Effects of inhomogeneities within the brain on EEG and MEG

The influence of ventricles and lesions on MEG and EEG is studied. The ventricles have an intricate shape and are filled with cerebrospinal fluid. Lesions can have various shapes and their conductivity is unknown. A realistically shaped three-compartment model is used, describing the scalp, skull and brain, which includes the realistically shaped ventricles or a spherical lesion. The potential is computed by means of the finite-element method, and the magnetic field by applying the law of Biot-Savart (Broek, S.P.v.d., Zhou, H. and Peters, M.J. 1996, computation of neuromagnetic fields using finite-element method and Biot-Savart law, Med. Biol. Eng. Comput., 34,21-26). An influence of the ventricles on the potential is only noticeable for dipoles that are within a few centimetres of a ventricle and on the relatively weak potentials on the opposite side of the head. The 'radial' component of the magnetic field generated by superficial dipoles is not influenced by the ventricles in a healthy subject. The influence on the other components, and on the field generated by dipoles near the ventricles can be large. A lesion has a large effect on the potential for sources near the lesion. The effects on the MEG are smaller, but noticeable. Care should be taken in explaining abnormalities in EEGs and MEGs, as it is possible that they are caused by the presence of an inhomogeneity

The influence of inhomogeneities in a head model on EEG and MEG

A realistically shaped model of the head, consisting of tetrahedral elements, is used to investigate the influence of inhomogeneities in the volume conductor (e.g., ventricles and holes) on EEG and MEG. The potential is computed using the finite-element method. The magnetic field is calculated from this potential distribution, applying the law of Biot-Savart. In order to study the influence of the ventricles, computations are carried out using two models: one in which the elements within the ventricles are given the same conductivity as the brain and one in which these elements have a higher conductivity. The influence of holes in the skull layer is examined by giving some elements in the skull layer the same conductivity as that of the brain. The geometry of compartments is obtained semiautomatically from Magnetic Resonance Imaging (MRI) scans. The surface of the ventricles is obtained by manually selecting points on the interface between ventricle and brain. The computation time depends on the total number of tetrahedrons. Therefore, the vertices are distributed in, such a way that a sufficiently high accuracy is obtained with as few tetrahedrons as possible

On the fetal magnetocardiogram

Fetal magnetocardiography is a non-invasive technique for studying the electrical activity of the fetal heart. Fetal magnetocardiograms (fMCG) can be used to diagnose and classify fetal cardiac arrhythmias reliably. An averaged fMCG shows a QRS-complex, a P-wave, and a T-wave. However, it is still unknown if the currents in the tissues surrounding the fetal heart disturb these features. Furthermore, the measuring technique is not yet optimised for fMCG registrations. Simulation studies may provide guidelines for the design of an appropriate magnetometer system. Therefore, finite-element and boundary-element models were constructed in order to study the possible influence of the volume conductor. Especially, the influence of the layer of vernix caseosa, a fatty layer that covers the fetus, was investigated. The computations showed that the layer of vernix caseosa will affect the waveform of the fMCG. The signal processing procedure used is also discussed. It turned out to be difficult to deduce the onset and offset of the T-wave from the resulting averaged signals. Possibly, the QRS-complex does not provide a correct trigger to obtain a distinguishable T-wave in the averaged signal, because the RT-interval may be variable

Asymptotics for turbulent flame speeds of the viscous G-equation enhanced by cellular and shear flows

G-equations are well-known front propagation models in turbulent combustion and describe the front motion law in the form of local normal velocity equal to a constant (laminar speed) plus the normal projection of fluid velocity. In level set formulation, G-equations are Hamilton-Jacobi equations with convex ($L^1$ type) but non-coercive Hamiltonians. Viscous G-equations arise from either numerical approximations or regularizations by small diffusion. The nonlinear eigenvalue $\bar H$ from the cell problem of the viscous G-equation can be viewed as an approximation of the inviscid turbulent flame speed $s_T$. An important problem in turbulent combustion theory is to study properties of $s_T$, in particular how $s_T$ depends on the flow amplitude $A$. In this paper, we will study the behavior of $\bar H=\bar H(A,d)$ as $A\to +\infty$ at any fixed diffusion constant $d > 0$. For the cellular flow, we show that $$\bar H(A,d)\leq O(\sqrt {\mathrm {log}A}) \quad \text{for all $d>0$}.$$ Compared with the inviscid G-equation ($d=0$), the diffusion dramatically slows down the front propagation. For the shear flow, the limit \nit $\lim_{A\to +\infty}{\bar H(A,d)\over A} = \lambda (d) >0$ where $\lambda (d)$ is strictly decreasing in $d$, and has zero derivative at $d=0$. The linear growth law is also valid for $s_T$ of the curvature dependent G-equation in shear flows.Comment: 27 pages. We improve the upper bound from no power growth to square root of log growt

Increased TLR4 Expression in Murine Placentas after Oral Infection with Periodontal Pathogens

Maternal periodontitis has emerged as a putative risk factor for preterm births in humans. The periodontitis-associated dental biofilm is thought to serve as an important source of oral bacteria and related virulence factors that hematogenously disseminate and affect the fetoplacental unit; however the underlying biological mechanisms are yet to be fully elucidated. This study hypothesized that an oral infection with the human periodontal pathogens Campylobacter rectus and Porphyromonas gingivalis is able to induce fetal growth restriction, placental inflammation and enhance Toll-like receptors type 4 (TLR4) expression in a murine pregnancy model. Female Balb/C mice (n=40) were orally infected with C. rectus and/or P. gingivalis over a 16-week period and mated once per week. Pregnant mice were sacrificed at embryonic day (E) 16.5 and placentas were collected and analyzed for TLR4 mRNA levels and qualitative protein expression by real time PCR and immunofluorescence. TLR4 mRNA expression was found to be increased in C. rectus-infected group (1.98±0.886 fold difference, P<0.01, ANOVA) compared to controls. Microscopic analysis of murine placentas showed enhanced immunofluorescence of TLR4 in trophoblasts, mainly in the placental labyrinth layer. Also, combined oral infection with C. rectus and P. gingivalis significantly reduced the overall fecundity compared to controls (16.7% vs. 75%, infected vs. non-infected mice respectively, P=0.03, Kaplan-Meier). The results supported an enhanced placental TLR4 expression after oral infection with periodontal pathogens. The TLR4 pathway has been implicated in the pathogenesis of preterm births; therefore the abnormal regulation of placental TLR4 may give new insights into how maternal periodontitis and periodontal pathogens might be linked to placental inflammation and preterm birth pathogenesis

Power, Connected Coalitions, and Efficiency: Challenges to the Council of the European Union

This article is concerned with challenges to reforming the voting procedures of the Council of the European Union (EU). The next major waves of EU enlargement will cause the Union to increase to a membership of first twenty-one, and then twenty-six or possibly even more states. How does enlargement affect the Council's inherent "capacity to act" under the currently used qualified majority voting rule? It is demon strated here that the expected increase in EU membership will most likely induce a larger "status quo bias" as compared to the present situation in the Council if the crucial majority decision quota is not lowered. In addition, the article is responding to some criticism that has been applied against assessing the leverage of EU governments in one of the EU's most important institutions: the Council of the EU. By resorting to techniques that capture the influence of a priori coalitions on the one hand and "connected coalitions" among EU governments on the other—applying n- person cooperative game theory—the piece illustrates how the assessment of relative voting leverage in the framework of weighted voting systems may be extended and applied to situations in which the specific distribu tion of members' preferences is known. These calculations are again relevant in the face of the upcoming rounds of EU enlargement and projects for institutional reform.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68064/2/10.1177_019251219902000404.pd

The reaction Δ+N→N+N+ϕ\Delta+N\to N+N+\phi in ion-ion collisions

We study the threshold $\phi$-meson production in the process $\Delta+N\to N+N+\phi$, which appears as a possible important mechanism in high energy nuclei-nuclei collisions. The isotopic invariance of the strong interaction and the selection rules due to P-parity and total angular momentum result in a general and model independent parametrization of the spin structure of the matrix element in terms of three partial amplitudes. In the framework of one-pion exchange model these amplitudes can be derived in terms of the two threshold partial amplitudes for the process $\pi+N\to N+\phi$. We predict the ratio of cross sections for $\phi-$meson production in $pp$- and $\Delta N$-collisions and the polarization properties of the $\phi$-meson, in $\Delta+N\to N+N+\phi$, as a function of a single parameter, which characterizes the relative role of transversal and longitudinal $\phi$-meson polarizations in the process $\pi+N\to N+\phi$.Comment: 10 pages 3 figure

The role of CD27-CD70-mediated T cell co-stimulation in vasculogenesis, arteriogenesis and angiogenesis

Cardiolog

Dragon-kings: mechanisms, statistical methods and empirical evidence

This introductory article presents the special Discussion and Debate volume "From black swans to dragon-kings, is there life beyond power laws?" published in Eur. Phys. J. Special Topics in May 2012. We summarize and put in perspective the contributions into three main themes: (i) mechanisms for dragon-kings, (ii) detection of dragon-kings and statistical tests and (iii) empirical evidence in a large variety of natural and social systems. Overall, we are pleased to witness significant advances both in the introduction and clarification of underlying mechanisms and in the development of novel efficient tests that demonstrate clear evidence for the presence of dragon-kings in many systems. However, this positive view should be balanced by the fact that this remains a very delicate and difficult field, if only due to the scarcity of data as well as the extraordinary important implications with respect to hazard assessment, risk control and predictability.Comment: 20 page

'Education, education, education' : legal, moral and clinical

This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students