In searching for clinical biomarkers of the somatosensory function, we studied reproducibility of somatosensory potentials (SEP) evoked by finger stimulation in healthy subjects. SEPs induced by ...electrical stimulation and especially after median nerve stimulation is a method widely used in the literature. It is unclear, however, if the EEG recordings after finger stimulation are reproducible within the same subject. We tested in five healthy subjects the consistency and reproducibility of responses through bootstrapping as well as test–retest recordings. We further evaluated the possibility to discriminate activity of different fingers both at electrode and at source level. The lack of consistency and reproducibility suggest responses to finger stimulation to be unreliable, even with reasonably high signal-to-noise ratio and adequate number of trials. At sources level, somatotopic arrangement of the fingers representation was only found in one of the subjects. Although finding distinct locations of the different fingers activation was possible, our protocol did not allow for non-overlapping dipole representations of the fingers. We conclude that despite its theoretical advantages, we cannot recommend the use of somatosensory potentials evoked by finger stimulation to extract clinical biomarkers.
Outdoor systems performance and upgrade Lopes, L.; Andringa, S.; Assis, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
September 2023, 2023-09-00, Letnik:
1054
Journal Article
Recenzirano
Odprti dostop
Over the last two decades, the possibility of using RPCs in outdoors systems has increased considerably. Our group has participated in this effort by installing several systems and continues to work ...on their optimization, while simultaneously studying and developing new approaches that can use RPCs in outdoor applications.
In particular, four detectors were deployed in the field at the Pierre Auger Observatory in 2019 remained inactive, awaiting the commissioning of support systems. During the pandemic the detectors were left without gas flow for more than two years, but were recently reactivated with no major problems.
The LouMu project combines particle physics and geophysics in order to map meter-scale geologic structures, using Muon Tomography. Transmission muography is sensitive to the total amount of matter crossed by the muons, allowing to separate targets of different densities. In this exploratory project, it serves to identify unconsolidated rock zones, like geological faults and ore masses around an old Pyrite mine, now converted into a science center. The general goal is to compare how effective is the muographic survey when compared with the more standard geophysical techniques. The development of the RPC system used and the data from the last two years will be presented.
Finally, recent advances in a large area (1 m2) double gap-sealed RPC will be presented.
We describe the measurement of the depth of maximum, X{max}, of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 10;{18} eV observed by the fluorescence ...detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106{-21}{+35}) g/cm{2}/decade below 10{18.24+/-0.05} eV, and (24+/-3) g/cm{2}/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm{2}. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.
Vector boson decays of the Higgs boson Romão, J.C.; Andringa, S.
The European physical journal. C, Particles and fields,
03/1999, Letnik:
7, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We derive the width of the Higgs boson into vector bosons. General formulas are derived both for the on–shell decay \(H \rightarrow VV\) as well for the off–shell decays, \(H \rightarrow V^* V\) and ...\(H \rightarrow V^* V^*\), where \(V=\gamma,W^{\pm},Z^0\). For the off-shell decays the width of the decaying vector boson is properly included. The formulas are valid both for the Standard Model as well as for arbitrary extensions. As an example we study in detail the gauge-invariant effective Lagrangian models where we can have sizable enhancements over the Standard Model that could be observed at LEP.
The direction of individual
B
8
solar neutrinos has been reconstructed using the
SNO
+
liquid scintillator detector. Prompt, directional Cherenkov light was separated from the slower, isotropic ...scintillation light using time information, and a maximum likelihood method was used to reconstruct the direction of individual scattered electrons. A clear directional signal was observed, correlated with the solar angle. The observation was aided by a period of low primary fluor concentration that resulted in a slower scintillator decay time. This is the first time that event-by-event direction reconstruction in high light-yield liquid scintillator has been demonstrated in a large-scale detector.
Published by the American Physical Society
2024
To evaluate tolerance of a new dynamic hand-wrist orthosis and effectiveness on the prevention of progressive wrist contracture and spasticity after stroke.
Chronic stroke patients (N = 6) with upper ...limb spasticity, who had not been able to endure a static orthosis, were provided with a custom-made dynamic orthosis. Tolerance of the orthosis was evaluated by the daily wearing time, and self-reported pain and spasticity. Effectiveness was measured by contracture of wrist and finger flexor muscles, upper limb spasticity and use of spasticity treatment. Outcome measures were collected at time of fitting of the dynamic orthosis (baseline) and after three and six months.
Five patients could endure the dynamic orthosis without discomfort for 6 hours daily during the 6-month period. Self-reported spasticity and pain decreased significantly (p < 0.05) compared to wearing the static orthosis. In comparison to baseline, the maximum passive wrist extension increased significantly from -29° to -12° (p < 0.05). Although, no significant change in spasticity was measured, the use of Botulinum Toxin injections decreased for two patients.
The majority of the included chronic stroke patients tolerated the new dynamic orthosis for at least 6 hours daily and the use significantly reduced wrist contractures in a 6-month period.
The SNO+ experiment collected data as a low-threshold water Cherenkov detector from September 2017 to July 2019. Measurements of the 2.2-MeV $\gamma$ produced by neutron capture on hydrogen have been ...made using an Am-Be calibration source, for which a large fraction of emitted neutrons are produced simultaneously with a 4.4-MeV $\gamma$. Analysis of the delayed coincidence between the 4.4-MeV $\gamma$ and the 2.2-MeV capture $\gamma$ revealed a neutron detection efficiency that is centered around 50% and varies at the level of 1% across the inner region of the detector, which to our knowledge is the highest efficiency achieved among pure water Cherenkov detectors. In addition, the neutron capture time constant was measured and converted to a thermal neutron-proton capture cross section of $336.3^{+1.2}_{-1.5}$ mb.
The Pierre Auger Observatory is the largest extensive air shower detector, covering 3000 km2 in Argentina. The Observatory makes available, for educational and outreach purposes, 1% of its cosmic ray ...data set, corresponding after 10 years of running to more than 35 000 cosmic ray events. Several different proposals of educational activities have been developed within the collaboration and are available. We will focus on the activity guide we developed with the aim of exploring the rich education and outreach potential of cosmic rays with Portuguese high school students. In this guide we use the Auger public data set as a starting point to introduce open questions on the origin, nature and spectrum of high energy cosmic rays. To address them, the students learn about the air-shower cascade development, data reconstruction and its statistical analysis. The guide has been used both in the context of student summer internships at research labs and directly in schools, under the supervision of trained teachers and in close collaboration with Auger researchers. It is now available in Portuguese, English and Spanish.
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