Shielding of a moving test charge in a quantum plasma

The linearized potential of a moving test charge in a one-component fully degenerate fermion plasma is studied using the Lindhard dielectric function. The motion is found to greatly enhance the Friedel oscillations behind the charge, especially for velocities larger than a half of the Fermi velocity, in which case the asymptotic behavior of their amplitude changes from 1/r^3 to 1/r^2.5. In the absence of the quantum recoil (tunneling) the potential reduces to a form similar to that in a classical Maxwellian plasma, with a difference being that the plasma oscillations behind the charge at velocities larger than the Fermi velocity are not Landau-damped.Comment: 9 pages, 11 figures. v3: Fixed typo, updated abstrac

Multi-label classification using ensembles of pruned sets

This paper presents a Pruned Sets method (PS) for multi-label classification. It is centred on the concept of treating sets of labels as single labels. This allows the classification process to inherently take into account correlations between labels. By pruning these sets, PS focuses only on the most important correlations, which reduces complexity and improves accuracy. By combining pruned sets in an ensemble scheme (EPS), new label sets can be formed to adapt to irregular or complex data. The results from experimental evaluation on a variety of multi-label datasets show that [E]PS can achieve better performance and train much faster than other multi-label methods

Effect of apolipoprotein E polymorphism on cognition and brain in the Cambridge Centre for Ageing and Neuroscience cohort.

Polymorphisms in the apolipoprotein E (APOE) gene have been associated with individual differences in cognition, brain structure and brain function. For example, the ε4 allele has been associated with cognitive and brain impairment in old age and increased risk of dementia, while the ε2 allele has been claimed to be neuroprotective. According to the 'antagonistic pleiotropy' hypothesis, these polymorphisms have different effects across the lifespan, with ε4, for example, postulated to confer benefits on cognitive and brain functions earlier in life. In this stage 2 of the Registered Report - https://osf.io/bufc4, we report the results from the cognitive and brain measures in the Cambridge Centre for Ageing and Neuroscience cohort (www.cam-can.org). We investigated the antagonistic pleiotropy hypothesis by testing for allele-by-age interactions in approximately 600 people across the adult lifespan (18-88 years), on six outcome variables related to cognition, brain structure and brain function (namely, fluid intelligence, verbal memory, hippocampal grey-matter volume, mean diffusion within white matter and resting-state connectivity measured by both functional magnetic resonance imaging and magnetoencephalography). We found no evidence to support the antagonistic pleiotropy hypothesis. Indeed, Bayes factors supported the null hypothesis in all cases, except for the (linear) interaction between age and possession of the ε4 allele on fluid intelligence, for which the evidence for faster decline in older ages was ambiguous. Overall, these pre-registered analyses question the antagonistic pleiotropy of APOE polymorphisms, at least in healthy adults

Head and neck paragangliomas: A two‐decade institutional experience and algorithm for management

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141924/1/lio2122.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/141924/2/lio2122_am.pd

Neural activation in the ventromedial prefrontal cortex precedes conscious experience of being in or out of a transient hallucinatory state

Background and Hypotheses Auditory verbal hallucinations (AVHs) is not only a common symptom in schizophrenia but also observed in individuals in the general population. Despite extensive research, AVHs are poorly understood, especially their underlying neuronal architecture. Neuroimaging methods have been used to identify brain areas and networks that are activated during hallucinations. A characteristic feature of AVHs is, however, that they fluctuate over time, with varying frequencies of starts and stops. An unanswered question is, therefore, what neuronal events co-occur with the initiation and inhibition of an AVH episode. Study Design We investigated brain activation with fMRI in 66 individuals who experienced multiple AVH-episodes while in the scanner. We extracted time-series fMRI-data and monitored changes second-by-second from 10 s before to 15 s after participants indicated the start and stop of an episode, respectively, by pressing a hand-held response-button. Study Results We found a region in the ventromedial prefrontal cortex (VMPFC) which showed a significant increase in activation initiated a few seconds before participants indicated the start of an episode, and a corresponding decrease in activation initiated a few seconds before the end of an episode. Conclusions The consistent increase and decrease in activation in this area in advance of the consciously experienced presence or absence of the “voice” imply that this region may act as a switch in turning episodes on and off. The activation is unlikely to be confounded by motor responses. The findings could have clinical implications for brain stimulation treatments, like transcranial magnetic stimulation.publishedVersio

Sex differences in antipsychotic efficacy and side effects in schizophrenia spectrum disorder:results from the BeSt InTro study

Current guidelines for patients with schizophrenia spectrum disease do not take sex differences into account, which may result in inappropriate sex-specific treatment. In the BeSt InTro study, a total of 144 patients (93 men and 51 women) with a schizophrenia spectrum diagnosis and ongoing psychosis were included and randomized to amisulpride, aripiprazole, or olanzapine in flexible dose. This trial is registered with ClinicalTrials.gov (NCT01446328). Primary outcomes were sex differences in dose, dose-corrected serum levels, efficacy, and tolerability. Dosing was higher for men than for women in the aripiprazole group (p = 0.025) and, at trend level, in the olanzapine group (p = 0.056). Dose-corrected serum levels were 71.9% higher in women than in men for amisulpride (p = 0.019) and 55.8% higher in women than in men for aripiprazole (p = 0.049). In the amisulpride group, men had a faster decrease in psychotic symptoms than women (p = 0.003). Moreover, amisulpride was more effective than the other medications in men but not in women. Prolactin levels were higher in women than in men, especially for amisulpride (p < 0.001). Also, women had higher BMI increase on amisulpride compared to the two other antipsychotics (p < 0.001). We conclude that clinicians should be aware of the risks of overdosing in women, especially for amisulpride and aripiprazole. Amisulpride is highly effective in men, but in women, amisulpride showed more severe side effects and may thus not be the drug of first choice. Our study shows that sex differences should be taken into account in future studies on antipsychotics. Future research is warranted to evaluate these preliminary results

Generalized Structured Component Analysis in candidate gene association studies: applications and limitations

Background: Generalized Structured Component Analysis (GSCA) is a component-based alternative to traditional covariance-based structural equation modelling. This method has previously been applied to test for association between candidate genes and clinical phenotypes, contrasting with traditional genetic association analyses that adopt univariate testing of many individual single nucleotide polymorphisms (SNPs) with correction for multiple testing. Methods: We first evaluate the ability of the GSCA method to replicate two previous findings from a genetics association study of developmental language disorders. We then present the results of a simulation study to test the validity of the GSCA method under more restrictive data conditions, using smaller sample sizes and larger numbers of SNPs than have previously been investigated. Finally, we compare GSCA performance against univariate association analysis conducted using PLINK v1.9. Results: Results from simulations show that power to detect effects depends not just on sample size, but also on the ratio of SNPs with effect to number of SNPs tested within a gene. Inclusion of many SNPs in a model dilutes true effects. Conclusions: We propose that GSCA is a useful method for replication studies, when candidate SNPs have been identified, but should not be used for exploratory analysis