A
bstract
The search for dark matter weakly interacting massive particles with noble liquids has probed masses down and below a GeV/
c
2
. The ultimate limit is represented by the experimental ...threshold on the energy transfer to the nuclear recoil. Currently, the experimental sensitivity has reached a threshold equivalent to a few ionization electrons. In these conditions, the contribution of a Bremsstrahlung photon or a so-called Migdal electron due to the sudden acceleration of a nucleus after a collision might be sizable. In the present work, we use a Bayesian approach to study how these effects can be exploited in experiments based on liquid argon detectors. In particular, taking inspiration from the DarkSide-50 public spectra, we develop a simulated experiment to show how the Migdal electron and the Bremsstrahlung photon allow to push the experimental sensitivity down to masses of 0.1 GeV
/c
2
, extending the search region for dark matter particles of previous results. For these masses we estimate the effect of the Earth shielding that, for strongly interacting dark matter, makes any detector blind. Finally, we show how the sensitivity scales for higher exposure.
Abstract
We studied, using a Bayesian approach, how the Migdal effect can be exploited in experiments based on liquid argon detectors. In particular we develop a simulated experiment to show how the ...Migdal electron allows to push the experimental sensitivity down to masses of 0.1 GeV/
c
2
, extending the search region for dark matter particles of previous results. Finally, given the relevance of the Migdal effect to the search for low mass Dark Matter, we discuss some new ideas on how to possibly measure such an effect with detectors based on a Time Projection Chamber exposed to an high neutron flux.
Abstract
We show an innovative approach based on Bayesian networks and linear algebra providing a solid and complete solution to the problem of the detector response and the related systematic ...effects. As a case study, we consider the dark matter direct detection searches. In this context, it is crucial to develop a reliable analysis framework, which is able to take into account all the relevant systematic effects in a clean and accessible way. The relations connecting the calibration parameters of the experiment to the final observed data spectrum are characterized by substantial complexity and non linearity. Usual approaches to direct detection data analysis involve multi-templates techniques. By means of our technique however it is possible to represent the full detector response to any background/signal event keeping the dependence on the detector parameters explicit. The advantage of this kind of approach is twofold: from the statistical point of view it is a solid and rigorous way to perform the analysis; from the computational point of view, we demonstrate that it is possible to represent the response of the detector by a set of matrices, allowing to use a GPU accelerated analysis code to improve the performance of the fit.
To document the occurrence of impulse control behaviours (ICBs) in patients with Parkinson's disease after 3 years of continuous deep brain stimulation (DBS) of the subthalamic nucleus (STN).
...Detailed neurological and ICB assessments were performed before STN DBS and up to 3 years after implant.
13 out of 56 patients (23.2%) had ICBs at baseline; they took higher doses of dopamine agonists (DAA). Three years after implant 11 had fully remitted with a 60.8% reduction of DAA medication; the remaining two, who had a similar medication reduction, had only compulsive eating, having recovered from hypersexuality. Six of the 43 patients without ICBs at baseline (14%) developed transient de novo ICBs after implant; none of them had ICBs at the 3-year observation.
ICBs were abolished in patients 3 years after STN DBS and DAA dosages were lowered. New ICBs may occur after implant and are transient in most cases. Compulsive eating may be specifically related to STN stimulation.
HD entails damage of the WM. Our aim was to explore in vivo the regional volume and microstructure of the brain WM in HD and to correlate such findings with clinical status of the patients.
Fifteen ...HD gene carriers in different clinical stages of the disease and 15 healthy controls were studied with T1-weighted images for VBM and DTI for TBSS. Maps of FA, MD, and λ∥ and λ⊥ were reconstructed.
Compared with controls, in addition to neostriatum and cortical GM volume loss, individuals with HD showed volume loss in the genu of the internal capsule and subcortical frontal WM bilaterally, the right splenium of the corpus callosum, and the left corona radiata. TBSS revealed symmetrically decreased FA in the corpus callosum, fornix, external/extreme capsule, inferior fronto-occipital fasciculus, and inferior longitudinal fasciculus. Areas of increased MD were more extensive and included arciform fibers of the cerebral hemispheres and cerebral peduncles. Increase of the λ∥ and a comparatively more pronounced increase of the λ⊥ underlay the decreased FA of the WM in HD. Areas of WM atrophy, decreased FA, and increased MD correlated with the severity of the motor and cognitive dysfunction, whereas only the areas with increased MD correlated with disease duration.
Microstructural damage accompanies volume decrease of the WM in HD and is correlated with the clinical deficits and disease duration. MR imaging-based measures could be considered as a biomarker of neurodegeneration in HD gene carriers.
Origin, yield and quality of the groundwater flows at high elevation in the Cimino volcano (central Italy) were examined. In this area, groundwater is geogenically contaminated by arsenic and ...fluoride, yet supplies drinking water for approximately 170,000 inhabitants. The origin of the high-elevation groundwater flows is strictly related to vertical and horizontal variability of the rock types (lava flows, lava domes and ignimbrite) in an area of limited size. In some cases, groundwater circuits are related to perched aquifers above noncontinuous aquitards; in other cases, they are due to flows in the highly fractured dome carapace, limited at the bottom by a low-permeability dome core. The high-elevation groundwater outflow represents about 30% of the total recharge of Cimino’s hydrogeological system, which has been estimated at 9.8 L/s/km
2
. Bicarbonate alkaline-earth, cold, neutral waters with low salinity, and notably with low arsenic and fluoride content, distinguish the high-elevation groundwaters from those of the basal aquifer. Given the quantity and quality of these resources, approaches in the capture and management of groundwater in this hydrogeological environment should be reconsidered. Appropriate tapping methods such as horizontal drains, could more efficiently capture the high-elevation groundwater resources, as opposed to the waters currently pumped from the basal aquifer which often require dearsenification treatments.
Background and purpose
Hereditary ataxias are heterogeneous groups of neurodegenerative disorders, characterized by cerebellar syndromes associated with dysarthria, oculomotor and corticospinal ...signs, neuropathy and cognitive impairment.
Recent reports have suggested mutations in the SPG7 gene, causing the most common form of autosomal recessive spastic paraplegia (MIM#607259), as a main cause of ataxias. The majority of described patients were homozygotes or compound heterozygotes for the c.1529C>T (p.Ala510Val) change. We screened a cohort of 895 Italian patients with ataxia for p.Ala510Val in order to define the prevalence and genotype–phenotype correlation of this variant.
Methods
We set up a rapid assay for c.1529C>T using restriction enzyme analysis after polymerase chain reaction amplification. We confirmed the diagnosis with Sanger sequencing.
Results
We identified eight homozygotes and 13 compound heterozygotes, including two novel variants affecting splicing.
Mutated patients showed a pure cerebellar ataxia at onset, evolving in mild spastic ataxia (alternatively) associated with dysarthria (~80% of patients), urinary urgency (~30%) and pyramidal signs (~70%). Comparing homozygotes and compound heterozygotes, we noted a difference in age at onset and Scale for the Assessment and Rating of Ataxia score between the two groups, supporting an earlier and more severe phenotype in compound heterozygotes versus homozygotes.
Conclusions
The SPG7 c.1529C>T (p.Ala510Val) mutants accounted for 2.3% of cerebellar ataxia cases in Italy, suggesting that this variant should be considered as a priority test in the presence of late‐onset pure ataxia. Moreover, the heterozygous/homozygous genotype appeared to predict the onset of clinical manifestation and disease progression.
Background
Recently, therapeutic attempts to control motor choreatic hyperkinesia of Huntington’s disease (HD) by means of pallidal deep brain stimulation (Gp-DBS) were successful. With respect to ...the clinical effects of Gp-DBS in juvenile hypokinetic-rigid HD (jHD; Westphal variant), only one single-case has been reported up to date. Oscillatory patterns of the Gp in jHD are not known.
Objectives and methods
This work aimed to analyse pallidal local field potential oscillations (LFP) in two patients with jHD treated with Gp-DBS. Safety data and clinical scores up to 12 months after DBS-electrode implantation were collected in the framework of a prospective trial (ClinicalTrials.gov; NCT00902889).
Results
Intraoperative LFP revealed local alpha and beta oscillations similar to those found in other movement disorders with akinetic rigid and dystonic presentation. Significant motor improvement was not found. There were no treatment-related complications or unresolved long-term adverse events.
Conclusions
In spite of similar intraoperative LFP patterns of jHD with those of movement disorders benefitting from DBS, clinical results were not convincing in our patients, so that Gp-DBS in jHD cannot be generally recommended.
► Impaired cholesterol biosynthesis in rodent models of Huntington Disease (HD). ► Reduced brain cholesterol turnover in HD patients as plasma 24S-hydroxycholesterol. ► Markers of cholesterol whole ...body synthesis reduced in HD patients. ► Cholesterol whole body and cerebral elimination reduced in HD patients. ► Reduced cerebral and whole body cholesterol metabolism in HD patients.
We previously reported impaired cholesterol biosynthesis in rodent Huntington Disease (HD) models and HD patients’ fibroblasts and post mortem brains. We also found that plasma levels of 24S-hydroxycholesterol (24OHC), the brain specific elimination product of cholesterol considered a marker of brain cholesterol turnover, were significantly reduced in HD patients at any disease stage. In the present study we analysed by mass spectrometry the
fasting plasma levels of cholesterol, its biosynthetic precursors lanosterol and lathosterol, of the whole-body elimination products 27-hydroxycholesterol and of brain 24OHC in a cohort of premanifest and HD patients at different disease stages. We found that the cholesterol precursors lanosterol and lathosterol (both index of whole body cholesterol synthesis), the levels of the bile acid precursor 27-hydroxycholesterol, and of the brain specific 24OHC, were all significantly reduced in manifest HD patients, suggesting that whole-body and brain cholesterol homeostasis are both impaired in HD.
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