Properties of the renormalized quark mass in the Schrodinger functional with a non-vanishing background field

We compute the current quark mass in the Schrodinger functional with a non-vanishing background field at one loop order of perturbation theory. The results are used to obtain the critical mass at which the renormalized quark mass vanishes, and some lattice artefacts at one loop order.Comment: 3 pages, based on a poster presented at 19th International Symposium on Lattice Field Theory (Lattice 2001), Berlin, Germany, 19-24 Aug 200

Coping with confounds in multivoxel pattern analysis: What should we do about reaction time differences? A comment on Todd, Nystrom & Cohen 2013

Multivoxel pattern analysis (MVPA) is a sensitive and increasingly popular method for examining differences between neural activation patterns that cannot be detected using classical mass-univariate analysis. Recently, Todd et al. (“Confounds in multivariate pattern analysis: Theory and rule representation case study”, 2013, NeuroImage 77: 157–165) highlighted a potential problem for these methods: high sensitivity to confounds at the level of individual participants due to the use of directionless summary statistics. Unlike traditional mass-univariate analyses where confounding activation differences in opposite directions tend to approximately average out at group level, group level MVPA results may be driven by any activation differences that can be discriminated in individual participants. In Todd et al.'s empirical data, factoring out differences in reaction time (RT) reduced a classifier's ability to distinguish patterns of activation pertaining to two task rules. This raises two significant questions for the field: to what extent have previous multivoxel discriminations in the literature been driven by RT differences, and by what methods should future studies take RT and other confounds into account? We build on the work of Todd et al. and compare two different approaches to remove the effect of RT in MVPA. We show that in our empirical data, in contrast to that of Todd et al., the effect of RT on rule decoding is negligible, and results were not affected by the specific details of RT modelling. We discuss the meaning of and sensitivity for confounds in traditional and multivoxel approaches to fMRI analysis. We observe that the increased sensitivity of MVPA comes at a price of reduced specificity, meaning that these methods in particular call for careful consideration of what differs between our conditions of interest. We conclude that the additional complexity of the experimental design, analysis and interpretation needed for MVPA is still not a reason to favour a less sensitive approach.National Science Foundation (U.S.). Division of Information & Intelligent Systems (Collaborative Research in Computational Neuroscience 0904625)National Institutes of Health (U.S.) (National Institute for Biomedical Imaging and Bioengineering (U.S.)/National Alliance for Medical Image Computing (U.S.) U54-EB005149) )National Institutes of Health (U.S.) (National Institute for Biomedical Imaging and Bioengineering (U.S.)/Neuroimaging Analysis Center (U.S.) P41-EB015902

With a little help from my friends: The effect of social proximity on emotion regulation-related brain activity

When experiencing negative emotions, individuals often reach out for social support to help regulate their emotions. In times of an acute crisis, however, close friends might not be available, and physical closeness might be impossible. This functional magnetic resonance imaging (fMRI) study investigated the effect of social proximity on the effectiveness of social support for regulating emotions and the underlying neural mechanisms. Participants regulated their emotions in response to negative images either alone (intrapersonal regulation), or with help of a picture and supporting sentence provided by the best friend, or by a stranger (interpersonal regulation). Regulation success was enhanced for the support of friends compared to regulating alone or with the support of strangers. This effect was accompanied by the interplay of large-scale brain networks involved in processing emotions, social cognition, and cognitive control. Interpersonal regulation appeared to be implemented by lateral prefrontal regions. The amygdala showed increased activation for strangers. The activation profile of the social cognition network suggests a role in supporting empathic and mentalizing processes. The results highlight the power of social connectedness for boosting emotion regulation ability and the different neural networks that contribute to this effect

Intracardiac Echocardiography during Catheter-Based Ablation of Atrial Fibrillation

Accurate delineation of the variable left atrial anatomy is of utmost importance during anatomically based ablation procedures for atrial fibrillation targeting the pulmonary veins and possibly other structures of the atria. Intracardiac echocardiography allows real-time visualisation of the left atrium and adjacent structures and thus facilitates precise guidance of catheter-based ablation of atrial fibrillation. In patients with abnormal anatomy of the atria and/or the interatrial septum, intracardiac ultrasound might be especially valuable to guide transseptal access. Software algorithms like CARTOSound (Biosense Webster, Diamond Bar, USA) offer the opportunity to reconstruct multiple two-dimensional ultrasound fans generated by intracardiac echocardiography to a three-dimensional object which can be merged to a computed tomography or magnetic resonance imaging reconstruction of the left atrium. Intracardiac ultrasound reduces dwell time of catheters in the left atrium, fluoroscopy, and procedural time and is invaluable concerning early identification of potential adverse events. The application of intracardiac echocardiography has the great capability to improve success rates of catheter-based ablation procedures

Uncovering contextual biases in human decision-making. A multivariate analysis approach for patterns of functional magnetic resonance imaging data and event-related potentials

Decision-making is a fundamental aspect of human cognition and behaviour. Every day, we make a multitude of decisions, ranging from rather simple perceptual choices to complex financial decisions. The underlying cognitive and neural mechanisms appear to directly deploy external information, gathered by our senses, as well as internal information, such as preferences and beliefs. Ideally, this results in well-informed decisions and successful goal-directed behaviour. In reality, however, we are often faced with decision situations in which we do not have clear preferences, or access to all information. In these situations, contextual factors appear to have a strong influence on decision-makers. This work highlights recent research supporting the hypothesis that contextual information can exert significant biases on a variety of decision processes outside decision-makers’ awareness. These studies further exemplify a content-based cognitive neuroscience approach to human decision-making research, building on multivariate analysis techniques for brain imaging data to directly predict the content of decision outcomes and other decision-related variables from brain activity

Excitonic interactions between light-harvesting pigments as contribution to photoprotection in plants

Pflanzen sind im Laufe eines Tages starken Helligkeitsschwankungen ausgesetzt, die ein Umschalten des Photosyntheseapparates erforderlich machen. Bei niedrigen Lichtintensitäten müssen die Pflanzen möglichst viel Energie sammeln und dem Photosyntheseprozess zuführen. Bei hoher Lichteinstrahlung müssen sie sich jedoch an die veränderten Bedingungen anpassen und für eine Umwandlung von überschüssiger Energie in Wärme sorgen, um eine Beschädigung des Photosyntheseapparates zu verhindern. Dieses Abfangen überschüssiger Energie durch den Photosyntheseapparat der Pflanzen wird auch als non-photochemical quenching (NPQ) bezeichnet. Im Rahmen dieser Arbeit wurden die NPQ-Mechanismen mittels selektiver Zwei-Photonen-Anregung der dunklen Carotinoid-Zustände in den Lichtsammelantennen LHCII, CP24, CP26 und CP29 sowie in verschiedenen Mutanten der Pflanze Arabidopsis thaliana untersucht. Es konnten Hinweise darauf gefunden werden, dass es in mit dem Carotinoid Zeaxanthin angereichertem LHCII bei niedrigem pH-Wert zur Ausbildung von Wechselwirkungen zwischen Chlorophyll und Carotinoid kommt, wodurch niedrigliegende exzitonische Zustände gebildet werden. Des Weiteren konnte ein Anstieg dieser Wechselwirkungen auch in Mutanten von Arabidopsis thaliana während der Lichtanpassung festgestellt werden. Die Wechselwirkungen waren dabei vom Vorhandensein von Zeaxanthin und des Proteins PsbS in den Mutanten abhängig. Es scheint, dass sich Pflanzen über die Ausbildung von exzitonischen Wechselwirkungen zwischen Carotinoid und Chlorophyll vor hohen Lichtintensitäten schützen. Die niedrig liegenden Zustände würden als Quenching-Zentren wirken und die überschüssige Energie in Wärme umwandeln können. PsbS nimmt bei dieser Ausbildung der Wechselwirkung in vivo eine sehr wichtige Rolle ein und auch Zeaxanthin scheint einen wichtigen Beitrag zu leisten. Diese Ergebnisse sind ein wichtiger Schritt zum vollständigen Verständnis der Prozesse der Photosynthese.Plants are exposed to extreme changing light conditions during a typical day which makes a switch of the photosynthetic apparatus necessary. At low light intensities plants have to collect as much energy as possible for the photosynthetic processes. At high light intensities they have to adapt to these new conditions and transform all excessive energy into heat in order to prevent damage of the photosynthetic apparatus. This quenching of excessive energy by the photosynthetic apparatus of plants is called non-photochemical quenching (NPQ). In this work these NPQ mechanisms were analyzed by selective two-photon excitation of the dark carotoniod states in the light harvesting complexes LHCII, CP24, CP26 and CP29 and in several mutants of the plant Arabidopsis thaliana. Indication was found that in LHCII enriched with the carotinoid zeaxanthin interactions between chlorophyll and carotenoid are formed at low pH resulting in low-lying excitonic states. Additionally, an increase of these interactions was observed in mutants of Arabidopsis thaliana during high light adaptation. The interactions were dependent on the existence of zeaxanthin and the Protein PsbS. It seems that plants are forming the excitonic interactions between carotenoid and chlorophyll to protect themselves from high light intensities. The low lying states would act as quenching centres and dissipate excessive energy into heat. PsbS is playing a key role for the formation of the interactions in vivo and Zeaxanthin seems to be important, too. These results are an important step to the complete understanding of the processes of photosynthesis

"Kompetenzverhandlungen" : zur Relevanz von Sozialkompetenz bei Führungskräften der Continental AG am Beispiel dual Studierender ; theoretische Grundlagen und empirische Befunde

[no abstract

Early Heparin Administration Reduces Risk for Left Atrial Thrombus Formation during Atrial Fibrillation Ablation Procedures

Objective. Despite the use of anticoagulation during left atrial (LA) ablation procedures, ischemic cerebrovascular accidents (CVAs) are recognized as a serious complication. Heparin is usually given after safe transseptal access has been obtained, resulting in a short unprotected dwell time of catheters within the LA, which may account for CVAs. We investigated the frequency of CVAs and LA thrombus formation as detected by intracardiac ultrasound (ICE) depending on the timing of heparin administration. Methods and Results. Sixty LA ablation procedures with the use of ICE were performed in 55 patients. Patients were grouped by heparin administration after (Group I, n = 13) and before (Group II, n = 47) transseptal access. Group I patients were younger (56.6 ± 13.7 versus 65.9 ± 9.9 years, P = .01); other clinical and echocardiographic characteristics did not differ between groups. Early thrombus formation was observed in 2 (15.4%) of group I patients as compared to 0% of group II patients (P = .04). One CVA (2.1%) occurred in one group II patient without prior thrombus detection, and none occurred in group I patients (P = ns). Conclusion. Early administration of heparin reduces the risk of early intracardiac thrombus formation during LA ablation procedures. This did not result in reduced rate of CVAs

The chirally rotated Schr\"odinger functional with Wilson fermions and automatic O(a) improvement

A modified formulation of the Schr\"odinger functional (SF) is proposed. In the continuum it is related to the standard SF by a non-singlet chiral field rotation and therefore referred to as the chirally rotated SF ($\chi$SF). On the lattice with Wilson fermions the relation is not exact, suggesting some interesting tests of universality. The main advantage of the $\chi$SF consists in its compatibility with the mechanism of automatic O($a$) improvement. In this paper the basic set-up is introduced and discussed. Chirally rotated SF boundary conditions are implemented on the lattice using an orbifold construction. The lattice symmetries imply a list of counterterms, which determine how the action and the basic fermionic two-point functions are renormalised and O($a$) improved. As with the standard SF, a logarithmically divergent boundary counterterm leads to a multiplicative renormalisation of the fermionic boundary fields. In addition, a finite dimension 3 boundary counterterm must be tuned in order to preserve the chirally rotated boundary conditions in the interacting theory. Once this is achieved, O($a$) effects originating from the bulk action or from insertions of composite operators in the bulk can be avoided by the mechanism of automatic O($a$) improvement. The remaining O($a$) effects arise from the boundaries and can be cancelled by tuning a couple of O($a$) boundary counterterms. The general results are illustrated in the free theory where the Sheikholeslami-Wohlert term is shown to affect correlation functions only at O($a^2$), irrespective of its coefficient.Comment: 51 pages, 2 figures, revised version: improved and extended discussion of Ward identities in section 3 and of the inclusion of counterterms in section 5; eliminated some typos, introduced new ones, results unchange

First results on the running coupling in QCD with two massless flavours

We report on the non-perturbative computation of the running coupling of two-flavour QCD in the Schr"odinger functional scheme. The corresponding Lambda-parameter, which describes the coupling strength at high energy, is related to a low energy scale which still remains to be connected to a hadronic ``experimentally'' observable quantity. We find the non-perturbative evolution of the coupling indispensable to avoid untolerable errors in the estimated Lambda-parameter.Comment: 14 pages, 5 figures, 3 tables, some changes in the data analysis after discovery and correction of an error in Nucl. Phys. B 525, 387 (1998) by C. Christou et al. (hep-lat/9801007v2, Erratum to appear