Long period Ap stars discovered with TESS data

Context. The TESS space mission has a primary goal to search for exoplanets around bright, nearby stars. Because of the high precision photometry required for the main mission, it also is producing superb data for asteroseismology, eclipsing binary stars, gyrochronology – any field of stellar astronomy where the data are variable light curves. Aims. In this work we show that the TESS data are excellent for astrophysical inference from peculiar stars that show no variability. The Ap stars have the strongest magnetic fields of any main-sequence stars. Some Ap stars have also been shown to have rotation periods of months, years, decades and even centuries. The astrophysical cause of their slow rotation – the braking mechanism – is not known with certainty. These stars are rare: there are currently about 3 dozen with known periods. Methods. The magnetic Ap stars have long-lived spots that allow precise determination of their rotation periods. We argue, and show, that most Ap stars with TESS data that show no low-frequency variability must have rotation periods longer than, at least, a TESS sector of 27 d. Results. From this we find 60 Ap stars in the southern ecliptic hemisphere TESS data with no rotational variability, of which at most a few can be pole-on, and six likely have nearly aligned magnetic and rotation axes. Of the other 54, 31 were previously known to have long rotation periods or very low projected equatorial velocities, which proves our technique; 23 are new discoveries. These are now prime targets for long-term magnetic studies. We also find that 12 of the 54 (22 per cent) long-period Ap stars are roAp stars, versus only 3 per cent (29 out of 960) of the other Ap stars studied with TESS in sectors 1−13, showing that the roAp phenomenon is correlated with rotation, although this correlation is not necessarily causal. In addition to probing rotation in Ap stars, these constant stars are also excellent targets to characterise the instrumental behaviour of the TESS cameras, as well as for the CHEOPS and PLATO missions. Conclusions. This work demonstrates astrophysical inference from nonvariable stars – we can get “something for nothing”

Consensus report: E. coli O104:H4 (HUSEC041) and the potential threat to European water supplies.

Among the 3rd Seminar for PhD students working on Water and Health which was held in Cannes on 27–29 June 2011, experts from a number of universities and research institutes took the opportunity to discuss the emergence of Escherichia coli O104:H4 in Europe. Especially, possible threats for European water suppliers were considered. The consensus is summarized in this report. The main conclusion was that E. coli O104:H4 would not pose a substantial risk to well managed water supplies, especially where regular monitoring of indicator E. coli is negative. However, this may not apply for small and very small water systems which are quite common in Europe. New strategies like the Water Safety Plan approach are needed to protect also small scale drinking water systems and private wells in Europe. Water used in the processing of foods likely to be eaten raw, especially sprouts, should be of drinking water quality

Refixation stability in shoulder hemiarthroplasty in case of four-part proximal humeral fracture

Primary stability of refixated fractures in case of shoulder hemiarthroplasty is a prerequisite to restore physiological glenohumeral joint function. Clinical observations often show a secondary dislocation and subsequent resorption of the bony anchor points like the greater and lesser tuberosity at the rotator cuff tendons. This failed integration leads to impaired glenohumeral load transmission and subsequent reduction of mobility. As a consequence, the optimisation of refixation methods is crucial for a better clinical outcome. To prove the stability of refixation techniques, a Finite Element fracture model was built. Resulting stresses at the bone surface and fragment migration relative to the prosthesis shaft were studied. The results of the calculations show that the isolated tuberosities show unstressed bone regions compared to the intact model. This circumstance may explain the clinically detected bone resorption due to the absence of mechanical stimuli. Furthermore, a cable guidance through lateral holes in the middle part of the proximal prosthesis results in a lower fragment displacement than a circumferential fixation method surrounding the entire proximal bon

Deviancy and Normative Training Processes in Experimental Groups of Delinquent and Nondelinquent Male Adolescents

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96268/1/ab21456.pd

Scene Construction, Visual Foraging, and Active Inference

This paper describes an active inference scheme for visual searches and the perceptual synthesis entailed by scene construction. Active inference assumes that perception and action minimize variational free energy, where actions are selected to minimize the free energy expected in the future. This assumption generalizes risk-sensitive control and expected utility theory to include epistemic value; namely, the value (or salience) of information inherent in resolving uncertainty about the causes of ambiguous cues or outcomes. Here, we apply active inference to saccadic searches of a visual scene. We consider the (difficult) problem of categorizing a scene, based on the spatial relationship among visual objects where, crucially, visual cues are sampled myopically through a sequence of saccadic eye movements. This means that evidence for competing hypotheses about the scene has to be accumulated sequentially, calling upon both prediction (planning) and postdiction (memory). Our aim is to highlight some simple but fundamental aspects of the requisite functional anatomy; namely, the link between approximate Bayesian inference under mean field assumptions and functional segregation in the visual cortex. This link rests upon the (neurobiologically plausible) process theory that accompanies the normative formulation of active inference for Markov decision processes. In future work, we hope to use this scheme to model empirical saccadic searches and identify the prior beliefs that underwrite intersubject variability in the way people forage for information in visual scenes (e.g., in schizophrenia). Copyright © 2016 Mirza, Adams, Mathys, Friston

Review of fixation techniques for the four-part fractured proximal humerus in hemiarthroplasty

<p>Abstract</p> <p>Introduction</p> <p>The clinical outcome of hemiarthroplasty for proximal humeral fractures is not satisfactory. Secondary fragment dislocation may prevent bone integration; the primary stability by a fixation technique is therefore needed to accomplish tuberosity healing. Present technical comparison of surgical fixation techniques reveals the state-of-the-art approach and highlights promising techniques for enhanced stability.</p> <p>Method</p> <p>A classification of available fixation techniques for three- and four part fractures was done. The placement of sutures and cables was described on the basis of anatomical landmarks such as the rotator cuff tendon insertions, the bicipital groove and the surgical neck. Groups with similar properties were categorized.</p> <p>Results</p> <p>Materials used for fragment fixation include heavy braided sutures and/or metallic cables, which are passed through drilling holes in the bone fragments. The classification resulted in four distinct groups: A: both tuberosities and shaft are fixed together by one suture, B: single tuberosities are independently connected to the shaft and among each other, C: metallic cables are used in addition to the sutures and D: the fragments are connected by short stitches, close to the fragment borderlines.</p> <p>Conclusions</p> <p>A plurality of techniques for the reconstruction of a fractured proximal humerus is found. The categorisation into similar strategies provides a broad overview of present techniques and supports a further development of optimized techniques. Prospective studies are necessary to correlate the technique with the clinical outcome.</p

Attractor-like dynamics in belief updating in schizophrenia

Subjects with a diagnosis of schizophrenia (Scz) overweight unexpected evidence in probabilistic inference: such evidence becomes 'aberrantly salient'. A neurobiological explanation for this effect is that diminished synaptic gain (e.g. hypofunction of cortical N-methyl-D-aspartate receptors) in Scz destabilizes quasi-stable neuronal network states (or 'attractors'). This attractor instability account predicts that i) Scz would overweight unexpected evidence but underweight consistent evidence, ii) belief updating would be more vulnerable to stochastic fluctuations in neural activity, and iii) these effects would correlate.Hierarchical Bayesian belief updating models were tested in two independent datasets (n=80 and n=167, male and female) comprising human subjects with schizophrenia, and both clinical and non-clinical controls (some tested when unwell and on recovery) performing the 'probability estimates' version of the beads task (a probabilistic inference task). Models with a standard learning rate, or including a parameter increasing updating to 'disconfirmatory evidence', or a parameter encoding belief instability were formally compared.The 'belief instability' model (based on the principles of attractor dynamics) had most evidence in all groups in both datasets. Two of four parameters differed between Scz and non-clinical controls in each dataset: belief instability and response stochasticity. These parameters correlated in both datasets. Furthermore, the clinical controls showed similar parameter distributions to Scz when unwell, but were no different to controls once recovered.These findings are consistent with the hypothesis that attractor network instability contributes to belief updating abnormalities in Scz, and suggest that similar changes may exist during acute illness in other psychiatric conditions.SIGNIFICANCE STATEMENTSubjects with a diagnosis of schizophrenia (Scz) make large adjustments to their beliefs following unexpected evidence, but also smaller adjustments than controls following consistent evidence. This has previously been construed as a bias towards 'disconfirmatory' information, but a more mechanistic explanation may be that in Scz, neural firing patterns ('attractor states') are less stable and hence easily altered in response to both new evidence and stochastic neural firing. We model belief updating in Scz and controls in two independent datasets using a hierarchical Bayesian model, and show that all subjects are best fit by a model containing a belief instability parameter. Both this and a response stochasticity parameter are consistently altered in Scz, as the unstable attractor hypothesis predicts

Long-period Ap stars discovered with TESS data: Cycles 3 and 4

One of the most challenging aspects of the Ap stars is the extreme differentiation of their rotation periods, which span more than five orders of magnitude. The physical origin of this differentiation remains poorly understood. The consideration of the most slowly rotating Ap stars represents a promising approach to gain insight into the processes responsible for the rotational braking to which the Ap stars are subject. However, historically, the study of these stars focused primarily on the most strongly magnetic among them. This bias introduced an ambiguity in the conclusions that could be drawn, as it did not allow the distinction between the rotational and magnetic effects, nor the investigation of possible correlations between rotational and magnetic properties. We previously showed that the identification of super-slowly rotating Ap (ssrAp) star candidates (defined as Ap stars that have rotation periods Prot > 50 d) through systematic exploitation of the available TESS photometric observations of Ap stars is an effective approach to build a sample devoid of magnetic bias. This approach rests on the presence of brightness spots on the surface of Ap stars that are not distributed symmetrically about their rotation axes and show long-term stability, hence are responsible for photometric variations with the stellar rotation period. In our previous analyses of TESS Cycle 1 and Cycle 2 data, we interpreted the Ap stars showing no such variability over the 27-d duration of a TESS sector as being ssrAp star candidates. Here, we applied the same approach to TESS Cycle 3 and Cycle 4 observations of Ap stars. We show, however, that two issues that had not been fully appreciated until now may lead to spurious identification of ssrAp star candidates. On the one hand, a considerable fraction of the Ap stars in the existing lists turn out to have erroneous or dubious spectral classifications. On the other hand, the TESS data processing may remove part of the variability signal, especially for stars with moderately long periods (20 d ≲ Prot ≲ 50 d). After critical evaluation of these effects, we report the identification of 25 new ssrAp star candidates and of eight stars with moderately long periods. Combining this list with the lists of ssrAp stars from Cycles 1 and 2 and with the list of ssrAp stars that were previously known but whose lack of variability was not detected in our study, we confirmed at a higher significance level the conclusions drawn in our earlier work. These include the lower rate of occurrence of super-slow rotation among weakly magnetic Ap stars than among strongly magnetic ones, the probable existence of a gap between ∼2 and ∼3 kG in the distribution of the magnetic field strengths of the ssrAp stars, and the much higher rate of occurrence of rapid oscillations in ssrAp stars than in the whole population of Ap stars. The next step to gain further understanding of the ssrAp stars will be to obtain high-resolution spectra of those for which such observations have not been made yet, to constrain their rotation velocities and their magnetic fields

Plasma Cleaning of Steam Ingressed ITER First Mirrors

In ITER, the first mirrors (FMs) are vulnerable to an in-vessel coolant leak which could severely diminish their optical properties. To understand the scope of this potential impact, several FM samples were exposed to a steam and humidity test simulating the event in ITER. Both rhodium and molybdenum mirrors, observed a loss in specular reflectivity as a result (the loss being greater for the Mo mirror). Their surfaces were tarnished with the development a thin Rh oxide and a thick Mo oxide (120–170 nm). This study focusses on capacitively coupled radio frequency (CCRF) plasma cleaning of steam ingressed (SI) FM samples and follow their optical recovery. Plasma cleaning experiments were performed with 13.56 MHz CCRF plasma using argon and/or hydrogen as process gas (with 230 eV ion energy). Initial and final reflectivity measurements, chemical surface analysis using in vaccuo X-ray photoelectron spectroscopy, scanning electron microscopy, focused ion beam and roughness measurements, were carried out for each sample to evaluate the cleaning efficiency. Using the plasma cleaning technique, it was possible to remove the SI induced contamination from the mirror surfaces and recover their optical properties to the pristine levels. Several ‘voids/inclusions’ were seen to arise along the grain boundaries as a result of the SI procedure. The concentration of these ‘voids/inclusions’ was observed to increase till a certain point followed by a decrease with increasing cleaning time

Spatial attention, precision, and Bayesian inference: a study of saccadic response speed

Inferring the environment's statistical structure and adapting behavior accordingly is a fundamental modus operandi of the brain. A simple form of this faculty based on spatial attentional orienting can be studied with Posner's location-cueing paradigm in which a cue indicates the target location with a known probability. The present study focuses on a more complex version of this task, where probabilistic context (percentage of cue validity) changes unpredictably over time, thereby creating a volatile environment. Saccadic response speed (RS) was recorded in 15 subjects and used to estimate subject-specific parameters of a Bayesian learning scheme modeling the subjects' trial-by-trial updates of beliefs. Different response models-specifying how computational states translate into observable behavior-were compared using Bayesian model selection. Saccadic RS was most plausibly explained as a function of the precision of the belief about the causes of sensory input. This finding is in accordance with current Bayesian theories of brain function, and specifically with the proposal that spatial attention is mediated by a precision-dependent gain modulation of sensory input. Our results provide empirical support for precision-dependent changes in beliefs about saccade target locations and motivate future neuroimaging and neuropharmacological studies of how Bayesian inference may determine spatial attention. © The Author 2013. Published by Oxford University Pres