Robust artifactual independent component classification for BCI practitioners

Objective. EEG artifacts of non-neural origin can be separated from neural signals by independent component analysis (ICA). It is unclear (1) how robustly recently proposed artifact classifiers transfer to novel users, novel paradigms or changed electrode setups, and (2) how artifact cleaning by a machine learning classifier impacts the performance of brain–computer interfaces (BCIs). Approach. Addressing (1), the robustness of different strategies with respect to the transfer between paradigms and electrode setups of a recently proposed classifier is investigated on offline data from 35 users and 3 EEG paradigms, which contain 6303 expert-labeled components from two ICA and preprocessing variants. Addressing (2), the effect of artifact removal on single-trial BCI classification is estimated on BCI trials from 101 users and 3 paradigms. Main results. We show that (1) the proposed artifact classifier generalizes to completely different EEG paradigms. To obtain similar results under massively reduced electrode setups, a proposed novel strategy improves artifact classification. Addressing (2), ICA artifact cleaning has little influence on average BCI performance when analyzed by state-of-the-art BCI methods. When slow motor-related features are exploited, performance varies strongly between individuals, as artifacts may obstruct relevant neural activity or are inadvertently used for BCI control. Significance. Robustness of the proposed strategies can be reproduced by EEG practitioners as the method is made available as an EEGLAB plug-in.EC/FP7/224631/EU/Tools for Brain-Computer Interaction/TOBIBMBF, 01GQ0850, Verbundprojekt: Bernstein Fokus Neurotechnologie - Nichtinvasive Neurotechnologie für Mensch-Maschine Interaktion - Teilprojekte A1, A3, A4, B4, W3, ZentrumDFG, 194657344, EXC 1086: BrainLinks-BrainTool

Biophysikalische und strukturbiologische Charakterisierung des ABC-Transporters OpuA aus Bacillus subtilis

Die Familie der ubiquitären ATP binding cassette (ABC)-Membranproteine katalysiert unter Hydrolyse von ATP die Translokation von Substraten über biologische Membranen. In der hier vorliegenden Arbeit wurde die Struktur und Funktion des osmoprotectant uptake (Opu) Systems A aus B. subtilis untersucht, das aus drei Untereinheiten, der ATPase OpuAA, dem integralen Membranprotein OpuAB und dem Substrat-Bindeprotein OpuAC, besteht und unter hyperosmolaren Bedingungen die kompatiblen Solute Glycin-Betain (GB) und Prolin-Betain (PB) in die Zelle importiert, um eine Plasmolyse zu verhindern. Sämtliche Untereinheiten wurden getrennt oder als OpuAA/AB Komplex in E. coli überproduziert und bis zur Homogenität isoliert. OpuAA zeigte ein dynamisches Monomer-Dimer Gleichgewicht (KD= 6 µM), das durch Nukleotide beeinflusst wurde. Unter Bedingungen hoher Ionenstärke konnten Monomer und Dimer getrennt isoliert und analysiert werden. Die Affinitäten und Stöchiometrien der OpuAA/Nukleotid Komplexe wurden unter Verwendung des fluoreszierenden TNP-ATP bzw. einer Nukleotid-sensitiven Trp-Mutante des OpuAA untersucht. Das Monomer hatte ein Molekül TNP-ATP gebunden, während zwei Moleküle TNP-ATP in dimerem OpuAA detektiert wurden. Die Affinität von Nukleotiden zu OpuAA nahm in folgender Reihe zu: ATP<ATP/Mg2+<ADP/Mg2+. Eine Erhöhung der Ionenstärke bewirkte nicht nur eine Erniedrigung der KD-Werte von OpuAA/Nukleotid Komplexen, sondern auch eine Steigerung der ATPase Aktivität. In 1 M NaCl zeigte das Monomer basale ATPase Aktivität, während das Dimer nur sehr geringe Aktivität hatte, jedoch durch Zugabe von OpuAB und OpuAC aktiviert wurde. K+ wurde als ein Modulator der ATPase Aktivität von OpuAA identifiziert. Die Zugabe von TNP-ADP/Mg2+ induzierte in dimeren OpuAA einen konformellen Wechsel, der zu einem Zerfall des Dimers führte. Monomer und Dimer hatten gegenüber Nukleotiden unterschiedliche Affinitäten, was eine unterschiedliche Architektur der Nukleotid-Bindetasche implizierte. Die Architektur des OpuAA Dimers wurde mittels FRET untersucht. Dazu wurde OpuAA ortspezifisch mit Fluorophoren markiert und ein Verfahren etabliert, in dem die intermolekularen Distanzen des Dimers bestimmt werden konnten. Ein Vergleich der Distanzen mit anderen NBD Dimeren zeigte, dass OpuAA eine zu BtuD oder MalKE. coli vergleichbare Dimer Architektur mit einer head-to-tail Orientierung hat. Die Struktur des OpuAC/GB und OpuAC/PB Komplexes wurde durch Röntgenstrukturanalyse mit einer Auflösung von 2,7 Å bzw. 2,8 Å aufgeklärt und zeigte zwei globuläre Domänen, die über zwei Peptidsegmente miteinander verbunden waren. Die delokalisierte positive Ladung des Liganden war von einem cluster aus drei Trp-Resten, dem sog. "Tryptophan-Prisma", über kationische-p-Interaktion komplexiert. Nach Ligandenbindung wurden beide Domänen durch eine Wasserstoffbrücke zwischen den konservierten Asp22 und Trp178 überbrückt. Dieser molekulare Schalter wurde von OpuAC genutzt, um Affinitäten von GB und PB zu regulieren.The family of the ubiquitous ATP binding cassette (ABC) membrane proteins catalyzes the translocation of substrates across biological membranes under the hydrolysis of ATP. In the present work the structure and function of the osmoprotectant uptake (Opu) system A from B. subtilis was investigated. OpuA is composed of three subunits: the ATPase OpuAA, the integral membrane protein OpuAB and the extracellular substrate-binding protein OpuAC. Under hyperosmotic growth conditions OpuA imports the compatible solutes glycine betaine (GB) and proline betaine (PB) into the cell to prevent plasmolysis. All three subunits were overproduced in E. coli as separate proteins or as OpuAA/AB complex and purified to homogeneity. OpuAA revealed a dynamic monomer-dimer equilibrium (KD= 6 µM) that was influenced by nucleotides indicating a coupling between oligomeric and functional state. Under conditions of high ionic strength both monomer and dimer could be isolated and analyzed separately. The affinities and stoichiometries of OpuAA/nucleotide complexes were determined by means of the fluorescent TNP-ATP or a nucleotide-sensitive Trp-mutant of OpuAA. The monomer bound one molecule TNP-ATP while two molecules TNP-ATP were associated with the dimer. The affinity of nucleotides to OpuAA increased in the following order: ATP<ATP/Mg2+<ADP/Mg2+. Increased ionic strength decreased the KD values of OpuAA/nucleotide complexes and increased ATPase activity. In the presence of 1 M NaCl, monomeric OpuAA showed a basal ATPase activity, whereas the dimer showed little ATPase activity that could however be stimulated by OpuAB and OpuAC. K+ was identified as a modulator of the ATPase activity. The addition of TNP-ADP/Mg2+ induced a conformational change in dimeric OpuAA that led to a decay of the dimer. Monomer and dimer had different affinities for nucleotides suggesting a different architecture of the nucleotide-binding pocket. The architecture of the OpuAA dimer was investigated by FRET. For that purpose, the catalytic or regulatory domain of OpuAA was labeled with fluorophores and a method was established to determine intermolecular distances. A comparison with distances of related dimeric ATPases indicated that OpuAA assembled with a dimer-interface similar to BtuCD or MalKE. coli in a head-to-tail orientation. The structure of OpuAC/GB and OpuAC/PB was solved by X-ray crystallography at a resolution of 2.7 Å and 2.8 Å, respectively. The complex showed two globular domains that were connected by two peptide segments and the ligand was localized in a cleft between the two domains. The delocalized positive charge of the ligand was coordinated by cationic-p-interactions in a cluster of three Trp residues, the so-called "tryptophane-prism". After ligand binding both domains were bridged by a hydrogen bond between the conserved Asp22 and Trp178. This molecular switch was used by OpuAC to regulate affinities of GB and PB, respectively

Enhanced gene trapping in mouse embryonic stem cells

Gene trapping is used to introduce insertional mutations into genes of mouse embryonic stem cells (ESCs). It is performed with gene trap vectors that simultaneously mutate and report the expression of the endogenous gene at the site of insertion and provide a DNA tag for rapid identification of the disrupted gene. Gene traps have been employed worldwide to assemble libraries of mouse ESC lines harboring mutations in single genes, which can be used to make mutant mice. However, most of the employed gene trap vectors require gene expression for reporting a gene trap event and therefore genes that are poorly expressed may be under-represented in the existing libraries. To address this problem, we have developed a novel class of gene trap vectors that can induce gene expression at insertion sites, thereby bypassing the problem of intrinsic poor expression. We show here that the insertion of the osteopontin enhancer into several conventional gene trap vectors significantly increases the gene trapping efficiency in high-throughput screens and facilitates the recovery of poorly expressed genes

Laminar air flow reduces particle load in TKA—even outside the LAF panel: a prospective, randomized cohort study

Purpose: Released particles are a major risk of airborne contamination during surgery. The present prospective study investigated the quantitative and qualitative particle load in the operating room (OR) depending on location, time of surgery and use of laminar air flow (LAF) system. Methods: The particle load/m(3) was measured during the implantation of 12 total knee arthroplasties (6 x LAF, 6 x Non-LAF) by using the Met One HHPC 6 + device (Beckmann Coulter GmbH, Germany). Measurement was based on the absorption and scattering of (laser) light by particles and was performed at three different time-points [empty OR, setting up, ongoing operation) at 3 fixed measurement points [OR table (central LAF area), anaesthesia tower (marginal LAF area), surgical image amplifier (outside LAF area)]. Results: Independent of time and location, all measurements showed a significantly higher particle load in the Non-LAF group (p < 0.01). With ongoing surgical procedure both groups showed increasing particle load. While there was a major increase of fine particles (size < 1 mu m) with advancing activity in the LAF group, the Non-LAF group showed higher particle gain with increasing particle size. The lowest particle load in the LAF group was measured at the operating column, increasing with greater distance from the operating table. The Non-LAF group presented a significantly higher particle load than the LAF group at all locations. Conclusion: The use of a LAF system significantly reduces the particle load and therefore potential bacterial contamination regardless of the time or place of measurement and therefore seems to be a useful tool for infection prevention. As LAF leads to a significant decrease of respirable particles, it appears to be a protective factor for the health of the surgical team regardless of its use in infection prevention. Level of evidence: I

Political parties and social groups: New perspectives and data on group and policy appeals

This article contributes to the literature on party appeals to social groups by introducing a new dataset on group and policy appeals in Scandinavia (2009–2015). In addition to coding to what social groups parties appeal, we collected information on what policies parties offer for the groups they mention and what goals and instruments they specify for such policies. The latter advance makes it possible to present new insights on the extent to which group appeals are actually substantial and meaningful. We find that left, centre, and right parties appeal to broad demographic categories rather than class. There are almost no appeals to the middle class, although the frequent reference to a category ‘all’ can be interpreted as a functional equivalent for middle class appeals. Finally, parties clearly still make substantial policy proposals and address concrete policy problems, but with only small differences in such appeals across the left-right spectrum

The illusion of class in welfare state politics?

Social class, with its potentially pivotal influence on both policy-making and electoral outcomes tied to the welfare state, is a frequent fixture in academic and political discussions about social policy. Yet these discussions presuppose that class identity is in fact tied up with distinct attitudes toward the welfare state. Using original data from ten surveys fielded in the United States and Western Europe, we investigate the relationship between class and general stances toward the welfare state as a whole, with the goal of determining whether class affects how individuals understand and relate to the welfare state. Our findings suggest that, although class markers are tied to objective and subjective positional considerations about one's place in the society, they nevertheless do not seem to shape stances toward the welfare state. What is more, this is equally true across the various welfare state types, as we find no evidence that so-called ‘middle-class welfare states’ engender more positive middle-class attitudes than other regimes. Based on our analysis, we propose that researchers would do better to focus on household income rather than class; while income may not be a perfect predictor of attitudes toward the welfare state, it is a markedly better one than class

Yardsticks of inequality: Preferences for redistribution in advanced democracies

This article explores how preferences for redistribution among voters are affected by the structure of inequality. There are strong theoretical reasons to believe that some voter segments matter more than others, not least the so-called median-income voter, but surprisingly little attention has been paid to directly analysing distinct income groups’ redistributive preferences. In addition, while much of the previous literature has focused on broad levels of inequality, as measured by the Gini coefficient, it is likely that individuals respond to different types of inequality in different ways. To rectify this gap, we use data from the European Social Survey and Eurostat to examine the interactive effect of income deciles and various measures of inequality. Results suggest that inequality especially affects the middle-income groups – that is, the assumed median-income voters. Moreover, not all inequality matters equally: it is inequality vis-à-vis those around the 80th percentile that shapes redistributive preferences