416 research outputs found

    An Experimental 11.5 T Nb3Sn LHC Type of Dipole Magnet

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    As part of the magnet development program for the LHC an experimental 1 m long 11.5 T single aperture Nb3Sn dipole magnet has been designed and is now under construction. The design is focused on full utilisation of the high current density in the powder tube Nb3Sn. A new field optimisation has led to a different winding layout and cable sizes as compared to the reference LHC design. Another important feature of the design is the implementation of a shrink fit ring collar system. An extensive study of the critical current of the Nb3Sn cables as a function of the transverse stress on the cables shows a permanent degradation by the cabling process of about 20%, still leaving a safety margin at the operation field of 11.5 T of 15%. A revised glass/mica glass insulation system is applied which improves the thermal conductivity of the windings as well as the impregnation process considerably. This paper describes various design and production details of the magnet system as well as component test

    A Dual Role for Prediction Error in Associative Learning

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    Confronted with a rich sensory environment, the brain must learn statistical regularities across sensory domains to construct causal models of the world. Here, we used functional magnetic resonance imaging and dynamic causal modeling (DCM) to furnish neurophysiological evidence that statistical associations are learnt, even when task-irrelevant. Subjects performed an audio-visual target-detection task while being exposed to distractor stimuli. Unknown to them, auditory distractors predicted the presence or absence of subsequent visual distractors. We modeled incidental learning of these associations using a Rescorla-Wagner (RW) model. Activity in primary visual cortex and putamen reflected learning-dependent surprise: these areas responded progressively more to unpredicted, and progressively less to predicted visual stimuli. Critically, this prediction-error response was observed even when the absence of a visual stimulus was surprising. We investigated the underlying mechanism by embedding the RW model into a DCM to show that auditory to visual connectivity changed significantly over time as a function of prediction error. Thus, consistent with predictive coding models of perception, associative learning is mediated by prediction-error dependent changes in connectivity. These results posit a dual role for prediction-error in encoding surprise and driving associative plasticit

    Observing the Observer (II): Deciding When to Decide

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    In a companion paper [1], we have presented a generic approach for inferring how subjects make optimal decisions under uncertainty. From a Bayesian decision theoretic perspective, uncertain representations correspond to “posterior” beliefs, which result from integrating (sensory) information with subjective “prior” beliefs. Preferences and goals are encoded through a “loss” (or “utility”) function, which measures the cost incurred by making any admissible decision for any given (hidden or unknown) state of the world. By assuming that subjects make optimal decisions on the basis of updated (posterior) beliefs and utility (loss) functions, one can evaluate the likelihood of observed behaviour. In this paper, we describe a concrete implementation of this meta-Bayesian approach (i.e. a Bayesian treatment of Bayesian decision theoretic predictions) and demonstrate its utility by applying it to both simulated and empirical reaction time data from an associative learning task. Here, inter-trial variability in reaction times is modelled as reflecting the dynamics of the subjects' internal recognition process, i.e. the updating of representations (posterior densities) of hidden states over trials while subjects learn probabilistic audio-visual associations. We use this paradigm to demonstrate that our meta-Bayesian framework allows for (i) probabilistic inference on the dynamics of the subject's representation of environmental states, and for (ii) model selection to disambiguate between alternative preferences (loss functions) human subjects could employ when dealing with trade-offs, such as between speed and accuracy. Finally, we illustrate how our approach can be used to quantify subjective beliefs and preferences that underlie inter-individual differences in behaviour

    Unravelling sexual care in chronically ill patients:The perspective of GP practice nurses

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    Background.  Assessment of sexual health is important in chronically ill patients, as many experience sexual dysfunction (SD). The general practice nurse (GPN) can play a crucial part in addressing SD. Objective.  The aim of this cross-sectional study was to examine to which extent GPNs discuss SD with chronically ill patients and what barriers may refrained them from discussing SD. Furthermore, we examined which factors had an association with a higher frequency of discussing SD. Methods.  A cross-sectional survey using a 48-item questionnaire was send to 637 GPNs across the Netherlands. Results.  In total, 407 GPNs returned the questionnaire (response rate 63.9%) of which 337 completed the survey. Two hundred and twenty-one responding GPNs (65.6%) found it important to discuss SD. More than half of the GPNS (n = 179, 53.3%) never discussed SD during a first consultation, 60 GPNs (18%) never discussed SD during follow-up consultations. The three most important barriers for discussing SD were insufficient training (54.7%), 'reasons related to language and ethnicity' (47.5%) and 'reasons related to culture and religion' (45.8%). More than half of the GPNs thought that they had not enough knowledge to discuss SD (n = 176, 54.8%). A protocol on addressing SD would significantly increase discussing during SD. Conclusions.  This study indicates that GPNs do not discuss SD with chronically ill patients routinely. Insufficient knowledge, training and reasons related to cultural diversity were identified as most important reasons for this practice pattern. Implementation of training in combination with guidelines on SD in the general practice could improve on the discussing of sexual health with chronic patients

    Do patients with schizophrenia exhibit aberrant salience?

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    BACKGROUND: It has been suggested that some psychotic symptoms reflect ‘aberrant salience’, related to dysfunctional reward learning. To test this hypothesis we investigated whether patients with schizophrenia showed impaired learning of task-relevant stimulusreinforcement associations in the presence of distracting task-irrelevant cues. METHODS: We tested 20 medicated patients with schizophrenia and 17 controls on a reaction time game, the Salience Attribution Test. In this game, participants made a speeded response to earn money in the presence of conditioned stimuli (CSs). Each CS comprised two visual dimensions, colour and form. Probability of reinforcement varied over one of these dimensions (task-relevant), but not the other (task-irrelevant). Measures of adaptive and aberrant motivational salience were calculated on the basis of latency and subjective reinforcement probability rating differences over the task-relevant and task-irrelevant dimensions respectively. RESULTS: Participants rated reinforcement significantly more likely and responded significantly faster on high-probability reinforced relative to lowprobability reinforced trials, representing adaptive motivational salience. Patients exhibited reduced adaptive salience relative to controls, but the two groups did not differ in terms of aberrant salience. Patients with delusions exhibited significantly greater aberrant salience than those without delusions, and aberrant salience also correlated with negative symptoms. In the controls, aberrant salience correlated significantly with ‘introvertive anhedonia’ schizotypy. CONCLUSIONS: These data support the hypothesis that aberrant salience is related to the presence of delusions in medicated patients with schizophrenia, but are also suggestive of a link with negative symptoms. The relationship between aberrant salience and psychotic symptoms warrants further investigation in unmedicated patients

    Population-based screen-detected type 2 diabetes mellitus is associated with less need for insulin therapy after 10 years

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    INTRODUCTION: With increased duration of type 2 diabetes, most people have a growing need of glucose-lowering medication and eventually might require insulin. Presumptive evidence is reported that early detection (eg, by population-based screening) and treatment of hyperglycemia will postpone the indication for insulin treatment. A treatment legacy effect of population-based screening for type 2 diabetes of about 3 years is estimated. Therefore, we aim to compare insulin prescription and glycemic control in people with screen-detected type 2 diabetes after 10 years with data from people diagnosed with type 2 diabetes seven (treatment legacy effect) and 10 years before during care-as-usual. RESEARCH DESIGN AND METHODS: Three cohorts were compared: one screen-detected cohort with 10 years diabetes duration (Anglo-Danish-Dutch study of Intensive Treatment in People with Screen-Detected Diabetes in Primary care (ADDITION-NL): n=391) and two care-as-usual cohorts, one with 7-year diabetes duration (Groningen Initiative to Analyze Type 2 Diabetes Treatment (GIANTT) and Zwolle Outpatient Diabetes project Integrating Available Care (ZODIAC): n=4473) and one with 10-year diabetes duration (GIANTT and ZODIAC: n=2660). Insulin prescription (primary outcome) and hemoglobin A1c (HbA1c) of people with a known diabetes duration of 7 years or 10 years at the index year 2014 were compared using regression analyses. RESULTS: Insulin was prescribed in 10.5% (10-year screen detection), 14.7% (7-year care-as-usual) and 19.0% (10-year care-as-usual). People in the 7-year and 10-year care-as-usual groups had a 1.5 (95% CI 1.0 to 2.1) and 1.8 (95% CI 1.3 to 2.7) higher adjusted odds for getting insulin prescribed than those after screen detection. Lower HbA1c values were found 10 years after screen detection (mean 50.1 mmol/mol (6.7%) vs 51.8 mmol/mol (6.9%) and 52.8 mmol/mol (7.0%)), compared with 7 years and 10 years after care-as-usual (MDadjusted: 1.6 mmol/mol (95% CI 0.6 to 2.6); 0.1% (95% CI 0.1 to 0.2) and 1.8 mmol/mol (95% CI 0.7 to 2.9); and 0.2% (95% CI 0.1 to 0.3)). CONCLUSION: Population-based screen-detected type 2 diabetes is associated with less need for insulin after 10 years compared with people diagnosed during care-as-usual. Glycemic control was better after screen detection but on average good in all groups

    Compulsivity is measurable across distinct psychiatric symptom domains and is associated with familial risk and reward-related attentional capture.

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    BACKGROUND: Compulsivity can be seen across various mental health conditions and refers to a tendency toward repetitive habitual acts that are persistent and functionally impairing. Compulsivity involves dysfunctional reward-related circuitry and is thought to be significantly heritable. Despite this, its measurement from a transdiagnostic perspective has received only scant research attention. Here we examine both the psychometric properties of a recently developed compulsivity scale, as well as its relationship with compulsive symptoms, familial risk, and reward-related attentional capture. METHODS: Two-hundred and sixty individuals participated in the study (mean age = 36.0 [SD = 10.8] years; 60.0% male) and completed the Cambridge-Chicago Compulsivity Trait Scale (CHI-T), along with measures of psychiatric symptoms and family history thereof. Participants also completed a task designed to measure reward-related attentional capture (n = 177). RESULTS: CHI-T total scores had a normal distribution and acceptable Cronbach's alpha (0.84). CHI-T total scores correlated significantly and positively (all p < 0.05, Bonferroni corrected) with Problematic Usage of the Internet, disordered gambling, obsessive-compulsive symptoms, alcohol misuse, and disordered eating. The scale was correlated significantly with history of addiction and obsessive-compulsive related disorders in first-degree relatives of participants and greater reward-related attentional capture. CONCLUSIONS: These findings suggest that the CHI-T is suitable for use in online studies and constitutes a transdiagnostic marker for a range of compulsive symptoms, their familial loading, and related cognitive markers. Future work should more extensively investigate the scale in normative and clinical cohorts, and the role of value-modulated attentional capture across compulsive disorders
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