Efficient Estimation of Mutual Information for Strongly Dependent Variables

We demonstrate that a popular class of nonparametric mutual information (MI) estimators based on k-nearest-neighbor graphs requires number of samples that scales exponentially with the true MI. Consequently, accurate estimation of MI between two strongly dependent variables is possible only for prohibitively large sample size. This important yet overlooked shortcoming of the existing estimators is due to their implicit reliance on local uniformity of the underlying joint distribution. We introduce a new estimator that is robust to local non-uniformity, works well with limited data, and is able to capture relationship strengths over many orders of magnitude. We demonstrate the superior performance of the proposed estimator on both synthetic and real-world data.Comment: 13 pages, to appear in International Conference on Artificial Intelligence and Statistics (AISTATS) 201

Concentrated suspensions of Brownian beads in water: dynamic heterogeneities trough a simple experimental technique

Concentrated suspensions of Brownian hard-spheres in water are an epitome for understanding the glassy dynamics of both soft materials and supercooled molecular liquids. From an experimental point of view, such systems are especially suited to perform particle tracking easily, and, therefore, are a benchmark for novel optical techniques, applicable when primary particles cannot be resolved. Differential Variance Analysis (DVA) is one such novel technique that simplifies significantly the characterization of structural relaxation processes of soft glassy materials, since it is directly applicable to digital image sequences of the sample. DVA succeeds in monitoring not only the average dynamics, but also its spatio-temporal fluctuations, known as dynamic heterogeneities. In this work, we study the dynamics of dense suspensions of Brownian beads in water, imaged through digital video-microscopy, by using both DVA and single-particle tracking. We focus on two commonly used signatures of dynamic heterogeneities: the dynamic susceptibility, $\chi_4$, and the non-Gaussian parameter, $\alpha_2$. By direct comparison of these two quantities, we are able to highlight similarities and differences. We do confirm that $\chi_4$ and $\alpha_2$ provide qualitatively similar information, but we find quantitative discrepancies in the scalings of characteristic time and length scale on approaching the glass transition.Comment: The original publication is available at http://www.scichina.com and http://www.springerlink.com http://engine.scichina.com/publisher/scp/journal/SCPMA/doi/10.1007/s11433-019-9401-x?slug=abstrac

Teaching critical appraisal to Sport & Exercise Sciences and Biosciences students

Seminars were implemented to develop undergraduates’ critical appraisal skills and their effectiveness was evaluated. Participants were 140 undergraduate students consisting of 103 students from Sport and Exercise Sciences and 37 from Biosciences. Four seminars were employed to develop and reinforce critical thinking and provide an opportunity for practise and group work. Source material included research proposals and published journal articles. Two linked pieces of coursework assessed critical thinking skills. Teaching method effectiveness was examined using the students’ questionnaire responses and comparison of coursework grades across the module. Students reported finding the seminars useful and helpful, and their self-ratings of critical appraisal skills improved from pre- to post-seminar. However, this was not generally reflected in assessment grades across the group. Overall, there was a significant decline in grades from the first to the second piece of coursework. However, although Sport and Exercise Sciences students’ scored significantly lower on the second coursework, Biosciences students scored higher. It is possible that this type of teaching helps to boost performance in students who originally are new to such skills. Future studies would need to examine whether different methods or longer follow-up might also yield improvements in objective measurements of students’ critical appraisal ability

Species-specific forest variable estimation using non-parametric modeling of multi-spectral photogrammetric point cloud data

The recent development in software for automatic photogrammetric processing of multispectral aerial imagery, and the growing nation-wide availability of Digital Elevation Model (DEM) data, are about to revolutionize data capture for forest management planning in Scandinavia. Using only already available aerial imagery and ALS-assessed DEM data, raster estimates of the forest variables mean tree height, basal area, total stem volume, and species-specific stem volumes were produced and evaluated. The study was conducted at a coniferous hemi-boreal test site in southern Sweden (lat. 58° N, long. 13° E). Digital aerial images from the Zeiss/Intergraph Digital Mapping Camera system were used to produce 3D point-cloud data with spectral information. Metrics were calculated for 696 field plots (10 m radius) from point-cloud data and used in k-MSN to estimate forest variables. For these stands, the tree height ranged from 1.4 to 33.0 m (18.1 m mean), stem volume from 0 to 829 m3 ha-1 (249 m3 ha-1 mean) and basal area from 0 to 62.2 m2 ha-1 (26.1 m2 ha-1 mean), with mean stand size of 2.8 ha. Estimates made using digital aerial images corresponding to the standard acquisition of the Swedish National Land Survey (Lantmäteriet) showed RMSEs (in percent of the surveyed stand mean) of 7.5% for tree height, 11.4% for basal area, 13.2% for total stem volume, 90.6% for pine stem volume, 26.4 for spruce stem volume, and 72.6% for deciduous stem volume. The results imply that photogrammetric matching of digital aerial images has significant potential for operational use in forestry

Synaptic Wnt/GSK3β Signaling Hub in Autism

Indexación: ScopusHundreds of genes have been associated with autism spectrum disorders (ASDs) and the interaction of weak and de novo variants derive from distinct autistic phenotypes thus making up the "spectrum." The convergence of these variants in networks of genes associated with synaptic function warrants the study of cell signaling pathways involved in the regulation of the synapse. The Wnt/β-catenin signaling pathway plays a central role in the development and regulation of the central nervous system and several genes belonging to the cascade have been genetically associated with ASDs. In the present paper, we review basic information regarding the role of Wnt/β-catenin signaling in excitatory/inhibitory balance (E/I balance) through the regulation of pre-and postsynaptic compartments. Furthermore, we integrate information supporting the role of the glycogen synthase kinase 3β (GSK3β) in the onset/development of ASDs through direct modulation of Wnt/β-catenin signaling. Finally, given GSK3β activity as key modulator of synaptic plasticity, we explore the potential of this kinase as a therapeutic target for ASD.https://www.hindawi.com/journals/np/2016/9603751

Analyzing Medication Documentation in Electronic Health Records: Dental Students’ Self-Reported Behaviors and Charting Practices

The aim of this two-part study was to assess third- and fourth-year dental students’ perceptions, self-reported behaviors, and actual charting practices regarding medication documentation in axiUm, the electronic health record (EHR) system. In part one of the study, in fall 2015, all 125 third- and 85 fourth-year dental students at one U.S. dental school were invited to complete a ten-item anonymous survey on medication history-taking. In part two of the study, the EHRs of 519 recent dental school patients were randomly chosen via axiUm query based on age >21 years and the presence of at least one documented medication. Documentation completeness was assessed per EHR and each medication based on proper medication name, classification, dose/frequency, indication, potential oral effects, and correct medication spelling. Consistency was evaluated by identifying the presence/absence of a medical reason for each medication. The survey response rate was 90.6% (N=187). In total, 64.5% of responding students reported that taking a complete medication history is important and useful in enhancing pharmacology knowledge; 90.4% perceived it helped improve their understanding of patients’ medical conditions. The fourth-year students were more likely than the third-year students to value the latter (p=0.0236). Overall, 48.6% reported reviewing patient medications with clinic faculty 76-100% of the time. The respondents’ most frequently cited perceived barriers to medication documentation were patients’ not knowing their medications (68.5%) and, to a much lesser degree, axiUm limitations (14%). Proper medication name was most often recorded (93.6%), and potential oral effects were recorded the least (3.0%). Medication/medical condition consistency was 70.6%. In this study, most of the students perceived patient medication documentation as important; however, many did not appreciate the importance of all elements of a complete medication history, and complete medication documentation was low

Applications of physical methods in high-frequency futures markets

In the present work we demonstrate the application of different physical methods to high-frequency or tick-by-tick financial time series data. In particular, we calculate the Hurst exponent and inverse statistics for the price time series taken from a range of futures indices. Additionally, we show that in a limit order book the relaxation times of an imbalanced book state with more demand or supply can be described by stretched exponential laws analogous to those seen in many physical systems.Comment: 14 Pages and 10 figures. Proceeding to the SPIE conference, 4 - 7 December 2007 Australian National Univ. Canberra, ACT, Australi