This paper introduces the use of magnetic field tomography (MFT), a noninvasive technique based on distributed source analysis of magnetoencephalography data, which makes possible the three-dimensional reconstruction of dynamic brain activity in humans. MFE has a temporal resolution better than 1 msec and a spatial accuracy of 2-5 mm at the cortical level, which deteriorates to 1-3 cm at depths of 6 cm or more. MFT is used here to visualize the origin of a spatiotemporally organized pattern of coherent 40-Hz electrical activity. This coherence, initially observed during auditory input, was proposed to be generated by recurrent corticothalamic oscillation. In support of this hypothesis, we illustrate well-defined 40-Hz coherence between corticalsubcortical sites with a time shift that is consistent with thalamocortical conduction times. Studies on Alzheimer patients indicate that, while a similar activity pattern is present, the cortical component is reduced in these subjects.In the past decade significant advances have been made in noninvasive technology capable of imaging brain activity with sufficient spatial resolution to complement the structural imaging analysis offered by magnetic resonance imaging (MRI) (1) and computerized tomography (2). However, all imaging techniques available to date fall short of the optimal temporal resolution.The utilization of electrical or magnetic signals has been known to afford the necessary temporal resolution but, until very recently, magnetoencephalography (MEG) analysis was based solely on the assumption of a single point source, the current dipole (3-7), which is only valid when the underlying activity is highly localized and, in general, cannot support imaging capabilities. The development of inverse problem algorithms with primary sources specified by continuous current densities confined to a well-defined region referred to as the source space (8-10) removes the limitations of point source models in the spatial domain without imposing restrictions on the temporal resolution. In earlier work, some of us used a two-dimensional surface as the source space (8,9). In this paper, we solve the inverse problem by using a three-dimensional source space (a cylinder). This threedimensional solution allows the generation of a set of twodimensional images that provide a sequence of slices through the source space. Each image shows the square of the magnitude of the current density at points in the appropriate slice, represented by a color map ranging from black (low activity) to yellow (high activity). By analogy with computerized tomography and positron emission tomography (11), we call this technique magnetic field tomography (MFT). The basic methodology utilized here has been extensively tested and the results have shown excellent reproducibility with computer-generated data (refs. 8 and 9; see Fig. 1C). The two-dimensional paradigm was initially tested on spontaneous and evoked activity in normal subjects and in patients (8,12).We describe here, as an example of the ap...

BackgroundThe Kessler Psychological Distress Scale has been widely used in assessing psychological distress among general and clinical populations from different cultural backgrounds. To our knowledge, however, researchers have not yet validated any translated versions in Arabic. The purpose of this study was to test the reliability and validity of Arabic translations of the ten item (K10) and six item (K6) versions among public sector employees in the Occupied Palestinian Territories.MethodsAs part of a larger research project on life satisfaction, researchers collected data from 234 Palestinian social workers in June and July of 2016. The survey included several mental health measures, including the K10, which were translated from English to Arabic by an experienced language expert. In the current study, we tested reliability by measuring internal consistency using Cronbach’s alpha coefficient. Next, we assessed factor structure using variance-covariance matrix with maximum likelihood estimation. Confirmatory factor analysis was performed to examine three competing models: unidimensional K10 model, unidimensional K6 model and two-factor K6 model. Fit indices and parameter estimates were reported. Last, convergent validity was examined by assessing correlations with Generalized Anxiety Disorder (GAD-7) and Somatic Symptoms Scale (SSS-8).ResultsThe mean scores for the K6 and K10 were, respectively, 12.87 (SD = 4.02) and 21.8 (SD = 6.7), indicative of mild to moderate levels of distress. Scale reliability analysis showed satisfactory results on both K6 and K10 versions (Cronbach’s α = .81 (K6) and .88 (K10)). Among three competing models, the two-factor K6 scale demonstrated the best model fit with high factorial correlations (r = .60, p < .001). Moreover, the K6 has high convergent validity with GAD-7 (r = .66, p < .001) and SSS-8 (r = .61, p < .001).ConclusionResults indicated that the translated version of the two-factor K6 scale is a valid and reliable measurement of psychological distress. Our findings suggest that practitioners and researchers can use this instrument in screening and assessing psychological symptoms with Arabic-speaking populations.

We study the bifurcation diagram for iterates of the non-analytic maps z -fC(z) = f2 + c, where c E @. The set MBAR = {c :f:(O) ++ }, which we call the Mandlebar set, displays many similarities to the Mandelbrot set. However, bifurcotions in MBAR can take place across boundary arcs rather than through boundary points.AMs classification scheme numbers: 30D05,58F08 foc(wz) = Ofc(Z). f"oc(wz) = wfZ(z>By induction, we deduce that, for z and c E @, and so the sequence f&(O) is simply a rotation by $n about 0 of the sequence f:(O).The desired symmetry follows.Remark. The proof of theorem 1 relies on the fact that the function ZHZ' commutes with the rotation by 2n/3 about 0. More generally, z H 2' commutes with all elements of the triangle group D3 (acting on C); i.e. z 2' is D,-equivariant. The authors are grateful to the referee for pointing out that the dynamics of various families of equivariant maps are studied by Chossat and Golubitsky in a recent paper [31.

No abstract