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Local Maximum (local + maximum)
Selected AbstractsConsistent Localization of Interictal Epileptiform Activity on EEGs of Patients with Tuberous Sclerosis ComplexEPILEPSIA, Issue 3 2005Floor E. Jansen Summary:,Purpose: We addressed consistent localization of focal interictal epileptiform activity on EEGs of patients with tuberous sclerosis complex (TSC) and epilepsy. Methods: Twenty-one patients with TSC with a 10-year history of epilepsy and interictal epileptiform activity in three or more EEG recordings were included. None of the patients had undergone epilepsy surgery. Local maxima of interictal epileptiform activity were measured from 76 EEG traces and 33 EEG reports. Information about the patients' clinical course was extracted from their medical records. Magnetic resonance imaging (MRI) and neuropsychological examinations were performed. Statistical analysis was performed with the Mann,Whitney U test. Results: In eight patients, interictal epileptiform activity was consistently detected in one or two regions (group 1), and in 13 patients, epileptiform activity was detected in three or more regions (group 2). The number of foci increased throughout the disease course in both groups. Age at seizure onset and IQ were significantly higher in group 1. Complex partial seizures occurred more often in the patients of group 1. In 19 of the 21 patients, the most consistent epileptiform activity was localized in the frontotemporal region. Conclusions: Ninety percent of patients with TSC showed at least one region of consistent interictal epileptiform activity. Patients with one or two regions of epileptiform activity were older at seizure onset, often experienced complex partial seizures, and had mild or no mental deficits. These patients may be candidates for epilepsy surgery. [source] Internal gravity wave resonance of thermal convection fields in rectangular cavities with heat-flux vibration (effects of aspect ratio on the fields)HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2007Shota Matsumura Abstract In this paper the thermal convection field and its resonance phenomena in a rectangular cavity with heat-flux vibration are numerically examined and the results are compared with those of a square cavity. As in the case of ,=1, the critical angular velocity at which the relative amplitude of the midplane Nusselt number ,m has a local maximum agrees very well with the resonance angular velocity of the internal gravity wave ,r, estimated by the theoretical equation proposed by Thorpe, even when the aspect ratio is ,=5 and the Prandtl number is Pr=0.71 for a range of the Rayleigh number Ra. However, ,m has two local maxima for a larger Ra, which is peculiar to the case of larger ,. The time variation of sub-components of the fluctuating component of the midplane Nusselt number shows that the phase at the maximum value of ,m agrees well with that of the sub-component of velocity for the first resonance angular velocity ,r. For the other angular velocity ,r2, the phase of ,m agrees with that of the sub-component of temperature. Moreover, we found that the boundary angular velocity ,0 between the first two of the five , regions, which classify the thermal convection fields against ,, can be expressed by a function of ,, Ra, and Pr and that ,m is independent of , and Ra for a relatively wide range of ,/,0. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 158, 171, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20149 [source] Accuracy of Galerkin finite elements for groundwater flow simulations in two and three-dimensional triangulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2001Christian Cordes Abstract In standard finite element simulations of groundwater flow the correspondence between hydraulic head gradients and groundwater fluxes is represented by the stiffness matrix. In two-dimensional problems the use of linear triangular elements on Delaunay triangulations guarantees a stiffness matrix of type M. This implies that the local numerical fluxes are physically consistent with Darcy's law. This condition is fundamental to avoid the occurrence of local maxima or minima, and is of crucial importance when the calculated flow field is used in contaminant transport simulations or pathline evaluation. In three spatial dimensions, the linear Galerkin approach on tetrahedra does not lead to M -matrices even on Delaunay meshes. By interpretation of the Galerkin approach as a subdomain collocation scheme, we develop a new approach (OSC, orthogonal subdomain collocation) that is shown to produce M -matrices in three-dimensional Delaunay triangulations. In case of heterogeneous and anisotropic coefficients, extra mesh properties required for M -stiffness matrices will also be discussed. Copyright © 2001 John Wiley & Sons, Ltd. [source] A phylogeny of anisopterous dragonflies (Insecta, Odonata) using mtRNA genes and mixed nucleotide/doublet modelsJOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 4 2008G. Fleck Abstract The application of mixed nucleotide/doublet substitution models has recently received attention in RNA-based phylogenetics. Within a Bayesian approach, it was shown that mixed models outperformed analyses relying on simple nucleotide models. We analysed an mt RNA data set of dragonflies representing all major lineages of Anisoptera plus outgroups, using a mixed model in a Bayesian and parsimony (MP) approach. We used a published mt 16S rRNA secondary consensus structure model and inferred consensus models for the mt 12S rRNA and tRNA valine. Secondary structure information was used to set data partitions for paired and unpaired sites on which doublet or nucleotide models were applied, respectively. Several different doublet models are currently available of which we chose the most appropriate one by a Bayes factor test. The MP reconstructions relied on recoded data for paired sites in order to account for character covariance and an application of the ratchet strategy to find most parsimonious trees. Bayesian and parsimony reconstructions are partly differently resolved, indicating sensitivity of the reconstructions to model specification. Our analyses depict a tree in which the damselfly family Lestidae is sister group to a monophyletic clade Epiophlebia + Anisoptera, contradicting recent morphological and molecular work. In Bayesian analyses, we found a deep split between Libelluloidea and a clade ,Aeshnoidea' within Anisoptera largely congruent with Tillyard's early ideas of anisopteran evolution, which had been based on evidently plesiomorphic character states. However, parsimony analysis did not support a clade ,Aeshnoidea', but instead, placed Gomphidae as sister taxon to Libelluloidea. Monophyly of Libelluloidea is only modestly supported, and many inter-family relationships within Libelluloidea do not receive substantial support in Bayesian and parsimony analyses. We checked whether high Bayesian node support was inflated owing to either: (i) wrong secondary consensus structures; (ii) under-sampling of the MCMC process, thereby missing other local maxima; or (iii) unrealistic prior assumptions on topologies or branch lengths. We found that different consensus structure models exert strong influence on the reconstruction, which demonstrates the importance of taxon-specific realistic secondary structure models in RNA phylogenetics. [source] Magnetic viscosity and activation volume in chromium substituted Pb,M hexaferritePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2005J. C. Faloh-Gandarilla Abstract PbFe11CrO19 polycrystalline samples were prepared by the chemical coprecipitation method. X-ray diffraction and Mössbauer spectroscopy confirm the formation of the M-type hexagonal structure. Time dependence of the magnetization was recorded on the demagnetization curve of the hysteresis loop. It is well described by a simple logarithmic law but also non-logarithmic behavior was detected. A two-peak dependence of the viscosity coefficient S with the applied field was encountered. Considering reversible susceptibility measurements and a M(H) curve at constant dM/dt in the irreversible susceptibility determination, the calculated activation volume as a function of the applied field shows two well defined zones. The zones observed in the activation volumes are related to the two local maxima that the total susceptibility exhibits. It points to the fact that the viscosity study is sensible enough to characterize this system, encountering two apparent activation volumes. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Prediction of flammability speciation for the lower alkanes, carboxylic acids, and estersPROCESS SAFETY PROGRESS, Issue 1 2007M. Palucis Abstract A Gibbs energy minimization procedure is used to predict the flammability envelopes of alkanes, carboxylic acids, and acetates. In addition to providing the calculated adiabatic flame temperature (CAFT), the product profiles reveal regions of incomplete combustion products and the onset of methane formation above 0.0001 mole fraction. Temperatures at the predicted onset of methane production appear to be closely related to the temperature at the upper flammability limit (UFL). Although a fixed CAFT value could be related to the lower flammability limit (LFL), it was found that this was not the case with the UFL and only for acetic acid could a single CAFT value of 1200K be used to conservatively predict the flammable region. Rather, in general, a single CAFT value could not conservatively predict the upper flammable region. The predictions also reveal local maxima and minima in the concentrations of reaction products. These maps of incomplete combustion products for the flammability region predict that incomplete combustion products are produced at fuel/oxygen ratios significantly below the fuel/oxygen stoichiometric ratio. This region decreases as the limiting oxygen concentration is approached. © 2006 American Institute of Chemical Engineers Process Saf Prog, 2006 [source] Electrophoresis of a charge-regulated toroid normal to a large diskELECTROPHORESIS, Issue 2 2008Jyh-Ping Hsu Abstract The electrophoresis of a charge-regulated toroid (doughnut-shaped entity) normal to a large disk is investigated under the conditions of low surface potential and weak applied electric field. The system considered is capable of modeling the electrophoretic behavior of various types of biocolloids such as bacterial DNA, plasmid DNA, and anabaenopsis near a perfectly conducting planar wall. The influences of the size of the toroid, the separation distance between the toroid and the disk, the charged conditions on the surfaces of the toroid and the disk, and the thickness of electric double layer on the electrophoretic mobility of the toroid are discussed. The results of numerical simulation reveal that under typical conditions the electrophoretic behavior of the toroid can be different from that of an integrated entity. For instance, if the surface of the toroid carries both acidic and basic functional groups, its mobility may have a local maximum as the thickness of double layer varies. We show that the electrophoretic behavior of the toroid is different, both qualitatively and quantitatively, from that of the corresponding integrated particle (particle without hole). [source] Estimating within-field variation using a nonparametric density algorithmENVIRONMETRICS, Issue 5 2006A. Castrignanò Abstract The application of site-specific techniques and technologies in precision farming requires subdividing a field into a generally small number of contiguous homogeneous zones. The proposed algorithm of clustering is based on nonparametric density estimate, where a cluster is defined as a region surrounding a local maximum of the probability density function. Soil samples were collected in a 2-ha field of the experimental farm of the Agricultural Research Institute, located in Foggia (Southern Italy) and some of the most production-affecting soil properties were interpolated by using the geostatistical techniques of kriging and cokriging. The application of the clustering approach to the (co)kriged surface variables produced the subdivision of the field into five distinct classes. The proposed algorithm proves quite promising in identifying spatially contiguous zones, which are more homogeneous in soil properties than the whole-field. Its great advantage consists in giving an additional description of the residual variation within the class and such a piece of information is very useful in precision farming as a basis for the variable-rate application of agronomic inputs. Copyright © 2005 John Wiley & Sons, Ltd. [source] Internal gravity wave resonance of thermal convection fields in rectangular cavities with heat-flux vibration (effects of aspect ratio on the fields)HEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 3 2007Shota Matsumura Abstract In this paper the thermal convection field and its resonance phenomena in a rectangular cavity with heat-flux vibration are numerically examined and the results are compared with those of a square cavity. As in the case of ,=1, the critical angular velocity at which the relative amplitude of the midplane Nusselt number ,m has a local maximum agrees very well with the resonance angular velocity of the internal gravity wave ,r, estimated by the theoretical equation proposed by Thorpe, even when the aspect ratio is ,=5 and the Prandtl number is Pr=0.71 for a range of the Rayleigh number Ra. However, ,m has two local maxima for a larger Ra, which is peculiar to the case of larger ,. The time variation of sub-components of the fluctuating component of the midplane Nusselt number shows that the phase at the maximum value of ,m agrees well with that of the sub-component of velocity for the first resonance angular velocity ,r. For the other angular velocity ,r2, the phase of ,m agrees with that of the sub-component of temperature. Moreover, we found that the boundary angular velocity ,0 between the first two of the five , regions, which classify the thermal convection fields against ,, can be expressed by a function of ,, Ra, and Pr and that ,m is independent of , and Ra for a relatively wide range of ,/,0. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(3): 158, 171, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20149 [source] A non-iterative derivation of the common plane for contact detection of polyhedral blocksINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2008Shu-Wei Chang Abstract A non-iterative derivation for finding the common plane between two polyhedral blocks is presented. By exploiting geometric relations between the normal of a plane and the closest vertex on a block, the common plane can be resolved without resorting to an iterative method. To facilitate derivations, normals in half-space are decomposed into finite subsets in which each subset corresponds to the same closest vertex on a block. The gap function, originally dependent on the normal and the two closest vertices, becomes a function of the normal only. To compute the gap for a given normal subset, the maximum theorem and the maximum projection theorem are introduced. The maximum theorem reduces finding the maximum in a subset to its boundary. Calculating the gap in 2D in a given subset thus reduces to checking two inner products. The maximum projection theorem further reduces finding the maximum on a 3D boundary to an explicit form. Three numerical examples are used to demonstrate the accuracy and efficiency of the proposed scheme. The example in which the blocks are in contact further shows the existence of a local maximum while calculating the gap and illustrates the potential deficiencies in using the Cundall's iterative scheme. Copyright © 2007 John Wiley & Sons, Ltd. [source] Estimation of the Dominating Frequency for Stationary and Nonstationary Fractional Autoregressive ModelsJOURNAL OF TIME SERIES ANALYSIS, Issue 5 2000Jan Beran This paper was motivated by the investigation of certain physiological series for premature infants. The question was whether the series exhibit periodic fluctuations with a certain dominating period. The observed series are nonstationary and/or have long-range dependence. The assumed model is a Gaussian process Xt whose mth difference Yt = (1 ,B)mXt is stationary with a spectral density f that may have a pole (or a zero) at the origin. the problem addressed in this paper is the estimation of the frequency ,max where f achieves the largest local maximum in the open interval (0, ,). The process Xt is assumed to belong to a class of parametric models, characterized by a parameter vector ,, defined in Beran (1995). An estimator of ,max is proposed and its asymptotic distribution is derived, with , being estimated by maximum likelihood. In particular, m and a fractional differencing parameter that models long memory are estimated from the data. Model choice is also incorporated. Thus, within the proposed framework, a data driven procedure is obtained that can be applied in situations where the primary interest is in estimating a dominating frequency. A simulation study illustrates the finite sample properties of the method. In particular, for short series, estimation of ,max is difficult, if the local maximum occurs close to the origin. The results are illustrated by two of the data examples that motivated this research. [source] Closed-form minimax time-delay filters for underdamped systemsOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 3 2007Tarunraj Singh Abstract This paper derives closed-form solutions for the parameters of a time-delay filter designed to be robust to uncertainties in frequencies to be cancelled. It is shown that the slope of the magnitude plot of the two time-delay filter is zero at the nominal frequency indicating that it is a local maximum. This information is used for deriving the solution of the parameters of the time-delay filter in closed form. Three time-delay filters are also designed which force a zero of the filter to be located at the nominal frequency of the system. Uniform and non-uniform distributions of the penalty over the uncertain regions are permitted in this formulation. The applicability of the proposed technique for the control of multi-mode systems is also illustrated. Copyright © 2006 John Wiley & Sons, Ltd. [source] Restoration of a species-rich fen-meadow after abandonment: response of 64 plant species to managementAPPLIED VEGETATION SCIENCE, Issue 1 2000A.B. Hald Hansen (1981) Abstract. Eleven years of abandonment of a species-rich fen-meadow under undisturbed environmental conditions resulted in transformation into areas with tall herb-, sedge- and rush-dominated communities and areas with Alnus thicket. Species cover was measured in permanent plots in both community types and succession was monitored during 14 yr of restoration following reintroduction of management. The annual increase in accumulated species number followed a log-log-time linear regression during 10 yr of grazing management. The expected number of years taken before this annual rate was equal to annual extinction, i.e. a stable situation according to species density, was up to six. The response of 64 species to management was evaluated through paired statistical tests of changes in cover and frequency over time. In total, 55 species could each be allocated to one unique response model (monotone or non-monotone, concave models) independently of the importance value used (cover or frequency) and type of management (grazing following felling or mowing and mowing without grazing). Species which increased in response to grazing had the most persistent seed banks and CR-strategies, while species decreasing in response to grazing had less persistent seed banks and CS-strategies. Some of the species which increased due to grazing followed a model with a local maximum in cover and frequency. The results are discussed in relation to management of species with high cover value during restoration succession. [source] | ||||||||||||||||