied. Using a high-resolution Digital Elevation Model (DEM) derived from LIDAR data and ancillary measurements of climatic and tidal conditions, changes in the multi-polarization L-band SAR responses over a three-year period are related to specific scattering mechanisms in the marsh. Results indicate that variations in polarization preference of herbaceous marshes are often more pronounced than those observed over upland areas. Succulent halophytic plants in the high marsh respond strongly to inundation but only mildly to climatic factors, such as average daily temperature. Conversely, the response of non-succulent halophytic plants in the low marsh is strongly dependent on climate, which in turn affects their response to inundation. Results indicate that some knowledge of the vegetation phenology is required, along with scattering simulations, for meaningful interpretation of multi-temporal SAR data over coastal wetlands.

Clint Slatton, K.; Crawford, Melba M.; Chang, Li-Der

8

Libration driven multipolar instabilities  

CERN Document Server

We consider rotating flows in non-axisymmetric enclosures that are driven by libration, i.e. by a small periodic modulation of the rotation rate. Thanks to its simplicity, this model is relevant to various contexts, from industrial containers (with small oscillations of the rotation rate) to fluid layers of terrestial planets (with length-of-day variations). Assuming a multipolar $n$-fold boundary deformation, we first obtain the two-dimensional basic flow. We then perform a short-wavelength local stability analysis of the basic flow, showing that an instability may occur in three dimensions. We christen it the Libration Driven Multipolar Instability (LDMI). The growth rates of the LDMI are computed by a Floquet analysis in a systematic way, and compared to analytical expressions obtained by perturbation methods. We then focus on the simplest geometry allowing the LDMI, a librating deformed cylinder. To take into account viscous and confinement effects, we perform a global stability analysis, which shows that...

Cébron, David; Herreman, Wietze

2014-01-01

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

Fully Complex Magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Complex numbers appear naturally in biology whenever a system can be analyzed in the frequency domain, such as physiological data from magnetoencephalography (MEG). For example, the MEG steady state response to a modulated auditory stimulus generates a complex magnetic field for each MEG channel, equal to the Fourier transform at the stimulus modulation frequency. The complex nature of these data sets, often not taken advantage of, is fully exploited here with new methods. W...

Simon, Jonathan Z.; Wang, Yadong

2005-01-01

11

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

12

Searching for the best model: ambiguity of inverse solutions and application to fetal magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Fetal brain signals produce weak magnetic fields at the maternal abdominal surface. In the presence of much stronger interference these weak fetal fields are often nearly indistinguishable from noise. Our initial objective was to validate these weak fetal brain fields by demonstrating that they agree with the electromagnetic model of the fetal brain. The fetal brain model is often not known and we have attempted to fit the data to not only the brain source position, orientation and magnitude, but also to the brain model position. Simulation tests of this extended model search on fetal MEG recordings using dipole fit and beamformers revealed a region of ambiguity. The region of ambiguity consists of a family of models which are not distinguishable in the presence of noise, and which exhibit large and comparable SNR when beamformers are used. Unlike the uncertainty of a dipole fit with known model plus noise, this extended ambiguity region yields nearly identical forward solutions, and is only weakly dependent on noise. The ambiguity region is located in a plane defined by the source position, orientation, and the true model centre, and will have a diameter approximately 0.67 of the modelled fetal head diameter. Existence of the ambiguity region allows us to only state that the fetal brain fields do not contradict the electromagnetic model; we can associate them with a family of models belonging to the ambiguity region, but not with any specific model. In addition to providing a level of confidence in the fetal brain signals, the ambiguity region knowledge in combination with beamformers allows detection of undistorted temporal waveforms with improved signal-to-noise ratio, even though the source position cannot be uniquely determined.

Vrba, J [VSM MedTech Ltd, Coquitlam, BC, V3K 7B2 (Canada); Robinson, S E [VSM MedTech Ltd, Coquitlam, BC, V3K 7B2 (Canada); McCubbin, J [Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205 (United States); Lowery, C L [Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205 (United States); Eswaran, H [Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205 (United States); Murphy, P [Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205 (United States); Preissl, H [Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, AR 72205 (United States)

2007-02-07

13

Searching for the best model: ambiguity of inverse solutions and application to fetal magnetoencephalography  

International Nuclear Information System (INIS)

Fetal brain signals produce weak magnetic fields at the maternal abdominal surface. In the presence of much stronger interference these weak fetal fields are often nearly indistinguishable from noise. Our initial objective was to validate these weak fetal brain fields by demonstrating that they agree with the electromagnetic model of the fetal brain. The fetal brain model is often not known and we have attempted to fit the data to not only the brain source position, orientation and magnitude, but also to the brain model position. Simulation tests of this extended model search on fetal MEG recordings using dipole fit and beamformers revealed a region of ambiguity. The region of ambiguity consists of a family of models which are not distinguishable in the presence of noise, and which exhibit large and comparable SNR when beamformers are used. Unlike the uncertainty of a dipole fit with known model plus noise, this extended ambiguity region yields nearly identical forward solutions, and is only weakly dependent on noise. The ambiguity region is located in a plane defined by the source position, orientation, and the true model centre, and will have a diameter approximately 0.67 of the modelled fetal head diameter. Existence of the ambiguity region allows us to only state that the fetal brain fields do not contradict the electromagnetic model; we can associate them with a family of models belonging to the ambiguity region, but not with any specific model. In addition to providing a level of confidence in the fetal brain signals, the ambiguity region knowledge in combination with beamformers allows detection of undistorted temporal waveforms with improved signal-to-noise ratio, even though the source position cannot be uniquely determined

2007-02-07

14

Multipolar proportional chambers  

International Nuclear Information System (INIS)

The parameters of the multipolar proportional chamber, which is the new track detector used in SFINKS setup experiments, are presented. The characteristics of the chambers with different gaps between the anode wires are also investigated. 3 refs.; 7 figs.; 1 tab

1991-01-01

15

Magnetoencephalography: Basic principles.  

Science.gov (United States)

Magnetoencephalography (MEG) is the measurement of the magnetic field generated by the electrical activity of neurons. It is usually combined with a magnetic resonance imaging to get what is called magnetic source imaging. The technology that has helped record these minute magnetic fields is super-conducting quantum interference detector which is like a highly sensitive magnetic field meter. To attenuate the external magnetic noise the MEG is housed inside a magnetically shielded room. The actual sensors recording magnetic fields are magnetometers and/or gradiometers. MEG fields pass through the head without any distortion. This is a significant advantage of MEG over electroencephalography. MEG provides a high spatial and temporal resolution. The recording and identification information should be according to the American Clinical Magnetoencephalography Society guidelines published in 2011. MEG currently has two approved indications in the United States, one is for pre-operative brain mapping and the other is for use in epilepsy surgery. MEG studies have shown functional brain tissue inside brain tumors. PMID:24791076

Singh, Sanjay P

2014-03-01

16

Libration-driven multipolar instabilities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider rotating flows in non-axisymmetric enclosures that are driven by libration, i.e. by a small periodic modulation of the rotation rate. Thanks to its simplicity, this model is relevant to various contexts, from industrial containers (with small oscillations of the rotation rate) to fluid layers of terrestrial planets (with length-of-day variations). Assuming a multipolar n-fold boundary deformation, we first obtain the two-dimensional basic flow. We then perform a short-wavelength l...

2014-01-01

17

A Textural–Contextual Model for Unsupervised Segmentation of Multipolarization Synthetic Aperture Radar Images  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a novel unsupervised, non-Gaussian, and contextual segmentation method that combines an advanced statistical distribution with spatial contextual informa-tion for multilook polarimetric synthetic aperture radar (PolSAR)data. This extends on previous studies that have shown the added value of both non-Gaussian modeling and contextual smoothing individually or for intensity channels only. The method is based on a Markov random field (MRF) model that integrates a K-Wishart d...

2013-01-01

18

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." Hum Brain Mapp 35:2789-2805, 2014. © 2013 Wiley Periodicals, Inc. PMID:24105895

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

2014-06-01

19

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

International Nuclear Information System (INIS)

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.

2013-03-01

20

Laboratory experiments on multipolar vortices in a rotating fluid  

Science.gov (United States)

The instability properties of isolated monopolar vortices have been investigated experimentally and the corresponding multipolar quasisteady states have been compared with semianalytical vorticity-distributed solutions to the Euler equations in two dimensions. A novel experimental technique was introduced to generate unstable monopolar vortices whose nonlinear evolution resulted in the formation of multipolar vortices. Dye-visualization and particle imaging techniques revealed the existence of tripolar, quadrupolar, and pentapolar vortices. Also evidence was found of the onset of hexapolar and heptapolar vortices. The observed multipolar vortices were found to be unstable and generally broke up into multipolar vortices of lesser complexity. The characteristic flow properties of the quadrupolar vortex were in close agreement with the semianalytical model solutions. Higher-order multipolar vortices were observed to be susceptible to strong inertial oscillations.

Trieling, R. R.; van Heijst, G. J. F.; Kizner, Z.

2010-09-01

 
 
 
 
21

Magnetoencephalography in pediatric epilepsy.  

Science.gov (United States)

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. PMID:24244211

Kim, Hunmin; Chung, Chun Kee; Hwang, Hee

2013-10-01

22

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

23

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

24

Independent Component Analysis of Magnetoencephalography Data.  

Science.gov (United States)

Independent Component Analysis (ICA) is applied to the Magnetoencephalography (MEC) data of a subject performing a yoga breathing exercise specific for the treatment of obsessive compulsive disorder, The spatio-temporal dynamics observed using a whole-hea...

L. Fortuna M. Bucolo M. Frasca M. LaRosa D. Shannahoff- Khalsa

2001-01-01

25

Multipolar excitation in triangular nanoprisms  

Science.gov (United States)

Theoretical studies on the optical properties of gold triangular prisms in solution are presented to determine how structural modifications affect the extinction spectrum. Well-defined trends in the particle extinction are found to depend on the triangular edge length and the prism thickness. Calculations performed on large, thin triangular prisms indicate multipolar excitation and display numerous peaks in the extinction spectrum. The dominant peaks are assigned to different in-plane modes corresponding to the lowest three orders of a multipole expansion. Vector polarization plots are presented to support the peak assignments. Altering the prisms by snipping off the points of the triangular cross section significantly blueshifts the dipole peak, but the higher-order modes are only slightly affected. Snipping off large volumes can lead to the suppression of high-order multipoles in the extinction spectrum.

Shuford, Kevin L.; Ratner, Mark A.; Schatz, George C.

2005-09-01

26

Multi-sensor magnetoencephalography with atomic magnetometers  

International Nuclear Information System (INIS)

The authors have detected magnetic fields from the human brain with two independent, simultaneously operating rubidium spin-exchange-relaxation-free magnetometers. Evoked responses from auditory stimulation were recorded from multiple subjects with two multi-channel magnetometers located on opposite sides of the head. Signal processing techniques enabled by multi-channel measurements were used to improve signal quality. This is the first demonstration of multi-sensor atomic magnetometer magnetoencephalography and provides a framework for developing a non-cryogenic, whole-head magnetoencephalography array for source localization. (paper)

2013-09-07

27

The role of multipolar magnetic fields in pulsar magnetospheres  

Science.gov (United States)

We explore the role of complex multipolar magnetic fields in determining physical processes near the surface of rotation powered pulsars. We model the actual magnetic field as the sum of global dipolar and star-centred multipolar fields. In configurations involving axisymmetric and uniform multipolar fields, `neutral points' and `neutral lines' exist close to the stellar surface. Also, the curvature radii of magnetic field lines near the stellar surface can never be smaller than the stellar radius, even for very high-order multipoles. Consequently, such configurations are unable to provide an efficient pair-creation process above pulsar polar caps, necessary for plasma mechanisms of generation of pulsar radiation. In configurations involving axisymmetric and non-uniform multipoles, the periphery of the pulsar polar cap becomes fragmented into symmetrically distributed narrow subregions where curvature radii of complex magnetic field lines are less than the radius of the star. The pair-production process is only possible just above these `favourable' subregions. As a result, the pair plasma flow is confined within narrow filaments regularly distributed around the margin of the open magnetic flux tube. Such a magnetic topology allows us to model the system of 20 isolated subbeams observed in PSR B0943+10 by Deshpande & Rankin. We suggest a physical mechanism for the generation of pulsar radio emission in the ensemble of finite subbeams, based on specific instabilities. We propose an explanation for the subpulse drift phenomenon observed in some long-period pulsars.

Asseo, Estelle; Khechinashvili, David

2002-08-01

28

Multipolar second harmonic generation from metallic nanoparticles  

Science.gov (United States)

We describe the multipolar Second Harmonic (SH) response from metallic particles with sizes up to 150 nm. A particular emphasis is given to the light polarization and size dependence of the SH intensity collected to identify the different field mechanisms involved and quantify the different sources to the nonlinear polarization. It is shown that the dipolar, quadrupolar and octupolar modes can be observed depending on the input fundamental and output harmonic polarization configurations chosen and the size of the particles. We furthermore develop a careful analysis of the experimental results obtained for the largest size of particles investigated, e.g. 150 nm diameter gold particles, in conjunction with finite element simulations to compute the different sources to the nonlinear polarization, namely the surface local and the bulk nonlocal contributions. It is then shown that their relative weight can be determined. These results are recast within the general model initially proposed by Rudnick and Stern (J. Rudnick and E. A. Stern, Phys. Rev. B, 4 (1971) 4274).

Butet, J.; Bachelier, G.; Russier-Antoine, I.; Jonin, Ch.; Benichou, E.; Brevet, P. F.

2011-02-01

29

Magnetoencephalography and its role in evaluation for epilepsy surgery.  

Science.gov (United States)

Magnetoencephalography is a newly developed technology used for diagnostic and brain mapping imaging during the presurgical evaluation of patients with medically intractable epilepsy. It provides comprehensive localisation of an epileptogenic focus using simultaneous recordings from the entire brain surface. Magnetoencephalography and electroencephalography are considered complementary and confirmatory to one another. We present a patient with magnetic resonance imaging-negative, non-lesional, neocortical epilepsy. Magnetoencephalography was used for re-evaluation of the epileptogenic zone and this enabled subsequent surgical removal of the epileptic focus. The role of magnetoencephalography in epilepsy surgery is discussed in this report. PMID:20124573

Poon, T L; Cheung, F C; Lui, C H T

2010-02-01

30

PARAMETER ESTIMATION AND DYNAMIC SOURCE LOCALIZATION FOR THE MAGNETOENCEPHALOGRAPHY (MEG) INVERSE PROBLEM  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dynamic estimation methods based on linear state-space models have been applied to the inverse problem of magnetoencephalography (MEG), and can improve source localization compared with static methods by incorporating temporal continuity as a constraint. The efficacy of these methods is influenced by how well the state-space model approximates the dynamics of the underlying brain current sources. While some components of the state-space model can be inferred from brain anatomy and knowledge o...

Lamus, C.; Long, C. J.; Ha?ma?la?inen, M. S.; Brown, E. N.; Purdon, P. L.

2007-01-01

31

A multipolar approach to liquid helium II  

International Nuclear Information System (INIS)

Using the general framework of multipolar continuum mechanics as developed by Green and Rivlin (1964) the authors discuss a possible alternative to the two-fluid theories of liquid helium II. They show in particular that the theory predicts the existence of second-sound waves which are attenuated in the manner observed both in the stationary fluid and also in the rotating fluid. Moreover they suggest a possible continuum analogue of the concept of quantised vortex lines. (Auth.)

1975-01-01

32

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

33

NQR investigation on multipolar ordering systems  

International Nuclear Information System (INIS)

We have carried out nuclear quadrupolar resonance (NQR) measurements on SmRu4P12 and YbAl3C3, both of which have attracted much interest in terms of multipolar ordering. Although no structural anomalies have been detected by diffraction experiments so far, the NQR resonance frequencies ?Q's of both compounds show marked anomalies just below each phase transition temperature, which probably probes the order parameters. The results provide important information to shed light on the ordered structures in the low temperature phases of these compounds

2008-04-01

34

Monte Carlo analysis of localization errors in magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

In magnetoencephalography (MEG), the magnetic fields created by electrical activity in the brain are measured on the surface of the skull. To determine the location of the activity, the measured field is fit to an assumed source generator model, such as a current dipole, by minimizing chi-square. For current dipoles and other nonlinear source models, the fit is performed by an iterative least squares procedure such as the Levenberg-Marquardt algorithm. Once the fit has been computed, analysis of the resulting value of chi-square can determine whether the assumed source model is adequate to account for the measurements. If the source model is adequate, then the effect of measurement error on the fitted model parameters must be analyzed. Although these kinds of simulation studies can provide a rough idea of the effect that measurement error can be expected to have on source localization, they cannot provide detailed enough information to determine the effects that the errors in a particular measurement situation will produce. In this work, we introduce and describe the use of Monte Carlo-based techniques to analyze model fitting errors for real data. Given the details of the measurement setup and a statistical description of the measurement errors, these techniques determine the effects the errors have on the fitted model parameters. The effects can then be summarized in various ways such as parameter variances/covariances or multidimensional confidence regions. 8 refs., 3 figs.

Medvick, P.A.; Lewis, P.S.; Aine, C.; Flynn, E.R.

1989-01-01

35

Astronomical relativistic reference systems with multipolar expansion: the global one  

CERN Multimedia

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

36

Magnetoencephalography in pediatric neurology and in epileptic syndromes.  

Science.gov (United States)

In recent years, great advances in the knowledge of neuromagnetism have permitted the application of Superconducting Quantum Interference Devices to the pathophysiologic study of the human brain. In particular, in pediatric neurology, the integration of biomagnetism with magnetic resonance imaging and other techniques for medical imaging have allowed for precise neuromagnetic measurements of the human brain. The more frequently used technique is magnetoencephalography. Recent data have illustrated the usefulness of magnetoencephalography in mapping activity of sensory and motor areas and in studying the spatiotemporal pattern of brain activation specific to somatosensory function. Moreover, magnetoencephalography is an important tool to localize epileptic activity; magnetic source imaging superimposes magnetoencephalographic localizations on the magnetic resonance imaging and yields improved spatial resolution as compared with surface electroencephalography. The role of magnetoencephalography in evaluating patients with epilepsy continues to evolve; in fact, it seems to be very useful in the localization of the epileptogenic zone in patients with partial epilepsy. This application of magnetoencephalography is essential in the selection of epileptic children candidates to surgical treatment of seizures. PMID:12849877

Verrotti, Alberto; Pizzella, Vittorio; Trotta, Daniela; Madonna, Laura; Chiarelli, Francesco; Romani, Gian Luca

2003-04-01

37

The precise ICC measurement of the high multipolarity transitions  

International Nuclear Information System (INIS)

The methods of ?-spectroscopy are used to measure internal conversion coefficients (ICC) on the K-shell and total ICC for M4,E4,E5-multipolarity transitions. The research is carried out using the 202,204Pb, 197Pt,114In isomers. The data obtained prove that the observed systematic excess of theoretical ICC for M4-multipolarity transitions as compared with the experimental values is most probably connected with the contribution of ''intranuclear'' conversion

1988-05-26

38

Estimates of multipolar coefficients for searching for cosmic ray anisotropies with non-uniform or partial sky coverage  

International Nuclear Information System (INIS)

We study the possibility of extracting the multipolar moments of an underlying distribution from a set of cosmic rays observed with non-uniform or even partial sky coverage. We show that if the degree is assumed to be upper bounded by L, each multipolar moment can be recovered whatever the coverage, but with a variance increasing exponentially with the bound L if the coverage is zero somewhere. Despite this limitation, we show the possibility of testing predictions of a model without any assumption on L by building an estimate of the covariance matrix seen through the exposure function

2008-02-01

39

Algebraic reconstruction combined with the signal space separation method for the inverse magnetoencephalography problem with a dipole-quadrupole source  

Science.gov (United States)

This paper presents an algebraic reconstruction method for dipole-quadrupole sources using magnetoencephalography data. Compared to the conventional methods with the equivalent current dipoles source model, our method can more accurately reconstruct two close, oppositely directed sources. Numerical simulations show that two sources on both sides of the longitudinal fissure of cerebrum are stably estimated. The method is verified using a quadrupolar source phantom, which is composed of two isosceles-triangle-coils with parallel bases.

Nara, T.; Koiwa, K.; Takagi, S.; Oyama, D.; Uehara, G.

2014-05-01

40

Magnetoencephalography in the study of human somatosensory cortical processing.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetoencephalography (MEG) is a totally non-invasive research method which provides information about cortical dynamics on a millisecond time-scale. Whole-scalp magnetic field patterns following stimulation of different peripheral nerves indicate activation of an extensive cortical network. At the SI cortex, the responses reflect mainly the activity of area 3b, with clearly somatotopical representations of different body parts. The SII cortex is activated bilaterally and it also receives, b...

Hari, R.; Forss, N.

1999-01-01

 
 
 
 
41

Adaptive cluster analysis approach for functional localization using magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 magnetoencephalography (MEG) brain signals. Reliable localization of brain areas with MEG has been difficult due to variations in signal strength, and the spatial extent of the reconstructed activity. The proposed approach to resolve this difficulty is based on adaptive clustering on reconstructed beamformer images ...

Alikhanian, Hooman; Crawford, J. Douglas; Desouza, Joseph F. X.; Cheyne, Douglas O.; Blohm, Gunnar

2013-01-01

42

Aberrant functional organization and maturation in early-onset psychosis: Evidence from magnetoencephalography  

Science.gov (United States)

Studies of the location of somatosensory and auditory cortical responses have shown anomalous hemispheric asymmetries in a variety of neurodevelopmental disorders. Although to date, abnormal asymmetries in the somatosensory region have shown greater specificity being reported only in psychotic adults. This study examines functional organization of somatosensory cortices using magnetoencephalography in adolescents with childhood-onset psychotic disorders. Eighteen young outpatients with history of psychotic illness and 15 healthy adolescents participated. Both groups underwent stimulation of the index finger as magnetoencephalography was acquired from the contralateral hemisphere. Neural generators of the M50 somatosensory response were modeled using an equivalent current dipole for each hemisphere, and later investigated for systematic variation with diagnosis. Consistent with adult psychosis data, adolescent patients showed hemispheric symmetry in the anterior-posterior dimension. In controls, a reversed pattern of hemispheric asymmetry was observed relative to previous findings in normal adults (Reite et al., 2003), but trend-level correlations suggested source location became more adult-like during transition from adolescence to adulthood. Source parameters also exhibited robust inter-hemispheric correlations only in adolescent controls. In sum, source locations, patterns of cerebral lateralization, and inter-hemispheric correlations all distinguish patients from their normally developing cohort. These findings suggest aberrant maturation underlies the reduction in cerebral laterality associated with psychosis.

Wilson, Tony W.; Rojas, Donald C.; Teale, Peter D.; Hernandez, Olivia O.; Asherin, Ryan M.; Reite, Martin L.

2007-01-01

43

Aberrant functional organization and maturation in early-onset psychosis: evidence from magnetoencephalography.  

Science.gov (United States)

Studies of the location of somatosensory and auditory cortical responses have shown anomalous hemispheric asymmetries in a variety of neurodevelopmental disorders. To date, abnormal asymmetries in the somatosensory region have shown greater specificity, being reported only in psychotic adults. This study examines the functional organization of the somatosensory cortices using magnetoencephalography in adolescents with childhood-onset psychotic disorders. Eighteen young outpatients with history of psychotic illness and 15 healthy adolescents participated. Both groups underwent stimulation of the index finger as magnetoencephalography was acquired from the contralateral hemisphere. Neural generators of the M50 somatosensory response were modeled using an equivalent current dipole for each hemisphere, and later investigated for systematic variation with diagnosis. Consistent with adult psychosis data, adolescent patients showed hemispheric symmetry in the anterior-posterior dimension. In controls, a reversed pattern of hemispheric asymmetry was observed relative to previous findings in normal adults [Reite, M., Teale, P., Rojas, D.C., Benkers, T.L., Carlson, J., 2003. Anomalous somatosensory cortical localization in schizophrenia. American Journal of Psychiatry 160, 2148-2153], but trend-level correlations suggested source location became more adult-like during the transition from adolescence to adulthood. Source parameters also exhibited robust inter-hemispheric correlations only in adolescent controls. In sum, source locations, patterns of cerebral lateralization, and inter-hemispheric correlations all distinguish patients from their normally developing cohort. These findings suggest aberrant maturation underlies the reduction in cerebral laterality associated with psychosis. PMID:17728112

Wilson, Tony W; Rojas, Donald C; Teale, Peter D; Hernandez, Olivia O; Asherin, Ryan M; Reite, Martin L

2007-10-15

44

Hepatic radiofrequency ablation using multiple probes: vivo and in vivo comparative studies of monopolar versus multipolar modes  

Energy Technology Data Exchange (ETDEWEB)

We wanted to compare the efficiency of multipolar radiofrequency ablation (RFA) using three perfused-cooled electrodes with multiple overlapping- and simultaneous monopolar techniques for creating an ablation zone in ex vivo bovine livers and in in vivo porcine livers. In the ex vivo experiments, we used a 200 W generator (Valleylab, CC-3 model) and three perfused-cooled electrodes or internally cooled electrodes to create 30 coagulation zones by performing consecutive monopolar RFA (group A, n=10), simultaneous monopolar RFA (group B, n=10) or multipolar RFA (group C, n=10) in explanted bovine livers. In the consecutive mode, three ablation spheres were created by sequentially applying 150 watts radiofrequency (RF) energy to the internally cooled electrodes for 12 minutes each for a total of 36 minutes. In the simultaneous monopolar and multipolar modes, RF energy was concurrently applied to the three perfused-cooled electrodes for 20 minutes at 150 watt with instillation of 6% hypertonic saline at 2 mL/min. During RFA, we measured the temperatures of the treated area at its center. The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups. In the in vivo experiments, three coagulations were created by performing multipolar RFA in a pig via laparotomy with using same parameter as the ex vivo study. In the ex vivo experiments, the impedance was gradually decreased during the RFA in groups B and C, but in group A, the impedance was increased during RFA and this induced activation by the pulsed RF technique. In groups A, B and C, the mean final-temperature values were 80 {+-} 10 {approx}, 69 {+-} 18 {approx} and 79 {+-} 12 {approx}, respectively ({rho} < 0.05). The multipolar mode created a larger volume of ablation than did the other modes: 37.6 {+-} 4.0 cm{sup 3} (group A); 44.9 {+-} 12.7 cm{sup 3} (group B); and 78.9 {+-} 6.9 cm{sup 3} (group C) ({rho} < 0.05). In the in vivo experiment, the pig well tolerated the RFA procedure and no major complications occurred during the 4 days of the follow-up period. The mean volume of coagulations produced by multipolar RFA in the pig liver was 60.5 {+-} 17.9 cm{sup 3}. For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes.

Lee, Jeong Min; Han, Joon Koo; Lee, Jae Young; Kim, Se Hyung; Choi, Jin Young; Lee, Min Woo; Choi, Seung Hong; Eo, Hong; Choi, Byung Ihn [Seoul National University College of Medicine, Seoul (Korea, Republic of)

2006-06-15

45

Optical Torque from Enhanced Scattering by Multipolar Plasmonic Resonance  

CERN Document Server

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, thereby producing 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 metamateria...

Lee, Yoonkyung E; Jin, Dafei; Fang, Nicholas

2014-01-01

46

Multipolar interactions in rare-earth metals and alloys  

International Nuclear Information System (INIS)

The Hamiltonian of the indirect quadrupole-quadrupole interaction of rare-earth ions in metals and alloys is constructed self-consistently, taking into account the exchange interactions and correlations in a system of conduction electrons (CE) and the antishielding effects. The manifestations of the indirect multipolar interactions of paramagnetic ions in the parameters of ESR on localized moments in metals and alloys are studied. (orig.)

1992-02-01

47

Identification of equivalent multipolar electromagnetic sources by spatial filtering  

Digital Repository Infrastructure Vision for European Research (DRIVER)

New sensors of magnetic induction in near field, dedicated to studies of electromagnetic compatibility, are proposed based on the Standard CISPR16-1 coils. The new coil shape allows the sensors to be sensitive only to specific components of the multipolar expansion, which is similar to a spatial filtering. In comparison with our previous approach in which we designed a complete set of coils, we aim to simplify the sensor coil geometry by rotating the spherical harmonics functions. After a des...

Vincent, Benjamin; Chadebec, Olivier; Schanen, Jean-luc; Berger, Ke?vin; Perrussel, Ronan; Kra?henbu?hl, Laurent

2010-01-01

48

Hooray for global justice? Emerging democracies in a multipolar world  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rising powers are fundamentally shifting the relations of power in the global economic and political landscape. International political theory, however, has so far failed to evaluate this nascent multipolarity. This article fills this lacuna by synthesizing empirical and normative modes of inquiry. It examines the transformation of sovereignty exercised by emerging democracies and shows that - in stark contrast to emerging democracies' foreign policy rhetoric - the softening of sovereignty ha...

Culp, Julian; Plagemann, Johannes

2013-01-01

49

State-space solutions to the dynamic magnetoencephalography inverse problem using high performance computing  

CERN Multimedia

Determining the magnitude and location of neural sources within the brain that are responsible for generating magnetoencephalography (MEG) signals measured on the surface of the head is a challenging problem in functional neuroimaging. The number of potential sources within the brain exceeds by an order of magnitude the number of recording sites. As a consequence, the estimates for the magnitude and location of the neural sources will be ill-conditioned because of the underdetermined nature of the problem. One well-known technique designed to address this imbalance is the minimum norm estimator (MNE). This approach imposes an $L^2$ regularization constraint that serves to stabilize and condition the source parameter estimates. However, these classes of regularizer are static in time and do not consider the temporal constraints inherent to the biophysics of the MEG experiment. In this paper we propose a dynamic state-space model that accounts for both spatial and temporal correlations within and across candida...

Long, Christopher J; Temereanca, Simona; Desai, Neil U; Hämäläinen, Matti S; Brown, Emery N; 10.1214/11-AOAS483

2011-01-01

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

Multipolar equations of motion for extended test bodies in General Relativity  

CERN Document Server

We derive the equations of motion of an extended test body in the context of Einstein's theory of gravitation. The equations of motion are obtained via a multipolar approximation method and are given up to the quadrupolar order. Special emphasis is put on the explicit construction of the so-called canonical form of the energy-momentum density. The set of gravitational multipolar moments and the corresponding equations of motion allow for a systematic comparison to competing multipolar approximation schemes.

Steinhoff, Jan

2009-01-01

52

Multipolar equations of motion for extended test bodies in general relativity  

International Nuclear Information System (INIS)

We derive the equations of motion of an extended test body in the context of Einstein's theory of gravitation. The equations of motion are obtained via a multipolar approximation method and are given up to the quadrupolar order. Special emphasis is put on the explicit construction of the so-called canonical form of the energy-momentum density. The set of gravitational multipolar moments and the corresponding equations of motion allow for a systematic comparison to competing multipolar approximation schemes.

2010-02-15

53

Adaptive cluster analysis approach for functional localization using magnetoencephalography.  

Science.gov (United States)

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 magnetoencephalography (MEG) brain signals. Reliable localization of brain areas with MEG has been difficult due to variations in signal strength, and the spatial extent 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. PMID:23675314

Alikhanian, Hooman; Crawford, J Douglas; Desouza, Joseph F X; Cheyne, Douglas O; Blohm, Gunnar

2013-01-01

54

Magnetoencephalography in the study of epilepsy and consciousness.  

Science.gov (United States)

The neural bases of altered consciousness in patients with epilepsy during seizures and at rest have raised significant interest in the last decade. This exponential growth has been supported by the parallel development of techniques and methods to investigate brain function noninvasively with unprecedented spatial and temporal resolution. In this article, we review the contribution of magnetoencephalography to deconvolve the bioelectrical changes associated with impaired consciousness during seizures. We use data collected from a patient with refractory absence seizures to discuss how spike-wave discharges are associated with perturbations in optimal connectivity within and between brain regions and discuss indirect evidence to suggest that this phenomenon might explain the cognitive deficits experienced during prolonged 3/s spike-wave discharges. PMID:24113567

Foley, Elaine; Cerquiglini, Antonella; Cavanna, Andrea; Nakubulwa, Mable Angela; Furlong, Paul Lawrence; Witton, Caroline; Seri, Stefano

2014-01-01

55

Presence of Strong Harmonics During Visual Entrainment: A Magnetoencephalography Study  

Science.gov (United States)

Visual neurons are known to synchronize their firing with stimuli that flicker at a constant rate (e.g., 12 Hz). These so-called visual steady-state responses (VSSR) are a well-studied phenomenon, yet the underlying mechanisms are widely disagreed upon. Furthermore, there is limited evidence that visual neurons may simultaneously synchronize at harmonics of the stimulation frequency. We utilized magnetoencephalography (MEG) to examine synchronization at harmonics of the visual stimulation frequency (18 Hz). MEG data were analyzed for event-related-synchronization (ERS) at the fundamental frequency, 36, 54, and 72 Hz. We found strong ERS in all bands. Only 31% of participants showed maximum entrainment at the fundamental; others showed stronger entrainment at either 36 or 54 Hz. The cortical foci of these responses indicated that the harmonics involved cortices that were partially distinct from the fundamental. These findings suggest that spatially-overlapping subpopulations of neurons are simultaneously entrained at different harmonics of the stimulus frequency.

Heinrichs-Graham, Elizabeth; Wilson, Tony W.

2012-01-01

56

Multipolar ordering in PrB6  

International Nuclear Information System (INIS)

We investigate the mechanism how the complex magnetic structure is stabilized in PrB6, paying attention to similarity to and difference from the case of CeB6. A Ginzburg-Landau-type expansion of the free energy is obtained with account of the ?5-triplet crystalline electric field (CEF) ground state in PrB6. It is found in the ?5 model that combination of the nearest-neighbor dipole interaction and the next-nearest neighbor pseudo-dipole-type one reproduces the successive magnetic transitions observed in PrB6: incommensurate phase followed by a commensurate non-collinear structure with further decreasing of temperature. Inclusion of the quadrupolar interaction modifies the second-order transition to the IC phase into first order by enhancing the mode-coupling of dipole and quadrupole degrees of freedom. (author)

2002-03-01

57

Magnetoencephalography - the Use of Multi-SQUID Systems for Noninvasive Brain Research  

Science.gov (United States)

Some of the basic concepts of magnetoencephalography (MEG) and neuromagnetic instrumentation are reviewed. Examples of multichannel SQUID magnetometers and results of measurements with them are presented. Current trends in MEG instrument development are discussed.

Knuutila, Jukka

1988-01-01

58

A multipolar SR motor and its application in EV  

Science.gov (United States)

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.

Goto, H.; Suzuki, Y.; Nakamura, K.; Watanabe, T.; Guo, H. J.; Ichinokura, O.

2005-04-01

59

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

2005-04-01

60

First-Principles Theory of Multipolar Order in Neptunium Dioxide  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We provide a first-principle, materials-specific theory of multipolar order and superexchange in NpO$_2$ by means of a non-collinear local-density approximation +$U$ (LDA+$U$) method. Our calculations offer a precise microscopic description of the triple-$q$-antiferro ordered phase in the absence of any dipolar moment. We find that, while the most common non-dipolar degrees of freedom (e.g., electric quadrupoles and magnetic octupoles) are active in the ordered phase, both t...

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

2010-01-01

 
 
 
 
61

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

62

Multipolar Electrode and Preamplifier Design for ENG-Signal Acquisition  

Science.gov (United States)

Cuff electrodes have several advantages for in situ recording ENG signal. They are easy to implant and not very invasive for the patient. Nevertheless, they are subject to background parasitic noise, especially the EMG generated by the muscles. We show that the use of cuff electrodes with large numbers of poles can increase their sensitivity and their selectivity with respect to an efficient noise rejection. We investigate several configurations and compare the performances of a tripolar cuff electrode versus a multipolar one in numerical simulation.

Soulier, Fabien; Gouyet, Lionel; Cathébras, Guy; Bernard, Serge; Guiraud, David; Bertrand, Yves

63

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

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

Hepatic radiofrequency ablation using multiple probes: vivo and in vivo comparative studies of monopolar versus multipolar modes  

International Nuclear Information System (INIS)

We wanted to compare the efficiency of multipolar radiofrequency ablation (RFA) using three perfused-cooled electrodes with multiple overlapping- and simultaneous monopolar techniques for creating an ablation zone in ex vivo bovine livers and in in vivo porcine livers. In the ex vivo experiments, we used a 200 W generator (Valleylab, CC-3 model) and three perfused-cooled electrodes or internally cooled electrodes to create 30 coagulation zones by performing consecutive monopolar RFA (group A, n=10), simultaneous monopolar RFA (group B, n=10) or multipolar RFA (group C, n=10) in explanted bovine livers. In the consecutive mode, three ablation spheres were created by sequentially applying 150 watts radiofrequency (RF) energy to the internally cooled electrodes for 12 minutes each for a total of 36 minutes. In the simultaneous monopolar and multipolar modes, RF energy was concurrently applied to the three perfused-cooled electrodes for 20 minutes at 150 watt with instillation of 6% hypertonic saline at 2 mL/min. During RFA, we measured the temperatures of the treated area at its center. The changes in impedance, the current and liver temperature during RFA, as well as the dimensions of the thermal ablation zones, were compared among the three groups. In the in vivo experiments, three coagulations were created by performing multipolar RFA in a pig via laparotomy with using same parameter as the ex vivo study. In the ex vivo experiments, the impedance was gradually decreased during the RFA in groups B and C, but in group A, the impedance was increased during RFA and this induced activation by the pulsed RF technique. In groups A, B and C, the mean final-temperature values were 80 ± 10 ?, 69 ± 18 ? and 79 ± 12 ?, respectively (? 3 (group A); 44.9 ± 12.7 cm3 (group B); and 78.9 ± 6.9 cm3 (group C) (? 3. For the multiple probe RFA, the multipolar mode with hypertonic saline instillation was more efficient in generating larger areas of thermal ablation than either the consecutive or simultaneous monopolar modes

2006-06-01

66

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

CERN Multimedia

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

67

Noise-free magnetoencephalography recordings of brain function  

International Nuclear Information System (INIS)

Perhaps the greatest impediment to acquiring high-quality magnetoencephalography (MEG) recordings is the ubiquitous ambient magnetic field noise. We have designed and built a whole-head MEG system using a helmet-like superconducting imaging surface (SIS) surrounding the array of superconducting quantum interference device (SQUID) magnetometers used to measure the MEG signal. We previously demonstrated that the SIS passively shields the SQUID array from ambient magnetic field noise, independent of frequency, by 25-60 dB depending on sensor location. SQUID 'reference sensors' located on the outside of the SIS helmet measure ambient magnetic fields in very close proximity to the MEG magnetometers while being nearly perfectly shielded from all sources in the brain. The fact that the reference sensors measure no brain signal yet are located in close proximity to the MEG sensors enables very accurate estimation and subtraction of the ambient field noise contribution to the MEG sensors using an adaptive algorithm. We have demonstrated total ambient noise reduction factors in excess of 106 (>120 dB). The residual noise for most MEG SQUID channels is at or near the intrinsic SQUID noise floor, typically 2-3 f T Hz-1/2. We are recording MEG signals with greater signal-to-noise than equivalent EEG measurements

2004-05-21

68

The value of Magnetoencephalography to guide electrode implantation in epilepsy.  

Science.gov (United States)

To investigate if Magnetoencephalography (MEG) can add non-redundant information to guide implantation sites for intracranial recordings (IR). The contribution of MEG to intracranial recording planning was evaluated in 12 consecutive patients assessed pre-surgically with MEG followed by IR. Primary outcome measures were the identification of focal seizure onset in IR and favorable surgical outcome. Outcome measures were compared to those of 12 patients matched for implantation type in whom non-invasive pre-surgical assessment suggested clear hypotheses for implantation (non-MEG group). In the MEG group, non-invasive assessment without MEG was inconclusive, and MEG was then used to further help identify implantation sites. In all MEG patients, at least one virtual MEG electrode generated suitable hypotheses for the location of implantations. No differences in outcome measures were found between non-MEG and MEG groups. Although the MEG group included more complex patients, it showed similar percentage of successful implantations as the non-MEG group. This suggests that MEG can contribute to identify implantation sites where standard methods failed. PMID:24249204

Agirre-Arrizubieta, Zaloa; Thai, Ngoc J; Valentín, Antonio; Furlong, Paul L; Seri, Stefano; Selway, Richard P; Elwes, Robert D C; Alarcón, Gonzalo

2014-01-01

69

Real-time robust signal space separation for magnetoencephalography.  

Science.gov (United States)

In this paper, we develop a robust signal space separation (rSSS) algorithm for real-time magnetoencephalography (MEG) data processing. rSSS is based on the spatial signal space separation (SSS) method and it applies robust regression to automatically detect and remove bad MEG channels so that the results of SSS are not distorted. We extend the existing robust regression algorithm via three important new contributions: 1) a low-rank solver that efficiently performs matrix operations; 2) a subspace iteration scheme that selects bad MEG channels using low-order spherical harmonic functions; and 3) a parallel computing implementation that simultaneously runs multiple tasks to further speed up numerical computation. Our experimental results based on both simulation and measurement data demonstrate that rSSS offers superior accuracy over the traditional SSS algorithm, if the MEG data contain significant outliers. Taking advantage of the proposed fast algorithm, rSSS achieves more than 75 x runtime speedup compared to a direct solver of robust regression. Even though rSSS is currently implemented with MATLAB, it already provides sufficient throughput for real-time applications. PMID:20176529

Guo, Chenlei; Li, Xin; Taulu, Samu; Wang, Wei; Weber, Douglas J

2010-08-01

70

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

71

Performance of a novel squid-based superconducting imaging-surface magnetoencephalography system  

Energy Technology Data Exchange (ETDEWEB)

Performance for a recently completed whole-head magnetoencephalography system using a superconducting imaging-surface (SIS) surrounding an array of 150 SQUID magnetometers is reported. The helmetlike SIS is hemispherical in shape with a brim. Conceptually, the SIS images nearby sources onto the SQUIDs while shielding sensors from distant 'noise' sources. A finite element method (FEM) description using the as-built geometry was developed to describe the SIS effect on source fields by imposing B(surface)=0. Sensors consist of 8mm x 8mm SQUID magnetometers with 0.84nT/F sensitivity and <3fT/vHz noise. A series of phantom experiments to verify system efficacy have been completed. Simple dry-wire phantoms were used to eliminate model dependence from our results. Phantom coils were distributed throughout the volume encompassed by the array with a variety of orientations. Each phantom coil was precisely machined and located to better than 25{micro}m and 10mRad accuracy. Excellent agreement between model-calculated and measured magnetic field distributions of all phantom coil positions and orientations was found. Good agreement was found between modeled and measured shielding of the SQUIDs from sources external to the array showing significant frequency-independent shielding. Phantom localization precision was better than 0.5mm at all locations with a mean of better than 0.3mm.

Matlochov, A. (Andrei); Espy, M. A. (Michelle A.); Volegov, P. (Petr); Maharajh, K. (Keeran); Flynn, E. R. (Edward. R.); Kraus, Robert H., Jr.

2001-01-01

72

Wavenumber Dependence of Multipolar Interactions in the Anderson Lattice  

CERN Document Server

Multipolar interactions are derived in the orbitally degenerate Anderson lattice with a spherical Fermi surface and one conduction electron per unit cell of the simple cubic lattice. As the crystalline-electric-field (CEF) ground state of $f^1$ configuration, the four-fold degenerate $\\Gamma_8$ is mainly studied. Intersite interactions up to a sufficiently distant pair are Fourier transformed to the wavenumber space. For the $\\Gamma_8$ case, quadrupolar and octupolar interactions favor the staggered order with $\\mib{q} = (1/2,1/2,1/2)$, while the dipolar interaction favors an incommensurate magnetic structure with a long modulation period. The latter is due to a Kohn anomaly which is found to be sharply peaked for interaction channels with large angular momenta. Implications of results are discussed for multipole orders in CeB$_6$, and the incommensurate magnetic structure in a quasi-cubic system CeB$_2$C$_2$.

Sakurai, G; Sakurai, Gen'ya; Kuramoto, Yoshio

2004-01-01

73

Multipolar Black Body Radiation Shifts for the Single Ion Clocks  

CERN Document Server

Appraising the projected $10^{-18}$ fractional uncertainty in the optical frequency standards using singly ionized ions, we estimate the black-body radiation (BBR) shifts due to the magnetic dipole (M1) and electric quadrupole (E2) multipoles of the magnetic and electric fields, respectively. Multipolar scalar polarizabilities are determined for the singly ionized calcium (Ca$^+$) and strontium (Sr$^+$) ions using the relativistic coupled-cluster method; though the theory can be exercised for any single ion clock proposal. The expected energy shifts for the respective clock transitions are estimated to be $4.38(3) \\times 10^{-4}$ Hz for Ca$^+$ and $9.50(7) \\times 10^{-5}$ Hz for Sr$^+$. These shifts are large enough and may be prerequisite for the frequency standards to achieve the foreseen $10^{-18}$ precision goal.

Arora, Bindiya; Sahoo, B K

2011-01-01

74

Multipolar blackbody radiation shifts for single-ion clocks  

Science.gov (United States)

Appraising the projected 10-18 fractional uncertainty in the optical frequency standards using singly ionized ions, we estimate the blackbody radiation (BBR) shifts due to the magnetic dipole (M1) and electric quadrupole (E2) multipoles of the applied external electromagnetic field. Multipolar scalar polarizabilities are determined for the singly ionized calcium (Ca+) and strontium (Sr+) ions using the relativistic coupled-cluster method, though the theory can be exercised for any single-ion clocks. The expected energy shifts for the respective clock transitions are estimated to be 4.38(3)×10-4 Hz for Ca+ and 9.50(7)×10-5 Hz for Sr+. These shifts are large enough and may be a prerequisite for the frequency standards to achieve the foreseen 10-18 precision goal.

Arora, Bindiya; Nandy, D. K.; Sahoo, B. K.

2012-01-01

75

Collective motion in system with general multipolar-deformations  

International Nuclear Information System (INIS)

A general formalism is given for the collective motion in a system with general multipolar-deformations, which is treated as vibrations in body-fixed frame and rotation of whole system about the axes of Lab-system, as well as the coupling between vibrations and rotation. 18 various body - fixed frames are defined for octupole deformed system, which shows they can be put into 9 various classifies and the determinants of metric matrix in the body-fixed frames defined by the variables a30, a31, a32 , b31 and a30, a31, b31, b32 are 9a322 and 9b322, which are the simplest

2000-08-01

76

Transition between viscous dipolar and inertial multipolar dynamos  

CERN Document Server

We show that the transition between steady dipolar and fluctuating multipolar dynamos is characterized by a three terms balance between the non-gradient parts of inertial, viscous and Coriolis forces. We derive from this equilibrium the sole parameter Ro E$^{-1/3} \\equiv$ Re E$^{2/3}$, 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 transition can be equivalently described by Ro/l$^\\star_u$ (resp. Re l$^{\\star\\, 2}_u$), which correspond to the two terms balance between the non-gradient part of the Coriolis force and of inertial (resp. viscous) forces. An appropriate definition of the non-dimensional dissipation length scale l$^\\star_u$ (as introduced in Oruba and Dormy, 2014) provides a critical value of this parameter of order unity at the transition.

Oruba, Ludivine

2014-01-01

77

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.

78

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

79

Detection of fetal auditory evoked responses by means of magnetoencephalography.  

Science.gov (United States)

MagnetoEncephaloGraphy (MEG) is proposed as a non-invasive technique to detect the physiological activity of fetal brain, due to its ability to record brain activity without direct contact with the head and the transparency of magnetic signals in passing through extracerebral fetal layers and the mother's abdomen. Healthy women with uncomplicated pregnancies and fetuses in breech presentation were examined; gestational ages at time of study ranged between 36 and 40 weeks. In order to evaluate fetal well-being, ultrasound and cardiotocographic data were assessed a few days before and after MEG recording sessions. The participating women were placed in a semi-reclining position in a magnetically shielded room; here the presentation of the fetus and precise region of the mother's abdomen corresponding to the fetal head were determined by ultrasound investigation in order to place the MEG detecting system as near as possible to the fetal brain. MEG recordings were performed by means of a 28-channel neuromagnetic system. Every MEG recording session was performed during the acoustic stimulation of fetuses, in order to detect the cerebral events evoked by peripheral stimuli. The auditory stimuli were delivered from a plastic tube placed on mother's abdomen, near the fetal head, and consisted of a 300 ms 103 dB pure tone at 500 and 1000 Hz, presented at a 0.4 c/s repetition rate. In six cases following accurate digital subtraction of maternal and fetal electrocardiographic (EKG) signals we remained with a stimulus-related response peaking at about 250 ms; this was considered to originate from the fetal brain. In favour of this in three cases a clear dipolar distribution was evident at the peak of brain response centered on the fetal head and consistent with a brain generator. Despite several technical problems requiring solution before a possible routine clinical application, MEG has been found to be suitable for the non-invasive exploration of the fetal brain. PMID:11640902

Zappasodi, F; Tecchio, F; Pizzella, V; Cassetta, E; Romano, G V; Filligoi, G; Rossini, P M

2001-11-01

80

Magnetoencephalography is feasible for infant assessment of auditory discrimination.  

Science.gov (United States)

Magnetoencephalography (MEG) detects the brain's magnetic fields as generated by neuronal electric currents arising from synaptic ion flow. It is noninvasive, has excellent temporal resolution, and it can localize neuronal activity with good precision. For these reasons, many scientists interested in the localization of brain functions have turned to MEG. The technique, however, is not without its drawbacks. Those reluctant to employ it cite its relative awkwardness among pediatric populations because MEG requires subjects to be fairly still during experiments. Due to these methodological challenges, infant MEG studies are not commonly pursued. In the present study, MEG was employed to study auditory discrimination in infants. We had two goals: first, to determine whether reliable results could be obtained from infants despite their movements; and second, to improve MEG data analysis methods. To get more reliable results from infants we employed novel hardware (real-time head-position tracking system) and software (signal space separation method, SSS) solutions to better deal with noise and movement. With these solutions, the location and orientation of the head can be tracked in real time and we were able to reduce noise and artifacts originating outside the helmet significantly. In the present study, these new methods were used to study the biomagnetic equivalents of event-related potentials (ERPs) in response to duration changes in harmonic tones in sleeping, healthy, full-term newborns. Our findings indicate that with the use of these new analysis routines, MEG will prove to be a very useful and more accessible experimental technique among pediatric populations. PMID:15498541

Cheour, Marie; Imada, Toshiaki; Taulu, Samu; Ahonen, Antti; Salonen, Johanna; Kuhl, Patricia

2004-11-01

 
 
 
 
81

Magnetoencephalography source localization using the source affine image reconstruction (SAFFIRE) algorithm.  

Science.gov (United States)

Nonparametric iterative algorithms have been previously proposed to achieve high-resolution, sparse solutions to the bioelectromagnetic inverse problem applicable to multichannel magnetoencephalography and EEG recordings. Using a mmse estimation framework, we propose a new algorithm of this type denoted as source affine image reconstruction (SAFFIRE) aiming to reduce the vulnerability to initialization bias, augment robustness to noise, and decrease sensitivity to the choice of regularization. The proposed approach operates in a normalized lead-field space and employs an initial estimate based on matched filtering to combat the potential biasing effect of previously proposed initialization methods. SAFFIRE minimizes difficulties associated with the selection of the most appropriate regularization parameter by using two separate loading terms: a fixed noise-dependent term that can be directly estimated from the data and arises naturally from the mmse formulation, and an adaptive term (adjusted according to the update of the source estimate) that accounts for uncertainties of the forward model in real-experimental applications. We also show that a noncoherent integration scheme can be used within the SAFFIRE algorithm structure to further enhance the reconstruction accuracy and improve robustness to noise. PMID:20409987

Popescu, Mihai; Blunt, Shannon D; Chan, Tszping

2010-07-01

82

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...

2013-01-01

83

Prdm8 Regulates the Morphological Transition at Multipolar Phase during Neocortical Development  

Science.gov (United States)

Here, we found that the PR domain protein Prdm8 serves as a key regulator of the length of the multipolar phase by controlling the timing of morphological transition. We used a mouse line with expression of Prdm8-mVenus reporter and found that Prdm8 is predominantly expressed in the middle and upper intermediate zone during both the late and terminal multipolar phases. Prdm8 expression was almost coincident with Unc5D expression, a marker for the late multipolar phase, although the expression of Unc5D was found to be gradually down-regulated to the point at which mVenus expression was gradually up-regulated. This expression pattern suggests the possible involvement of Prdm8 in the control of the late and terminal multipolar phases, which controls the timing for morphological transition. To test this hypothesis, we performed gain- and loss-of-function analysis of neocortical development by using in utero electroporation. We found that the knockdown of Prdm8 results in premature change from multipolar to bipolar morphology, whereas the overexpression of Prdm8 maintained the multipolar morphology. Additionally, the postnatal analysis showed that the Prdm8 knockdown stimulated the number of early born neurons, and differentiated neurons located more deeply in the neocortex, however, majority of those cells could not acquire molecular features consistent with laminar location. Furthermore, we found the candidate genes that were predominantly utilized in both the late and terminal multipolar phases, and these candidate genes included those encoding for guidance molecules. In addition, we also found that the expression level of these guidance molecules was inhibited by the introduction of the Prdm8 expression vector. These results indicate that the Prdm8-mediated regulation of morphological changes that normally occur during the late and terminal multipolar phases plays an important role in neocortical development.

Inoue, Mayuko; Kuroda, Takao; Honda, Aya; Komabayashi-Suzuki, Mariko; Komai, Tae; Shinkai, Yoichi; Mizutani, Ken-ichi

2014-01-01

84

Ambipolar diffusion of a collisional plasma through an inhomogeneous magnetic field. Application to a multipolar discharge  

International Nuclear Information System (INIS)

Making use of an ambipolar diffusion theory, the differential equation governing the electronic density of a collisional plasma diffusing through an inhomogeneous magnetic field is established. The diffusion equation is solved numerically in the case of a multipolar field and the profile of the potential is calculated. The results enable to interpret the fact that density are located in the vicinity of the wall as well as the occurrence of high potential regions in a multipolar discharge

1982-01-01

85

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

86

Aberrant functional organization and maturation in early-onset psychosis: Evidence from magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies of the location of somatosensory and auditory cortical responses have shown anomalous hemispheric asymmetries in a variety of neurodevelopmental disorders. Although to date, abnormal asymmetries in the somatosensory region have shown greater specificity being reported only in psychotic adults. This study examines functional organization of somatosensory cortices using magnetoencephalography in adolescents with childhood-onset psychotic disorders. Eighteen young outpatients with histor...

Wilson, Tony W.; Rojas, Donald C.; Teale, Peter D.; Hernandez, Olivia O.; Asherin, Ryan M.; Reite, Martin L.

2007-01-01

87

Towards source volume estimation of interictal spikes in focal epilepsy using magnetoencephalography.  

Science.gov (United States)

Interictal spikes are a hallmark of cortical epileptogenicity; their spatial distribution in the cortex defines the so-called 'irritative' zone or spiking volume (SV). Delineating the SV precisely is a challenge during the presurgical evaluation of patients with epilepsy. Magnetoencephalography (MEG) recordings enable determination of the brain sources of epileptic spikes using source localization procedures. Most previous clinical MEG studies have relied on dipole modeling of epileptic spikes, which does not permit a volumetric estimation of the spiking cortex. In the present study, we propose a new source modeling procedure, Volumetric Imaging of Epileptic Spikes (VIES). In VIES, the SV is identified as the 3D region where sources of the high frequency activities (>20 Hz) associated with epileptic spikes are distributed. We localized these sources using a beamforming approach (DICS, Dynamic Imaging of Coherent Neural Sources). To determine the optimal parameters and accuracy of the method, we compared the SV obtained by VIES with the SV defined by the invasive gold standard, intracranial stereotactic EEG recordings (SEEG), in 21 patients with focal epilepsy. Using rigorous validation criteria based on the exact anatomical location of SEEG contacts, we found that the overall sensitivity of VIES for detecting spiking SEEG contacts was 76% and its specificity for correctly identifying non-spiking SEEG contacts was 67%, indicating a good agreement between VIES and SEEG. Moreover, we found that classical dipole clustering was not informative in 9/21 patients, while VIES enable to delineate the SV in all patients. For the 12 patients having a SV delineated both with VIES and dipole clustering, VIES method had higher sensitivity and lower specificity. This proof-of-concept study shows that VIES is a promising approach to non-invasive estimation of the SV in focal epilepsy. PMID:22036998

Bouet, Romain; Jung, Julien; Delpuech, Claude; Ryvlin, Philippe; Isnard, Jean; Guenot, Marc; Bertrand, Olivier; Mauguière, François

2012-02-15

88

Gamma-ray multipolarity assignments in 132La  

International Nuclear Information System (INIS)

Complete text of publication follows. Understanding the nature of the chiralcandidate strongly linked ?I=1 rotational band structures, where results of lifetime experiments rule out chiral explanation is a challenge for the present high-spin nuclear structure studies. The observed three linked ?I=1 bands in 132La is one of these cases. Recently SPAC calculations seemed to describe successfully the properties of these bands. However, the experimental spins and parities of one of these bands, that were used in the comparison with the SPAC results, are only tentatively known. Therefore we have started studying the experimental properties of these bands based on Euroball and Gammasphere experiments. In the present phase of the analysis angular correlation (DCO) study [2] was performed using the data from both experiments in order to obtaine ?-ray multipolarity assignments. In Fig. 1 we plotted the results obtained from the Gammasphere data. This analysis was carried out using a BLUE data base. The background subtraction was performed according to the prescription of Ref.[3]. For the analysis the three most forward and the three most backward detector rings were used against the three rings around 90 degrees. In this experimental arrangement DCO ratios of ?0.5 and 1.0 are expected for the stretched dipole and stretched quadrupole transitions, respectively, when the gate is set on a quadrupole transition. Also ?1.0 DCO ratio value is expected for the ?I=0 dipole transitions in this case. Using a dipole gate, the expected DCO ratios are ?1.0 and ?2.0 for the stretched dipole and for the stretched quadrupole as well as for the ?I=0 dipole transitions, respectively. Based on the observed DCO ratios, and the formerly known spins of lower states, spins were assigned to the band member states where they were not known previously.

2009-01-01

89

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 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.)

1999-05-01

90

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

Energy Technology Data Exchange (ETDEWEB)

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{sup -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{sup -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 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.)

Anderson, S.J. [Department of Psychology, Royal Holloway, University of London, Egham, Surrey (United Kingdom); Holliday, I.E.; Harding, G.F.A. [Clinical Neurophysiology Unit, Department of Psychology, Aston University, Birmingham (United Kingdom)

1999-05-01

91

Observational Characteristics of Radio Emission Related to Multi-polar Magnetic Configuration  

Science.gov (United States)

We present a large complex radio burst and its associated fast time structures observed on 2001 April 10 in the frequency range of 0.65 7.6 GHz. The NoRH radio image observation shows very complex radio source structures which include preexisting, newly emerging, submerging/cancelling polarities and a bipolar, a tripolar (a `bipolar + remote unipolar'), and a quadrupolar structure. This suggests that the radio burst is generated from a very complicated loop structure. According to the spectral and image observations, we assume that the beginning of this flare was caused by a single bipolar loop configuration with a `Y-type' reconnection structure. A composite of radio continuum and fast time structures is contained in this flare. The various fast radio emission phenomena include normal and reverse drifting type III bursts, and slowly drifting and no-drift structures. The tripolar configurations may form a double-loop with a `three-legged' structure, which is an important source of the various types of fast time structures. The two-loop reconnection model can lead simultaneously to electron acceleration and corona heating. We have also analyzed the behaviors of coronal magnetic polarities and the emission processes of different types radio emission qualitatively. Interactions of a bipolar or multi-polar loop are consistent with our observational results. Our observations favor the magnetic reconnection configurations of the `inverted Y-type' (bipolar) and the `three-legged' structures (tripolar or quadrupolar).

Wang, Min; Xie, Rui-Xiang; Xu, Chun; Shi, Shuo-Biao; Yan, Yi-Hua

2005-10-01

92

Feasibility study of a double-lens internal-pair spectrometer for multipolarity analysis  

International Nuclear Information System (INIS)

A combination of semicircular Si(Li) detectors with two magnetic-lens spectrometers is shown to offer a possibility to construct an effective spectroscopic instrument for multipolarity determinations. The proposed method is based on the fact that the angular correlation between the electron-positron pair is sensitive to multipolarity, even at high transition energies. Response characteristics and multipole discrimination power are given for different conversion-electron or internal-pair spectrometers. The results show that for multipolarity analysis of high-energy nuclear transitions internal-pair spectrometry with a double lens spectrometer may be a superior method in the low- and intermediate-Z region. Optimum multipole discrimination effects are obtained using two detectors on the spectrometer axis placed at 1800 relative to the target. The calculations are based on the zero-order Born approximation (ZBA) and are sufficiently accurate for at least E>1.5 MeV and Z<50. (orig.)

1986-04-01

93

The role of angular momentum in the construction of electromagnetic multipolar fields  

International Nuclear Information System (INIS)

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 originating from different derivations can be difficult to compare. Some of the derivations of the multipolar solutions do not explicitly show their relation to the angular momentum operators, thus hiding important properties of these solutions. In this paper, the relation between two of the most common derivations of this set of solutions is explicitly shown and their relation to the angular momentum operators is exposed. (paper)

2012-09-10

94

Vibrational multipolar analyses in isotropic media: Combining IR, Raman and hyper-Raman spectroscopies  

Science.gov (United States)

We introduce combined vibrational multipolar decompositions of IR, polarized Raman and hyper-Raman spectra as a powerful way to study isotropic materials. This new procedure has been applied to the molecular liquid HCCl3 and to silica glass, which are made of elementary structural units (ESU) weakly interacting and covalently 3Dlinked, respectively. Through the vibrational multipolar analyses of these two different isotropic media, new structural and dynamical insights have been drawn. In particular, for silica we propose an ESU which fits the multipolar spectral activity. It is derived from the ?-Cristoballite structure, with an octupolar S4 symmetry, which consists of a central SiO4 tetrahedron embedded in a super Si4/4 tetrahedron with bent Si-O-Si bonds.

Rodriguez, Vincent

2012-12-01

95

The neurochemical basis of human cortical auditory processing: combining proton magnetic resonance spectroscopy and magnetoencephalography  

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Abstract Background A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic sti...

2006-01-01

96

Oscillatory neuronal dynamics associated with manual acupuncture: a magnetoencephalography study using beamforming analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetoencephalography (MEG) enables non-invasive recording of neuronal activity, with reconstruction methods providing estimates of underlying brain source locations and oscillatory dynamics from externally recorded neuromagnetic fields. The aim of our study was to use MEG to determine the effect of manual acupuncture on neuronal oscillatory dynamics. A major problem in MEG investigations of manual acupuncture is the absence of onset times for each needle manipulation. Given that beamforming...

Asghar, Aziz U. R.; Johnson, Robyn L.; Woods, William; Green, Gary G. R.; Lewith, George; Macpherson, Hugh

2012-01-01

97

Cortical somatosensory processing measured by magnetoencephalography predicts neurodevelopment in extremely low-gestational-age infants  

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BACKGROUND: Higher cortical function during sensory processing can be examined by recording specific somatosensoryevoked magnetic fields (SEFs) with magnetoencephalography (MEG). We evaluated whether, in extremely low-gestational-age (ELGA) infants, abnormalities in MEG-recorded SEFs at term age are associated with adverse neurodevelopment at 2 y of corrected age. METHODS: SEFs to tactile stimulation of the index finger were recorded at term age in 30 ELGA infants (26.5 +/- 1.2 wk, birth weig...

2013-01-01

98

Multipolar radiofrequency ablation using internally cooled electrodes in ex vivo bovine liver: Correlation between volume of coagulation and amount of applied energy  

International Nuclear Information System (INIS)

Purpose: To evaluate the relationship between applied energy and volume of coagulation induced by multipolar radiofrequency (RF) ablation. Methods and materials: Multipolar RF ablations (n = 80) were performed in ex vivo bovine liver. Three bipolar applicators with two electrodes located on each applicator shaft were placed in a triangular array. The power-output (75–225 W) and the distance between the different applicators (2, 3, 4, 5 cm) were systematically varied. The volume of confluent white coagulation and the amount of applied energy were assessed. Based on our experimental data the relationship between the volume of coagulation and applied energy was assessed by nonlinear regression analysis. The variability explained by the model was determined by the parameter r2. Results: The volume of coagulation increases with higher amounts of applied energy. The maximum amount of energy was applied at a power-output of 75 W and an applicator distance of 5 cm. The corresponding maximum volume of coagulation was 324 cm3 and required an application of 453 kJ. The relationship between amount of applied energy (E) and volume (V) of coagulation can be described by the function, V = 4.39E0.7 (r2 = 0.88). By approximation the volume of coagulation can be calculated by the linear function V = 0.61E + 40.7 (r2 = 0.87). Conclusion: Ex vivo the relationship between volume of coagulation and amount of applied energy can be described by mathematical modeling. The amount of applied energy correlates to the volume of coagulation and may be a useful parameter to monitor multipolar RF ablation.

2012-01-01

99

A comparison of vector and radial magnetometer arrays for whole-head magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

The number of detectors in magnetometer arrays for magnetoencephalography (MEG) has been steadily increasing, with systems containing or more detectors now possible. It is of considerable interest to know how best to configure such a large array. In particular, is it useful to measure all three components of the magnetic field, rather than just the radial component? This paper compares the information content provided by three different magnetometer arrays for whole-head measurements, using a definition of information content developed by Kemppainen and Ilmoniemi.

Hughett, P. [Lawrence Berkeley National Lab., CA (United States); Miyauchi, S. [Ministry of Post and Telecommunications, Tokyo (Japan). Communications Research Lab.

1996-02-01

100

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

 
 
 
 
101

Multipolar polarizations of methane from isotropic and anisotropic collision-induced light scattering  

International Nuclear Information System (INIS)

The anisotropic and isotropic binary collision-induced spectra scattered by gaseous methane have been measured in absolute units up to 900 cm-1 from the Rayleigh line. Corresponding theoretical intensities taking into account multipolar polarizabilities have been calculated using a semiclassical procedure. From the analysis of, mainly, our isotropic scattering data, values of the dipole-quadrupole and dipole-octopole polarizabilities are deduced. They are found to be in good agreement with recent ab initio calculations

2004-06-01

102

A New Configuration of Multipolar Cuff Electrode and Dedicated IC for Afferent Signal Recording  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Sensory information coming from natural sensors and being propagated on afferent nerve fibers could be used as feedback for a more efficient closed-loop control of a Functional Electrical Stimulation system. In order to extract and separate these signals according to their nerve fascicule origins, we propose a new architecture of a multipolar cuff electrode and an optimized integrated acquisition circuit. Concerning the electrode, we propose a specific configuration using a large number of po...

Bernard, Serge; Bertrand, Yves; Cathebras, Guy; Gouyet, Lionel; Guiraud, David

2007-01-01

103

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.)

1983-08-01

104

Nonlinear Accelerator Problems via Wavelets: 2. Orbital Dynamics in General Multipolar Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this series of eight papers we present the applications of methods from wavelet analysis to polynomial approximations for a number of accelerator physics problems. In this part we consider orbital motion in transverse plane for a single particle in a circular magnetic lattice in case when we take into account multipolar expansion up to an arbitrary finite number. We reduce initial dynamical problem to the finite number (equal to the number of n-poles) of standard algebrai...

Fedorova, Antonina N.; Zeitlin, Michael G.

1999-01-01

105

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

106

POWER-SHIFTS IN THE GLOBAL ECONOMY. TRANSITION TOWARDS A MULTIPOLAR WORLD ORDER  

Directory of Open Access Journals (Sweden)

Full Text Available The paper aims to analyze the new realities and trends related to the new polarity of the global economy, and thus the reconfiguration of global power centers, a process characterized by two simultaneous trends: the rise of new powers and the relative decline of traditional powers. At the beginning of 21st century, global power is suffering two major changes: on the one hand it manifests a transition from West to East, from Atlantic to the Asia-Pacific, and on the other hand, a diffusion from state to non-state actors. Current global economic power has a multipolar distribution, shared between the United States, European Union, Japan and BRICs, with no balance of power between these poles, opposed by the strong ambition of rising countries, China especially, China that rivals the traditional powers represented by the developed countries. The evolution of the main macroeconomic indicators given by the most important global organizations, shows a gradual transition towards a multipolar world. Therefore, the United States is and will remain for a long period of time the global economic leader. However, as China, India and Brazil are growing rapidly, and Russia is looking for lost status, the world is becoming multipolar.

Ion IGNAT

2013-12-01

107

Atypical coupling between posterior regions of the default mode network in attention-deficit/hyperactivity disorder: a pharmaco-magnetoencephalography study  

Science.gov (United States)

Background Dysfunction in the default mode network (DMN), a group of cortical areas more active during the resting state, has been linked to attentional deficits and symptoms associated with attention-deficit/hyperactivity disorder (ADHD). Prior imaging studies have shown decreased functional connectivity between DMN nodes in patients with ADHD, primarily between anterior and posterior regions. Using magnetoencephalography (MEG), we evaluated phase coherence (i.e., functional connectivity) among regions of the DMN in healthy controls and adults with ADHD before and after stimulant therapy. Methods We obtained a resting-state MEG recording for all participants. Magnetoencephalography data were transformed into a ~30 node regional source model using inverse spatial filtering, including regions corresponding to the DMN. We computed the zero-lag phase coherence between these regions pairwise for 5 distinct frequency bands, and we assessed group and medication effects. Results Twelve adults with and 13 without ADHD participated in our study. Functional connectivity was stronger between particular node pairs and showed frequency-specific effects. Unmedicated patients showed reduced phase locking between posterior cingulate/precuneus regions (PCC) and right inferior parietal cortices (RIPL), and between medial prefrontal regions (MPFC) and the left inferior parietal region (LIPL) and the PCC. Unmedicated patients had increased phase locking between the RIPL and LIPL regions compared with controls. Administration of stimulants improved phase locking abnormalities along the MPFC–PCC and LIPL–RIPL pathways in patients with ADHD. Limitations Modest sample size and lack of duration of patient treatment history may limit the generalizability of our findings. Conclusion Adults with ADHD exhibit hyper- and hypoconnectivity between regions of the DMN during rest, which were suppressed after stimulant medication administration.

Franzen, John D.; Heinrichs-Graham, Elizabeth; White, Matthew L.; Wetzel, Martin W.; Knott, Nichole L.; Wilson, Tony W.

2013-01-01

108

Implementation of a beam forming technique in real-time magnetoencephalography.  

Science.gov (United States)

Real-time magnetoencephalography (rtMEG) is an emerging neurofeedback technology that could potentially benefit multiple areas of basic and clinical neuroscience. In the present study, we implemented voxel-based real-time coherence measurements in a rtMEG system in which we employed a beamformer to localize signal sources in the anatomical space prior to computing imaginary coherence. Our rtMEG experiment showed that a healthy subject could increase coherence between the parietal cortex and visual cortex when attending to a flickering visual stimulus. This finding suggests that our system is suitable for neurofeedback training and can be useful for practical brain-machine interface applications or neurofeedback rehabilitation. PMID:24070057

Ora, Hiroki; Takano, Kouji; Kawase, Toshihiro; Iwaki, Sunao; Parkkonen, Lauri; Kansaku, Kenji

2013-09-01

109

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

Directory of Open Access Journals (Sweden)

Full Text Available 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, 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

2008-01-01

110

The neurochemical basis of human cortical auditory processing: combining proton magnetic resonance spectroscopy and magnetoencephalography  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background A combination of magnetoencephalography and proton magnetic resonance spectroscopy was used to correlate the electrophysiology of rapid auditory processing and the neurochemistry of the auditory cortex in 15 healthy adults. To assess rapid auditory processing in the left auditory cortex, the amplitude and decrement of the N1m peak, the major component of the late auditory evoked response, were measured during rapidly successive presentation of acoustic stimuli. We tested the hypothesis that: (i the amplitude of the N1m response and (ii its decrement during rapid stimulation are associated with the cortical neurochemistry as determined by proton magnetic resonance spectroscopy. Results Our results demonstrated a significant association between the concentrations of N-acetylaspartate, a marker of neuronal integrity, and the amplitudes of individual N1m responses. In addition, the concentrations of choline-containing compounds, representing the functional integrity of membranes, were significantly associated with N1m amplitudes. No significant association was found between the concentrations of the glutamate/glutamine pool and the amplitudes of the first N1m. No significant associations were seen between the decrement of the N1m (the relative amplitude of the second N1m peak and the concentrations of N-acetylaspartate, choline-containing compounds, or the glutamate/glutamine pool. However, there was a trend for higher glutamate/glutamine concentrations in individuals with higher relative N1m amplitude. Conclusion These results suggest that neuronal and membrane functions are important for rapid auditory processing. This investigation provides a first link between the electrophysiology, as recorded by magnetoencephalography, and the neurochemistry, as assessed by proton magnetic resonance spectroscopy, of the auditory cortex.

Tollkötter Melanie

2006-08-01

111

Effective medium multipolar tensor analysis of second-harmonic generation from metal nanoparticles  

International Nuclear Information System (INIS)

We present a detailed multipolar tensor analysis of second-harmonic (SH) generation from arrays of L-shaped gold nanoparticles. We define three effective nonlinear tensors, which include electric dipoles only (Aeee) and lowest-order magnetic (and quadrupole) effects at the fundamental (Aeem) and the SH (Amee) frequency. The components of the various tensors are distinguished through their different transformations as the experimental geometry is varied. The response is dominated by electric-dipole effects. However, the higher multipoles also play a significant role and are more important at the fundamental frequency than at the SH frequency. The results correlate well with the particles' plasmonic resonances and symmetry rules.

2011-02-01

112

Study on the radiations in the 205At decay. Transition multipolarities in the 205Po  

International Nuclear Information System (INIS)

Spectra of radiations in the 205At decay (Tsub(1/2=26.2 min)) are studied by means of semiconductor detectors and iron-free toroidal ?-spectrometer. In the measurements was used the monoisotopic sources of the 205At. 148 ?-transitions have been discovered which accompany the 205At decay, information about 94 transition has been derived for the first time. The total 70 transition multipolarity has been determined, for 54 of them - for the first time. The measurements of e-? - coincidences were performed. (author)

1982-03-01

113

[Pulmonary vein isolation with multipolar ablation catheters for the treatment of paroxysmal atrial fibrillation].  

Science.gov (United States)

Atrial fibrillation (AFIB) is the most common atrial rhythm disease and is associated with an increased risk of thromboembolic and cardiac complications. Different therapies are used in clinical routine: frequency control with anticoagulants and rhythm control. In patients with paroxysmal AFIB but without structural heart disease, antiarrhythmic drug therapy was previously first priority; however, pulmonary vein catheter ablation is becoming more important. "Single tip" systems, ultrasound, and various balloon techniques have been used in clinical routine. New radiofrequency systems with multipolar radiofrequency ablation catheters, however, give hope for better outcomes with fewer intraprocedural complications, as well as shorter procedure and fluoroscopy times. PMID:19543933

Bauerle, H; Japha, T; Gonska, B-D

2009-06-01

114

Evolution of Multipolar Magnetic Fields in Isolated Neutron Stars and its effect on Pulsar Radio Emission  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. Lower orders ($\\le 25$) of multipole are seen to evolve in a manner similar to the dipole suggesting little or no evolution of the expected pulse shape. We also study the multifrequency polarization position angle traverse of PSR B0329+54 and find a significant frequency dependence above 2.7 GHz. We interpret this as an evidence of strong mult...

Mitra, D.; Konar, S.; Bhattacharya, D.; Hoensbroech, A. V.; Seiradakis, J. H.; Wielebinski, R.

2009-01-01

115

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)

2000-09-15

116

Cross-Correlation of Motor Activity Signals from dc-Magnetoencephalography, Near-Infrared Spectroscopy, and Electromyography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neuronal and vascular responses due to finger movements were synchronously measured using dc-magnetoencephalography (dcMEG) and time-resolved near-infrared spectroscopy (trNIRS). The finger movements were monitored with electromyography (EMG). Cortical responses related to the finger movement sequence were extracted by independent component analysis from both the dcMEG and the trNIRS data. The temporal relations between EMG rate, dcMEG, and trNIRS responses were assessed pairwise using the cr...

Sander, Tilmann H.; Leistner, Stefanie; Wabnitz, Heidrun; Mackert, Bruno-marcel; Macdonald, Rainer; Trahms, Lutz

2010-01-01

117

A study of the multipolar composition of the electrofission cross section of "2"3"7Np  

International Nuclear Information System (INIS)

The electrofission cross section for "2"3"7Np 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.)

1987-01-01

118

The value of magnetoencephalography for seizure-onset zone localization in magnetic resonance imaging-negative partial epilepsy  

Science.gov (United States)

Surgical treatment of epilepsy is a challenge for patients with non-contributive brain magnetic resonance imaging. However, surgery is feasible if the seizure-onset zone is precisely delineated through intracranial electroencephalography recording. We recently described a method, volumetric imaging of epileptic spikes, to delineate the spiking volume of patients with focal epilepsy using magnetoencephalography. We postulated that the extent of the spiking volume delineated with volumetric imaging of epileptic spikes could predict the localizability of the seizure-onset zone by intracranial electroencephalography investigation and outcome of surgical treatment. Twenty-one patients with non-contributive magnetic resonance imaging findings were included. All patients underwent intracerebral electroencephalography investigation through stereotactically implanted depth electrodes (stereo-electroencephalography) and magnetoencephalography with delineation of the spiking volume using volumetric imaging of epileptic spikes. We evaluated the spatial congruence between the spiking volume determined by magnetoencephalography and the localization of the seizure-onset zone determined by stereo-electroencephalography. We also evaluated the outcome of stereo-electroencephalography and surgical treatment according to the extent of the spiking volume (focal, lateralized but non-focal or non-lateralized). For all patients, we found a spatial overlap between the seizure-onset zone and the spiking volume. For patients with a focal spiking volume, the seizure-onset zone defined by stereo-electroencephalography was clearly localized in all cases and most patients (6/7, 86%) had a good surgical outcome. Conversely, stereo-electroencephalography failed to delineate a seizure-onset zone in 57% of patients with a lateralized spiking volume, and in the two patients with bilateral spiking volume. Four of the 12 patients with non-focal spiking volumes were operated upon, none became seizure-free. As a whole, patients having focal magnetoencephalography results with volumetric imaging of epileptic spikes are good surgical candidates and the implantation strategy should incorporate volumetric imaging of epileptic spikes results. On the contrary, patients with non-focal magnetoencephalography results are less likely to have a localized seizure-onset zone and stereo electroencephalography is not advised unless clear localizing information is provided by other presurgical investigation methods.

Bouet, Romain; Delpuech, Claude; Ryvlin, Philippe; Isnard, Jean; Guenot, Marc; Bertrand, Olivier; Hammers, Alexander; Mauguiere, Francois

2013-01-01

119

The value of magnetoencephalography for seizure-onset zone localization in magnetic resonance imaging-negative partial epilepsy.  

Science.gov (United States)

Surgical treatment of epilepsy is a challenge for patients with non-contributive brain magnetic resonance imaging. However, surgery is feasible if the seizure-onset zone is precisely delineated through intracranial electroencephalography recording. We recently described a method, volumetric imaging of epileptic spikes, to delineate the spiking volume of patients with focal epilepsy using magnetoencephalography. We postulated that the extent of the spiking volume delineated with volumetric imaging of epileptic spikes could predict the localizability of the seizure-onset zone by intracranial electroencephalography investigation and outcome of surgical treatment. Twenty-one patients with non-contributive magnetic resonance imaging findings were included. All patients underwent intracerebral electroencephalography investigation through stereotactically implanted depth electrodes (stereo-electroencephalography) and magnetoencephalography with delineation of the spiking volume using volumetric imaging of epileptic spikes. We evaluated the spatial congruence between the spiking volume determined by magnetoencephalography and the localization of the seizure-onset zone determined by stereo-electroencephalography. We also evaluated the outcome of stereo-electroencephalography and surgical treatment according to the extent of the spiking volume (focal, lateralized but non-focal or non-lateralized). For all patients, we found a spatial overlap between the seizure-onset zone and the spiking volume. For patients with a focal spiking volume, the seizure-onset zone defined by stereo-electroencephalography was clearly localized in all cases and most patients (6/7, 86%) had a good surgical outcome. Conversely, stereo-electroencephalography failed to delineate a seizure-onset zone in 57% of patients with a lateralized spiking volume, and in the two patients with bilateral spiking volume. Four of the 12 patients with non-focal spiking volumes were operated upon, none became seizure-free. As a whole, patients having focal magnetoencephalography results with volumetric imaging of epileptic spikes are good surgical candidates and the implantation strategy should incorporate volumetric imaging of epileptic spikes results. On the contrary, patients with non-focal magnetoencephalography results are less likely to have a localized seizure-onset zone and stereo electroencephalography is not advised unless clear localizing information is provided by other presurgical investigation methods. PMID:24014520

Jung, Julien; Bouet, Romain; Delpuech, Claude; Ryvlin, Philippe; Isnard, Jean; Guenot, Marc; Bertrand, Olivier; Hammers, Alexander; Mauguière, François

2013-10-01

120

Magnetoencephalography reveals a unique neurophysiological profile of focal-onset epileptic spasms.  

Science.gov (United States)

Epilepsy is defined as a disorder of the brain characterized by an enduring predisposition to experience epileptic seizures and the neurobiological, cognitive, psychological, and social difficulties relating to the condition. An epileptic spasm (ES) is a type of seizure characterized by clusters of short contractions involving axial muscles and proximal segments. However, the precise mechanism of ESs remains unknown. Despite the potential of magnetoencephalography (MEG) as a tool for investigating the neurophysiological mechanism of ESs, it has been difficult to use this methodology due to magnetic artifacts attributable to patient movement. We report on an 8-year-old girl suffering from intractable epileptic spasms from the age of 7 months. She was diagnosed with possible Aicardi syndrome [corrected] (AGS), characterized by the triad of callosal agenesis, infantile spasms, and chorioretinal lacunae. She is now intellectually delayed and suffers from intractable ES. We used both MEG and electroencephalography to investigate her epilepsy. The recording captured two series of spasm clusters. Spikes were clearly identified with MEG in about four-fifths of all spasms but were identified poorly or not at all in the remainder. MEG findings support previous studies that used intracranial electrodes to analyze patients with ESs and that showed variability in ES-associated spikes in terms of manner of cortical involvement and magnitude. Given the limitations of intracranial electrodes, such as sampling restrictions and invasiveness, MEG may be a helpful tool for non-invasively investigating the unique pathophysiological profile of focal-onset ESs. PMID:23343709

Kakisaka, Yosuke; Gupta, Ajay; Enatsu, Rei; Wang, Zhong I; Alexopoulos, Andreas V; Mosher, John C; Dubarry, Anne-Sophie; Hino-Fukuyo, Naomi; Burgess, Richard C

2013-01-01

 
 
 
 
121

Algorithms and architectures for adaptive least squares signal processing, with applications in magnetoencephalography  

Energy Technology Data Exchange (ETDEWEB)

Least squares techniques are widely used in adaptive signal processing. While algorithms based on least squares are robust and offer rapid convergence properties, they also tend to be complex and computationally intensive. To enable the use of least squares techniques in real-time applications, it is necessary to develop adaptive algorithms that are efficient and numerically stable, and can be readily implemented in hardware. The first part of this work presents a uniform development of general recursive least squares (RLS) algorithms, and multichannel least squares lattice (LSL) algorithms. RLS algorithms are developed for both direct estimators, in which a desired signal is present, and for mixed estimators, in which no desired signal is available, but the signal-to-data cross-correlation is known. In the second part of this work, new and more flexible techniques of mapping algorithms to array architectures are presented. These techniques, based on the synthesis and manipulation of locally recursive algorithms (LRAs), have evolved from existing data dependence graph-based approaches, but offer the increased flexibility needed to deal with the structural complexities of the RLS and LSL algorithms. Using these techniques, various array architectures are developed for each of the RLS and LSL algorithms and the associated space/time tradeoffs presented. In the final part of this work, the application of these algorithms is demonstrated by their employment in the enhancement of single-trial auditory evoked responses in magnetoencephalography. 118 refs., 49 figs., 36 tabs.

Lewis, P.S.

1988-10-01

122

Development of human somatosensory cortical functions – what have we learned from magnetoencephalography: A review  

Directory of Open Access Journals (Sweden)

Full Text Available The mysteries of early development of cortical processing in humans have started to unravel with the help of new noninvasive brain research tools like multichannel magnetoencephalography (MEG. In this review, we evaluate, within a wider neuroscientific and clinical context, the value of MEG in studying normal and disturbed functional development of the human somatosensory system. The combination of excellent temporal resolution and good localization accuracy provided by MEG has, in the case of somatosensory studies, enabled the differentiation of activation patterns from the newborn’s primary (SI and secondary somatosensory (SII areas. Furthermore, MEG has shown that the functioning of both SI and SII in newborns has particular immature features in comparison with adults. In extremely preterm infants, the neonatal MEG response from SII also seems to potentially predict developmental outcome: those lacking SII responses at term show worse motor performance at age two years than those with normal SII responses at term. In older children with unilateral early brain lesions, bilateral alterations in somatosensory cortical activation detected in MEG imply that the impact of a localized insult may have an unexpectedly wide effect on cortical somatosensory networks. The achievements over the last decade show that MEG provides a unique approach for studying the development of the somatosensory system and its disturbances in childhood. MEG well complements other neuroimaging methods in studies of cortical processes in the developing brain.

PäiviNevalainen

2014-03-01

123

Inhibition of auditory cortical responses to ipsilateral stimuli during dichotic listening: evidence from magnetoencephalography.  

Science.gov (United States)

The present magnetoencephalography (MEG) study on auditory evoked magnetic fields (AEFs) was aimed at verifying whether during dichotic listening the contralateral auditory pathway inhibits the ipsilateral one, as suggested by behavioural and patient studies. Ten healthy subjects were given a randomized series of three complex tones (261, 293 and 391 Hz, 500 ms duration), which were delivered monotically and dichotically with different intensities [60, 70 or 80 dBA (audio decibels)]. MEG data were recorded from the right auditory cortex. Results showed that the M100 amplitude over the right auditory cortex increased progressively when tones of increasing intensity were provided at the ipsilateral (right) ear. This effect on M100 was abolished when a concurrent tone of constant intensity was delivered dichotically at the contralateral (left) ear, suggesting that the contralateral pathway inhibited the ipsilateral one. The ipsilateral inhibition was present only when the contralateral tone fundamental frequency was similar to the ipsilateral tone. It was proposed that the occlusion mechanism would be exerted in cortical auditory areas as the dichotic effects were observed at M100 but not M50 component. This is the first evidence showing a neurophysiological inhibition driven by the contralateral auditory pathway over the ipsilateral one during dichotic listening. PMID:15090059

Brancucci, Alfredo; Babiloni, Claudio; Babiloni, Fabio; Galderisi, Silvana; Mucci, Armida; Tecchio, Franca; Zappasodi, Filippo; Pizzella, Vittorio; Romani, Gian Luca; Rossini, Paolo Maria

2004-04-01

124

Human alpha rhythms during visual delayed choice reaction time tasks: a magnetoencephalography study.  

Science.gov (United States)

Magnetoencephalography (MEG) includes fast and comfortable recording procedures very suitable for the neurophysiological study of cognitive functions in aged people. In this exploratory MEG study in normal young adults, we tested whether very simple short-term memory (STM) demands induce visible changes in amplitude and latency of surface alpha rhythms. Two delayed response tasks were used. In the STM condition, a simple cue stimulus (one bit) was memorized along a brief delay period (3.5-5.5 s). In the control (no short-term memory; NSTM) condition, the cue stimulus remained available along the delay period. To make extremely simple the tasks, the explicit demand was visuospatial but the retention could be also based on phonological and somatomotor coding. Compared to the control condition, the amplitude of the alpha 1 (6-8 Hz) ERD decreased in the left hemisphere, whereas the amplitude of the alpha 2 (8-10 Hz) and alpha 3 (10-12 Hz) event-related desynchronization (ERD) increased in right and left parietal areas, respectively. Furthermore, the latency of the alpha ERD peak was slightly but significantly (P < 0.05) later in STM compared to control condition. In conclusion, whole-head MEG technology and very simple STM demands revealed significant changes of human neuromagnetic alpha rhythms in normal young adults. PMID:15495216

Babiloni, Claudio; Babiloni, Fabio; Carducci, Filippo; Cincotti, Febo; Del Percio, Claudio; Della Penna, Stefania; Franciotti, Raffaella; Pignotti, Sandro; Pizzella, Vittorio; Rossini, Paolo Maria; Sabatini, Elisabetta; Torquati, Kathya; Romani, Gian Luca

2005-03-01

125

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

CERN Multimedia

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

126

Magnetoencephalography---theory, instrumentation, and applications to noninvasive studies of the working human brain  

International Nuclear Information System (INIS)

Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial discrimination is, under favorable circumstances, 2--3 mm for sources in the cerebral cortex. In MEG studies, the weak 10 fT--1 pT magnetic fields produced by electric currents flowing in neurons are measured with multichannel SQUID (superconducting quantum interference device) gradiometers. The sites in the cerebral cortex that are activated by a stimulus can be found from the detected magnetic-field distribution, provided that appropriate assumptions about the source render the solution of the inverse problem unique. Many interesting properties of the working human brain can be studied, including spontaneous activity and signal processing following external stimuli. For clinical purposes, determination of the locations of epileptic foci is of interest. The authors begin with a general introduction and a short discussion of the neural basis of MEG. The mathematical theory of the method is then explained in detail, followed by a thorough description of MEG instrumentation, data analysis, and practical construction of multi-SQUID devices. Finally, several MEG experiments performed in the authors' laboratory are described, covering studies of evoked responses and of spontaneous activity in both healthy and diseased brains. Many MEG studies by other groups are discussed briefly as well

1993-04-01

127

Visual motion direction is represented in population-level neural response as measured by magnetoencephalography.  

Science.gov (United States)

We investigated whether direction information is represented in the population-level neural response evoked by the visual motion stimulus, as measured by magnetoencephalography. Coherent motions with varied speed, varied direction, and different coherence level were presented using random dot kinematography. Peak latency of responses to motion onset was inversely related to speed in all directions, as previously reported, but no significant effect of direction on latency changes was identified. Mutual information entropy (IE) calculated using four-direction response data increased significantly (>2.14) after motion onset in 41.3% of response data and maximum IE was distributed at approximately 20 ms after peak response latency. When response waveforms showing significant differences (by multivariate discriminant analysis) in distribution of the three waveform parameters (peak amplitude, peak latency, and 75% waveform width) with stimulus directions were analyzed, 87 waveform stimulus directions (80.6%) were correctly estimated using these parameters. Correct estimation rate was unaffected by stimulus speed, but was affected by coherence level, even though both speed and coherence affected response amplitude similarly. Our results indicate that speed and direction of stimulus motion are represented in the distinct properties of a response waveform, suggesting that the human brain processes speed and direction separately, at least in part. PMID:19285543

Kaneoke, Y; Urakawa, T; Kakigi, R

2009-05-19

128

Development of Human Somatosensory Cortical Functions - What have We Learned from Magnetoencephalography: A Review  

Science.gov (United States)

The mysteries of early development of cortical processing in humans have started to unravel with the help of new non-invasive brain research tools like multichannel magnetoencephalography (MEG). In this review, we evaluate, within a wider neuroscientific and clinical context, the value of MEG in studying normal and disturbed functional development of the human somatosensory system. The combination of excellent temporal resolution and good localization accuracy provided by MEG has, in the case of somatosensory studies, enabled the differentiation of activation patterns from the newborn’s primary (SI) and secondary somatosensory (SII) areas. Furthermore, MEG has shown that the functioning of both SI and SII in newborns has particular immature features in comparison with adults. In extremely preterm infants, the neonatal MEG response from SII also seems to potentially predict developmental outcome: those lacking SII responses at term show worse motor performance at age 2?years than those with normal SII responses at term. In older children with unilateral early brain lesions, bilateral alterations in somatosensory cortical activation detected in MEG imply that the impact of a localized insult may have an unexpectedly wide effect on cortical somatosensory networks. The achievements over the last decade show that MEG provides a unique approach for studying the development of the somatosensory system and its disturbances in childhood. MEG well complements other neuroimaging methods in studies of cortical processes in the developing brain.

Nevalainen, Paivi; Lauronen, Leena; Pihko, Elina

2014-01-01

129

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

2012-02-01

130

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

131

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

132

Through a glass darkly: some insights on change talk via magnetoencephalography.  

Science.gov (United States)

Motivational interviewing (MI) is a directive, client-centered therapeutic method employed in the treatment of substance abuse, with strong evidence of effectiveness. To date, the sole mechanism of action in MI with any consistent empirical support is "change talk" (CT), which is generally defined as client within-session speech in support of a behavior change. "Sustain talk" (ST) incorporates speech in support of the status quo. MI maintains that during treatment, clients essentially talk themselves into change. Multiple studies have now supported this theory, linking within-session speech to substance use outcomes. Although a causal chain has been established linking therapist behavior, client CT, and substance use outcome, the neural substrate of CT has been largely uncharted. We addressed this gap by measuring neural responses to clients' own CT using magnetoencephalography (MEG), a noninvasive neuroimaging technique with excellent spatial and temporal resolution. Following a recorded MI session, MEG was used to measure brain activity while participants heard multiple repetitions of their CT and ST utterances from that session, intermingled and presented in a random order. Results suggest that CT processing occurs in a right-hemisphere network that includes the inferior frontal gyrus, insula, and superior temporal cortex. These results support a representation of CT at the neural level, consistent with the role of these structures in self-perception. This suggests that during treatment sessions, clinicians who are able to evoke this special kind of language are tapping into neural circuitry that may be essential to behavior change. PMID:22946856

Houck, Jon M; Moyers, Theresa B; Tesche, Claudia D

2013-06-01

133

Neural correlation of successful cognitive behaviour therapy for spider phobia: a magnetoencephalography study.  

Science.gov (United States)

Cognitive behavioural therapy (CBT) can be an effective treatment for spider phobia, but the underlying neural correlates of therapeutic change are yet to be specified. The present study used magnetoencephalography (MEG) to study responses within the first half second, to phobogenic stimuli in a group of individuals with spider phobia prior to treatment (n=12) and then in nine of them following successful CBT (where they could touch and manage live large common house spiders) at least 9 months later. We also compared responses to a group of age-matched healthy control participants (n=11). Participants viewed static photographs of real spiders, other fear-inducing images (e.g. snakes, sharks) and neutral stimuli (e.g. kittens). Beamforming methods were used to localise sources of significant power changes in response to stimuli. Prior to treatment, participants with spider phobia showed a significant maximum response in the right frontal pole when viewing images of real spiders specifically. No significant frontal response was observed for either control participants or participants with spider phobia post-treatment. In addition, participants' subjective ratings of spider stimuli significantly predicted peak responses in right frontal regions. The implications for understanding brain-based effects of cognitive therapies are discussed. PMID:24139305

Wright, Barry; Alderson-Day, Ben; Prendergast, Garreth; Kennedy, Juliette; Bennett, Sophie; Docherty, Mary; Whitton, Clare; Manea, Laura; Gouws, Andre; Tomlinson, Heather; Green, Gary

2013-12-30

134

Magnetoencephalography non-invasively reveals a unique neurophysiological profile of focal-onset epileptic spasms  

Science.gov (United States)

Epilepsy is defined as a disorder of the brain characterized by an enduring predisposition to experience epileptic seizures and the neurobiological, cognitive, psychological, and social difficulties relating to the condition. An epileptic spasm (ES) is a type of seizure characterized by clusters of short contractions involving axial muscles and proximal segments. However, the precise mechanism of ESs remains unknown. Despite the potential of magnetoencephalography (MEG) as a tool for investigating the neurophysiological mechanism of ESs, it has been difficult to use this methodology due to magnetic artifacts attributable to patient movement. We report on an 8-year-old girl suffering from intractable epileptic spasms from the age of 7 months. She was diagnosed with possible Aicardi-Goutières syndrome (AGS), characterized by the triad of callosal agenesis, infantile spasms, and chorioretinal lacunae. She is now intellectually delayed and suffers from intractable ES. We used both MEG and electroencephalography to investigate her epilepsy. The recording captured two series of spasm clusters. Spikes were clearly identified with MEG in about four-fifths of all spasms but were identified poorly or not at all in the remainder. MEG findings support previous studies that used intracranial electrodes with patients with ESs and that showed variability in ES-associated spikes in terms of manner of cortical involvement and magnitude. Given the limitations of intracranial electrodes, such as sampling restrictions and invasiveness, MEG may be a helpful tool for non-invasively investigating the unique pathophysiological profile of focal-onset ESs.

Kakisaka, Yosuke; Gupta, Ajay; Enatsu, Rei; Wang, Zhong I.; Alexopoulos, Andreas V.; Mosher, John C.; Dubarry, Anne-Sophie; Hino-Fukuyo, Naomi; Burgess, Richard C.

2013-01-01

135

Effective medium multipolar tensor analysis of second-harmonic generation from metal nanoparticles  

Energy Technology Data Exchange (ETDEWEB)

We present a detailed multipolar tensor analysis of second-harmonic (SH) generation from arrays of L-shaped gold nanoparticles. We define three effective nonlinear tensors, which include electric dipoles only (A{sup eee}) and lowest-order magnetic (and quadrupole) effects at the fundamental (A{sup eem}) and the SH (A{sup mee}) frequency. The components of the various tensors are distinguished through their different transformations as the experimental geometry is varied. The response is dominated by electric-dipole effects. However, the higher multipoles also play a significant role and are more important at the fundamental frequency than at the SH frequency. The results correlate well with the particles' plasmonic resonances and symmetry rules.

Zdanowicz, Mariusz; Kujala, Sami; Husu, Hannu; Kauranen, Martti, E-mail: mariusz.zdanowicz@tut.fi [Department of Physics, Optics Laboratory, Tampere University of Technology, PO Box 692, FI-33101 Tampere (Finland)

2011-02-15

136

Direct observation of an incommensurate multipolar order in CeB6 doped with Pr  

International Nuclear Information System (INIS)

Observations on an ordered alloy Ce0.7Pr0.3B6 by non-resonant X-ray diffraction are reported. We find incommensurate reflections (2?, 1/2, 0) (??0.23) below about 3 K in zero applied magnetic field. The wave vector dependence of the intensity is compelling evidence for the first direct observation of an incommensurate multipolar ordering (MPO). The incommensurate MPO appears to coexist with a commensurate MPO with a wave vector (1/2, 1/2, 1/2), which is the ground state configuration. Additional insight to the properties is derived from extensive measurements made with the alloy placed in a magnetic field ranging up to 6T. We propose that a competition among RKKY-like exchange interactions between the Ce-Ce, Ce-Pr, and Pr-Pr multipoles is a main source for the appearance of the incommensurate MPO. (author)

2006-07-01

137

Role of pairing degrees of freedom and higher multipolarity deformations in spontaneous fission process  

International Nuclear Information System (INIS)

Spontaneous fission (Tsf) and alpha-decay half-lives (T?) of the heaviest nuclei with atomic number 100 ? Z ? 114 are calculated on the basis of the deformed Woods-Saxon potential. The calculations of (Tsf) are performed by the WKB approximation, in the multi-dimensional dynamical-programing method (MDP). We have examined three different effects: the effect of higher even-multipolarity shape parameters (?6 and ?8), the role of reflection-asymmetry (?3 and ?5) and the influence of pairing degrees of freedom (?p and ?n). Alpha-decay half-lives (T?) have been calculated by the Viola-Seaborg (V-S) formula with the parameters modified to the latest experimental data

1999-09-20

138

Role of pairing degrees of freedom and higher multipolarity deformations in spontaneous fission process  

CERN Document Server

Spontaneous fission (T sub s sub f) and alpha-decay half-lives (T subalpha) of the heaviest nuclei with atomic number 100 <= Z <= 114 are calculated on the basis of the deformed Woods-Saxon potential. The calculations of (T sub s sub f) are performed by the WKB approximation, in the multi-dimensional dynamical-programing method (MDP). We have examined three different effects: the effect of higher even-multipolarity shape parameters (beta sub 6 and beta sub 8), the role of reflection-asymmetry (beta sub 3 and beta sub 5) and the influence of pairing degrees of freedom (DELTA sub p and DELTA sub n). Alpha-decay half-lives (T subalpha) have been calculated by the Viola-Seaborg (V-S) formula with the parameters modified to the latest experimental data.

Lojewski, Z

1999-01-01

139

Role of pairing degrees of freedom and higher multipolarity deformations in spontaneous fission process  

Energy Technology Data Exchange (ETDEWEB)

Spontaneous fission (T{sub sf}) and alpha-decay half-lives (T{sub {alpha}}) of the heaviest nuclei with atomic number 100 {<=} Z {<=} 114 are calculated on the basis of the deformed Woods-Saxon potential. The calculations of (T{sub sf}) are performed by the WKB approximation, in the multi-dimensional dynamical-programing method (MDP). We have examined three different effects: the effect of higher even-multipolarity shape parameters ({beta}{sub 6} and {beta}{sub 8}), the role of reflection-asymmetry ({beta}{sub 3} and {beta}{sub 5}) and the influence of pairing degrees of freedom ({delta}{sub p} and {delta}{sub n}). Alpha-decay half-lives (T{sub {alpha}}) have been calculated by the Viola-Seaborg (V-S) formula with the parameters modified to the latest experimental data.

Lojewski, Z.; Staszczak, A

1999-09-20

140

Interactions between visual and motor areas during the recognition of plausible actions as revealed by magnetoencephalography.  

Science.gov (United States)

Several studies have shown activation of the mirror neuron system (MNS), comprising the temporal, posterior parietal, and sensorimotor areas when observing plausible actions, but far less is known on how these cortical areas interact during the recognition of a plausible action. Here, we recorded neural activity with magnetoencephalography while subjects viewed point-light displays of biologically plausible and scrambled versions of actions. We were interested in modulations of oscillatory activity and, specifically, in coupling of oscillatory activity between visual and motor areas. Both plausible and scrambled actions elicited modulations of ? (5-7 Hz), ? (7-13 Hz), ? (13-35 Hz), and ? (55-100 Hz) power within visual and motor areas. When comparing between the two actions, we observed sequential and spatially distinct increases of ? (?65 Hz), ? (?25 Hz), and ? (?11 Hz) power between 0.5 and 1.3 s in parieto-occipital, sensorimotor, and left temporal areas. In addition, significant clusters of ? (?65 Hz) and ?/? (?15 Hz) power decrease were observed in right temporal and parieto-occipital areas between 1.3 and 2.0 s. We found ?-power in sensorimotor areas to be positively correlated on a trial-by-trial basis with parieto-occipital ? and left temporal ?-power for the plausible but not for the scrambled condition. These results provide new insights in the neuronal oscillatory activity of the areas involved in the recognition of plausible action movements and their interaction. The power correlations between specific areas underscore the importance of interactions between visual and motor areas of the MNS during the recognition of a plausible action. PMID:23117670

Pavlidou, Anastasia; Schnitzler, Alfons; Lange, Joachim

2014-02-01

 
 
 
 
141

Producing speech with a newly learned morphosyntax and vocabulary: an magnetoencephalography study.  

Science.gov (United States)

Ten participants learned a miniature language (Anigram), which they later employed to verbally describe a pictured event. Using magnetoencephalography, the cortical dynamics of sentence production in Anigram was compared with that in the native tongue from the preparation phase up to the production of the final word. At the preparation phase, a cartoon image with two animals prompted the participants to plan either the corresponding simple sentence (e.g., "the bear hits the lion") or a grammar-free list of the two nouns ("the bear, the lion"). For the newly learned language, this stage induced stronger left angular and adjacent inferior parietal activations than for the native language, likely reflecting a higher load on lexical retrieval and STM storage. The preparation phase was followed by a cloze task where the participants were prompted to produce the last word of the sentence or word sequence. Production of the sentence-final word required retrieval of rule-based inflectional morphology and was accompanied by increased activation of the left middle superior temporal cortex that did not differ between the two languages. Activation of the right temporal cortex during the cloze task suggested that this area plays a role in integrating word meanings into the sentence frame. The present results indicate that, after just a few days of exposure, the newly learned language harnesses the neural resources for multiword production much the same way as the native tongue and that the left and right temporal cortices seem to have functionally different roles in this processing. PMID:24392893

Hultén, Annika; Karvonen, Leena; Laine, Matti; Salmelin, Riitta

2014-08-01

142

Oscillatory neuronal dynamics associated with manual acupuncture: a magnetoencephalography study using beamforming analysis  

Directory of Open Access Journals (Sweden)

Full Text Available Magnetoencephalography (MEG enables non-invasive recording of neuronal activity, with reconstruction methods providing estimates of underlying brain source locations and oscillatory dynamics from externally recorded neuromagnetic fields. The aim of our study was to use MEG to determine the effect of manual acupuncture on neuronal oscillatory dynamics. A major problem in MEG investigations of manual acupuncture is the absence of onset times for each needle manipulation. Given that beamforming (spatial filtering analysis is not dependent upon stimulus-driven responses being phase-locked to stimulus onset, we postulated that beamforming could reveal source locations and induced changes in neuronal activity during manual acupuncture. In a beamformer analysis, a two-minute period of manual acupuncture needle manipulation delivered to the ipsilateral right LI-4 (Hegu acupoint was contrasted with a two-minute baseline period. We considered oscillatory power changes in the theta (4-8Hz, alpha (8-13Hz, beta (13-30Hz and gamma (30-100Hz frequency bands. We found significant decreases in beta band power in the contralateral primary somatosensory cortex and superior frontal gyrus. In the ipsilateral cerebral hemisphere, we found significant power decreases in beta and gamma frequency bands in only the superior frontal gyrus. No significant power modulations were found in theta and alpha bands. Our results indicate that beamforming is a useful analytical tool to reconstruct underlying neuronal activity associated with manual acupuncture. Our main finding was of beta power decreases in primary somatosensory cortex and superior frontal gyrus, which opens up a line of future investigation regarding whether this contributes towards an underlying mechanism of acupuncture.

AzizAsghar

2012-11-01

143

Oscillatory neuronal dynamics associated with manual acupuncture: a magnetoencephalography study using beamforming analysis.  

Science.gov (United States)

Magnetoencephalography (MEG) enables non-invasive recording of neuronal activity, with reconstruction methods providing estimates of underlying brain source locations and oscillatory dynamics from externally recorded neuromagnetic fields. The aim of our study was to use MEG to determine the effect of manual acupuncture on neuronal oscillatory dynamics. A major problem in MEG investigations of manual acupuncture is the absence of onset times for each needle manipulation. Given that beamforming (spatial filtering) analysis is not dependent upon stimulus-driven responses being phase-locked to stimulus onset, we postulated that beamforming could reveal source locations and induced changes in neuronal activity during manual acupuncture. In a beamformer analysis, a two-minute period of manual acupuncture needle manipulation delivered to the ipsilateral right LI-4 (Hegu) acupoint was contrasted with a two-minute baseline period. We considered oscillatory power changes in the theta (4-8 Hz), alpha (8-13 Hz), beta (13-30 Hz), and gamma (30-100 Hz) frequency bands. We found significant decreases in beta band power in the contralateral primary somatosensory cortex and superior frontal gyrus (SFG). In the ipsilateral cerebral hemisphere, we found significant power decreases in beta and gamma frequency bands in only the SFG. No significant power modulations were found in theta and alpha bands. Our results indicate that beamforming is a useful analytical tool to reconstruct underlying neuronal activity associated with manual acupuncture. Our main finding was of beta power decreases in primary somatosensory cortex and SFG, which opens up a line of future investigation regarding whether this contributes toward an underlying mechanism of acupuncture. PMID:23248594

Asghar, Aziz U R; Johnson, Robyn L; Woods, William; Green, Gary G R; Lewith, George; Macpherson, Hugh

2012-01-01

144

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

CERN Multimedia

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

145

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.

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

146

Multipolar theory of black-body radiation shift of atomic energy levels and its implications for optical lattice clocks  

CERN Document Server

A black-body radiation (BBR) shifts of (nsnp ^3P_0) - (ns^2 ^1S_0) clock transition in divalent atoms Mg, Ca, Sr, and Yb are evaluated. A theory of multipolar BBR shifts is developed and its implications are discussed. At room temperatures, the resulting uncertainties in the BBR shifts are relatively large and substantially affect the projected 10^{-18} fractional accuracy of the optical-lattice-based clocks.

Porsev, S G; Derevianko, Andrei; Porsev, Sergey G.

2006-01-01

147

Multipolar symmetric squaraines with large two-photon absorption cross-sections in the NIR region.  

Science.gov (United States)

The two-photon absorption (TPA) properties of two extended symmetric squaraine dyes are thoroughly characterized from the experimental and quantum-chemical point of view. The two molecules are specially engineered to have a multipolar structure with increasing complexity, D-?-A-?-D and A'-?-D-?-A-?-D-?-A', respectively. The experimental TPA spectra, measured by means of the Z-scan technique in the femtoseconds regime, display considerably high values of TPA cross sections (?(TPA)) for both molecules. In particular, the squaraine with the more extended structure shows the highest value of ?(TPA) ever reported for this class of molecules. CIS and TDDFT calculations of the one and two-photon absorption properties are carried out to clarify the origin of the observed TPA properties and fully characterize the electronic properties of these compounds. The calculations, in good agreement with the experimental data, suggest that the origin of this exceptionally high ?(TPA) can be ascribed to the presence of a peripheral A' group, that increases the density of excited states involved in the TPA process. PMID:21625702

Collini, E; Carlotto, S; Ferrante, C; Bozio, R; Polimeno, A; Bloino, J; Barone, V; Ronchi, E; Beverina, L; Pagani, G A

2011-07-01

148

Transverse versus longitudinal tripolar configuration for selective stimulation with multipolar cuff electrodes.  

Science.gov (United States)

The ability to stimulate subareas of a nerve selectively is highly desirable, since it has the potential of simplifying surgery to implanting one cuff on a large nerve instead of many cuffs on smaller nerves or muscles, or alternatively can improve function where surgical access to the smaller nerves is limited. In this paper, stimulation was performed with a four-channel multipolar cuff electrode implanted on the sciatic nerve of nine rabbits to compare the extensively researched longitudinal tripolar configuration with the transverse tripolar configuration, which has received less interest. The performance of these configurations was evaluated in terms of selectivity in recruitment of the three branches of the sciatic nerve. The results showed that the transverse configuration was able to selectively activate the sciatic nerve branches to a functionally relevant level in more cases than the longitudinal configuration (20/27 versus 11/27 branches) and overall achieved a higher mean selectivity [0.79 ± 0.13 versus 0.61 ± 0.09 (mean ± standard deviation)]. The transverse configuration was most successful at recruiting the small cutaneous and medium-sized peroneal branches, and less successful at recruiting the large tibial nerve. PMID:21421427

Nielsen, Thomas N; Kurstjens, G A Mathijs; Struijk, Johannes J

2011-04-01

149

Toward improving the laplacian estimation with novel multipolar concentric ring electrodes.  

Science.gov (United States)

Conventional electroencephalography with disc electrodes has major drawbacks including poor spatial resolution, selectivity and low signal-to-noise ratio that are critically limiting its use. Concentric ring electrodes are a promising alternative with potential to improve all of the aforementioned aspects significantly. In our previous work, the tripolar concentric ring electrode was successfully used in a wide range of applications demonstrating its superiority to conventional disc electrode, in particular, in accuracy of Laplacian estimation. This paper takes the first fundamental step toward further improving the Laplacian estimation of the novel multipolar concentric ring electrodes by proposing a general approach to estimation of the Laplacian for an (n + 1)-polar electrode with n rings using the (4n + 1)-point method for n ? 2 that allows cancellation of all the truncation terms up to the order of 2n. Examples of using the proposed approach to estimate the Laplacian for the cases of tripolar and, for the first time, quadripolar concentric ring electrode are presented. PMID:24109980

Makeyev, Oleksandr; Ding, Quan; Kay, Steven M; Besio, Walter G

2013-01-01

150

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

151

The Slope Imaging Multi-Polarization Photon-Counting Lidar: Development and Performance Results  

Science.gov (United States)

The Slope Imaging Multi-polarization Photon-counting Lidar is an airborne instrument developed to demonstrate laser altimetry measurement methods that will enable more efficient observations of topography and surface properties from space. The instrument was developed through the NASA Earth Science Technology Office Instrument Incubator Program with a focus on cryosphere remote sensing. The SIMPL transmitter is an 11 KHz, 1064 nm, plane-polarized micropulse laser transmitter that is frequency doubled to 532 nm and split into four push-broom beams. The receiver employs single-photon, polarimetric ranging at 532 and 1064 nm using Single Photon Counting Modules in order to achieve simultaneous sampling of surface elevation, slope, roughness and depolarizing scattering properties, the latter used to differentiate surface types. Data acquired over ice-covered Lake Erie in February, 2009 are documenting SIMPL s measurement performance and capabilities, demonstrating differentiation of open water and several ice cover types. ICESat-2 will employ several of the technologies advanced by SIMPL, including micropulse, single photon ranging in a multi-beam, push-broom configuration operating at 532 nm.

Dabney, Phillip

2010-01-01

152

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

International Nuclear Information System (INIS)

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 m2 before RF ablation vs. 47.2 ± 11.9 ml/min/1.73 m2 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.

2013-06-01

153

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

154

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

155

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

156

Calculation of vapor-liquid equilibrium and PVTx properties of geological fluid system with SAFT-LJ EOS including multi-polar contribution. Part III. Extension to water-light hydrocarbons systems  

Science.gov (United States)

The SAFT-LJ EOS improved by Sun and Dubessy (2010, 2012) is extended to water-light hydrocarbon systems. Light hydrocarbons (including CH4, C2H6, C3H8 and nC4H10) are modeled as chain molecules without multi-polar moments. The contributions of the shape of molecules and main intermolecular interactions existing in water-light hydrocarbon systems (including repulsive and attractive forces between Lennard-Jones segments, the hydrogen-bonding force and the multi-polar interaction between water molecules) to the residual Helmholtz energy were accounted for by this EOS. The adjustable parameters for the interactions of H2O-CH4, H2O-C2H6, H2O-C3H8, and H2O-nC4H10 pairs were evaluated from mutual solubility data of binary water-hydrocarbon systems at vapor-liquid equilibria. Comparison with the experimental data shows this SAFT-LJ EOS can represent well vapor-liquid (and liquid-liquid) equilibria of binary water-light hydrocarbon systems over a wide P-T range. The accuracy of this EOS for mutual solubilities of methane, ethane, propane and water is within the experimental uncertainty generally. Moreover, the model is able to accurately predict the vapor-liquid equilibria and PVTx properties of multi-component systems composed of water, light hydrocarbon as well as CO2. As we know, this EOS is the first one allowing quantitative calculation of the mutual solubilities of water and light hydrocarbons over a wide P-T range among SAFT-type EOSs. This work indicates that the molecular-based EOS combined with conventional mixing rule can well describe the thermodynamic behavior of highly non-ideal systems such as water-light hydrocarbons mixtures except in the critical region for which long range density fluctuations cannot be taken into account by this analytical model.

Sun, Rui; Lai, Shaocong; Dubessy, Jean

2014-01-01

157

Multipolar theory of blackbody radiation shift of atomic energy levels and its implications for optical lattice clocks  

International Nuclear Information System (INIS)

Blackbody radiation (BBR) shifts of the 3P0-1S0 clock transition in the divalent atoms Mg, Ca, Sr, and Yb are evaluated. The dominant electric-dipole contributions are computed using accurate relativistic many-body techniques of atomic structure. At room temperatures, the resulting uncertainties in the E1 BBR shifts are large and substantially affect the projected 10-18 fractional accuracy of the optical-lattice-based clocks. A peculiarity of these clocks is that the characteristic BBR wavelength is comparable to the 3P fine-structure intervals. To evaluate relevant M1 and E2 contributions, a theory of multipolar BBR shifts is developed. The resulting corrections, although presently masked by the uncertainties in the E1 contribution, are required at the 10-18 accuracy goal

2006-08-01

158

Multipolar theory of blackbody radiation shift of atomic energy levels and its implications for optical lattice clocks  

Science.gov (United States)

Blackbody radiation (BBR) shifts of the P03-S01 clock transition in the divalent atoms Mg, Ca, Sr, and Yb are evaluated. The dominant electric-dipole contributions are computed using accurate relativistic many-body techniques of atomic structure. At room temperatures, the resulting uncertainties in the E1 BBR shifts are large and substantially affect the projected 10-18 fractional accuracy of the optical-lattice-based clocks. A peculiarity of these clocks is that the characteristic BBR wavelength is comparable to the P3 fine-structure intervals. To evaluate relevant M1 and E2 contributions, a theory of multipolar BBR shifts is developed. The resulting corrections, although presently masked by the uncertainties in the E1 contribution, are required at the 10-18 accuracy goal.

Porsev, Sergey G.; Derevianko, Andrei

2006-08-01

159

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

160

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 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)

2003-06-01

 
 
 
 
161

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

162

Improvement of an on-line electron spectrometer. Determination of transition multipolarity. Application to "1"0"2Ag and "1"0"8In  

International Nuclear Information System (INIS)

The aim of this work has been to optimize the transmission, resolution and background of an electron 'Orange' spectrometer, set-up on-line at the Grenoble isochronous cyclotron. The transitions multipolarities in "1"0"2Ag and "1"0"8In nuclei have been determined measuring the internal conversion coefficients and a cascade of five pure transitions Ml without cross-over E2 has been found in "1"0"8In

1979-01-01

163

High rate sputtering for Ni films by an rf-dc coupled magnetron sputtering system with multipolar magnetic plasma confinement  

International Nuclear Information System (INIS)

Ni films were prepared by an rf-dc coupled magnetron sputtering with multipolar magnetic plasma confinement (MMPC) at the low pressure of 6.7x10-2 Pa and at the long distance of 120 mm, when permanent magnets were placed around a nickel target (200 mm ?, 5 mm thick) outside the chamber. When rf power and dc bias voltages were applied simultaneously to the target, the deposition rate of the Ni films significantly increased with the target dc bias voltage (VT). The highest value of the deposition rate was about 250 nm/min at VT=-820 V. The high rate sputtering for Ni films was possible at the low Ar gas pressure of 6.7x10-2 Pa. The resistivity for all the films deposited at different dc bias voltages was 7.1-8.2 ?? cm whose value was close to the bulk value. It is shown that the sputtering system with MMPC has some advantages in comparison with conventional magnetron sputtering, such as high deposition rate, plasma discharge stability, and the preparation of high quality magnetic thin films

2001-07-01

164

Dipole localization of human induced focal afterdischarge seizure in simultaneous magnetoencephalography and electrocorticography.  

Science.gov (United States)

Localizations were compared for the same human seizure between simultaneously measured MEG and iEEG, which were both co-registered to MRI. The whole-cortex neuromagnetometer localized a dipole in a sphere phantom, co-registered to the MEG sensor array, with an error of 1.4 mm. A focal afterdischarge seizure was induced in a patient with partial epilepsy, by stimulation at a subdural electrocorticography (ECoG) electrode with a known location, which was co-registered to the MRI and to the MEG sensor array. The simultaneous MEG and ECoG during the 30-second seizure was measured and analyzed using the single, moving dipole model, which is the localization model used clinically. The dipole localizations from simultaneous whole cortex 68-channel MEG and 64-channel ECoG were then compared for the repetitive spiking at six different times during the seizure. There were two main regions of MEG and ECoG activity. The locations of these regions were confirmed by determining the location clusters of 8,000 dipoles on ECoG at consecutive time points during the seizure. The mean distances between the stimulated electrode location versus the dipole location of the MEG and versus the dipole location of the ECoG were each about one (1) centimeter. The mean distance between the dipole locations of the MEG versus the dipole locations of the ECoG was about 2 cm. These errors were compared to errors of MEG and ECoG reported previously for phantoms and for somatosensory evoked responses (SER) in patients. Comparing the findings from the present study to those from prior studies, there appeared to be the expected stepwise increase in mean localization error progressing from the phantom, to the SER, to the seizure. PMID:11797809

Sutherling, W W; Akhtari, M; Mamelak, A N; Mosher, J; Arthur, D; Sands, S; Weiss, P; Lopez, N; DiMauro, M; Flynn, E; Leah, R

2001-01-01

165

Occurrence of multipolar mitoses and association with Aurora-A/-B kinases and p53 mutations in aneuploid esophageal carcinoma cells  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Aurora kinases and loss of p53 function are implicated in the carcinogenesis of aneuploid esophageal cancers. Their association with occurrence of multipolar mitoses in the two main histotypes of aneuploid esophageal squamous cell carcinoma (ESCC and Barrett's adenocarcinoma (BAC remains unclear. Here, we investigated the occurrence of multipolar mitoses, Aurora-A/-B gene copy numbers and expression/activation as well as p53 alterations in aneuploid ESCC and BAC cancer cell lines. Results A control esophageal epithelial cell line (EPC-hTERT had normal Aurora-A and -B gene copy numbers and expression, was p53 wild type and displayed bipolar mitoses. In contrast, both ESCC (OE21, Kyse-410 and BAC (OE33, OE19 cell lines were aneuploid and displayed elevated gene copy numbers of Aurora-A (chromosome 20 polysomy: OE21, OE33, OE19; gene amplification: Kyse-410 and Aurora-B (chromosome 17 polysomy: OE21, Kyse-410. Aurora-B gene copy numbers were not elevated in OE19 and OE33 cells despite chromosome 17 polysomy. Aurora-A expression and activity (Aurora-A/phosphoT288 was not directly linked to gene copy numbers and was highest in Kyse-410 and OE33 cells. Aurora-B expression and activity (Aurora-B/phosphoT232 was higher in OE21 and Kyse-410 than in OE33 and OE19 cells. The mitotic index was highest in OE21, followed by OE33 > OE19 > Kyse-410 and EPC-hTERT cells. Multipolar mitoses occurred with high frequency in OE33 (13.8 ± 4.2%, followed by OE21 (7.7 ± 5.0% and Kyse-410 (6.3 ± 2.0% cells. Single multipolar mitoses occurred in OE19 (1.0 ± 1.0% cells. Distinct p53 mutations and p53 protein expression patterns were found in all esophageal cancer cell lines, but complete functional p53 inactivation occurred in OE21 and OE33 only. Conclusions High Aurora-A expression alone is not associated with overt multipolar mitoses in aneuploid ESCC and BAC cancer cells, as specifically shown here for OE21 and OE33 cells, respectively. Additional p53 loss of function mutations are necessary for this to occur, at least for invasive esophageal cancer cells. Further assessment of Aurora kinases and p53 interactions in cells or tissue specimens derived from non-invasive dysplasia (ESCC or intestinal metaplasia (BAC are necessary to disclose a potential causative role of Aurora kinases and p53 for development of aneuploid, invasive esophageal cancers.

Münch Claudia

2011-04-01

166

Neural mechanisms of movement speed and tau as revealed by magnetoencephalography.  

Science.gov (United States)

A fundamental aspect of goal-directed behavior concerns the closure of motion-gaps in a timely fashion. In this context, the critical variable is the time-to-closure, called tau (Lee in Perception 5:437-459, 1976), and is defined as the ratio of the current distance-to-goal gap over the current instantaneous speed towards the goal. In this study, we investigated the neural mechanisms of speed and tau in pointing hand movements by recording MEG activity from the whole brain of 20 right-handed healthy human subjects operating a joystick with their right hand. The relations between neural signals and speed and tau were analyzed using an autoregressive multiple regression model, where the time-varying MEG signal was the dependent variable and the corresponding value of speed and tau were the independent variables. With respect to speed, we found that 81% of sensors showed significant relations over the left frontal-parietal, left parieto-temporal, and, less prominently, the right temporo-occipital sensor space. These results document the widespread involvement of brain areas with movement speed, especially in the left hemisphere (i.e., contralateral to the moving limb), in accord with previous studies. With respect to tau, 22% of sensors showed significant relations over the parietal (bilaterally), right parietal-temporal, and, less prominently, the left temporo-occipital sensor space. The tau effects often occurred concurrently with speed effects and spatially overlapped in the left fronto-parietal sensors. These findings document for the first time the time-varying, dynamic processing of information regarding tau in specific brain areas, including the right parietal cortex. This is of special interest, for that area has been found to be involved in processing information concerning the duration of time intervals in perceptual tasks (Harrington et al. in J Neurosci 18:1085-1095, 1998; Rao et al. in Nat Neurosci 4:317-323, 2001). Since tau is itself a time interval, we hypothesize that the right parietal focus of tau processing observed in this study reflects the ongoing processing of tau as an interval for a timely arrival of the hand to the target. PMID:19424687

Tan, Heng-Ru May; Leuthold, Arthur C; Lee, David N; Lynch, Joshua K; Georgopoulos, Apostolos P

2009-06-01

167

Comparison between etching in Cl2 and BCl3 for compound semiconductors using a multipolar electron cyclotron resonance source  

International Nuclear Information System (INIS)

Controllable dry etching of GaAs and InP using a multipolar electron cyclotron resonance (ECR) source and a radio frequency (rf)-powered electrode was investigated. The etch characteristics were studied as a function of microwave power, rf power, distance from the ECR source, pressure, and temperature. Etch rate is found to increase with microwave power initially, then decrease at higher microwave power due to reduction in ion energy. Surface morphology becomes rougher and etch profile is more undercut at higher microwave power, but can be improved using higher rf power or by Ar addition. As the ECR source distance increases, the concentration of ions and neutral species decrease, but the ion energy increases. Therefore, when etching is limited by the arrival rate of reactive radicals, etch rate decreases with source distance. When the process is limited by the ion-enhanced reaction or removal rates, etch rate increases with source distance. Etch rate and self-induced dc bias voltage (|Vdc|) typically increase with pressure. The increase in | Vdc| is believed to be caused by the lower ion flux at higher pressure. However, when the reactive species concentrations and the ion energy are low, etch rate decreases with pressure. Low pressure was observed to favor smooth surface morphology and vertical etch profile. Etch rates for both GaAs and InP increase with temperature, with InP etch rate exceeding GaAs at 380 degrees C. Using a Cl2/Ar mixture with 10% Cl2, 70 W rf power and 25 W microwave power at 0.5 mTorr, 0.1 ?m wide features that are 1?m deep have been fabricated in GaAs with vertical profile and smooth surface morphology. 16 refs., 6 figs

1992-05-26

168

Multipolar SPM machines for direct drive application: a comprehensive design approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A closed-form, per-unit formulation is proposed, for the design of surface mounted permanent magnet motors with high number of poles. The model evaluates the shear stress, the power factor and the specific Joule loss as the indicators of the machine performance, and demonstrates that this is determined by the correct choice of a very limited set of key-geometrical parameters. The design criteria are described analytically and then applied to example designs, FEA validated. Distributed- and co...

Boazzo, Barbara; Pellegrino, Gian-mario Luigi; Vagati, Alfredo

2012-01-01

169

Generation of trisomies in cancer cells by multipolar mitosis and incomplete cytokinesis.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One extra chromosome copy (i.e., trisomy) is the most common type of chromosome aberration in cancer cells. The mechanisms behind the generation of trisomies in tumor cells are largely unknown, although it has been suggested that dysfunction of the spindle assembly checkpoint (SAC) leads to an accumulation of trisomies through failure to correctly segregate sister chromatids in successive cell divisions. By using Wilms tumor as a model for cancers with trisomies, we now show that trisomic cel...

2010-01-01

170

Generation of trisomies in cancer cells by multipolar mitosis and incomplete cytokinesis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One extra chromosome copy (i.e., trisomy) is the most common type of chromosome aberration in cancer cells. The mechanisms behind the generation of trisomies in tumor cells are largely unknown, although it has been suggested that dysfunction of the spindle assembly checkpoint (SAC) leads to an accumulation of trisomies through failure to correctly segregate sister chromatids in successive cell divisions. By using Wilms tumor as a model for cancers with trisomies, we now show that trisomic cel...

2010-01-01

171

Generation of trisomies in cancer cells by multipolar mitosis and incomplete cytokinesis.  

Science.gov (United States)

One extra chromosome copy (i.e., trisomy) is the most common type of chromosome aberration in cancer cells. The mechanisms behind the generation of trisomies in tumor cells are largely unknown, although it has been suggested that dysfunction of the spindle assembly checkpoint (SAC) leads to an accumulation of trisomies through failure to correctly segregate sister chromatids in successive cell divisions. By using Wilms tumor as a model for cancers with trisomies, we now show that trisomic cells can form even in the presence of a functional SAC through tripolar cell divisions in which sister chromatid separation proceeds in a regular fashion, but cytokinesis failure nevertheless leads to an asymmetrical segregation of chromosomes into two daughter cells. A model for the generation of trisomies by such asymmetrical cell division accurately predicted several features of clones having extra chromosomes in vivo, including the ratio between trisomies and tetrasomies and the observation that different trisomies found in the same tumor occupy identical proportions of cells and colocalize in tumor tissue. Our findings provide an experimentally validated model explaining how multiple trisomies can occur in tumor cells that still maintain accurate sister chromatid separation at metaphase-anaphase transition and thereby physiologically satisfy the SAC. PMID:21059955

Gisselsson, David; Jin, Yuesheng; Lindgren, David; Persson, Johan; Gisselsson, Lennart; Hanks, Sandra; Sehic, Daniel; Mengelbier, Linda Holmquist; Øra, Ingrid; Rahman, Nazneen; Mertens, Fredrik; Mitelman, Felix; Mandahl, Nils

2010-11-23

172

Relation of the rotational motion with axial vibrations of multipolarity 2 and 4  

International Nuclear Information System (INIS)

The nonadiabatic effects related to the coupling between the rotational and vibrational degrees of freedom are investigated. The collective Hamiltonian is constructed using the concepts of the Bohr theory and includes the degrees of freedom corresponding to the axial quadrupole and hexadecapole vibrations. The coupling of the nuclear vibrations with the rotational motion is so strong that one has to multiply the mass parameters and the moment of inertia by the factor 1.7 in order to get the experimental energies spacing in the ground state bands. The dynamical effects in formation of the electric quadrupole and hexadecapole moments are considered. The parameter of nonadiabaticity ? calculated within the model agrees well with the experimental data

1983-01-01

173

Coupling of the rotational motion with the axial vibrations of multipolarity 2 and 4  

International Nuclear Information System (INIS)

The unadiabatic effects related to the coupling between the rotational and vibrational degrees of freedom are investigated. The collective Hamiltonian is constructed using the concepts of the Bohr theory and includes the degrees of freedom corresponding to the axial quadrupole and hexadecapole vibrations. The coupling of the nuclear vibrations with the rotational motion is so strong that one has to multiply the inertial parameters and the moment of inertia by the factor 1.7 in order to get the experimental energies spacing in the ground state bands. The dynamical effect to the electric quadrupole and hexadecapole moments are considered. The parameter of unadiabaticity ? calculated within the model agrees well with the experimental data. (orig.)

1984-05-01

174

Coupling of the rotational motion with the axial vibrations of multipolarity 2 and 4  

Energy Technology Data Exchange (ETDEWEB)

The unadiabatic effects related to the coupling between the rotational and vibrational degrees of freedom are investigated. The collective Hamiltonian is constructed using the concepts of the Bohr theory and includes the degrees of freedom corresponding to the axial quadrupole and hexadecapole vibrations. The coupling of the nuclear vibrations with the rotational motion is so strong that one has to multiply the inertial parameters and the moment of inertia by the factor 1.7 in order to get the experimental energies spacing in the ground state bands. The dynamical effect to the electric quadrupole and hexadecapole moments are considered. The parameter of unadiabaticity ..cap alpha.. calculated within the model agrees well with the experimental data.

Lojewski, Z.; Mikhailov, I.N.; Pomorski, K.

1984-05-01

175

ZnO thin films with c-axis orientation prepared on the room temperature substrate by the ECR multipolar plasma sputtering method  

International Nuclear Information System (INIS)

Zinc oxide (ZnO) films with c-axis orientation have been prepared on the room temperature substrates by a reactive sputtering deposition utilizing electron-cyclotron-resonance multipolar (ECRM) plasma apparatus built with Nd-Fe-B magnets and 2.45 GHz, TE_1_0 mode microwave. The plasma distributions in the axial direction were found to be sensitive to the magnetic field configurations in the plasma cavity. The XRD, TEM, SEM analyses indicated that the deposited ZnO films were of nanometre size, smoothness and dense with high c-axis orientation

1992-01-01

176

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Sakai, Osamu; Shiina, Ryousuke; Shiba, Hiroyuki

2004-01-01

177

The Fate of Sub-micron Circumplanetary Dust Grains II: Multipolar Fields  

CERN Document Server

We study the radial and vertical stability of dust grains launched with all charge-to-mass ratios at arbitrary distances from rotating planets with complex magnetic fields. We show that the aligned dipole magnetic field model analyzed by Jontof-Hutter and Hamilton (2012) is an excellent approximation in most cases, but that fundamentally new physics arises with the inclusion of non-axisymmetric magnetic field terms. In particular, large numbers of distant negatively-charged dust grains, stable in a magnetic dipole, can be driven to escape by a more complex field. We trace the origin of the instability to overlapping Lorentz resonances which are extremely powerful when the gravitational and electromagnetic forces on a dust grain are comparable. These resonances enable a dust grain to tap the spin energy of the planet to power its escape. We also explore the relatively minor influence of different launch speeds and the far more important effects of variable grain charge. Only the latter are capable of significa...

Jontof-Hutter, Daniel

2012-01-01

178

General methodology to optimize damping functions to account for charge penetration effects in electrostatic calculations using multicentered multipolar expansions.  

Science.gov (United States)

We developed a methodology to optimize exponential damping functions to account for charge penetration effects when computing molecular electrostatic properties using the multicentered multipolar expansion method (MME). This methodology is based in the optimization of a damping parameter set using a two-step fast local fitting procedure and the ab initio (Hartree-Fock/6-31G** and 6-31G**+) electrostatic potential calculated in a set of concentric grid of points as reference. The principal aspect of the methodology is a first local fitting step which generates a focused initial guess to improve the performance of a simplex method avoiding the use of multiple runs and the choice of initial guesses. Three different strategies for the determination of optimized damping parameters were tested in the following studies: (1) investigation of the error in the calculation of the electrostatic interaction energy for five hydrogen-bonded dimers at standard and nonstandard hydrogen-bonded geometries and at nonequilibrium geometries; (2) calculation of the electrostatic molecular properties (potential and electric field) for eight small molecular systems (methanol, ammonia, water, formamide, dichloromethane, acetone, dimethyl sulfoxide, and acetonitrile) and for the 20 amino acids. Our results show that the methodology performs well not only for small molecules but also for relatively larger molecular systems. The analysis of the distinct parameter sets associated with different optimization strategies show that (i) a specific parameter set is more suitable and more general for electrostatic interaction energy calculations, with an average absolute error of 0.46 kcal/mol at hydrogen-bond geometries; (ii) a second parameter set is more suitable for electrostatic potential and electric field calculations at and outside the van der Waals (vdW) envelope, with an average error decrease >72% at the vdW surface. A more general amino acid damping parameter set was constructed from the original damping parameters derived for the small fragments and for the amino acids. This damping set is more insensitive to protein backbone and residue side-chain conformational changes and can be very useful for future docking and molecular dynamics protein simulations using ab initio based polarizable classical methods. PMID:18095663

Werneck, Araken S; Filho, Tarcísio M Rocha; Dardenne, Laurent E

2008-01-17

179

Per-point and per-field contextual classification of multipolarization and multiple incidence angle aircraft L-band radar data  

Science.gov (United States)

Multipolarized aircraft L-band radar data are classified using two different image classification algorithms: (1) a per-point classifier, and (2) a contextual, or per-field, classifier. Due to the distinct variations in radar backscatter as a function of incidence angle, the data are stratified into three incidence-angle groupings, and training and test data are defined for each stratum. A low-pass digital mean filter with varied window size (i.e., 3x3, 5x5, and 7x7 pixels) is applied to the data prior to the classification. A predominately forested area in northern Florida was the study site. The results obtained by using these image classifiers are then presented and discussed.

Hoffer, Roger M.; Hussin, Yousif Ali

1989-01-01

180

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

 
 
 
 
181

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 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 analyze transnational motion of shperically sy

2004-11-01

182

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 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.

2011-03-15

183

Inspiral-merger-ringdown multipolar waveforms of nonspinning black-hole binaries using the effective-one-body formalism  

CERN Document Server

We calibrate an effective-one-body (EOB) model to numerical-relativity simulations of mass ratios 1, 2, 3, 4, and 6, by maximizing phase and amplitude agreement of the leading (2,2) mode and of the subleading modes (2,1), (3,3), (4,4) and (5,5). Aligning the calibrated EOB waveforms and the numerical waveforms at low frequency, the phase difference of the (2,2) mode between model and numerical simulation remains below 0.1 rad throughout the evolution for all mass ratios considered. The fractional amplitude difference at peak amplitude of the (2,2) mode is 2% and grows to 12% during the ringdown. Using the Advanced LIGO noise curve we study the effectualness and measurement accuracy of the EOB model, and stress the relevance of modeling the higher-order modes for parameter estimation. We find that the effectualness, measured by the mismatch, between the EOB and numerical-relativity polarizations which include only the (2,2) mode is smaller than 0.2% for binaries with total mass 20-200 Msun and mass ratios 1, 2...

Pan, Yi; Boyle, Michael; Buchman, Luisa T; Kidder, Lawrence E; Pfeiffer, Harald P; Scheel, Mark A

2011-01-01

184

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 H [...] H (emissão e recebimento 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.

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

185

Determination of the E1+M2+E3 multipolarity mixture for 921 keV ?-transition and analysis of the 1285 kehV, 5"- level structure in "1"8"4W  

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"-"1"8"4W level. "1"8"4Re and sup(184m)Re were used as "1"8"4W 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"-"1"8"4 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

1985-11-01

186

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

187

US ASAT Policy for a Multipolar World.  

Science.gov (United States)

Whether to pursue the continued development of a US ASAT in the 1990s will prove a difficult choice for defense planners. Making a case for the weapon system in the bipolar world seemed perhaps 'intuitively obvious' to ASAT advocates. The US was faced wit...

R. C. Hunter

1992-01-01

188

High-multipolarity magnetic sum rule  

International Nuclear Information System (INIS)

A spin flip magnetic multipole sum rule for magnetic dipole (ML) transitions is derived for the L >= 2 of T =1 type which is valid in the long-wavelength limit. It is applied to known ML transitions in several light nuclei, including recently-measured M6 and M8 transitions in inelastic electron scattering, and the degree of sum-rule exhaustion is determined

1981-01-01

189

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

190

Transfer entropy--a model-free measure of effective connectivity for the neurosciences.  

Science.gov (United States)

Understanding causal relationships, or effective connectivity, between parts of the brain is of utmost importance because a large part of the brain's activity is thought to be internally generated and, hence, quantifying stimulus response relationships alone does not fully describe brain dynamics. Past efforts to determine effective connectivity mostly relied on model based approaches such as Granger causality or dynamic causal modeling. Transfer entropy (TE) is an alternative measure of effective connectivity based on information theory. TE does not require a model of the interaction and is inherently non-linear. We investigated the applicability of TE as a metric in a test for effective connectivity to electrophysiological data based on simulations and magnetoencephalography (MEG) recordings in a simple motor task. In particular, we demonstrate that TE improved the detectability of effective connectivity for non-linear interactions, and for sensor level MEG signals where linear methods are hampered by signal-cross-talk due to volume conduction. PMID:20706781

Vicente, Raul; Wibral, Michael; Lindner, Michael; Pipa, Gordon

2011-02-01

191

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)

1999-02-01

192

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

193

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 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

2007-09-07

194

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)

1984-01-01

195

Integrating the disaster cycle model into traditional disaster diplomacy concepts.  

Science.gov (United States)

Disaster diplomacy is an evolving contemporary model that examines how disaster response strategies can facilitate cooperation between parties in conflict. The concept of disaster diplomacy has emerged during the past decade to address how disaster response can be leveraged to promote peace, facilitate communication, promote human rights, and strengthen intercommunity ties in the increasingly multipolar modern world. Historically, the concept has evolved through two camps, one that focuses on the interactions between national governments in conflict and another that emphasizes the grassroots movements that can promote change. The two divergent approaches can be reconciled and disaster diplomacy further matured by contextualizing the concept within the disaster cycle, a model well established within the disaster risk management community. In particular, access to available health care, especially for the most vulnerable populations, may need to be negotiated. As such, disaster response professionals, including emergency medicine specialists, can play an important role in the development and implementation of disaster diplomacy concepts. PMID:22490937

Callaway, David W; Yim, Eugene S; Stack, Colin; Burkle, Frederick M

2012-03-01

196

A mean-field formalism to model current source densities and extracellular potentials in biological tissue  

CERN Document Server

The standard model of electric fields and potentials in biological tissue assumes that current sources are exclusively made by dipoles, and that the surrounding medium is resistive and uniform. Because of these assumptions, this standard model cannot be used to estimate the contributions of monopolar sources or of non-resistive aspects of the extracellular medium. We propose here a general framework to model electric fields and potentials resulting from current source densities, without relying on such assumptions. We develop a mean-field formalism which is a generalization of the standard model, and which can directly incorporate macroscopic measurements of electric parameters and non-resistive (non-ohmic) properties of the extracellular medium, such as ionic diffusion effects. This formalism recovers the classic results of the standard model such as the current-source density (CSD) analysis, but can generalize the CSD approach to situations with non-resistive media and arbitrarily complex multipolar configu...

Bedard, Claude

2011-01-01

197

Neural mass model parameter identification for MEG/EEG  

Science.gov (United States)

Electroencephalography (EEG) and magnetoencephalography (MEG) have excellent time resolution. However, the poor spatial resolution and small number of sensors do not permit to reconstruct a general spatial activation pattern. Moreover, the low signal to noise ratio (SNR) makes accurate reconstruction of a time course also challenging. We therefore propose to use constrained reconstruction, modeling the relevant part of the brain using a neural mass model: There is a small number of zones that are considered as entities, neurons within a zone are assumed to be activated simultaneously. The location and spatial extend of the zones as well as the interzonal connection pattern can be determined from functional MRI (fMRI), diffusion tensor MRI (DTMRI), and other anatomical and brain mapping observation techniques. The observation model is linear, its deterministic part is known from EEG/MEG forward modeling, the statistics of the stochastic part can be estimated. The dynamics of the neural model is described by a moderate number of parameters that can be estimated from the recorded EEG/MEG data. We explicitly model the long-distance communication delays. Our parameters have physiological meaning and their plausible range is known. Since the problem is highly nonlinear, a quasi-Newton optimization method with random sampling and automatic success evaluation is used. The actual connection topology can be identified from several possibilities. The method was tested on synthetic data as well as on true MEG somatosensory-evoked field (SEF) data.

Kybic, Jan; Faugeras, Olivier; Clerc, Maureen; Papadopoulo, Théo

2007-03-01

198

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...

2011-01-01

199

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

200

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

 
 
 
 
201

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

202

Mz 3, a Multipolar Nebula in the Making  

CERN Multimedia

The nebula Mz 3 has arguably the most complex bipolar morphology, consisting of three nested pairs of bipolar lobes and an equatorial ellipse. Its three pairs of bipolar lobes share the same axis of symmetry, but have very different opening angles and morphologies: the innermost pair of bipolar lobes shows closed lobe morphology, while the other two have open lobes with cylindrical and conical shapes, respectively. We have carried out high-dispersion spectroscopic observations of Mz 3, and detected distinct kinematic properties among the different morphological components. The expansion characteristics of the two outer pairs of lobes suggest that they originated in an explosive event, whereas the innermost pair of lobes resulted from the interaction of a fast wind with the surrounding material. The equatorial ellipse is associated with a fast equatorial outflow which is unique among bipolar nebulae. The dynamical ages of the different structures in Mz 3 suggest episodic bipolar ejections, and the distinct mor...

Guerrero, M A; Miranda, L F

2004-01-01

203

Mz 3, a Multipolar Nebula in the Making  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nebula Mz 3 has arguably the most complex bipolar morphology, consisting of three nested pairs of bipolar lobes and an equatorial ellipse. Its three pairs of bipolar lobes share the same axis of symmetry, but have very different opening angles and morphologies: the innermost pair of bipolar lobes shows closed lobe morphology, while the other two have open lobes with cylindrical and conical shapes, respectively. We have carried out high-dispersion spectroscopic observatio...

Guerrero, Martin A.; Chu, You-hua; Miranda, Luis F.

2004-01-01

204

Photon angular momentum: selection rules and multipolar transition moments  

International Nuclear Information System (INIS)

The representation of electromagnetic radiation by means of vector spherical harmonics and Bessel functions is described and used to derive selection rules for atomic electronic transitions which, as expected, show that the angular momentum of the system-atom plus photon-is conserved and, more importantly, provide a very precise description of the angular momentum of the photon involved. Examples of matrix elements for electric dipole, electric quadrupole and magnetic dipole transition moments of the hydrogen atom are calculated and the results compared with those obtained by the usual plane-wave expansion and with more recent results obtained in connection with studies of 'twisted' beams

2008-05-14

205

Theory of electron scattering from multipolar vibrations of adsorbates  

Energy Technology Data Exchange (ETDEWEB)

The electronic vibrational scattering from a molecule adsorbed on a flat surface is analyzed. In the energy region where the long-range Coulomb interaction is the main scattering mechanism the molecule is described as a point multipole. The cross sections are derived for both the screened and the unscreened multipoles, which enables us to obtain the ''surface multipole selection rule'' in a rather general form. We compare the multipole with the dipole scattering, and we discuss in detail the scattering from the quadrupole, which can give effects at least comparable with the impact scattering. The molecular vibrations perpendicular and parallel to the surface are analyzed in detail and the resulting angular and energy dependent cross sections are given for parameters corresponding to the electron scattering from H adsorbed on W(100). The comparison shows that the multipole scattering can play an important role in that case.

Lenac, Z.; S-hacekunjic-acute-accent, M.

1986-09-01

206

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

207

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.

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

208

Nanoscale interference patterns of gap-mode multipolar plasmonic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Arbitrary spatial distributions of the electric field of light are formed through the interference of individual wavenumber mode fields with appropriate amplitudes and phases, while the maximum wavenumber in the far field is limited by the wavelength of light. In contrast, localized surface plasmons (LSPs) possess the ability to confine photons strongly into nanometer-scale areas, exceeding the diffraction limit. In particular, gap-mode LSPs produce single-nanometer-sized, highly intense loca...

Yoshito Tanaka; Akio Sanada; Keiji Sasaki

2012-01-01

209

Mercado Simbólico: um modelo de comunicação para políticas públicas / The symbolic market: a communication model for public policies / Mercado Simbólico: un modelo de comunicación para políticas públicas  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese O trabalho tem como objetivo propor um modelo para análise e planejamento estratégico da comunicação nas políticas públicas, considerando que os modelos correntes não dão conta adequadamente da prática comunicativa nos processos de intervenção social, frustrando os altos investimentos e expectativas [...] que despertam. O "Modelo do Mercado Simbólico", em rede, descentrado e multipolar, é composto por uma formulação teórica, uma representação gráfica dos principais componentes e suas relações e de uma matriz de análise e planejamento estratégico das relações comunicativas. A representação gráfica contempla: a rede de sentidos sociais, os interlocutores e seus contextos e "lugar de interlocução". A matriz inclui fontes, campos, instâncias, comunidades discursivas e uma tipologia de fatores de mediação. Abstract in spanish El trabajo tiene como objetivo proponer un modelo para análisis y planificación estratégica de la comunicación en las políticas públicas, considerando que los modelos corrientes no sustentan adecuadamente la práctica comunicativa en los procesos de intervención social, frustrando las altas inversion [...] es y expectativas que despiertan. El "Modelo del Mercado Simbólico", en red, descentrado y multipolar, es compuesto por una formulación teórica, una representación gráfica de los principales componentes y sus relaciones y de una matriz de análisis y planificación estratégica de las relaciones comunicativas. La representación gráfica contempla: la red de sentidos sociales, los interlocutores y sus contextos y "lugar de interlocución". La matriz incluye fuentes, campos, instancias, comunidades discursivas y una tipología de factores de mediación. Abstract in english The purpose of this paper is to put forth a model for the analysis and strategic planning of the communication of public policies, given that the current models fail to adequately fulfill communication requirements in the processes of social intervention, frustrating the high investments and expecta [...] tions that they give rise to. The "Symbolic Market Model", in network form, both decentralized and multipolar, is comprised of (i) a theoretical formulation, (ii) a graphical representation of the main components and the relations between them and (iii) an analysis and strategic planning matrix of communicative relations. The graphic representation takes into account: the network of social senses, the interlocutors and their contexts, and the "place of dialogue". The matrix includes sources, fields, instances, discursive communities and a typology of mediation factors.

Inesita Soares de, Araújo.

210

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

211

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. 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

2008-09-01

212

Modeling  

Directory of Open Access Journals (Sweden)

Full Text Available Recently, there have been a large number of studies using resting state fMRI to characterize abnormal brain connectivity in patients with a variety of neurological, psychiatric and developmental disorders. However, interpreting what the differences in resting state functional connectivity (rsfMRI-FC actually reflect in terms of the underlying neural pathology has proved to be elusive because of the complexity of brain anatomical connectivity. The same is the case for task-based fMRI studies. In the last few years, several groups have used large-scale neural modeling to help provide some insight into the relationship between brain anatomical connectivity and the corresponding patterns of fMRI-FC. In this paper we review several efforts at using large-scale neural modeling to investigate the relationship between structural connectivity and functional/effective connectivity to determine how alterations in structural connectivity are manifested in altered patterns of functional/effective connectivity. Because the alterations made in the anatomical connectivity between specific brain regions in the model are known in detail, one can use the results of these simulations to determine the corresponding alterations in rsfMRI-FC. Many of these simulation studies found that structural connectivity changes do not necessarily result in matching changes in functional/effective connectivity in the areas of structural modification. Often, it was observed that increases in functional/effective connectivity in the altered brain did not necessarily correspond to increases in the strength of the anatomical connection weights. Note that increases in rsfMRI-FC in patients have been interpreted in some cases as resulting from neural plasticity. These results suggest that this interpretation can be mistaken. The relevance of these simulation findings to the use of functional/effective fMRI connectivity as biomarkers for brain disorders is also discussed.

BarryHorwitz

2013-11-01

213

A simple model of the chaotic eccentricity of Mercury  

CERN Document Server

Mercury's eccentricity is chaotic and can increase so much that collisions with Venus or the Sun become possible (Laskar, 1989, 1990, 1994, 2008, Batygin & Laughlin, 2008, Laskar & Gastineau, 2009). This chaotic behavior results from an intricate network of secular resonances, but in this paper, we show that a simple integrable model with only one degree of freedom is actually able to reproduce the large variations in Mercury's eccentricity, with the correct amplitude and timescale. We show that this behavior occurs in the vicinity of the separatrices of the resonance g1-g5 between the precession frequencies of Mercury and Jupiter. However, the main contribution does not come from the direct interaction between these two planets. It is due to the excitation of Venus' orbit at Jupiter's precession frequency g5. We use a multipolar model that is not expanded with respect to Mercury's eccentricity, but because of the proximity of Mercury and Venus, the Hamiltonian is expanded up to order 20 and more in t...

Boué, Gwenaël; Farago, François

2012-01-01

214

A Skew-t space-varying regression model for the spectral analysis of resting state brain activity.  

Science.gov (United States)

It is known that in many neurological disorders such as Down syndrome, main brain rhythms shift their frequencies slightly, and characterizing the spatial distribution of these shifts is of interest. This article reports on the development of a Skew-t mixed model for the spatial analysis of resting state brain activity in healthy controls and individuals with Down syndrome. Time series of oscillatory brain activity are recorded using magnetoencephalography, and spectral summaries are examined at multiple sensor locations across the scalp. We focus on the mean frequency of the power spectral density, and use space-varying regression to examine associations with age, gender and Down syndrome across several scalp regions. Spatial smoothing priors are incorporated based on a multivariate Markov random field, and the markedly non-Gaussian nature of the spectral response variable is accommodated by the use of a Skew-t distribution. A range of models representing different assumptions on the association structure and response distribution are examined, and we conduct model selection using the deviance information criterion. (1) Our analysis suggests region-specific differences between healthy controls and individuals with Down syndrome, particularly in the left and right temporal regions, and produces smoothed maps indicating the scalp topography of the estimated differences. PMID:22614763

Ismail, Salimah; Sun, Wenqi; Nathoo, Farouk S; Babul, Arif; Moiseev, Alexader; Beg, Mirza Faisal; Virji-Babul, Naznin

2013-08-01

215

Modeling the horizon-absorbed gravitational flux for equatorial-circular orbits in Kerr spacetime  

CERN Document Server

We propose an improved analytical model for the horizon-absorbed gravitational-wave energy flux of a small body in circular orbit in the equatorial plane of a Kerr black hole. Post-Newtonian (PN) theory provides an analytical description of the multipolar components of the absorption flux through Taylor expansions in the orbital frequency. Building on previous work, we construct a mode-by-mode factorization of the absorbed flux whose Taylor expansion agrees with current PN results. This factorized form significantly improves the agreement with numerical results obtained with a frequency-domain Teukolsky code, which evolves through a sequence of circular orbits up to the photon orbit. We perform the comparison between model and numerical data for dimensionless Kerr spins $-0.99 \\leq q \\leq 0.99$ and for frequencies up to the light ring of the Kerr black hole. Our proposed model enforces the presence of a zero in the flux at an orbital frequency equal to the frequency of the horizon, as predicted by perturbatio...

Taracchini, Andrea; Hughes, Scott A; Khanna, Gaurav

2013-01-01

216

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

217

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

218

The structure of 193Au within the Interacting Boson Fermion Model  

International Nuclear Information System (INIS)

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 d3/2 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 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

2014-02-01

219

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

International Nuclear Information System (INIS)

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

2005-05-24

220

Modeling extracellular electrical neural stimulation: from basic understanding to MEA-based applications.  

Science.gov (United States)

Extracellular electrical stimulation of neural networks has been widely used empirically for decades with individual electrodes. Since recently, microtechnology provides advanced systems with high-density microelectrode arrays (MEAs). Taking the most of these devices for fundamental goals or developing neural prosthesis requires a good knowledge of the mechanisms underlying electrical stimulation. Here, we review modeling approaches used to determine (1) the electric potential field created by a stimulation and (2) the response of an excitable cell to an applied field. Computation of the potential field requires solving the Poisson equation. While this can be performed analytically in simple electrode-neuron configurations, numerical models are required for realistic geometries. In these models, special care must be taken to model the potential drop at the electrode/tissue interface using appropriate boundary conditions. The neural response to the field can then be calculated using compartmentalized cell models, by solving a cable equation, the source term of which (called activating function) is proportional to the second derivative of the extracellular field along the neural arborization. Analytical and numerical solutions to this equation are first presented. Then, we discuss the use of approximated solutions to intuitively predict the neuronal response: Either the "activating function" or the "mirror estimate", depending on the pulse duration and the cell space constant. Finally, we address the design of optimal electrode configurations allowing the selective activation of neurons near each stimulation site. This can be achieved using either multipolar configurations, or the "ground surface" configuration, which can be easily integrated in high-density MEAs. Overall, models highlighting the mechanisms of electrical microstimulation and improving stimulating devices should help understanding the influence of extracellular fields on neural elements and developing optimized neural prostheses for rehabilitation. PMID:22036892

Joucla, Sébastien; Yvert, Blaise

2012-01-01

 
 
 
 
221

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

222

Temporal processing of audiovisual stimuli is enhanced in musicians: evidence from magnetoencephalography (MEG).  

Science.gov (United States)

Numerous studies have demonstrated that the structural and functional differences between professional musicians and non-musicians are not only found within a single modality, but also with regard to multisensory integration. In this study we have combined psychophysical with neurophysiological measurements investigating the processing of non-musical, synchronous or various levels of asynchronous audiovisual events. We hypothesize that long-term multisensory experience alters temporal audiovisual processing already at a non-musical stage. Behaviorally, musicians scored significantly better than non-musicians in judging whether the auditory and visual stimuli were synchronous or asynchronous. At the neural level, the statistical analysis for the audiovisual asynchronous response revealed three clusters of activations including the ACC and the SFG and two bilaterally located activations in IFG and STG in both groups. Musicians, in comparison to the non-musicians, responded to synchronous audiovisual events with enhanced neuronal activity in a broad left posterior temporal region that covers the STG, the insula and the Postcentral Gyrus. Musicians also showed significantly greater activation in the left Cerebellum, when confronted with an audiovisual asynchrony. Taken together, our MEG results form a strong indication that long-term musical training alters the basic audiovisual temporal processing already in an early stage (direct after the auditory N1 wave), while the psychophysical results indicate that musical training may also provide behavioral benefits in the accuracy of the estimates regarding the timing of audiovisual events. PMID:24595014

Lu, Yao; Paraskevopoulos, Evangelos; Herholz, Sibylle C; Kuchenbuch, Anja; Pantev, Christo

2014-01-01

223

Development of Theory of Mind Stimuli in Magnetoencephalography for Nursing Evaluation  

Directory of Open Access Journals (Sweden)

Full Text Available We introduce the development of animation stimuli for theory of mind (ToM in magnetoencepalography (MEG. We will discuss apparatus for presenting animation stimuli and a technical problem like an eye movement signal generated from following triangles in the animations, and its rejection using independent component analysis (ICA. With the ToM animations and the apparatus, we conducted MEG measurements for 8 normal controls and 6 schizophrenic patients. We present a preliminary assessment result for the developed animation stimuli as a tool for ToM test, which has been obtained by scoring in the followingup interview after the MEG measurement.

Sungwon Park

2009-09-01

224

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

225

The Unique Determination of Neuronal Currents in the Brain via Magnetoencephalography  

CERN Multimedia

The problem of determining the neuronal current inside the brain from measurements of the induced magnetic field outside the head is discussed under the assumption that the space occupied by the brain is approximately spherical. By inverting the Geselowitz equation, the part of the current which can be reconstructed from the measurements is precisely determined. This actually consists of only certain moments of one of the two functions specifying the tangential part of the current. The other function specifying the tangential part of the current as well as the radial part of the current are completely arbitrary. However, it is also shown that with the assumption of energy minimization, the current can be reconstructed uniquely. A numerical implementation of this unique reconstruction is also presented.

Fokas, A S; Marinakis, V

2004-01-01

226

The Nature of Abstract Orthographic Codes: Evidence from Masked Priming and Magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

What kind of mental objects are letters? Research on letter perception has mainly focussed on the visual properties of letters, showing that orthographic representations are abstract and size/shape invariant. But given that letters are, by definition, mappings between symbols and sounds, what is the role of sound in orthographic representation? We present two experiments suggesting that letters are fundamentally sound-based representations. To examine the role of sound in orthographic represe...

Pylkka?nen, Liina; Okano, Kana

2010-01-01

227

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 obtained from 17 LGG patients ...

2008-01-01

228

Spatiotemporal Patterns of Brain Activation During an Action Naming Task Using Magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Eight right-handed subjects were asked to silently generate a verb to a visual stimulus while the magnetic flux normal to the scalp surface was recorded with a whole-head neuromagnetometer. The spatiotemporal patterns of activation in lateral occipital, inferior parietal, superior temporal, basal temporal, and inferior frontal cortices were estimated using minimum estimation, a distributed source analysis methodology. Although there was significant variability among subjects, averaged data in...

Breier, Joshua I.; Papanicolaou, Andrew C.

2008-01-01

229

Gustatory Imagery Reveals Functional Connectivity from the Prefrontal to Insular Cortices Traced with Magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Our experience and prejudice concerning food play an important role in modulating gustatory information processing; gustatory memory stored in the central nervous system influences gustatory information arising from the peripheral nervous system. We have elucidated the mechanism of the 'top-down" modulation of taste perception in humans using functional magnetic resonance imaging (fMRI) and demonstrated that gustatory imagery is mediated by the prefrontal (PFC) and insular cortices (IC). Howe...

Kobayashi, M.; Sasabe, T.; Shigihara, Y.; Tanaka, M.; Watanabe, Y.

2011-01-01

230

Temporal Processing of Audiovisual Stimuli Is Enhanced in Musicians: Evidence from Magnetoencephalography (MEG)  

Science.gov (United States)

Numerous studies have demonstrated that the structural and functional differences between professional musicians and non-musicians are not only found within a single modality, but also with regard to multisensory integration. In this study we have combined psychophysical with neurophysiological measurements investigating the processing of non-musical, synchronous or various levels of asynchronous audiovisual events. We hypothesize that long-term multisensory experience alters temporal audiovisual processing already at a non-musical stage. Behaviorally, musicians scored significantly better than non-musicians in judging whether the auditory and visual stimuli were synchronous or asynchronous. At the neural level, the statistical analysis for the audiovisual asynchronous response revealed three clusters of activations including the ACC and the SFG and two bilaterally located activations in IFG and STG in both groups. Musicians, in comparison to the non-musicians, responded to synchronous audiovisual events with enhanced neuronal activity in a broad left posterior temporal region that covers the STG, the insula and the Postcentral Gyrus. Musicians also showed significantly greater activation in the left Cerebellum, when confronted with an audiovisual asynchrony. Taken together, our MEG results form a strong indication that long-term musical training alters the basic audiovisual temporal processing already in an early stage (direct after the auditory N1 wave), while the psychophysical results indicate that musical training may also provide behavioral benefits in the accuracy of the estimates regarding the timing of audiovisual events.

Lu, Yao; Paraskevopoulos, Evangelos; Herholz, Sibylle C.; Kuchenbuch, Anja; Pantev, Christo

2014-01-01

231

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

232

The breakdown of dipolar magnetic field generation in planetary dynamo models (Invited)  

Science.gov (United States)

Magnetic field measurements show that each dynamo in our solar system is distinct with field strengths that differ by many orders of magnitude and morphologies that range from titled dipoles to nearly axisymmetric dipole-quadrupoles to non-axisymmetric multipoles. The characteristics of stellar and astrophysical magnetic fields are similarly wide-ranging. Towards understanding the diversity of this dynamo zoo, we investigate the breakdown of dipole-dominated magnetic fields in a suite of planetary dynamo and otherwise identical non-magnetic simulations where the convective vigor and rotation rate are varied systematically. This survey considers models with Prandtl number Pr=1, magnetic Prandtl numbers up to Pm = 5, Ekman numbers in the range 1e-3 <= E <= 1e-5, and Rayleigh numbers from near onset to more than 1000 times critical. A sharp transition from dipolar to multipolar dynamos is observed in models with moderate to high Ekman numbers. This breakdown of the dipole happens when inertial and viscous forces become comparable and coincides with a degradation of helicity in the flow, which also occurs when no magnetic field is present. Large-scale poloidal magnetic fields in these models then appear to be generated by a viscously controlled, macro-scale alpha-effect. Our lowest Ekman number cases, however, suggest that the dynamics may be changing as the viscous force decreases. Since viscosity is expected to be negligible in planetary and stellar interiors, an extrapolation of our results implies that moderate Ekman number models may not simulate the physical mechanisms of magnetic field generation in these bodies correctly.

Soderlund, K. M.; King, E. M.; Aurnou, J. M.

2013-12-01

233

Searching for Surficial Deposits on Venus Using Multi-Polarization Radar  

Science.gov (United States)

Introduction. The Magellan spacecraft returned hundreds of images of craters, radardark halos, and wind features on Venus. It is clear that surficial layers are associated with some of these features; for example, 59 of the craters have parabolic shaped deposits that are thought to be a few centimeters to a meter in thickness. Magellan also revealed about 400 radar dark "splotches" that may be places where a smooth rubble layer was formed when the shock wave from an impactor hit the surface and crushed the rock. Two dune fields and several areas of microdunes were identified in Magellan data, as well a few thousand windstreaks, so it is clear that dust is transported and redeposited by wind. Thin surficial layers that are not clearly visible in the Magellan imagery may be present in other regions as well. In fact, many surfaces on Venus that were imaged by Magellan SAR may look much different when viewed at optical wavelengths, since radar waves penetrate surface layers and show details of the underlying terrain. A good example is the L-Band (24 cm wavelength) shuttle imaging radar (SIRA) observations by McKauley et al. who detected buried river valleys in the Arbain Desert in southern Egypt.

Carter, Lynn M.; Campbell, Donald B.; Campbell, Bruce A.; Margot, Jean-Luc

2003-01-01

234

Reshaping Europe In A Multipolar World: Can The EU Rise To The Challenge?  

Directory of Open Access Journals (Sweden)

Full Text Available Globalisation and the emergence of economic players such as Brazil, Russia, India and China (BRIC have led to predictions that US hegemony will quickly decline as a new world order emerges. With the European Union (EU also facing a downgrading of its own status – as economic, political and cultural power shifts from west to east – now is the time to ensure the Union has a strategy in place to remain an influential global actor despite its lack of natural resources and member state sovereign debt arising from the 2008/9 economic crisis. Only concerted efforts at institutional future-proofing (or widening and deepening plus by the EU and a global vision for the supranational body will ensure its survival and prosperity.

Dean Carroll

2011-09-01

235

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

Directory of Open Access Journals (Sweden)

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

236

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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 antiarrhythm [...] ic 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.

Almino C., Rocha Neto; Roberto Lima, Farias; Angelo A. V., de Paola.

237

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.)

1986-01-16

238

The effect of antiferromagnetic interchain coupling on multipolar phases in quasi-1D quantum helimagnets  

International Nuclear Information System (INIS)

Coupled s = 1/2 frustrated Heisenberg chains with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor exchange interactions in high magnetic field are studied by density-matrix renormalization group (DMRG) and hard-core boson (HCB) approaches at T = 0. First, we propose an appropriate one-dimensional array for the construction of a 3D system to be studied with the DMRG method and demonstrate the performance by comparing the ground-state energy to the exact solution. Next, the binding energy of multimagnon bound state is calculated as a function of interchain coupling. We find that the multimagnon bound state is easily destroyed by weak interchain coupling. In the 2-magnon phase the DMRG results are supported by the HCB approach.

2012-12-17

239

The effect of antiferromagnetic interchain coupling on multipolar phases in quasi-1D quantum helimagnets  

Science.gov (United States)

Coupled s = 1/2 frustrated Heisenberg chains with ferromagnetic nearest-neighbor and antiferromagnetic next-nearest-neighbor exchange interactions in high magnetic field are studied by density-matrix renormalization group (DMRG) and hard-core boson (HCB) approaches at T = 0. First, we propose an appropriate one-dimensional array for the construction of a 3D system to be studied with the DMRG method and demonstrate the performance by comparing the ground-state energy to the exact solution. Next, the binding energy of multimagnon bound state is calculated as a function of interchain coupling. We find that the multimagnon bound state is easily destroyed by weak interchain coupling. In the 2-magnon phase the DMRG results are supported by the HCB approach.

Nishimoto, S.; Drechsler, S.-L.; Kuzian, R. O.; Richter, J.; van den Brink, J.

2012-12-01

240

Kinematics and H_2 morphology of the multipolar Post-AGB star IRAS 16594-4656  

CERN Document Server

context: The spectrum of IRAS 16594-4656 shows shock excited H_2 emission and collisionally excited emission lines such as[O I],[C I],and [Fe II]. aim: The goal is to determine the location of the H_2 and [Fe II] shock emission, to determine the shock velocities,and constrain the physical properties in the shock. methods: High resolution spectra of the H_2 1-0 S(1),H_2 2-1 S(1), [Fe II], and Pa$\\beta$ emission lines were obtained with the near infrared spectrograph Phoenix on Gemini South. results: The position-velocity diagrams of H_2 1-0 S(1), H_2 2-1 S(1), and [Fe II] are presented. The H_2 and [Fe II] emission is spatially extended. The collisionally excited [O I] and [C I] optical emission lines have a similar double peaked profile compared to the extracted H_2 profile and appear to be produced in the same shock. They all indicate an expansion velocity of ~8 km/s and the presence of a neutral, very high density region with $n_{\\rm e}$ about 3 x 10^6 to 5 x10^7 cm$^{-3}$. The [Fe II] emission however is s...

Van de Steene, G C; Van Hoof, P A M; Reyniers, M; Ginsburg, A G

2008-01-01

 
 
 
 
241

Kinematics and H_2 morphology of the multipolar Post-AGB star IRAS 16594-4656  

Digital Repository Infrastructure Vision for European Research (DRIVER)

context: The spectrum of IRAS 16594-4656 shows shock excited H_2 emission and collisionally excited emission lines such as[O I],[C I],and [Fe II]. aim: The goal is to determine the location of the H_2 and [Fe II] shock emission, to determine the shock velocities,and constrain the physical properties in the shock. methods: High resolution spectra of the H_2 1-0 S(1),H_2 2-1 S(1), [Fe II], and Pa$\\beta$ emission lines were obtained with the near infrared spectrograph Phoenix o...

Steene, G. C.; Ueta, T.; Hoof, P. A. M.; Reyniers, M.; Ginsburg, A. G.

2008-01-01

242

Multifrequency and multipolarization radar scatterometry of sand dunes and comparison with spaceborne and airborne radar images  

Science.gov (United States)

Airborne radar scatterometer data on sand dunes, acquired at multiple frequencies and polarizations, are reported. Radar backscatter from sand dunes is very sensitive to the imaging geometry. At small incidence angles the radar return is mainly due to quasi-specular reflection from dune slopes favorably oriented toward the radar. A peak return usually occurs at the incidence angle equal to the angle of repose for the dunes. The peak angle is the same at all frequencies as computed from specular reflection theory. At larger angles the return is significantly weaker. The scatterometer measurements verified observations made with airborne and spaceborne radar images acquired over a number of dune fields in the U.S., central Africa, and the Arabian peninsula. The imaging geometry constraints indicate that possible dunes on other planets, such as Venus, will probably not be detected in radar images unless the incidence angle is less than the angles of repose of such dunes and the radar look direction is approximately orthogonal to the dune trends.

Blom, Ronald; Elachi, Charles

1987-01-01

243

Multi-Polarization ASAR Backscattering from Herbaceous Wetlands in Poyang Lake Region, China  

Directory of Open Access Journals (Sweden)

Full Text Available Wetlands are one of the most important ecosystems on Earth. There is an urgent need to quantify the biophysical parameters (e.g., plant height, aboveground biomass and map total remaining areas of wetlands in order to evaluate the ecological status of wetlands. In this study, Environmental Satellite/Advanced Synthetic Aperture Radar (ENVISAT/ASAR dual-polarization C-band data acquired in 2005 is tested to investigate radar backscattering mechanisms with the variation of hydrological conditions during the growing cycle of two types of herbaceous wetland species, which colonize lake borders with different elevation in Poyang Lake region, China. Phragmites communis (L. Trin. is semi-aquatic emergent vegetation with vertical stem and blade-like leaves, and the emergent Carex spp. has rhizome and long leaves. In this study, the potential of ASAR data in HH-, HV-, and VV-polarization in mapping different wetland types is examined, by observing their dynamic variations throughout the whole flooding cycle. The sensitivity of ASAR backscattering coefficients to vegetation parameters of plant height, fresh and dry biomass, and vegetation water content is also analyzed for Phragmites communis (L. Trin. and Carex spp. The research for Phragmites communis (L. Trin. shows that HH polarization is more sensitive to plant height and dry biomass than HV polarization. ASAR backscattering coefficients are relatively less sensitive to fresh biomass, especially in HV polarization. However, both are highly dependent on canopy water content. In contrast, the dependence of HH- and HV- backscattering from Carex community on vegetation parameters is poor, and the radar backscattering mechanism is controlled by ground water level.

Huiyong Sang

2014-05-01

244

The World Bank and the emerging world order: Adjusting to multipolarity at the second decimal point  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The report provides a brief overview of the World Bank’s key governance arrangements and the evolution of the voice reform agenda at the bank from 2003 to 2007. It further examines two bank reform phases (in 2008 and 2010), and critically assesses the key components of the voice reform process (or voting power realignment), and identifies some problems that will arise as a result, especially with respect to future shareholding reviews.

2011-01-01

245

The Paris financial market in the 19th century: an efficient multi-polar organization?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The literature in financial history usually considers London as the only centre of the late 19th century's financial globalization, and explains it at least in part by the efficient microstructure (organization) of the London Stock Exchange (LSE). The LSE is characterized as having been a little regulated market, where entry was easy both for traders and issuers [Michie (1998), Neal (2004), White (2006)]. The LSE microstructure is also considered as the natural and optimal one by much of the ...

Hautcoeur, Pierre-cyrille; Riva, Angelo

2007-01-01

246

Multipolarity of the 228.5-keV transition in 80Y  

International Nuclear Information System (INIS)

We have unambiguously characterized the deexcitation of the 228.5-keV T1/2=4.7-s isomer in 80Y as an M3 transition. This result determines, in conjunction with other experimental data, the spin and parity of the 228.5-keV isomer and the 80Y ground state as 1- and 4-, respectively. (c) 2000 The American Physical Society

2000-04-01

247

The Fate of Chrysotile-Induced Multipolar Mitosis and Aneuploid Population in Cultured Lung Cancer Cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Chrysotile is one of the six types of asbestos, and it is the only one that can still be commercialized in many countries. Exposure to other types of asbestos has been associated with serious diseases, such as lung carcinomas and pleural mesotheliomas. The association of chrysotile exposure with disease is controversial. However, in vitro studies show the mutagenic potential of chrysotile, which can induce DNA and cell damage. The present work aimed to analyze alterations in lung small cell c...

Araujo Cortez, Beatriz; Quassollo, Gonzalo; Caceres, Alfredo; Machado-santelli, Glaucia Maria

2011-01-01

248

Multi-frequency, multi-polarization SAR and radiometer sea ice classification  

Science.gov (United States)

Microwave remotely sensed data were acquired simultaneously in March 1988 over Beaufort, Chukchi, and Bering Sea ice using the JPL multifrequency, polarimetric synthetic aperture radar (SAR), and multifrequency dual-polarization GSFC radiometer. The experiment was conducted as a series of coordinated underflights of the DMSP SSM/I satellite radiometer to validate ice products derived from its radiance values. Concurrent flights by an NRL P-3 aircraft enabled overlapping high-resolution, single-frequency images to be acquired over the same surfaces using a Ka-band scanning microwave radiometer. Precise coregistration to an accuracy of 100 m, +/- 25 m enables comparison of temporally and spatially coincident active and passive microwave datasets. Three-channel polarimetric SAR data are compared with dual-polarized radiometer data at several SSM/I frequencies, showing backscatter signatures to be highly correlated with radiometric temperatures. Further comparisons are used to evaluate ice concentration retrievals and to show how multiparameter datasets can be used to resolve ambiguities present in identifying certain sea ice forms with a single microwave instrument.

Drinkwater, Mark R.; Crawford, John P.; Cavalieri, Donald J.

1991-01-01

249

On Fast, Polarimetric Non-Reciprocal Calibration and Multipolarization Measurements on Weather Radars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study a calibration concept for a multi-polarimetric weather radar is developed. Several common calibration techniques are analysed, but many are insufficient due to the non-reciprocal behaviour of the employed radar. Hence, an electronic calibration device was developed, which was designed for fast polarization determination of any polarization (including elliptical ones). The non-reciprocal behaviour was overcome by splitting receive and transmit calibration, which virtually uses th...

2014-01-01

250

Antihydrogen formation dynamics in a multipolar neutral anti-atom trap  

International Nuclear Information System (INIS)

Antihydrogen production in a neutral atom trap formed by an octupole-based magnetic field minimum is demonstrated using field-ionization of weakly bound anti-atoms. Using our unique annihilation imaging detector, we correlate antihydrogen detection by imaging and by field-ionization for the first time. We further establish how field-ionization causes radial redistribution of the antiprotons during antihydrogen formation and use this effect for the first simultaneous measurements of strongly and weakly bound antihydrogen atoms. Distinguishing between these provides critical information needed in the process of optimizing for trappable antihydrogen. These observations are of crucial importance to the ultimate goal of performing CPT tests involving antihydrogen, which likely depends upon trapping the anti-atom.

2010-03-01

251

Resonant X-ray scattering and multipolar order in actinide dioxides  

International Nuclear Information System (INIS)

Full text of publication follows: The discovery in 2002 of electric quadrupole ordering in the NpO2 opened a new chapter in the understanding of the low-temperature ground states of actinide dioxides, insulating compounds with the simple cubic CaF2 crystal structure and general formula U1-xNpxO2 (0 ? x ? 1). The phenomenon found at 25 K in NpO2 is that the 5f charge distribution develops an anisotropic component, with long-range ordering of the charge quadrupoles driven by a primary magnetic octupolar order parameter belonging to the totally symmetric irreducible representation of L = 3 in D3d symmetry (?1). The experiments consist of tuning the photon energy to the actinide M absorption edge (at which photon energy core 3d electrons are promoted to the partially occupied 5f valence states), and then, once the repeat of the anisotropic charge distribution is known, to measure the azimuthal distribution of the scattered resonant x-ray intensity. This intensity distribution is related to the symmetry of the 5f anisotropic charge distribution. The experiments were performed at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, with the single crystals mounted in ITU. NpO2 shows no measurable magnetic dipole component. In 2003 experiments were performed on a single crystal with x = 0.25. Dipole ordering was found on both the U and Np ions, and quadrupolar ordering was also found associated with both ions. However, these were different from those in pure NpO2. Whereas a longitudinal (L) 3-k configuration was found for NpO2, the x = 0.25 sample was found to have a transverse (T) 3-k configuration. The understanding of these different configurations then allowed an experiment to be performed in 2005 on a single crystal of UO2. The azimuthal dependence of the intensity from non-specular reflections reveals 3-k T anti-ferro-electric-quadrupolar order also UO2. The complication in UO2 is that both dipole ordering and an internal distortion of the oxygen atoms due to the quadrupole ordering are present; these have contrived to make it difficult to observe directly the quadrupole ordering in UO2, although such ordering was predicted almost 40 years ago, and the oxygen displacements reported 30 years ago [5]. These experiments also suggest a qualitative explanation of the unusual behaviour of the mixed oxides with 0.40 < x < 0.80. In this region there is competition between the L and T quadrupole ordering, resulting in quadrupolar frustration and only short-range dipole and quadrupole ordering. (authors)

2007-01-01

252

High-multipolar effects on the Casimir force: the non-retarded limit  

CERN Document Server

We calculate exactly the Casimir force or dispersive force, in the non-retarded limit, between a spherical nanoparticle and a substrate beyond the London's or dipolar approximation. We find that the force is a non-monotonic function of the distance between the sphere and the substrate, such that, it is enhanced by several orders of magnitude as the sphere approaches the substrate. Our results do not agree with previous predictions like the Proximity theorem approach.

Noguez, C; Esquivel-Sirvent, R; Villarreal, C; Noguez, Cecilia; Roman-Velazquez, Carlos E.; Esquivel-Sirvent, Raul; Villarreal, Carlos

2003-01-01

253

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

254

The impact of the new Earth gravity models on the measurement of the Lense-Thirring effect with a new satellite  

CERN Document Server

In this paper we investigate the opportunities offered by the new Earth gravity models from the dedicated CHAMP and, especially, GRACE missions to the project of measuring the general relativistic Lense-Thirring effect with a new Earth's artificial satellite. It turns out that it would be possible to abandon the stringent, and expensive, requirements on the orbital geometry of the originally prosed LARES mission (same semimajor axis a=12270 km of the existing LAGEOS and inclination i=70 deg) by inserting the new spacecraft in a relatively low, and cheaper, orbit (a=7500-8000 km, i\\sim 70 deg) and suitably combining its node Omega with those of LAGEOS and LAGEOS II in order to cancel out the first even zonal harmonic coefficients of the multipolar expansion of the terrestrial gravitational potential J_2, J_4 along with their temporal variations. The total systematic error due to the mismodelling in the remaining even zonal harmonics would amount to \\sim 1% and would be insensitive to departures of the inclinat...

Iorio, L

2005-01-01

255

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.  

Science.gov (United States)

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 microV (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. PMID:19491442

Gilad, O; Horesh, L; Holder, D S

2009-06-01

256

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. 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

2005-07-07

257

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Skoblov Nikita

2011-09-01

258

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

259

Modeling the variability of EEG/MEG data through statistical machine learning  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Brain neural activity generates electrical discharges, which manifest as electrical and magnetic potentials around the scalp. Those potentials can be registered with magnetoencephalography (MEG) and electroencephalography (EEG) devices. Data acquired by M/EEG is extremely difficult to work with due to the inherent complexity of underlying brain processes and low signal-to-noise ratio (SNR). Machine learning techniques have to be employed in order to reveal the underlying structure of the sign...

Zaremba, Wojciech

2012-01-01

260

Testing the geomagnetic dipole and reversing dynamo models over Earth's cooling history  

Science.gov (United States)

Continental drift reconstructions rely on the assumption that Earth's mean magnetic field has been a geocentric axial dipole over geologic time. However, the coupled dynamics of mantle and core convection may have had profound effects on the magnetic field in the distant past. Previous dynamo models have linked differences between polar and equatorial mantle heat flow to apparently anomalous paleomagnetic fields, and changes in reversal frequency. Here we use the inclination test (Evans, 1976) to interpret observational magnetic field models and polarity-reversing numerical dynamos representing various convective states of the mantle and core. Dynamo models with uniform buoyancy flux represent three convective states of the mantle and core: (1) present era Earth, driven thermo-chemically at the inner core boundary; (2) mantle overturn, with elevated heat flux at the core-mantle boundary, and (3) ancient Earth prior to inner core nucleation, with buoyancy production solely at the CMB. Consistent with Earth's present magnetic field, dynamos driven by buoyancy due to inner core growth are nearly dipolar. In contrast, elevated CMB heat flow yields small to moderate inclination flattening due to a persistent octupole that reverses synchronously with the dipole. For the ancient Earth models the relatively strong octupole component tends to stabilize the dynamo and decrease the reversal frequency. Our results, along with evidence of a young inner core, imply that an entirely liquid core contributed to shallow inclinations in Precambrian time. We also run models with latitudinally variable heat flux boundary conditions to further investigate the relationship between dynamo flow fields, the octupole component, magnetic inclinations and reversal frequency. For models with increased polar CMB heat flux we find that the relative strength of the octupole component increases in proportion to latitudinal heat flux variation. On the other hand, models are very sensitive to enhanced equatorial CMB cooling, which rapidly leads to unstable, multipolar dynamos with high reversal frequencies. This asymmetry in sensitivity to latitudinal variations in CMB heat flux implies that such variations are likely to yield only small inclination anomalies.

Heimpel, Moritz; Evans, Ted

2014-05-01

 
 
 
 
261

Solution for MEG inverse problem using Signal Space Separation and Magnetic Field Tomography  

Science.gov (United States)

Magnetic Field Tomography (MFT) is a source localization method for Magnetoencephalography (MEG), a non-invasive method to observe the brain activity. MFT just requires the source to be a linear combination of lead fields that describe the distribution of the sensitivity of each sensor, while other commonly used MEG source localization methods such as equivalent current dipole (ECD) fitting or the beamformer require some more inappropriate assumptions. However, less requirements on the source results in a huge amount of computational load in MFT. In this paper, the reduction of the computational load for MFT was achieved by considering the coefficients of multipolar expansion as the measurements of virtual sensors. These coefficients are obtained by performing Signal Space Separation (SSS) in which the exclusion of external magnetic field generated by the external sensor arrays is enabled. Based on our simulation, the calculation time was reduced from 6 hours to about 10 seconds preserving the source localization ability.

Kitahara, Tadashi; Honda, Satoshi

2011-06-01

262

Chaoticity and Dissipation of Nuclear Collective Motion in a Classical Model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We analyze the behavior of a gas of classical particles moving in a two-dimensional "nuclear" billiard whose multipole-deformed walls undergo periodic shape oscillations. We demonstrate that a single particle Hamiltonian containing coupling terms between the particles' motion and the collective coordinate induces a chaotic dynamics for any multipolarity, independently on the geometry of the billiard. The absence of coupling terms allows us to recover qualitatively the "wall ...

Baldo, M.; Burgio, G. F.; Rapisarda, A.; Schuck, P.

1996-01-01

263

Departure from Network Equilibrium (DNE): an efficient and scalable measure of instantaneous network dynamics, with an application to magnetoencephalography.  

Science.gov (United States)

The assessment of the dynamic status of a network is currently unavailable. It is important to know how far a network is away from its equilibrium (as an indicator of instability) at a moment, and over periods of time. Here, we introduce the Departure from Network Equilibrium (DNE), a new measure of instantaneous network dynamics. DNE is simple, fast to compute, and scalable with network size. We present the results of its application on white noise networks (as a basis) and on networks derived from magnetoencephalographic recordings from the human brain. PMID:24154959

Mahan, Margaret Y; Leuthold, Arthur C; Georgopoulos, Apostolos P

2014-01-01

264

Neural responses to auditory stimulus deviance under threat of electric shock revealed by spatially-filtered magnetoencephalography  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Stimulus novelty or deviance may be especially salient in anxiety-related states due to sensitization to environmental change, a key symptom of anxiety disorders such as posttraumatic stress disorder (PTSD). We aimed to identify human brain regions that show potentiated responses to stimulus deviance during anticipatory anxiety. Twenty participants (14 men) were presented a passive oddball auditory task in which they were exposed to uniform auditory stimulation of tones with occasional deviat...

Cornwell, Brian R.; Baas, Johanna M. P.; Johnson, Linda; Holroyd, Tom; Carver, Frederick W.; Lissek, Shmuel; Grillon, Christian

2007-01-01

265

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.

Llinas, Rodolfo R.; Ustinin, Mikhail N.

2014-01-01

266

Potential role for magnetoencephalography in distinguishing low- and high-grade gliomas: a preliminary study with histopathological confirmation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Gliomas are the most common form of tumor in the CNS and are exceptionally heterogeneous. Accurately characterizing gliomas, in terms of grade and type, is essential for predicting the rate of tumor progression. Histopathological grading and analysis based on biopsied tissue remains the gold standard, but non- and semi-invasive neuroimaging also plays a key role. Neuroimaging has been used to guide and optimize biopsies for several decades, but more recently molecular imaging and variants of ...

Wilson, Tony W.; Heinrichs-graham, Elizabeth; Aizenberg, Michele R.

2012-01-01

267

Potential role for magnetoencephalography in distinguishing low- and high-grade gliomas: a preliminary study with histopathological confirmation  

Science.gov (United States)

Gliomas are the most common form of tumor in the CNS and are exceptionally heterogeneous. Accurately characterizing gliomas, in terms of grade and type, is essential for predicting the rate of tumor progression. Histopathological grading and analysis based on biopsied tissue remains the gold standard, but non- and semi-invasive neuroimaging also plays a key role. Neuroimaging has been used to guide and optimize biopsies for several decades, but more recently molecular imaging and variants of MRI have shown promise in independently predicting glioma grade. Here we evaluated whether magnetoencephalographic (MEG) measurements of population-level physiology within the glioma space were predictive of the inherent grade of the tissue, based on definitive histopathological analyses. High-density MEG data were recorded from 11 patients who were undergoing functional mapping in preparation for resective surgery. The primary results indicated that glioma grade was positively correlated with the local amplitude of activity within the glioma space in the theta (4–7 Hz), alpha (8–14 Hz), and beta bands (14–30 Hz). Additionally, activity within the glioma was significantly elevated relative to the nonaffected homologue area in the same frequency bands. These results indicate that pathological levels of synchronization exist within the tumor space and that MEG may be a viable tool for noninvasively differentiating gliomas by their grade. Although these results should be considered preliminary and are only correlative in nature, these data suggest that MEG can potentially detect neurophysiological signatures or markers that predict the inherent grade of a glial tumor.

Wilson, Tony W.; Heinrichs-Graham, Elizabeth; Aizenberg, Michele R.

2012-01-01

268

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

269

Las relaciones entre Colombia y Brasil en un contexto de regionalización diversificada en Suramérica y de un mundo multipolar emergente / The Relationship between Colombia and Brazil in the Context of Regional Diversification in South America and an Increasingly Multipolar World  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: Spanish Abstract in spanish El artículo interpreta los desafíos que tiene la política exterior colombiana, tanto en el plano regional como en el global, de cara a la proyección de Brasil como potencia regional y jugador global. Para ello, en primer lugar, se lleva a cabo un acercamiento teórico al escenario regional actual y a [...] l horizonte de las relaciones colombo-brasileñas, desde la perspectiva de algunos presupuestos del realismo neoclásico (predominantemente) y del neoliberalismo institucional (subsidiariamente). En segundo lugar, se examinan las fuentes y alcances de la presunta caída de la hegemonía norteamericana y el ascenso gradual de la hegemonía brasileña en Suramérica. En tercer lugar, se analiza la calidad de Colombia como potencia secundaria, luego la diversificación geográfica y temática de su política exterior a partir de agosto de 2010, y sus estrategias de competencia y cooperación con respecto a Brasil en la región. Finalmente, se identifican y se interpretan las perspectivas bilaterales y multilaterales de la profundización de los intercambios y compromisos entre Colombia y Brasil, que tendrían un alto potencial para institucionalizar una alianza estratégica multitemática con repercusiones importantes para impulsar y afianzar el proceso de regionalización en Suramérica. Abstract in english This article interprets the challenges of Colombia's foreign policy, both on a regional and global level, with regard to Brazil's ambitions as a regional power and global player. First, a theoretical analysis of the current regional scenario and the horizon of the Colombian-Brazilian relations is do [...] ne, mainly from various neoclassical realist positions and also from institutional neoliberal viewpoints. Second, sources and impact of the proclaimed decay of the North American hegemony and the gradual rise of a Brasilian hegemony in South America are examined. Third, Colombia's capacity as a secondary power is analized, followed by an analysis of the geographic and thematic diversification of its foreign policy since August 2010, as well as its strategy of competition and cooperation with Brazil in the region. Finally, those bilateral and multilateral perspectives of profundization of the exchanges and committments between Brazil and Colombia are identified and interpreted, which would have a high potential to be institutionalized as a strategic multithematic alliance with an important impact to promote and strengthen the regionalization process in South America.

Eduardo, Pastrana Buelvas; Diego, Vera Piñeros.

270

Política e acção pública: Entre uma regulação centralizada e uma regulação multipolar / Politique et action publique.: D’une régulation centrale à une régulation multipolaire / Policy and public action.: From central regulation to multipolar regulation  

Scientific Electronic Library Online (English)

Full Text Available SciELO Portugal | Language: Portuguese Abstract in portuguese Este texto situa-se no campo alargado da análise política e tem o propósito de contribuir para a compreensão do processo de construção e regulação das políticas públicas, dando conta da complexidade do processo que vai muito para além do momento da decisão, implicando diferentes instâncias e uma gra [...] nde multiplicidade de actores. Constitui uma reflexão, construída a partir das análises, interrogações, comentários e críticas produzidas por diferentes autores, a partir de diferentes prismas, que incidiram sobre a política educativa portuguesa das últimas décadas, no que diz respeito à autonomia das escolas e aos efeitos observados na aplicação das medidas que a invocaram, particularmente no que se refere aos projectos, aqui considerados como instrumentos para resolver problemas e criar oportunidades na fronteira entre o social e o político. Representa ainda a oportunidade de mostrar a importância do tempo na construção e análise das políticas públicas. Abstract in english This text provides an overview of the broadened field of the policy analysis with the aim of contributing for the understanding of the process of construction and regulation of public policies. It gives account of the complexity of the process that goes beyond the moment of decision, implying differ [...] ent spaces and a great multiplicity of actors. Our reflection derives from the critical analyses, interrogations and commentaries on the Portuguese educational policy, made by different authors, and from different prisms, in the last decades, on the autonomy of the schools, and the effects observed in the implementation of the measures invoked by that autonomy. Particularly, we will consider projects, considered here as tools to solve problems and create opportunities on the borders between the social and the political. It also represents an opportunity to show the importance of the space and temporal dimension for the construction and analysis of the public policies.

Maria Madalena, Fontoura.

271

Multi-frequency and multi-polarization measurements of water surface radar cross section and brightness temperature angular dependences  

Science.gov (United States)

In this paper the results of simultaneous and spatially coincident, multi-frequency, polarimetric, spatio-temporally collocated measurements of waved pool water surface microwave reflective (radar backscattering coefficient) and emissive (brightness temperature) characteristics angular dependences at 5.6GHz, 15GHz and 37GHz are presented. Angular measurements were carried out for various water surface roughness parameters at clear air, cloudy and rain conditions. For these measurements C-, Ku and Ka-band, polarimetric, combined scatterometric-radiometric systems were used, set jointly on a mobile buggy moving along the measuring platform. Structures, operational features and the main technical characteristics of the utilized systems are presented too. The paper has an aim as well to attract attention of interested researchers and to invite them to perform their own or joint researches using available devices and facilities.

Arakelyan, Artashes K.; Hambaryan, Astghik K.; Arakelyan, Arsen A.; Grigoryan, Melanya L.

2011-10-01

272

Actant Models  

DEFF Research Database (Denmark)

This paper presents a functional modelling method called Actant Modelling rooted in linguistics and semiotics. Actant modelling can be integrated with Multilevel Flow Modelling (MFM) in order to give an interpretation of actants.

Poulsen, Helle

1996-01-01

273

Saturation and time dependence of geodynamo models  

CERN Document Server

In this study we address the question under which conditions a saturated velocity field stemming from geodynamo simulations leads to an exponential growth of the magnetic field in a corresponding kinematic calculation. We perform global self-consistent geodynamo simulations and calculate the evolution of a kinematically advanced tracer field. The self-consistent velocity field enters the induction equation in each time step, but the tracer field does not contribute to the Lorentz force. This experiment has been performed by Cattaneo & Tobias (2009) and is closely related to the test field method by Schrinner et al. (2005, 2007). We find two dynamo regimes in which the tracer field either grows exponentially or approaches a state aligned with the actual self-consistent magnetic field after an initial transition period. Both regimes can be distinguished by the Rossby number and coincide with the dipolar and multipolar dynamo regimes identified by Christensen & Aubert (2006). Dipolar dynamos with low Ros...

Schrinner, M; Cameron, R; Hoyng, P

2009-01-01

274

Modelling the models  

CERN Multimedia

By analysing the production of mesons in the forward region of LHC proton-proton collisions, the LHCf collaboration has provided key information needed to calibrate extremely high-energy cosmic ray models.   Average transverse momentum (pT) as a function of rapidity loss ?y. Black dots represent LHCf data and the red diamonds represent SPS experiment UA7 results. The predictions of hadronic interaction models are shown by open boxes (sibyll 2.1), open circles (qgsjet II-03) and open triangles (epos 1.99). Among these models, epos 1.99 shows the best overall agreement with the LHCf data. LHCf is dedicated to the measurement of neutral particles emitted at extremely small angles in the very forward region of LHC collisions. Two imaging calorimeters – Arm1 and Arm2 – take data 140 m either side of the ATLAS interaction point. “The physics goal of this type of analysis is to provide data for calibrating the hadron interaction models – the well-known &...

Anaïs Schaeffer

2012-01-01

275

Modelling SDL, Modelling Languages  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

2007-01-01

276

Promoting Models  

Science.gov (United States)

There can be multitudinous models specifying aspects of the same system. Each model has a bias towards one aspect. These models often override in specific aspects though they have different expressions. A specification written in one model can be refined by introducing additional information from other models. The paper proposes a concept of promoting models which is a methodology to obtain refinements with support from cooperating models. It refines a primary model by integrating the information from a secondary model. The promotion principle is not merely an academic point, but also a reliable and robust engineering technique which can be used to develop software and hardware systems. It can also check the consistency between two specifications from different models. A case of modeling a simple online shopping system with the cooperation of the guarded design model and CSP model illustrates the practicability of the promotion principle.

Li, Qin; Zhao, Yongxin; Wu, Xiaofeng; Liu, Si

277

Models within models  

International Nuclear Information System (INIS)

Anyone who worries that physicists are running out of interesting challenges to tackle and important problems to solve should read the two, very different feature articles in this issue. In 'Climate change: complexity in action', Klaus Hasselmann and colleagues write about the challenges of including economic and political dimensions in computer simulations of climate change. It is hard to imagine a physics-based topic that has a greater impact on the world at large. In 'Quarks, diquarks and pentaquarks', Robert Jaffe and Frank Wilczek describe our current understanding of quantum chromodynamics and the strong nuclear force. In this case it is hard to think of many more difficult problems in fundamental physics. Traditional climate modelling is difficult enough because a whole range of effects in the atmosphere and the oceans have to be taken into account. It typically takes weeks for a state-of-the-art supercomputer to simulate 100 years of climate change with a horizontal resolution of 100 km. But climate change is about much more than solving difficult differential equations - there are crucial social, political and economic influences as well. Some researchers, including a significant number of physicists, have started to look at this integrated-assessment approach. The first challenge is to develop climate models that take minutes to run on a laptop. The next challenge is to develop analogous models that work in the social, political and economic arenas - which is not a trivial task - and then integrate all these different models and explore all the possible global-warming scenarios. Physicists also hope to integrate quantum chromodynamics (QCD) into the larger framework of a so-called theory of everything. Like climate modellers, particle theorists working on QCD require enormous computational resources for their calculations, and even then there are limits to what can be achieved (e.g. the mass of the proton has yet to be calculated from first principles). However, QCD can explain the results of an enormous range of experiments, and has recently been given some new particles - 'pentaquarks' - to get its teeth into. Moreover, physicists searching for a theory of everything can take heart from the fact that, unlike researchers working on integrated-assessment models, they already have highly successful theories for the phenomena they are trying to unify. However, the ultimate challenge for the climate community will be to persuade governments and big business that they need to do something to avoid the potentially disastrous consequences of climate change. The UK's chief scientific advisor, David King, made headlines recently when he wrote that, in his view, 'climate change is the most severe problem that we are facing today - more serious even than the threat of terrorism' (Science 303 176-177). It is too soon to say if the message is getting through, but at least climate scientists now have an unlikely ally in the shape of the climate-change disaster movie The Day After Tomorrow. (U.K.)

2004-06-01

278

Task-modulated “what” and “where” pathways in human auditory cortex  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Human neuroimaging studies suggest that localization and identification of relevant auditory objects are accomplished via parallel parietal-to-lateral-prefrontal “where” and anterior-temporal-to-inferior-frontal “what” pathways, respectively. Using combined hemodynamic (functional MRI) and electromagnetic (magnetoencephalography) measurements, we investigated whether such dual pathways exist already in the human nonprimary auditory cortex, as suggested by animal models, and whether se...

Ahveninen, Jyrki; Ja?a?skela?inen, Iiro P.; Raij, Tommi; Bonmassar, Giorgio; Devore, Sasha; Ha?ma?la?inen, Matti; Leva?nen, Sari; Lin, Fa-hsuan; Sams, Mikko; Shinn-cunningham, Barbara G.; Witzel, Thomas; Belliveau, John W.

2006-01-01

279

Energy-level transitions between low-lying states of the 38Cl  

International Nuclear Information System (INIS)

Analyzed were given probabilities (GP) of electromagnetic transitions between lower states of negative 38Cl nucleus parity in an odd nucleus+neutron model. The analysis results were: energies, spins parities and configurations of levels; transitions energies and multipolarities, measured and estimated values of transition GP and their matrix elements are tabulated 4- spin is suggested for 1785 keV state. Obtained estimates of probabilities of a number of mixed E2 transitions need to be tested, therefore it is necessary to measure the mixture of 38Cl transition multipolarities and to determine the sign of the coefficient for the 1/2+ ? 3/2+37Cl transition multipolarities mixture. The analytical results have shown the feasibility of estimates of considered transition GP in the odd nucleus+neutron model

1980-05-01

280

The hydration of serine: multipole moments versus point charges.  

Science.gov (United States)

Next-generation force fields must incorporate improved electrostatic potentials in order to increase the reliability of their predictions. A crucial decision toward this goal is to abandon point charges in favour of multipole moments centered on nuclear sites. Here we compare the geometries generated by quantum topological multipole moments with those generated by four popular point charge models (TAFF, OPLS-AA, MMFF94x and PFROSST) for a hydrated serine. A main feature of this study is the dual comparison made, both at static level (geometry optimisation via energy minimisation) and at dynamic level (via molecular dynamics and radial/spatial distribution function analysis). At static level, multipolar electrostatics best reproduces the ab initio reference geometry. At dynamic level, multipolar electrostatics produces more structure than point charge electrostatics does, over the whole range. From our previous work on liquid water [Int. J. Quantum. Chem., 2004, 99, 685], where agreement with experiment only occurs when using multipole moments, we deduce that our predictions for hydrated serine will also be closer to experiment when using multipolar electrostatics. The spatial distribution function shows that only multipolar electrostatics shows pronounced structure at long range. Even at short range there are many regions where waters appear in the system governed by multipolar electrostatics but not in that governed by point charges. PMID:24448691

Liem, Steven Y; Popelier, Paul L A

2014-03-01

 
 
 
 
281

Hydrological models are mediating models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Despite the increasing role of models in hydrological research and decision-making processes, only few accounts of the nature and function of models exist in hydrology. Earlier considerations have traditionally been conducted while making a clear distinction between physically-based and conceptual models. A new philosophical account, primarily based on the fields of physics and economics, transcends classes of models and scientific disciplines by considering models as "mediators" betwe...

Babel, L. V.; Karssenberg, D.

2013-01-01

282

Climate modelling  

Energy Technology Data Exchange (ETDEWEB)

The factors affecting the inaccuracies and uncertainties in climate models are outlined. Despite these, most advanced climate models are capable of simulating the observed climate with a good level of accuracy. Climate models are useful in predicting climatic change. However, model results have been found to vary widely. With the Hadley Centre model, for example, the predicted increase in global mean surface temperature ranged from 1.9{degree}C to 5.2{degree}C using different cloud schemes. Climate model results although successful overall, must be treated with caution. 3 refs.

Lynch, P. [Meteorological Service, Dublin (Ireland)

1994-12-31

283

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)

1990-09-19

284

Differential Model  

Directory of Open Access Journals (Sweden)

Full Text Available In order to push table tennis into more cutting-edge area, we need to conduct sound research and simulation for the flying condition of table tennis in the air. This study analyzes the force characteristic of objects moving in the air and establishes differential equation model of three force conditions for the characteristics of table tennis, namely the flight model of table tennis only by gravity, the flight model of table tennis only by gravity and air resistance, as well as the flight model of table tennis only by gravity and air resistance and Magnus force. The research results: For the table tennis flight condition of the first model and the third model it conducts Matlab trajectory situation and achieves good simulation results. The model and simulation methods established in this study provide a theoretical basis for the flight conditions of table tennis in the air and provide a model-based simulation for the movement.

Ping Du

2013-01-01

285

SIR Model  

Science.gov (United States)

This worksheet implements an SIR (Susceptible/ Infected/ Resistant) model of epidemiology for vector-borne diseases. Up to three microbial strains with different virulence and transmission parameters can be modeled and the results graphed. Originally designed to explore coevolution of myxoma and rabbits, the model is easily generalized to other systems.

Tony Weisstein (Truman State University;Biology)

2007-06-20

286

Phoenix model  

Science.gov (United States)

Phoenix (formerly referred to as the Second Generation Model or SGM) is a global general equilibrium model designed to analyze energy-economy-climate related questions and policy implications in the medium- to long-term. This model disaggregates the global economy into 26 industr...

287

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.

Piccolo, Chiara; Heitzig, Martina

2011-01-01

288

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

1985-01-01

289

Ventilation Model  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this analysis and model report (AMR) for the Ventilation Model is to analyze the effects of pre-closure continuous ventilation in the Engineered Barrier System (EBS) emplacement drifts and provide heat removal data to support EBS design. It will also provide input data (initial conditions, and time varying boundary conditions) for the EBS post-closure performance assessment and the EBS Water Distribution and Removal Process Model. The objective of the analysis is to develop, describe, and apply calculation methods and models that can be used to predict thermal conditions within emplacement drifts under forced ventilation during the pre-closure period. The scope of this analysis includes: (1) Provide a general description of effects and heat transfer process of emplacement drift ventilation. (2) Develop a modeling approach to simulate the impacts of pre-closure ventilation on the thermal conditions in emplacement drifts. (3) Identify and document inputs to be used for modeling emplacement ventilation. (4) Perform calculations of temperatures and heat removal in the emplacement drift. (5) Address general considerations of the effect of water/moisture removal by ventilation on the repository thermal conditions. The numerical modeling in this document will be limited to heat-only modeling and calculations. Only a preliminary assessment of the heat/moisture ventilation effects and modeling method will be performed in this revision. Modeling of moisture effects on heat removal and emplacement drift temperature may be performed in the future.

H. Yang

1999-11-04

290

Climate Models  

Science.gov (United States)

Climate models is a very broad topic, so a single volume can only offer a small sampling of relevant research activities. This volume of 14 chapters includes descriptions of a variety of modeling studies for a variety of geographic regions by an international roster of authors. The climate research community generally uses the rubric climate models to refer to organized sets of computer instructions that produce simulations of climate evolution. The code is based on physical relationships that describe the shared variability of meteorological parameters such as temperature, humidity, precipitation rate, circulation, radiation fluxes, etc. Three-dimensional climate models are integrated over time in order to compute the temporal and spatial variations of these parameters. Model domains can be global or regional and the horizontal and vertical resolutions of the computational grid vary from model to model. Considering the entire climate system requires accounting for interactions between solar insolation, atmospheric, oceanic and continental processes, the latter including land hydrology and vegetation. Model simulations may concentrate on one or more of these components, but the most sophisticated models will estimate the mutual interactions of all of these environments. Advances in computer technology have prompted investments in more complex model configurations that consider more phenomena interactions than were possible with yesterday s computers. However, not every attempt to add to the computational layers is rewarded by better model performance. Extensive research is required to test and document any advantages gained by greater sophistication in model formulation. One purpose for publishing climate model research results is to present purported advances for evaluation by the scientific community.

Druyan, Leonard M.

2012-01-01

291

Landau damping and one-body dissipation in nuclei  

International Nuclear Information System (INIS)

In the framework of the theory of Fermi liquids, the wall formula describes a type of Landau damping of the collective motion. It is found that in this model the ratio between width and energy of the giant resonances is of the order of 1, essentially independent of the multipolarity. This result, which is in contradiction with the experimental findings, is due to the fact that the boundary is externally imposed. With the possible exception of the monopole, the Landau damping is not the appropriate process for describing the dissipation of the low-multipole giant resonances, being only effective for deformations corresponding to high multipolarities (? ? 6)

1985-07-06

292

Interregional modelling  

International Nuclear Information System (INIS)

This paper presents a review of (in principal) operational models which describe the transport, diffusion and chemical transformation of air pollutants, to a horizontal scale varying from 50 to 5000 km. The various formulations used to describe the physical and chemical processes are discussed and the properties of each model are described separately in tabulated form. Interregional transport models are classified according to their objective and their spatial and temporal scales, and models are divided according to their mathematical framework (Eulerian models and Lagrangian (or trajectory) models). Air pollution components are discussed including: SO_2 and sulphate, NO /SUB x/ and photochemical products, acid rain, and radioactive gases. Chemical processes and deposition are considered

1985-01-01

293

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

294

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)

2002-01-01

295

Hydrodynamic models  

CERN Document Server

Recent developments based on relativistic hydrodynamic models in high energy heavy ion collisions are discussed. I focus especially on how hydrodynamics works at RHIC energies and how one can use the most of it in analyses of jet quenching and thermal electromagnetic radiations. I also comment on improvement of initial conditions and viscosity in hydrodynamic models.

Hirano, T

2004-01-01

296

BF Models  

International Nuclear Information System (INIS)

The problem of investigating consistent interactions that can be added to a set of scalar fields, two collections of one-forms and a system of two-forms, described in the free limit by a sum of abelian BF models, is reported. The couplings of this class of BF models to matter fields and vector fields are also discussed. (author)

2004-08-26

297

Scale Models  

Science.gov (United States)

In this activity, learners explore the relative sizes and distances of objects in the solar system. Without being informed of the expected product, learners will make a Play-doh model of the Earth-Moon system, scaled to size and distance. The facilitator reveals the true identity of the system at the conclusion of the activity. During the construction phase, learners try to guess what members of the solar system their model represents. Each group receives different amounts of Play-doh, with each group assigned a color (red, blue, yellow, white). At the end, groups set up their models and inspect the models of other groups. They report patterns of scale that they notice; as the amount of Play-doh increases, for example, so do the size and distance of the model. This resource guide includes background information about the Earth to Moon ratio and solar eclipses.

Observatory, Mcdonald

2011-01-01

298

ETALON MODEL  

Science.gov (United States)

Fabry-Perot etalons are wavelength selecting optical devices with widespread applications in lasers, radiometers, and other electro-optical devices. The Etalon Model program generates a stand-alone model of an etalon. It is designed to perform calculations over many wavelengths. The model may be used to determine the sensitivity of the filter to temperature changes, thickness tolerances, or alignment angles of an etalon design. A pre and post-processor are included to facilitate case studies. The Etalon Model program calculates several etalon performance parameters using closed form equations. It calculates the transmission as a function of wavelength, and uses the transmission data to determine additional etalon performance parameters. The calculations are done for two etalons: The first etalon which is the collimated, untilted etalon, is placed in a collimated optical beam with the beam at normal incidence; the second etalon which is the uncollimated, tilted etalon is placed in a converging beam at non-normal incidence. The program is intended to be used for comparison of measurements of an etalon in a collimated beam with the performance of the etalon in an alternative system. The program will calculate the parameters for multiple passes through the etalon. The Etalon Model program was developed on an IBM PS/2 Model 80-071 computer using the Microsoft version 4.01 FORTRAN compiler. It has been implemented under DOS 3.21 and has a memory requirement of 167K. The Etalon Model program was developed in 1988.

Cross, P. L.

1994-01-01

299

Nucleon models  

International Nuclear Information System (INIS)

Theoretical models for the structure of the nucleons and the hyperons are constructed for the purpose of obtaining an understanding of the dynamics that gives rise to their complex spectra. The most modest goal is to explain the ground state energies and the corresponding static observables - magnetic moments and rms radii. More ambitious models attempt in addition to explain the dynamic observables as, e.g., the electromagnetic form factors, which requires that not only overall features are understood, but that at least some parts of the short-range dynamics are understood as well. The rich structure of the baryon spectrum, with 5 known successive flavor generations [the nucleons (up and down quarks), the strange, the charmed and the bottom hyperons] makes the construction of a realistic nucleon model a complex task. Naturally, if it were possible, one would like to take the Lagrangian density of quantum chromodynamics as the starting point. This is formed of quark and gluon field operators. While the mass scale of the baryons is 1 GeV, that of the light u and d quarks and the gluons is essentially 0 (mu congruent 5 MeV, md congruent 8 MeV, mgluon = 0). That baryons with masses of the order of 1 GeV or more can be formed of such light constituents is a consequence of the very strong gluon exchange interaction at low energies. The topics covered in this report are: Chiral Symmetry; The Chiral Bag Model; Chiral Meson Theory; The Skyrmion; Currents and Form Factors; The Skyrme Model and the Chiral Bag Model; Extensions of the Model; Explicit Vector Meson Fields; The Hyperons; The Hyperon Spectrum; The Hyperon Magnetic Moments; Exotics; The Limits of the Bound State Model; and The End of the Nucleon Models

1996-01-01

300

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 Ni-56 produced therein is reviewed. The expected nucleosynthesis and gamma-line spectra for this model of type I explosions and a model for type II explosions 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. While the theoretical results of existing models are predicated upon the assumption of a successful core bounce calculation and the neglect of such two-dimensional effects as rotation and magnetic fields the new model suggests an entirely different scenario in which a considerable portion of the energy carried by an equatorially ejected blob is deposited in the red giant envelope overlying the mantle of the star

1981-12-29

 
 
 
 
301

Tariff Modelling  

standing charge that depends on the Council Tax band of the property. ..... The \\modelling takes account of real changes (i.e. after inflation) in average water .... \\have the largest pool of households who could potentially gain from opting for.

302

Modeling Arcs  

CERN Multimedia

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 electrostatic codes for to evaluate surface properties. Since any given experiment seems to have more variables than data points, we have tried to consider a wide variety of arcing (rf structures, e beam welding, laser ablation, etc.) to help constrain the problem, and concentrate on common mechanisms. While the mechanisms can be comparatively simple, modeling can be challenging.

Insepov, Zeke; Veitzer, Seth; Mahalingam, Sudhakar

2011-01-01

303

Model theory  

CERN Document Server

An up-to-date and integrated introduction to model theory, designed to be used for graduate courses (for students who are familiar with first-order logic), and as a reference for more experienced logicians and mathematicians.

Hodges, Wilfrid

1993-01-01

304

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

305

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

306

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 formalismâ??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

307

Modelling Entrepreneurship  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two approaches can be distinguished with respect to modelling entrepreneurship: (i) the approach focusing on the net development of the number of entrepreneurs in an equilibrium framework and (ii) the approach focusing on the entries and exits of entrepreneurs. In this paper we unify these ap- proaches to arrive at a model explaining the equilibrium and actual number of entrepreneurs and the entry and exit rate of entrepreneurs simultaneously and consistently. We apply our unified approach to...

Bosma, N.; Wit, G.; Carree, M. A.

2003-01-01

308

Measured magnetic moments in 169Tm and the particle-rotor model; implications for transient field calibration  

International Nuclear Information System (INIS)

Gyromagnetic ratios were measured in the (1(2))+ [411] ground-state band of 169Tm by the transient field technique in such a manner that the extracted g-factors are independent of assumptions concerning the strength and velocity dependence of the transient field. Precise ?-ray branching intensities and multipolarity mixing ratios were determined from measured particle-?-ray angular correlations. The electromagnetic properties of the low-lying natural parity states in 169Tm are compared with particle-rotor calculations based on the Woods-Saxon potential and the implications of the measured magnetic moments for the calibration of the transient field strength are discussed

1999-03-08

309

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.

2013-01-01

310

Spurious continuum effects on excited giant resonances  

International Nuclear Information System (INIS)

Using a fully variational time-dependent Thomas-Fermi (TDTF) model, we show the spurious influence of the external nucleon gas on the calculated finite temperature (T) isoscalar monopole strength function. This effect, which is independent of the multipolarity of the resonance, is very likely present in other more microscopic approaches to finite temperature giant resonances. (orig.)

1987-03-02

311

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)

1984-01-01

312

Micrometer Model  

Science.gov (United States)

The Micrometer Model shows the principle of operation and the physical parts of a real micrometer. Micrometers use a screw to amplify distances that are too small to measure directly into large rotations of the screw that are big enough to read from a scale. The accuracy of a micrometer derives from the accuracy of the thread that is at its heart. The basic operating principle of a micrometer is that the rotation of an accurately made screw can be directly and precisely correlated to a certain amount of axial movement (and vice-versa), through the constant known as the screw's lead. The Micrometer model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double click the ejs_ntnu_Micrometer.jar file to run the program (Java must be installed).

Hwang, Fu-Kwun

2009-09-11

313

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

1980-12-19

314

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

315

Circulation modelling  

Science.gov (United States)

Summer upwelling on the continental shelf north of Cape Canaveral, Florida, has been previously observed to result from wind forcing. A two-layer, finite element model reproduces reasonably well the characteristics of the wind-driven upwelling in respect to location and magnitude. Model investigation also shows that upwelling results from offshore current forcing which is imposed through an along-shelf sea level slope. This sea level slope, which has been found to be of the order of -10 -7, represents a mean Gulf Stream effect. The results suggest that the strongest upwelling events near Cape Canaveral occur when the wind and Gulf Stream forcings act together.

Lorenzzetti, Jo?o; Wang, John D.; Lee, Thomas N.

316

Supernova models  

Energy Technology Data Exchange (ETDEWEB)

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 /sup 56/Ni 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.

Woosley, S.E.; Weaver, T.A.

1980-01-01

317

Functional brain connectivity and neurocognitive functioning in patients with long-standing type 1 diabetes with and without microvascular complications: a magnetoencephalography study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

OBJECTIVE: Hyperglycemia-associated microvascular disease may underlie changes in cerebral functioning and cognitive performance in patients with type 1 diabetes. Functional connectivity, an indicator of functional interactions and information exchange between brain regions, provides a measure of cerebral functioning. This study addresses functional connectivity and cognition in type 1 diabetic patients with and without proliferative retinopathy, relative to healthy control subjects, using ma...

2009-01-01

318

Time-Constrained Functional Connectivity Analysis of Cortical Networks Underlying Phonological Decoding in Typically Developing School-Aged Children: A Magnetoencephalography Study  

Science.gov (United States)

The study investigated functional associations between left hemisphere occipitotemporal, temporoparietal, and inferior frontal regions during oral pseudoword reading in 58 school-aged children with typical reading skills (aged 10.4 [plus or minus] 1.6, range 7.5-12.5 years). Event-related neuromagnetic data were used to compute source-current…

Simos, Panagiotis G.; Rezaie, Roozbeh; Fletcher, Jack M.; Papanicolaou, Andrew C.

2013-01-01

319

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

320

Why Model?  

Directory of Open Access Journals (Sweden)

Full Text Available Next generation sequencing technologies are bringing about a renaissance of mining approaches. A comprehensive picture of the genetic landscape of an individual patient will be useful, for example, to identify groups of patients that do or do not respond to certain therapies. The high expectations may however not be satisfied if the number of patient groups with similar characteristics is going to be very large. I therefore doubt that mining sequence data will give us an understanding of why and when therapies work. For understanding the mechanisms underlying diseases, an alternative approach is to model small networks in quantitative mechanistic detail, to elucidate the role of gene and proteins in dynamically changing the functioning of cells. Here an obvious critique is that these models consider too few components, compared to what might be relevant for any particular cell function. I show here that mining approaches and dynamical systems theory are two ends of a spectrum of methodologies to choose from. Drawing upon personal experience in numerous interdisciplinary collaborations, I provide guidance on how to model by discussing the question "Why model?"

OlafWolkenhauer

2014-01-01

 
 
 
 
321

Modeling Muscles  

Science.gov (United States)

Teaching the anatomy of the muscle system to high school students can be challenging. Students often learn about muscle anatomy by memorizing information from textbooks or by observing plastic, inflexible models. Although these mediums help students learn about muscle placement, the mediums do not facilitate understanding regarding integration of…

Goodwyn, Lauren; Salm, Sarah

2007-01-01

322

Diffusion Models  

Science.gov (United States)

Web-based intructional material describing the use of diffusion models in population ecology. This page is part of a set of on-line lectures on Quantitative Population Ecology produced by Alexei Sharov in the Department of Entomology at Virginia Tech.

Sharov, Alexei

323

Cancer modeling  

Energy Technology Data Exchange (ETDEWEB)

This book contains 10 chapters. Some of the titles are: Intracellular electrolytes and their role in cancer etiology; Quantitative theories of carcinogenesis; Repair of radiation injury and the time factor in radiotherapy; and A modeling approach to metastatic progression of cancer.

Thompson, J.R. (Dept. of Statistics, Rice Univ., Houston, TX (US)); Brown, B.W. (Dept. of Biomathematics, Univ. of Texas, System Cancer Center, M.D. Anderson Hospital and Tumor Institute, Houston, TX (US))

1987-01-01

324

Emerging models.  

Science.gov (United States)

In all these models, the potential of child psychiatrists and other mental health professionals in decreasing student barriers to learning is promising. While expanding the traditional client service model, child psychiatrists can serve as advocates for identifying student's unmet mental health needs, encourage schools to build capacity for effective responses, be vigilant for quality assurance, develop and initiate new programs that systematically respond to needs of the school community, and provide training opportunities that demystify the psychiatric concepts that can help administrators and teachers. Relatively few child psychiatrists are active in the school setting or have developed a presence in the national movement to provide mental health services in schools. In recognition of the fact that traditional models of psychiatric care such as outpatient clinics and hospital-based programs do not reach many children and adolescents, it is hoped that child psychiatrists will be more motivated to have a more active and rewarding presence in the school setting. Even with the variety of responses to the need for increasing mental health services to children, there are a lot of unanswered questions. With only 8000 child psychiatrists in the United States and 80,000 schools, it is clear that we need to be strategic about how best to utilize our resources. The big question is whether there are predictable and alterable characteristics, mechanisms, and interactive processes that enable high-risk students to attain educational and personal success, despite seemingly poor odds. Emerging models have the potential to begin answering this question. PMID:11214410

Rappaport, N

2001-01-01

325

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

326

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. 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. 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

327

Lens Model  

DEFF Research Database (Denmark)

Firms consist of people who make decisions to achieve goals. How do these people develop the expectations which underpin the choices they make? The lens model provides one answer to this question. It was developed by cognitive psychologist Egon Brunswik (1952) to illustrate his theory of probabilistic functionalism, and concerns the environment and the mind, and adaptation by the latter to the former. This entry is about the lens model, and probabilistic functionalism more broadly. Focus will mostly be on firms and their employees, but, to fully appreciate the scope, we have to keep in mind the fact that probabilistic functionalism extends to all purposive organisms. Probabilistic functionalism is currently experiencing growing interest among strategy scholars, and some very recent papers are highlighted in conclusion.

Nash, Ulrik William

2014-01-01

328

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

329

Modeling fatigue.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The American Board of Family Practice is developing a patient simulation program to evaluate diagnostic and management skills. The simulator must give temporally and physiologically reasonable answers to symptom questions such as "Have you been tired?" A three-step process generates symptom histories. In the first step, the simulator determines points in time where it should calculate instantaneous symptom status. In the second step, a Bayesian network implementing a roughly physiologic model...

Sumner, Walton; Xu, Jin Zhong

2002-01-01

330

Gyroscope Model  

Science.gov (United States)

The Gyroscope example computes and displays the dynamics of gyroscope under the influence of a gravitational torque acting on the center of mass. The gyroscope is supported at one end and given an initial angular velocity component about its axis of symmetry and a component perpendicular to its axis of symmetry. The numerical solution shows the motion for all initial conditions including zero initial angular momentum. The model is designed to show the cycloidal motion (precession and nutation) of the gyroscope axle when the initial angular velocity is large. Users can very the position and radius of the spinning mass as well as the initial angle and can display the angular momentum, angular velocity, and torque vectors. A second window shows the elevation angle of the axle and the angular momentum vector.   Units are chosen such that the total mass M and the acceleration of gravity g are one. The rotor is an ellipsoid with a uniform mass distribution and with major axes 2*R and minor axis R/5. The ellipsoid's moment of inertia through the center of mass is 4MR2/5 about the major axes and 26MR2/125 about the minor axis. The Gyroscope model is a supplemental simulation for the article "It Has to Go Down a Little, in Order to Go Around" by Svilen Kostov and Daniel Hammer in The Physics Teacher 49(4), 216-219 (2011) and has been approved by the authors and The Physics Teacher editor. The model was developed using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_csm_ch17_Gyroscope.jar file will run the program if Java is installed.

Christian, Wolfgang

2011-02-10

331

Biomimetic modelling.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Biomimetics is seen as a path from biology to engineering. The only path from engineering to biology in current use is the application of engineering concepts and models to biological systems. However, there is another pathway: the verification of biological mechanisms by manufacture, leading to an iterative process between biology and engineering in which the new understanding that the engineering implementation of a biological system can bring is fed back into biology, allowing a more compl...

Vincent, Julian F. V.

2003-01-01

332

Modelling osteomyelitis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background This work focuses on the computational modelling of osteomyelitis, a bone pathology caused by bacteria infection (mostly Staphylococcus aureus). The infection alters the RANK/RANKL/OPG signalling dynamics that regulates osteoblasts and osteoclasts behaviour in bone remodelling, i.e. the resorption and mineralization activity. The infection rapidly leads to severe bone loss, necrosis of the affected portion, and it may even spread to other parts of...

Liò Pietro; Paoletti Nicola; Moni Mohammad; Atwell Kathryn; Merelli Emanuela; Viceconti Marco

2012-01-01

333

Independence Models.  

Czech Academy of Sciences Publication Activity Database

. Prague : University of Economics, 2006 - (Vejnarová, J.; Kroupa, T.), s. 151-161 ISBN 80-245-1079-0.[Workshop on Uncertainty Processing 2006 /7./. Mikulov (CZ), 16.09.2006-20.09.2006]Grant CEP: GA ?R GD201/05/H007Výzkumný zám?r: CEZ:AV0Z10750506Klí?ová slova: independence modelsKód oboru RIV: BD - Teorie informace

Šime?ek, Petr

334

Mortality modeling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Using data for six OECD countries, this paper studies the effect of macroeconomic conditions on the mortality index kt in the well-known Lee-Carter model. Significant correlations are found with real GDP growth rates in Australia, Canada, and the United States, and with unemployment rate changes in Japan, for the period 1950–2005. In recent years, the relationship between the state of the economy and mortality is found to change from procyclical to countercyclical in all six countries. Base...

Hanewald, Katja

2009-01-01

335

Ozone modeling  

International Nuclear Information System (INIS)

Exhaust gases from power plants that burn fossil fuels contain concentrations of sulfur dioxide (SO_2), 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 NO_x 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 NO_x coordinates of the point, known as the NMOC/NO_x ratio. Results obtained by the described model are presented

1994-07-01

336

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

337

From Perception to Conception: How Meaningful Objects Are Processed over Time  

Digital Repository Infrastructure Vision for European Research (DRIVER)

To recognize visual objects, our sensory perceptions are transformed through dynamic neural interactions into meaningful representations of the world but exactly how visual inputs invoke object meaning remains unclear. To address this issue, we apply a regression approach to magnetoencephalography data, modeling perceptual and conceptual variables. Key conceptual measures were derived from semantic feature-based models claiming shared features (e.g., has eyes) provide broad category informati...

2013-01-01

338

Statistical analysis of multipole components in the magnetic field of the RHIC arc regions  

Energy Technology Data Exchange (ETDEWEB)

The existence of multipolar components in the dipole and quadrupole magnets is one of the factors limiting the beam stability in the RHIC operations. Therefore, the statistical properties of the non-linear fields are crucial for understanding the beam behavior and for achieving the superior performance in RHIC. In an earlier work [1], the field quality analysis of the RHIC interaction regions (IR) was presented. Furthermore, a procedure for developing non-linear IR models constructed from measured multipolar data of RHIC IR magnets was described. However, the field quality in the regions outside of the RHIC IR had not yet been addressed. In this paper, we present the statistical analysis of multipolar components in the magnetic fields of the RHIC arc regions. The emphasis is on the lower order components, especially the sextupole in the arc dipole and the 12-pole in the quadrupole magnets, since they are shown to have the strongest effects on the beam stability. Finally, the inclusion of the measured multipolar components data of RHIC arc regions and their statistical properties into tracking models is discussed.

Beebe-Wang,J.; Jain, A.

2009-05-04

339

Experimental and theoretical charge density studies at subatomic resolution.  

Science.gov (United States)

Analysis of accurate experimental and theoretical structure factors of diamond and silicon reveals that the contraction of the core shell due to covalent bond formation causes significant perturbations of the total charge density that cannot be ignored in precise charge density studies. We outline that the nature and origin of core contraction/expansion and core polarization phenomena can be analyzed by experimental studies employing an extended Hansen-Coppens multipolar model. Omission or insufficient treatment of these subatomic charge density phenomena might yield erroneous thermal displacement parameters and high residual densities in multipolar refinements. Our detailed studies therefore suggest that the refinement of contraction/expansion and population parameters of all atomic shells is essential to the precise reconstruction of electron density distributions by a multipolar model. Furthermore, our results imply that also the polarization of the inner shells needs to be adopted, especially in cases where second row or even heavier elements are involved in covalent bonding. These theoretical studies are supported by direct multipolar refinements of X-ray powder diffraction data of diamond obtained from a third-generation synchrotron-radiation source (SPring-8, BL02B2). PMID:21863852

Fischer, A; Tiana, D; Scherer, W; Batke, K; Eickerling, G; Svendsen, H; Bindzus, N; Iversen, B B

2011-11-17

340

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

 
 
 
 
341

SEWER MODEL AUDIT SCOPE  

…/ reliable Extent of previous audit (A/B/C) Model documentation, QA, procedures Model History Software Model Software Conversions Model Checks Connectivity Stability Initial/Routine Model Purpose Original Proposed Model Type (I/II/III/IV) and detail Model extents A B C Model Feature or Data Documented…

342

Modeling of Heat Transfer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Modeling of heat transfer using Dymola. In this report a evaporator, economizer and superheater where modeled. The report describes how the models where modeled and what input was most suitable for a accurate model.

Wahlberg, Tobias

2011-01-01

343

Modeling materials with phase field crystal models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The phase field crystal (PFC) model is a novel approach for modeling phenomena on atomistic length and diffusive time scales. In this dissertation, we present new advances in the methodology of the PFC model and describe applications to solidification and grain boundaries. We present an extended phase diagram for the original formulation of the PFC model that allows to model three dimensional hexagonal and cubic close-packed crystal structures. The original PFC model is also applied to study ...

2010-01-01

344

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

345

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

1999-03-01

346

Source reconstruction accuracy of MEG and EEG Bayesian inversion approaches.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Electro- and magnetoencephalography allow for non-invasive investigation of human brain activation and corresponding networks with high temporal resolution. Still, no correct network detection is possible without reliable source localization. In this paper, we examine four different source localization schemes under a common Variational Bayesian framework. A Bayesian approach to the Minimum Norm Model (MNM), an Empirical Bayesian Beamformer (EBB) and two iterative Bayesian schemes (Automatic ...

Belardinelli, P.; Ortiz, E.; Barnes, G.; Noppeney, U.; Preissl, H.

2012-01-01

347

Linear constraint minimum variance beamformer functional magnetic resonance inverse imaging  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Accurate estimation of the timing of neural activity is required to fully model the information flow among functionally specialized regions whose joint activity underlies perception, cognition and action. Attempts to detect the fine temporal structure of task-related activity would benefit from functional imaging methods allowing higher sampling rates. Spatial filtering techniques have been used in magnetoencephalography source imaging applications. In this work, we use the linear constraint ...

Lin, Fa-hsuan; Witzel, Thomas; Zeffiro, Thomas A.; Belliveau, John W.

2008-01-01

348

I&C Modeling in SPAR Models  

Energy Technology Data Exchange (ETDEWEB)

The Standardized Plant Analysis Risk (SPAR) models for the U.S. commercial nuclear power plants currently have very limited instrumentation and control (I&C) modeling [1]. Most of the I&C components in the operating plant SPAR models are related to the reactor protection system. This was identified as a finding during the industry peer review of SPAR models. While the Emergency Safeguard Features (ESF) actuation and control system was incorporated into the Peach Bottom Unit 2 SPAR model in a recent effort [2], various approaches to expend resources for detailed I&C modeling in other SPAR models are investigated.

John A. Schroeder

2012-06-01

349

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.)

1984-01-01

350

Models, modelling and modellers: An application to risk analysis  

Energy Technology Data Exchange (ETDEWEB)

Risk analysis has become increasingly important with the emergence of new, unknown and potentially dangerous technologies. Risk analysis builds on the use of models. If the models are valid representations of reality, they can be used to predict and thus also to minimize the risks. Any model is, however, a simplification and a generalization which implies that it has only a limited region of validity. If a model in the risk analysis process is used outside its region of validity it can introduce serious flaws in the actions on different risks. The use of deficient models actually poses the most serious threat to the validity of risk assessments. To understand the origins of deficient models, it is necessary to consider the modelling process and the people involved in using the models. Models in risk analysis are based on many assumptions which have to be understood if erroneous interpretations are to be avoided. The paper considers theoretical foundations of risk analysis, models used in risk analysis and the modelling process leading to these models

Wahlstroem, B. (Technical Research Centre of Finland, VTT/SAeH, Espoo (Finland))

1994-06-30

351

Common Modeling Language for Model Checkers  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: There are many different model checkers that have been developed. Each of the model checkers is based on different input languages and they are suitable for model checking different types of systems. Thus it is important for us to choose the right model checker or modeling and verifying a given system. However, moving from one model checker to another is not an easy task since we have to deal with different input languages. Approach: In order to solve the problem we propose a common modeling language that is based on UML state chart. Some translation rules for translating the model described in the common modeling language into the input languages of model checkers are also presented. Results: The result of the case study shows that our approach has been successfully applied in modeling the control system through the process of transformation and translation. Conclusion: Common modeling language can be used as a front end to help users to properly model a system before it is translated into input language of model checkers.

Pathiah A.  Samat

2012-01-01

352

Bayesian model comparison of solar radiation models  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we propose a new statistical method: the Bayesian Model Comparison (BMC) method for selecting an adequate hourly diffuse fraction correlation. Six models are investigated and compared according to the BMC method. The selection of the best model is based on a Bayesian criterion called the Deviance Information Criterion (DIC). In this article, we demonstrate the usefulness of the DIC criterion in the model selection process and we issue a caution regarding the selection of a model with standard statistical methods. The aim of this paper is also to introduce the DIC to the solar radiation modeling community. (orig.)

Lauret, Philippe; Riviere, Carine [Lab. de Physique du Batiment et des Systemes, Saint-Denis (France)

2008-07-01

353

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

1982-08-18

354

Models for preequilibrium decay  

International Nuclear Information System (INIS)

After a qualitative discussion of the most substantial features of preequilibrium decay, four models related to this mechanism have been presented: the exciton model, the Harp-Miller-Berne (H.M.B.) model, the hybrid model, the geometry-dependent model (G.D.H.). This includes: formulation of the model, comparisons with experimental data, associated computer codes, and, finally, intercomparisons of models. (author)

1979-01-01

355

Structuring process models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One can fairly adopt the ideas of Donald E. Knuth to conclude that process modeling is both a science and an art. Process modeling does have an aesthetic sense. Similar to composing an opera or writing a novel, process modeling is carried out by humans who undergo creative practices when engineering a process model. Therefore, the very same process can be modeled in a myriad number of ways. Once modeled, processes can be analyzed by employing scientific methods. Usually, process models ar...

Polyvyanyy, Artem

2012-01-01

356

Modeling, computation and optimization  

CERN Multimedia

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

357

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: â?¢ What are the requirements for a multi business model innovation model (BMIM)? â?¢ 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

358

Nonlinear empirical modeling using local PLS models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis proposes some new iterative local modeling algorithms for the multivariate approximation problem (mapping from R P to R). Partial Least Squares Regression (PLS)is used as the local linear modeling technique. The local models are interpolated by means of normalized Gaussian weight functions, providing a smooth total nonlinear model. The algorithms are tested on both artificial and real world set of data, yielding good predictions compared to other linear and nonlinear techniques.

Aarhus, Lars Thore

1994-01-01

359

QSMSR QUALITATIVE MODEL  

Directory of Open Access Journals (Sweden)

Full Text Available Software architecture design and requirement engineering are core and independent areas of engineering. A lot of research, education and practice are carried on Requirement elicitation and doing refine it, but it is a major issue of engineering. QSMSR model act as a bridge between requirement and design there is a huge gap between these two areas of software architecture and requirement engineering. The QSMSR model divide into two sub model qualitative model and Principal model in this research we focus on Qualitative model which further divide into two sub models fabricated model and classified model. Classified model make the sub groups of the role and match it with components. The Fabricated model link QSMSR Principal Model to an architecture design. At the end it provides the QSMSR Architecture model of the system as output.

Tahir Abdullah

2012-02-01

360

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

 
 
 
 
361

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

362

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.

2010-01-01

363

Bayesian Model Selection and Statistical Modeling  

CERN Multimedia

Bayesian model selection is a fundamental part of the Bayesian statistical modeling process. The quality of these solutions usually depends on the goodness of the constructed Bayesian model. Realizing how crucial this issue is, many researchers and practitioners have been extensively investigating the Bayesian model selection problem. This book provides comprehensive explanations of the concepts and derivations of the Bayesian approach for model selection and related criteria, including the Bayes factor, the Bayesian information criterion (BIC), the generalized BIC, and the pseudo marginal lik

Ando, Tomohiro

2010-01-01

364

Model Theory and Applications  

CERN Multimedia

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

365

Modeling in Computer Graphics  

Science.gov (United States)

A discussion of different modeling techniques in computer graphics including t polygon mesh, parametric cubic curves and patches, implicit functions such as metaballs, procedural modeling (plants and flowers) and modeling transformations.

2003-02-15

366

The impact of yuan internationalization on the euro-dollar exchange rate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the implication of a multipolarization of the international monetary system on cross-currency volatility. More specifically, we analyze whether the internationalization of the yuan could modify the impact of asset supply and trade shocks on the euro-dollar exchange rate, within a three-country, three-currency portfolio model. Our static model shows that the internationalization of the yuan (defined as a rise in the yuan in international portfolios) would be either neutral or stabiliz...

2013-01-01

367

The Impact of Yuan Internationalization on the Euro-Dollar Exchange Rate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the implication of a multipolarization of the international monetary system on cross-currency volatility. More specifically, we analyze whether the internationalization of the yuan could modify the impact of asset supply and trade shocks on the euro-dollar exchange rate, within a three-country, three-currency portfolio model. Our static model shows that the internationalization of the yuan (defined as a rise in the yuan in international portfolios) would be either neutral or stabiliz...

2013-01-01

368

The Impact of Yuan Internationalization on the Euro-Dollar Exchange Rate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the implication of a multipolarization of the international monetary system on crosscurrency volatility. More specifically, we analyze whether the internationalization of the yuan could modify the impact of asset supply and trade shocks on the euro-dollar exchange rate, within a threecountry, three-currency portfolio model. Our static model shows that the internationalization of the yuan (defined as a rise in the yuan in international portfolios) would be either neutral or stabilizin...

2013-01-01

369

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

2000-01-01

370

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

371

Modeling of geothermal systems  

Energy Technology Data Exchange (ETDEWEB)

During the last decade the use of numerical modeling for geothermal resource evaluation has grown significantly, and new modeling approaches have been developed. In this paper we present a summary of the present status in numerical modeling of geothermal systems, emphasizing recent developments. Different modeling approaches are described and their applicability discussed. The various modeling tasks, including natural-state, exploitation, injection, multi-component and subsidence modeling, are illustrated with geothermal field examples. 99 refs., 14 figs.

Bodvarsson, G.S.; Pruess, K.; Lippmann, M.J.

1985-03-01

372

Orbital Debris Modeling  

Science.gov (United States)

Presentation outlne: (1) The NASA Orbital Debris (OD) Engineering Model -- A mathematical model capable of predicting OD impact risks for the ISS and other critical space assets (2) The NASA OD Evolutionary Model -- A physical model capable of predicting future debris environment based on user-specified scenarios (3) The NASA Standard Satellite Breakup Model -- A model describing the outcome of a satellite breakup (explosion or collision)

Liou, J. C.

2012-01-01

373

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...

2008-01-01

374

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

375

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.

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

376

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

377

Operator spin foam models  

International Nuclear Information System (INIS)

ay we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin foam models which are not symmetric with respect to one or more moves we consider.

2011-05-21

378

Simplicity, Complexity and Modelling  

CERN Multimedia

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

379

What controls the magnetic geometry of M dwarfs?  

CERN Document Server

Context: observations of rapidly rotating M dwarfs show a broad variety of large-scale magnetic fields encompassing dipole-dominated and multipolar geometries. In dynamo models, the relative importance of inertia in the force balance -- quantified by the local Rossby number -- is known to have a strong impact on the magnetic field geometry. Aims: we aim to assess the relevance of the local Rossby number in controlling the large-scale magnetic field geometry of M dwarfs. Methods: we explore the similarities between anelastic dynamo models in spherical shells and observations of active M-dwarfs, focusing on field geometries derived from spectropolarimetric studies. To do so, we construct observation-based quantities aimed to reflect the diagnostic parameters employed in numerical models. Results: the transition between dipole-dominated and multipolar large-scale fields in early to mid M dwarfs is tentatively attributed to a Rossby number threshold. We interpret late M dwarfs magnetism to result from a dynamo bi...

Gastine, T; Duarte, L; Reiners, A; Christensen, U R; Wicht, J

2012-01-01

380

Modeling of muscle fatigue using Hill's model.  

Science.gov (United States)

A new model incorporating muscle fatigue has been developed to predict the effect of muscle fatigue on the force-time relationship of skeletal muscle by using the PAK-program. Differential equations in the incremental form have been implemented into Hill's muscle model. In order to describe the effect of muscle fatigue and recovery on skeletal muscle behaviors, a set of equations in terms of three phenomenological parameters which are a fatigue curve under sustained maximal activation, a recovery curve and an endurance function were developed. With reference to existing models and experimental results, the input parameters for fatigue curve under sustained maximal activation and endurance function were determined. The model has been investigated under an isometric condition. The effects of different shapes of the recovery curves have also been considered in this model. Validation of the model has been performed by comparing the predicted results with the experimental data from an existing literature. PMID:16179754

Tang, C Y; Stojanovic, B; Tsui, C P; Kojic, M

2005-01-01

 
 
 
 
381

MARTE modelling, model transformations and their usages  

Digital Repository Infrastructure Vision for European Research (DRIVER)

After introducing general concepts about model transformations, two presentations provide an overview of the MARTE profile. Model-driven implementations of software and hardware architectures are then given, covering the most common aspects of Model-Driven Development for Distributed Real-Time Systems: structuring architectures using components, mapping between different levels of abstraction, designing hardware and software architecture, evaluation and validation through tests and performanc...

Sabetta, Antonino; Babau, Jean-philippe; Blay-fornarino, Mireille; Champeau, Joel; Sylvain, Robert; (eds.), .

2010-01-01

382

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

2000-01-01

383

Wastewater Treatment Models  

DEFF Research Database (Denmark)

The state-of-the-art level reached in modeling wastewater treatment plants (WWTPs) is reported. For suspended growth systems, WWTP models have evolved from simple description of biological removal of organic carbon and nitrogen in aeration tanks (ASM1 in 1987) to more advanced levels including description of biological phosphorus removal, physicalâ??chemical processes, hydraulics, and settling tanks. For attached growth systems, biofilm models have progressed from analytical steady-state models to more complex 2-D/3-D dynamic numerical models. Plant-wide modeling is set to advance further the practice of WWTP modeling by linking the wastewater treatment line with the sludge handling line in one modeling platform. Application of WWTP models is currently rather time consuming and thus expensive due to the high model complexity, and requires a great deal of process knowledge and modeling expertise. Efficient and good modeling practice therefore requires the use of a proper set of guidelines, thus grounding the modeling studies on a general and systematic framework. Last but not least, general limitations of WWTP models â?? more specifically, activated sludge models â?? are introduced since these define a boundary of validity for WWTP model applications.

Gernaey, Krist; Sin, Gürkan

2008-01-01

384

Wastewater treatment models  

DEFF Research Database (Denmark)

The state-of-the-art level reached in modeling wastewater treatment plants (WWTPs) is reported. For suspended growth systems, WWTP models have evolved from simple description of biological removal of organic carbon and nitrogen in aeration tanks (ASM1 in 1987) to more advanced levels including description of biological phosphorus removal, physicalchemical processes, hydraulics and settling tanks. For attached growth systems, biofilm models have progressed from analytical steady-state models to more complex 2D/3D dynamic numerical models. Plant-wide modeling is set to advance further the practice of WWTP modeling by linking the wastewater treatment line with the sludge handling line in one modeling platform. Application of WWTP models is currently rather time consuming and thus expensive due to the high model complexity, and requires a great deal of process knowledge and modeling expertise. Efficient and good modeling practice therefore requires the use of a proper set of guidelines, thus grounding the modeling studies on a general and systematic framework. Last but not least, general limitations of WWTP models â?? more specifically activated sludge models â?? are introduced since these define a boundary of validity for WWTP model applications.

Gernaey, Krist; Sin, Gürkan

2011-01-01

385

Lanchester combat models  

CERN Multimedia

An overview of Lanchester combat models, emphasising their pedagogical possibilities. After a description of the aimed-fire model and comments on the literature, we introduce briefly a range of further topics: a discrete equivalent, the unaimed-fire model, mixed forces, the meaning of a 'unit', support troops, Bracken's generalization and an asymmetric model.

MacKay, N J

2006-01-01

386

Multivariate GARCH models  

DEFF Research Database (Denmark)

This article contains a review of multivariate GARCH models. Most common GARCH models are presented and their properties considered. This also includes nonparametric and semiparametric models. Existing specification and misspecification tests are discussed. Finally, there is an empirical example in which several multivariate GARCH models are fitted to the same data set and the results compared.

Silvennoinen, Annastiina; Teräsvirta, Timo

2008-01-01

387

SEWER MODEL AUDIT SCOPE  

…Extent of previous audit (A/B/C) Model Boundary Conditions Model Simplification Modelled DWF Data Foul flow Infiltration Trade Flows Runoff Model Rain induced infiltration Flow Calibration Data Flow Quality Calibration Data Global defaults Pipe Data Manhole Surveys Sewer Condition Surveys Sewer Sediments…

388

Dynamic cable analysis models  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a summary of the development and validation of undersea cable dynamics computer models by the Naval Civil Engineering Laboratory (NCEL) under the sponsorship of the Naval Facilities Engineering Command. These models allow for the analysis of both small displacement (strumming) and large displacement (static and dynamic) deformations of arbitrarily configured cable structures. All of the large displacement models described in this paper are available to the public. This paper does not emphasize the theoretical development of the models (this information is available in other references) but emphasizes the various features of the models, the comparisons between model output and experimental data, and applications for which the models have been used.

Palo, P.A.; Meggitt, D.J.; Nordell, W.J.

1983-05-01

389

Calibrated Properties Model  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this Analysis/Model Report (AMR) is to document the Calibrated Properties Model that provides calibrated parameter sets for unsaturated zone (UZ) flow and transport process models for the Yucca Mountain Site Characterization Project (YMP). This work was performed in accordance with the ''AMR Development Plan for U0035 Calibrated Properties Model REV00. These calibrated property sets include matrix and fracture parameters for the UZ Flow and Transport Model (UZ Model), drift seepage models, drift-scale and mountain-scale coupled-processes models, and Total System Performance Assessment (TSPA) models as well as Performance Assessment (PA) and other participating national laboratories and government agencies. These process models provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic and thermal-loading conditions.

C. Ahlers; H. Liu

2000-03-12

390

Protein Models Comparator  

CERN Document Server

The process of comparison of computer generated protein structural models is an important element of protein structure prediction. It has many uses including model quality evaluation, selection of the final models from a large set of candidates or optimisation of parameters of energy functions used in template free modelling and refinement. Although many protein comparison methods are available online on numerous web servers, their ability to handle a large scale model comparison is often very limited. Most of the servers offer only a single pairwise structural comparison, and they usually do not provide a model-specific comparison with a fixed alignment between the models. To bridge the gap between the protein and model structure comparison we have developed the Protein Models Comparator (pm-cmp). To be able to deliver the scalability on demand and handle large comparison experiments the pm-cmp was implemented "in the cloud". Protein Models Comparator is a scalable web application for a fast distributed comp...

Widera, Pawe?

2011-01-01

391

Calibrated Properties Model  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this Analysis/Model Report (AMR) is to document the Calibrated Properties Model that provides calibrated parameter sets for unsaturated zone (UZ) flow and transport process models for the Yucca Mountain Site Characterization Project (YMP). This work was performed in accordance with the AMR Development Plan for U0035 Calibrated Properties Model REV00 (CRWMS M&O 1999c). These calibrated property sets include matrix and fracture parameters for the UZ Flow and Transport Model (UZ Model), drift seepage models, drift-scale and mountain-scale coupled-processes models, and Total System Performance Assessment (TSPA) models as well as Performance Assessment (PA) and other participating national laboratories and government agencies. These process models provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic and thermal-loading conditions.

C.F. Ahlers, H.H. Liu

2001-12-18

392

Lumped Thermal Household Model  

DEFF Research Database (Denmark)

In this paper we discuss two different approaches to model the flexible power consumption of heat pump heated households: individual household modeling and lumped modeling. We illustrate that a benefit of individual modeling is that we can overview and optimize the complete flexibility of a heat pump portfolio. Following, we illustrate two disadvantages of individual models, namely that it requires much computational effort to optimize over a large portfolio, and second that it is difficult to accurately model the houses in certain time periods due to local disturbances. Finally, we propose a lumped model approach as an alternative to the individual models. In the lumped model, the portfolio is seen as baseline consumption superimposed with an ideal storage of limited power and energy capacity. The benefit of such a lumped model is that the computational effort of flexibility optimization is significantly reduced. Further, the individual disturbances will smooth out as the number of houses in the portfolio increases.

Biegel, Benjamin; Andersen, Palle

2013-01-01

393

Nuclear cluster models  

International Nuclear Information System (INIS)

A review on different simple and microscopic cluster models is given. The main features of cluster models (cluster correlations, Pauli principle, exact mass spectrum motion, uniform treatment of bound and scattering states, use of a variational principle) are analyzed and illustrated by simle models (local alpha model of Buck, Saito model of orthogonality condition). The oscillatory cluster model is discussed to demonstate the effect of anti-symmetrization according to the Pauli principle. Two advanced microscopic cluster models, the resonating-group model and the generator-coordinate model are described in detail and their connections are shown. The capacities, advantages and problems of different cluster models are described and compared. (D.Gy.)

1985-01-01

394

Controlling Modelling Artifacts  

Digital Repository Infrastructure Vision for European Research (DRIVER)

When analysing the performance of a complex system, we typically build abstract models that are small enough to analyse, but still capture the relevant details of the system. But it is difficult to know whether the model accurately describes the real system, or if its behaviour is due to modelling artifacts that were inadvertently introduced. In this paper, we propose a novel methodology to reason about modelling artifacts, given a detailed model and a highlevel (more ...

Smith, Michael James Andrew; Nielson, Flemming; Nielson, Hanne Riis

2011-01-01

395

Asso : Designing model Transformations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

ASSO, an innovative conceptual methodology which combines features of database design with the formal method B, has been defined in order to ensure the flexibility of semantic data models, the efficiency of object models and the design correctness. Starting from a directed acyclic graph of classes supported by semantic data models, a formal mapping generates classes supported by object models. The classes supported by semantic data models are then extended with aspects of behavioural modellin...

2003-01-01

396

Model Checking of Boolean Process Models  

CERN Multimedia

In the field of Business Process Management formal models for the control flow of business processes have been designed since more than 15 years. Which methods are best suited to verify the bulk of these models? The first step is to select a formal language which fixes the semantics of the models. We adopt the language of Boolean systems as reference language for Boolean process models. Boolean systems form a simple subclass of coloured Petri nets. Their characteristics are low tokens to model explicitly states with a subsequent skipping of activations and arbitrary logical rules of type AND, XOR, OR etc. to model the split and join of the control flow. We apply model checking as a verification method for the safeness and liveness of Boolean systems. Model checking of Boolean systems uses the elementary theory of propositional logic, no modal operators are needed. Our verification builds on a finite complete prefix of a certain T-system attached to the Boolean system. It splits the processes of the Boolean sy...

Schneider, Christoph

2011-01-01

397

Geochemistry Model Validation Report: External Accumulation Model  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this Analysis and Modeling Report (AMR) is to validate the External Accumulation Model that predicts accumulation of fissile materials in fractures and lithophysae in the rock beneath a degrading waste package (WP) in the potential monitored geologic repository at Yucca Mountain. (Lithophysae are voids in the rock having concentric shells of finely crystalline alkali feldspar, quartz, and other materials that were formed due to entrapped gas that later escaped, DOE 1998, p. A-25.) The intended use of this model is to estimate the quantities of external accumulation of fissile material for use in external criticality risk assessments for different types of degrading WPs: U.S. Department of Energy (DOE) Spent Nuclear Fuel (SNF) codisposed with High Level Waste (HLW) glass, commercial SNF, and Immobilized Plutonium Ceramic (Pu-ceramic) codisposed with HLW glass. The scope of the model validation is to (1) describe the model and the parameters used to develop the model, (2) provide rationale for selection of the parameters by comparisons with measured values, and (3) demonstrate that the parameters chosen are the most conservative selection for external criticality risk calculations. To demonstrate the applicability of the model, a Pu-ceramic WP is used as an example. The model begins with a source term from separately documented EQ6 calculations; where the source term is defined as the composition versus time of the water flowing out of a breached waste package (WP). Next, PHREEQC, is used to simulate the transport and interaction of the source term with the resident water and fractured tuff below the repository. In these simulations the primary mechanism for accumulation is mixing of the high pH, actinide-laden source term with resident water; thus lowering the pH values sufficiently for fissile minerals to become insoluble and precipitate. In the final section of the model, the outputs from PHREEQC, are processed to produce mass of accumulation, density of accumulation, and the geometry of the accumulation zone. The density of accumulation and the geometry of the accumulation zone are calculated using a characterization of the fracture system based on field measurements made in the proposed repository (BSC 2001k). The model predicts that accumulation would spread out in a conical accumulation volume. The accumulation volume is represented with layers as shown in Figure 1. This model does not directly feed the assessment of system performance. The output from this model is used by several other models, such as the configuration generator, criticality, and criticality consequence models, prior to the evaluation of system performance.

K. Zarrabi

2001-09-27

398

Geochemistry Model Validation Report: External Accumulation Model  

International Nuclear Information System (INIS)

The purpose of this Analysis and Modeling Report (AMR) is to validate the External Accumulation Model that predicts accumulation of fissile materials in fractures and lithophysae in the rock beneath a degrading waste package (WP) in the potential monitored geologic repository at Yucca Mountain. (Lithophysae are voids in the rock having concentric shells of finely crystalline alkali feldspar, quartz, and other materials that were formed due to entrapped gas that later escaped, DOE 1998, p. A-25.) The intended use of this model is to estimate the quantities of external accumulation of fissile material for use in external criticality risk assessments for different types of degrading WPs: U.S. Department of Energy (DOE) Spent Nuclear Fuel (SNF) codisposed with High Level Waste (HLW) glass, commercial SNF, and Immobilized Plutonium Ceramic (Pu-ceramic) codisposed with HLW glass. The scope of the model validation is to (1) describe the model and the parameters used to develop the model, (2) provide rationale for selection of the parameters by comparisons with measured values, and (3) demonstrate that the parameters chosen are the most conservative selection for external criticality risk calculations. To demonstrate the applicability of the model, a Pu-ceramic WP is used as an example. The model begins with a source term from separately documented EQ6 calculations; where the source term is defined as the composition versus time of the water flowing out of a breached waste package (WP). Next, PHREEQC, is used to simulate the transport and interaction of the source term with the resident water and fractured tuff below the repository. In these simulations the primary mechanism for accumulation is mixing of the high pH, actinide-laden source term with resident water; thus lowering the pH values sufficiently for fissile minerals to become insoluble and precipitate. In the final section of the model, the outputs from PHREEQC, are processed to produce mass of accumulation, density of accumulation, and the geometry of the accumulation zone. The density of accumulation and the geometry of the accumulation zone are calculated using a characterization of the fracture system based on field measurements made in the proposed repository (BSC 2001k). The model predicts that accumulation would spread out in a conical accumulation volume. The accumulation volume is represented with layers as shown in Figure 1. This model does not directly feed the assessment of system performance. The output from this model is used by several other models, such as the configuration generator, criticality, and criticality consequence models, prior to the evaluation of system performance

2001-01-01