From EEG to BOLD: Brain mapping and estimating transfer functions in simultaneous EEG-fMRI acquisitions

Simultaneous acquisition of electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) aims to disentangle the description of brain processes by exploiting the advantages of each technique. Most studies in this field focus on exploring the relationships between fMRI signals and the power spectrum at some specific frequency bands (alpha, beta, etc.). On the other hand, brain mapping of EEG signals (e.g., interictal spikes in epileptic patients) usually assumes an haemodynamic response function for a parametric analysis applying the GLM, as a rough approximation. The integration of the information provided by the high spatial resolution of MR images and the high temporal resolution of EEG may be improved by referencing them by transfer functions, which allows the identification of neural driven areas without strong assumptions about haemodynamic response shapes or brain haemodynamic`s homogeneity. The difference on sampling rate is the first obstacle for a full integration of EEG and fMRI information. Moreover, a parametric specification of a function representing the commonalities of both signals is not established. In this study, we introduce a new data-driven method for estimating the transfer function from EEG signal to fMRI signal at EEG sampling rate. This approach avoids EEG subsampling to fMRI time resolution and naturally provides a test for EEG predictive power over BOLD signal fluctuations, in a well-established statistical framework. We illustrate this concept in resting state (eyes closed) and visual simultaneous fMRI-EEG experiments. The results point out that it is possible to predict the BOLD fluctuations in occipital cortex by using EEG measurements. (C) 2010 Elsevier Inc. All rights reserved.

Comparison of different nonlinear functions to describe Nelore cattle growth

This work aims to compare different nonlinear functions for describing the growth curves of Nelore females. The growth curve parameters, their (co) variance components, and environmental and genetic effects were estimated jointly through a Bayesian hierarchical model. In the first stage of the hierarchy, 4 nonlinear functions were compared: Brody, Von Bertalanffy, Gompertz, and logistic. The analyses were carried out using 3 different data sets to check goodness of fit while having animals with few records. Three different assumptions about SD of fitting errors were considered: constancy throughout the trajectory, linear increasing until 3 yr of age and constancy thereafter, and variation following the nonlinear function applied in the first stage of the hierarchy. Comparisons of the overall goodness of fit were based on Akaike information criterion, the Bayesian information criterion, and the deviance information criterion. Goodness of fit at different points of the growth curve was compared applying the Gelfand`s check function. The posterior means of adult BW ranged from 531.78 to 586.89 kg. Greater estimates of adult BW were observed when the fitting error variance was considered constant along the trajectory. The models were not suitable to describe the SD of fitting errors at the beginning of the growth curve. All functions provided less accurate predictions at the beginning of growth, and predictions were more accurate after 48 mo of age. The prediction of adult BW using nonlinear functions can be accurate when growth curve parameters and their (co) variance components are estimated jointly. The hierarchical model used in the present study can be applied to the prediction of mature BW in herds in which a portion of the animals are culled before adult age. Gompertz, Von Bertalanffy, and Brody functions were adequate to establish mean growth patterns and to predict the adult BW of Nelore females. The Brody model was more accurate in predicting the birth weight of these animals and presented the best overall goodness of fit.

Calculation of product state distributions from resonance decay via Lanczos subspace filter diagonalization: Application to HO2

Resonance phenomena associated with the unimolecular dissociation of HO2 have been investigated quantum-mechanically by the Lanczos homogeneous filter diagonalization (LHFD) method. The calculated resonance energies, rates (widths), and product state distributions are compared to results from an autocorrelation function-based filter diagonalization (ACFFD) method. For calculating resonance wave functions via ACFFD, an analytical expression for the expansion coefficients of the modified Chebyshev polynomials is introduced. Both dissociation rates and product state distributions of O-2 show strong fluctuations, indicating the dissociation of HO2 is essentially irregular. (C) 2001 American Institute of Physics.

Ataxia-telangiectasia: chronic activation of damage-responsive functions is reduced by alpha-lipoic acid

Cells from patients with the genetic disorder ataxia-telangiectasia (A-T) are hypersensitive to ionizing radiation and radiomimetic agents, both of which generate reactive oxygen species capable of causing oxidative damage to DNA and other macromolecules. We describe in A-T cells constitutive activation of pathways that normally respond to genotoxic stress, Basal levels of p53 and p21(WAF1/CIP1), phosphorylation on serine 15 of p53, and the Tyr15-phosphorylated form of cdc2 are chronically elevated in these cells. Treatment of A-T cells with the antioxidant alpha -lipoic acid significantly reduced the levels of these proteins, pointing to the involvement of reactive oxygen species in their chronic activation. These findings suggest that the absence of functional ATM results in a mild but continuous state of oxidative stress, which could account for several features of the pleiotropic phenotype of A-T.

On the fast approximation of Green's functions in MPIE formulations for planar layered media

The numerical implementation of the complex image approach for the Green's function of a mixed-potential integralequation formulation is examined and is found to be limited to low values of k(0) rho (in this context k(0) rho = 2 pirho/ lambda(0), where rho is the distance between the source and the field points of the Green's function and lambda(0) is the free space wavelength). This is a clear limitation for problems of large dimension or high frequency where this limit is easily exceeded. This paper examines the various strategies and proposes a hybrid method whereby most of the above problems can be avoided. An efficient integral method that is valid for large k(0) rho is combined with the complex image method in order to take advantage of the relative merits of both schemes. It is found that a wide overlapping region exists between the two techniques allowing a very efficient and consistent approach for accurately calculating the Green's functions. In this paper, the method developed for the computation of the Green's function is used for planar structures containing both lossless and lossy media.

Chebyshev real wave packet propagation: H+O-2 (J=0) state-to-state reactive scattering calculations

In this paper we explore the relative performance of two recently developed wave packet methodologies for reactive scattering, namely the real wave packet Chebyshev domain propagation of Gray and Balint-Kurti [J. Chem. Phys. 108, 950 (1998)] and the Lanczos subspace wave packet approach of Smith [J. Chem. Phys. 116, 2354 (2002); Chem. Phys. Lett. 336, 149 (2001)]. In the former method, a modified Schrodinger equation is employed to propagate the real part of the wave packet via the well-known Chebyshev iteration. While the time-dependent wave packet from the modified Schrodinger equation is different from that obtained using the standard Schrodinger equation, time-to-energy Fourier transformation yields wave functions which differ only trivially by normalization. In the Lanczos subspace approach the linear system of equations defining the action of the Green operator may be solved via either time-dependent or time-independent methods, both of which are extremely efficient due to the simple tridiagonal structure of the Hamiltonian in the Lanczos representation. The two different wave packet methods are applied to three dimensional reactive scattering of H+O-2 (total J=0). State-to-state reaction probabilities, product state distributions, as well as initial-state-resolved cumulative reaction probabilities are examined. (C) 2002 American Institute of Physics.

Electron exchange coupling for single-donor solid-state spin qubits

Intervalley interference between degenerate conduction band minima has been shown to lead to oscillations in the exchange energy between neighboring phosphorus donor electron states in silicon [B. Koiller, X. Hu, and S. Das Sarma, Phys. Rev. Lett. 88, 027903 (2002); Phys. Rev. B 66, 115201 (2002)]. These same effects lead to an extreme sensitivity of the exchange energy on the relative orientation of the donor atoms, an issue of crucial importance in the construction of silicon-based spin quantum computers. In this article we calculate the donor electron exchange coupling as a function of donor position incorporating the full Bloch structure of the Kohn-Luttinger electron wave functions. It is found that due to the rapidly oscillating nature of the terms they produce, the periodic part of the Bloch functions can be safely ignored in the Heitler-London integrals as was done by Koiller, Hu, and Das Sarma, significantly reducing the complexity of calculations. We address issues of fabrication and calculate the expected exchange coupling between neighboring donors that have been implanted into the silicon substrate using an 15 keV ion beam in the so-called top down fabrication scheme for a Kane solid-state quantum computer. In addition, we calculate the exchange coupling as a function of the voltage bias on control gates used to manipulate the electron wave functions and implement quantum logic operations in the Kane proposal, and find that these gate biases can be used to both increase and decrease the magnitude of the exchange coupling between neighboring donor electrons. The zero-bias results reconfirm those previously obtained by Koiller, Hu, and Das Sarma.

Is maximizing resilience compatible with established ecological goal functions?

Cropp and Gabric [Ecosystem adaptation: do ecosystems maximise resilience? Ecology. In press] used a simple phytoplanktonzooplankton-nutrient model and a genetic algorithm to determine the parameter values that would maximize the value of certain goal functions. These goal functions were to maximize biomass, maximize flux, maximize flux to biomass ratio, and maximize resilience. It was found that maximizing goal functions maximized resilience. The objective of this study was to investigate whether the Cropp and Gabric [Ecosystem adaptation: do ecosystems maximise resilience? Ecology. In press] result was indicative of a general ecosystem principle, or peculiar to the model and parameter ranges used. This study successfully replicated the Cropp and Gabric [Ecosystem adaptation: do ecosystems maximise resilience? Ecology. In press] experiment for a number of different model types, however, a different interpretation of the results is made. A new metric, concordance, was devised to describe the agreement between goal functions. It was found that resilience has the highest concordance of all goal functions trialled. for most model types. This implies that resilience offers a compromise between the established ecological goal functions. The parameter value range used is found to affect the parameter versus goal function relationships. Local maxima and minima affected the relationship between parameters and goal functions, and between goal functions. (C) 2003 Elsevier B.V. All rights reserved.

Optical experiments beyond the quantum limit: Squeezing entanglement and teleportation

Results of experiments recently performed are reported, in which two optical parametric amplifiers were set up to generate two independently quadrature squeezed continuous wave laser beams. The transformation of quadrature squeezed states into polarization squeezed states and into states with spatial quantum correlations is demonstrated. By utilizing two squeezed laser beams, a polarization squeezed state exhibiting three simultaneously squeezed Stokes operator variances was generated. Continuous variable polarization entanglement was generated and the Einstein-Podolsky-Rosen paradox was observed. A pair of Stokes operators satisfied both the inseparability criterion and the conditional variance criterion. Values of 0.49 and 0.77, respectively, were observed, with entanglement requiring values below unity. The inseparability measure of the observed quadrature entanglement was 0.44. This value is sufficient for a demonstration of quantum teleportation, which is the next experimental goal of the authors.

Logic functions based on optical bias controlled SIC Tandem devices

The purpose of this paper is the design of an optoelectronic circuit based on a-SiC technology, able to act simultaneously as a 4-bit binary encoder or a binary decoder in a 4-to-16 line configurations and show multiplexer-based logical functions. The device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n multilayered structure produced by PECVD. To analyze it under information-modulated wave (color channels) and uniform irradiation (background) four monochromatic pulsed lights (input channels): red, green, blue and violet shine on the device. Steady state optical bias was superimposed separately from the front and the back sides, and the generated photocurrent was measured. Results show that the devices, under appropriate optical bias, act as reconfigurable active filters that allow optical switching and optoelectronic logic functions development providing the possibility for selective removal of useless wavelengths. The logic functions needed to construct any other complex logic functions are the NOT, and both or either an AND or an OR. Any other complex logic function that might be found can also be used as building blocks to achieve the functions needed for the retrieval of channels within the WDM communication link. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Mantle beneath the Gibraltar Arc from receiver functions

P and S receiver functions (PRF and SRF) from 19 seismograph stations in the Gibraltar Arc and the Iberian Massif reveal new details of the regional deep structure. Within the high-velocity mantle body below southern Spain the 660-km discontinuity is depressed by at least 20 km. The Ps phase from the 410-km discontinuity is missing at most stations in the Gibraltar Arc. A thin (similar to 50 km) low-S-velocity layer atop the 410-km discontinuity is found under the Atlantic margin. At most stations the S410p phase in the SRFs arrives 1.0-2.5 s earlier than predicted by IASP91 model, but, for the propagation paths through the upper mantle below southern Spain, the arrivals of S410p are delayed by up to +1.5 s. The early arrivals can be explained by elevated Vp/Vs ratio in the upper mantle or by a depressed 410-km discontinuity. The positive residuals are indicative of a low (similar to 1.7 versus similar to 1.8 in IASP91) Vp/Vs ratio. Previously, the low ratio was found in depleted lithosphere of Precambrian cratons. From simultaneous inversion of the PRFs and SRFs we recognize two types of the mantle: 'continental' and 'oceanic'. In the 'continental' upper mantle the S-wave velocity in the high-velocity lid is 4.4-4.5 km s(-1), the S-velocity contrast between the lid and the underlying mantle is often near the limit of resolution (0.1 km s(-1)), and the bottom of the lid is at a depth reaching 90 100 km. In the 'oceanic' domain, the S-wave velocities in the lid and the underlying mantle are typically 4.2-4.3 and similar to 4.0 km s(-1), respectively. The bottom of the lid is at a shallow depth (around 50 km), and at some locations the lid is replaced by a low S-wave velocity layer. The narrow S-N-oriented band of earthquakes at depths from 70 to 120 km in the Alboran Sea is in the 'continental' domain, near the boundary between the 'continental' and 'oceanic' domains, and the intermediate seismicity may be an effect of ongoing destruction of the continental lithosphere.

Is there space for senior civil servants hybrid management models across political- administrative systems?

Comunicação apresentada na 17.ª conferência anual da NISPACee, realizada de 14 a 16 de Maio de 2009.

Gender asymmetries in family and work spheres: strategies and conflicts of qualified women working in portuguese state administration

In Portugal, feminine activity rate of working mother is high but remains structural asymmetries of responsibilities between women and men in familiar spheres. Based on quantitative and qualitative data results are presented that show that, in spite of a global feminization rate of 58,6%, women workers in State Administration remains with major responsibilities in familiar/private lives than men. Women in technical and leadership functions have the same patterns of familiar and domestic responsibilities but different patterns of work-time. Women in technical functions tend to have a strategy of work-family time balance, despite less career opportunities, while women in leadership functions adopt a supremacy of wok-time, just as men. Nevertheless, both women, in technical and leadership functions, feel a permanent conflict between career and family responsibilities, which is not felt by men. Gender roles define dominant models of work and family organisation which conduct to different professional strategies and career opportunities.

Disposable solid state probe for optical screening of chlorpromazine

We are presenting a simple, low-cost and rapid solid-state optical probe for screening chlorpromazine (CPZ) in aquacultures. The method exploits the colourimetric reaction between CPZ and Fe(III) ion that occurs at a solid/liquid interface, the solid layer consisting of ferric iron entrapped in a layer of plasticized PVC. If solutions containing CPZ are dropped onto such a layer, a colour change occurs from light yellow to dark pink or even light blue, depending on the concentration of CPZ. Visual inspection enables the concentration of CPZ to be estimated. The resulting colouration was also monitored by digital image collection for a more accurate quantification. The three coordinates of the hue, saturation and lightness system were obtained by standard image processing along with mathematical data treatment. The parameters affecting colour were assessed and optimized. Studies were conducted by visible spectrophotometry and digital image acquisition, respectively. The response of the optimized probe towards the concentration of CPZ was tested for several mathematical transformations of the colour coordinates, and a linear relation was found for the sum of hue and luminosity. The limit of detection is 50 μM (corresponding to about 16 μg per mL). The probe enables quick screening for CPZ in real water samples with prior sample treatment.

Fractional order describing functions

This paper addresses limit cycles and signal propagation in dynamical systems with backlash. The study follows the describing function (DF) method for approximate analysis of nonlinearities and generalizes it in the perspective of the fractional calculus. The concept of fractional order describing function (FDF) is illustrated and the results for several numerical experiments are analysed. FDF leads to a novel viewpoint for limit cycle signal propagation as time-space waves within system structure.