Mutual Information in Frequency and its Application to Measure Cross-Frequency Coupling in Epilepsy

We define a metric, mutual information in frequency (MI-in-frequency), to detect and quantify the statistical dependence between different frequency components in the data, referred to as cross-frequency coupling and apply it to electrophysiological recordings from the brain to infer cross-frequency coupling. The current metrics used to quantify the cross-frequency coupling in neuroscience cannot detect if two frequency components in non-Gaussian brain recordings are statistically independent or not. Our MI-in-frequency metric, based on Shannon's mutual information between the Cramer's representation of stochastic processes, overcomes this shortcoming and can detect statistical dependence in frequency between non-Gaussian signals. We then describe two data-driven estimators of MI-in-frequency: one based on kernel density estimation and the other based on the nearest neighbor algorithm and validate their performance on simulated data. We then use MI-in-frequency to estimate mutual information between two data streams that are dependent across time, without making any parametric model assumptions. Finally, we use the MI-in- frequency metric to investigate the cross-frequency coupling in seizure onset zone from electrocorticographic recordings during seizures. The inferred cross-frequency coupling characteristics are essential to optimize the spatial and spectral parameters of electrical stimulation based treatments of epilepsy.Comment: This paper is accepted for publication in IEEE Transactions on Signal Processing and contains 15 pages, 9 figures and 1 tabl

The Role of Pelvic Neurophysiology Testing in the Assessment of Patients with Voiding Dysfunction

PURPOSE OF REVIEW: The role of pelvic neurophysiology testing in the evaluation of patients with lower urinary tract (LUT) symptoms is explored in this review. RECENT FINDINGS: Different neurophysiology tests such as sphincter EMG and pudendal somatosensory evoked potentials are useful in evaluating the sacral somatic afferent and efferent innervation. S2 and S3 dermatomal evoked potentials assess individual sacral roots and are feasible to perform using standard neurophysiology machines. SUMMARY: The innervation of the LUT has a substantial contribution from splanchnic and somatic nerves arising from the sacral segments. Pelvic neurophysiology tests, which assess somatic nerve functions, are therefore a useful tool in assessing sacral nerve functions in patients presenting with unexplained voiding dysfunction. In this review, the commonly performed neurophysiology studies that assess the S2, S3 and S4 sacral afferent and efferent pathways are outlined, and their clinical applications reviewed

Theories Used in Information Systems Research: Identifying Theory Networks in Leading IS Journals

Though use of theory is critical in Information Systems (IS) research, the theoretical foundations of IS research have been understudied. Using Social Network Analysis, we analyze theory usage in IS research published in MIS Quarterly and Information Systems Research from 1998 to 2006. We find Technology Acceptance Model, Resource- Based View and Game Theory to be the three most frequently used theories. While strong dominance is found in research focusing on Information Technology (IT) for individuals, organizations and markets, no theoretical dominance is found in IT for groups and IS development. Psychology, Economics and Sociology are disciplines IS researchers most frequently leverage for theories. Psychology contributes several theories representing a large fraction of the long tail of theories. Our analysis suggests that IS consists of a few distinctive clusters of research instead of a single core. Our results provide insights on theoretical foundations of IS and suggest research opportunities for scholars

Theories Used in Information Systems Research: Insights from Complex Network Analysis

Effective application of theory is critical to the development of new knowledge in Information Systems (IS) research. However, theory foundations of IS research are understudied. Using Complex Network Analysis, we analyze theory usage in IS research published in two premier journals (MIS Quarterly and Information Systems Research) from 1998 to 2006. Four principal findings emerge from our analysis. First, in contrast with prior studies which found a lack of dominant theories at an aggregate level, we find stronger dominance of theory usage within individual streams of IS research. Second, IS research draws from diverse set of disciplines, with Psychology emerging as a consistently dominant source of theories for IS during our study period. Moreover, theories originating in IS were found to be widely used in two streams of research (‘IS development’ and ‘IT and Individuals’ streams) and more sparingly used in other streams. Third, IS research tends to form clusters of theory usage, with little crossover across clusters. Moreover, streams of IS research constitute distinct clusters of theory usage. Finally, theories originating from Economics, Strategy and Organization Science tend to be used together, whereas those originating from Psychology, Sociology and IS tend to be used together. Taken together, our results contribute to scholarly understanding of theory foundations of IS research and illustrate methodological innovations in the study of theory use by employing Complex Network Analysis

Correlation analysis of lidar derived optical parameters for investigations on thin cirrus features at a tropical station Gadanki(13.5ºN and 79.2ºE), India

The optical characterization of thin cirrus clouds is very important to understand its radiative effects. The optical parameters of cirrus clouds namely extinction

On the segmentation of astronomical images via level-set methods

Astronomical images are of crucial importance for astronomers since they contain a lot of information about celestial bodies that can not be directly accessible. Most of the information available for the analysis of these objects starts with sky explorations via telescopes and satellites. Unfortunately, the quality of astronomical images is usually very low with respect to other real images and this is due to technical and physical features related to their acquisition process. This increases the percentage of noise and makes more difficult to use directly standard segmentation methods on the original image. In this work we will describe how to process astronomical images in two steps: in the first step we improve the image quality by a rescaling of light intensity whereas in the second step we apply level-set methods to identify the objects. Several experiments will show the effectiveness of this procedure and the results obtained via various discretization techniques for level-set equations.Comment: 24 pages, 59 figures, paper submitte

Macro-physical, optical and radiative properties of tropical cirrus clouds and its temperature dependence at Gadanki (13.5° N, 79.2° E) observed by ground based lidar

The macro-physical and optical properties of cirrus clouds and its temperature dependencies have been investigated at the National Atmospheric Research Laboratory (NARL; 13.5° N, 79.2° E), Gadanki, Andhra Pradesh, India; an inland tropical station during the period of observation January to December 2009 using a ground based pulsed monostatic lidar system data and radiosonde measurements. Based on the analysis of measurements the cirrus macrophysical properties such as occurrence height, mid cloud temperature, cloud geometrical thickness, and optical properties such as extinction coefficient, optical depth, depolarization ratio and lidar ratio have been determined. The variation of cirrus macrophysical and optical properties with mid cloud temperature have also been studied. The cirrus clouds mean height has been generally observed in the range of 9-17 km with a peak occurrence at 13-14 km. The cirrus mid cloud temperatures were in the range from -81 °C to -46 °C. The cirrus geometrical thickness ranges from 0.9-4.5 km and 56% of cirrus occurrences have thickness 1.0 -2.7 km. The monthly cirrus optical depth ranges from 0.01-0.47, but most (>80%) of the cirrus have values less than 0.1. The monthly mean cirrus extinction ranges from 2.8E-06 to 8E-05 and depolarization ratio and lidar ratio varies from 0.13 to 0.77 and 2 to 52 respectively. The temperature and thickness dependencies on cirrus optical properties have also been studied. A maximum cirrus geometrical thickness of 4.5 km is found at temperatures around – 46 °C with an indication that optical depth increases with increasing thickness and mid cloud temperature. The cloud radiative properties such as outgoing long-wave radiation (OLR) flux and cirrus IR forcing are studied. OLR flux during the cirrus occurrence days ranged from 348-456 W/m2 with a low value in the monsoon period. The cirrus IR forcing varied from 3.13 – 110.54 W/m2 and shows a peak at monsoon period

Satellite downlink scheduling problem: A case study

The synthetic aperture radar (SAR) technology enables satellites to efficiently acquire high quality images of the Earth surface. This generates significant communication traffic from the satellite to the ground stations, and, thus, image downlinking often becomes the bottleneck in the efficiency of the whole system. In this paper we address the downlink scheduling problem for Canada's Earth observing SAR satellite, RADARSAT-2. Being an applied problem, downlink scheduling is characterised with a number of constraints that make it difficult not only to optimise the schedule but even to produce a feasible solution. We propose a fast schedule generation procedure that abstracts the problem specific constraints and provides a simple interface to optimisation algorithms. By comparing empirically several standard meta-heuristics applied to the problem, we select the most suitable one and show that it is clearly superior to the approach currently in use.Comment: 23 page

Potent Adjuvantic Activity of a CCR1-agonistic Bis-Quinoline

A bis-quinoline compound, (7-chloro-N-(4-(7-chloroquinolin-4-ylamino)butyl)quinolin-4-amine; RE-660) was found to have C-C chemokine receptor type 1 (CCR1)-agonistic properties.RE-660 displayed strong adjuvantic activity in mice when co-administered with bovine α-lactalbumin used as a model subunit protein antigen. RE-660 evoked a balanced Th1 (IgG2)/Th2 (IgG1) antibody profile, and the quality of antibodies elicited by the bis-quinoline was found to be superior to that evoked by glucopyranosyl lipid A by surface plasmon resonance experiments. No evidence of proinflammatory activity was observed in human blood ex vivo models. In preliminary acute toxicity studies, the compound was found to be of lower toxicity than chloroquine in mice, and was non-mutagenic in an Ames screen