The cost of space independence in P300-BCI spellers.

Background: Though non-invasive EEG-based Brain Computer Interfaces (BCI) have been researched extensively over the last two decades, most designs require control of spatial attention and/or gaze on the part of the user. Methods: In healthy adults, we compared the offline performance of a space-independent P300-based BCI for spelling words using Rapid Serial Visual Presentation (RSVP), to the well-known space-dependent Matrix P300 speller. Results: EEG classifiability with the RSVP speller was as good as with the Matrix speller. While the Matrix speller’s performance was significantly reliant on early, gaze-dependent Visual Evoked Potentials (VEPs), the RSVP speller depended only on the space-independent P300b. However, there was a cost to true spatial independence: the RSVP speller was less efficient in terms of spelling speed. Conclusions: The advantage of space independence in the RSVP speller was concomitant with a marked reduction in spelling efficiency. Nevertheless, with key improvements to the RSVP design, truly space-independent BCIs could approach efficiencies on par with the Matrix speller. With sufficiently high letter spelling rates fused with predictive language modelling, they would be viable for potential applications with patients unable to direct overt visual gaze or covert attentional focus

The Bizarre Spectral Variability of Central Stars of Planetary Nebulae

A radial velocity (RV) survey to detect central stars in binary systems was carried out between 2002 and 2004. De Marco et al. (2004) reported that 10 out of 11 monitored stars exhibited strong RV variability, but periods were not detected. Since other mechanisms, such as wind variability, can cause apparent RV variations, we monitored 4 of the 10 RV-variable stars at echelle resolutions to determine the origin of the variability. Although RV changes are confirmed for all four stars, none of them can be ascribed to binarity at this time. However, only for IC4593 is wind variability able to explain most (though not all) spectral variability. For BD+332642, no wind and no pulsations appear to be the origin of the RV changes. Finally, M1-77 and M2-54, both known to be irregular photometric variables, exhibit dramatic RV and line shape variability of the hydrogen and HeI absorption lines, as well as large RV variability of weaker lines, which do not change in shape. There is no satisfactory explanation of this variability, though a combination of wind variability and pulsations is still the best guess at what makes these stars so variable. We suggest that luminous central stars are ill suited to detect spectroscopic binaries, because winds (and possibly pulsations) are pervasive and would mask even strong periodicities. It it likely that a sample of intrinsically faint central stars would more readily yield binary information.Comment: 7 pages, 3 figures. To appear in the proceedings of the conference "Asymmetric Planetary Nebulae IV

DNA Authentication of St John’s Wort (Hypericum perforatum L.) Commercial Products Targeting the ITS Region

open access articleThere is considerable potential for the use of DNA barcoding methods to authenticate raw medicinal plant materials, but their application to testing commercial products has been controversial. A simple PCR test targeting species-specific sequences within the nuclear ribosomal internal transcribed spacer (ITS) region was adapted to screen commercial products for the presence of Hypericum perforatum L. material. DNA differing widely in amount and extent of fragmentation was detected in a number of product types. Two assays were designed to further analyse this DNA using a curated database of selected Hypericum ITS sequences: A qPCR assay based on a species-specific primer pair spanning the ITS1 and ITS2 regions, using synthetic DNA reference standards for DNA quantitation and a Next Generation Sequencing (NGS) assay separately targeting the ITS1 and ITS2 regions. The ability of the assays to detect H. perforatum DNA sequences in processed medicines was investigated. Out of twenty different matrices tested, both assays detected H. perforatum DNA in five samples with more than 103 ITS copies µL−1 DNA extract, whilst the qPCR assay was also able to detect lower levels of DNA in two further samples. The NGS assay confirmed that H. perforatum was the major species in all five positive samples, though trace contaminants were also detected

The CP-conserving 2HDM after the 8 TeV run

We confront the most common CP-conserving 2HDM with the LHC data analysed so far while taking into account all previously available experimental data. A special allowed corner of the parameter space is analysed - the so-called wrong-sign scenario where the Higgs coupling to down-type quarks changes sign relative to the Standard Model while the coupling to the massive vector bosons does not.Comment: 6 pages, 2 figures, to appear in the proceedings of the 22nd International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2014), 28 April - 2 May 2014 Warsaw (Poland

The Wrong Sign limit in the 2HDM

A sign change in the Higgs couplings to fermions and massive gauge bosons is still allowed in the framework of two-Higgs doublet models (2HDM). In this work we discuss the possible sign changes in the Higgs couplings to fermions and gauge bosons, while reviewing the status of the 8-parameter CP-conserving 2HDM after the Large Hadron Collider 8 TeV run.Comment: 6 pages, 3 figures. Proceedings of the Second Annual Conference on Large Hadron Collider Physics, Columbia University, New York, U.S.A, June 2-7, 2014. arXiv admin note: text overlap with arXiv:1407.439

A new method for detecting deception in Event Related Potentials using individual-specific weight templates [Abstract]

A new method called the weight template (WT) is proposed for classifying Event related potentials (ERPs) into deceiving and non-deceiving. In this study, EEG data from two P300-based lie detection experiments were analyzed to demonstrate the efficiency of the WT method in detecting deception. A comparison was made with a common method used to measure P300 presence, called Peak-to-Peak, which is believed to be more accurate than other methods in measuring P300 amplitudes [1, 2]. One experiment consisted of presenting participants with birth date stimuli and 12 participants were instructed to lie about their own birthday. The other experiment consisted of 15 participants who were instructed to lie about their first names [3]. Using simulated EEG data [4], Receiver Operating Characteristic (ROC) curves were also generated to examine the efficiency of the proposed method in detecting deception in low signal-to-noise ERPs. Typically, P300-based lie detection systems employ the P300 component to detect concealed information. They present three stimulus types: Probes (P), which represent concealed information or crime details and can be recognized only by the guilty person; Irrelevants (I), which are frequent and task (crime)-irrelevant, and Targets (T), which are irrelevant items, but participants are asked to do a task whenever they see a Target. For practical lie detection, the key comparison is between Probe and Irrelevant ERPs, since, for the nondeceiver, the former would be an Irrelevant. Importantly, the Probe for a deceiver typically generates a P300 ERP component, which is absent for the Irrelevant. The principle underlying the WT method is that as the Target stimulus is task-relevant, it will evoke a robust P300 pattern for each subject, which we hypothesize is characteristic in form and polarity of that individual's P300. Accordingly, this TERP can serve as an individual-specific template, with which to search for the Probe P300. Specifically, the difference between Tand IERPs was used as a template (i.e. effectively as a kernel) and this template was applied to Pand IERPs. Using such a template, with some pre-processing steps, we found that the WT achieved significantly better detection performance in comparison to Peak-to-Peak. In the names lie detection, the WT was able to detect deception for 93% in the guilty group compared with 80% by Peak-to peak. The false alarm rates using WT and Peak-to-Peak were 2% and 8% respectively. In the birthdays lie detection, hit rates were 50% using WT and 33% using Peak-to-Peak. The false alarm rates of both methods were 5%. ROC curve analysis also showed that in ERPs with high signal-to-noise ratio (SNR), both methods could detect deception successfully and almost equally. However, the WT performed better in ERPs with low SNR. We thus conclude that the WT is simple and very effective for detecting deception, even in ERPs with low SNR

Attention is more than prediction precision [Commentary on target article]

A cornerstone of the target article is that, in a predictive coding framework, attention can be modelled by weighting prediction error with a measure of precision. We argue that this is not a complete explanation, especially in the light of ERP (event-related potentials) data showing large evoked responses for frequently presented target stimuli, which thus are predicted

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability III: The Central Star of Abell 65

A growing number of close binary stars are being discovered among central stars of planetary nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10 to 15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary--nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989--2009 we also provide a more precise orbital period of 1.0037577 days.Comment: Accepted for publication in the Astronomical Journa