336 research outputs found
Altered sleep and neurovascular dysfunction in alpha-synucleinopathies: the perfect storm for glymphatic failure
Clinical and cognitive progression in alpha-synucleinopathies is highly heterogeneous. While some patients remain stable over long periods of time, other suffer early dementia or fast motor deterioration. Sleep disturbances and nocturnal blood pressure abnormalities have been identified as independent risk factors for clinical progression but a mechanistic explanation linking both aspects is lacking. We hypothesize that impaired glymphatic system might play a key role on clinical progression. Glymphatic system clears brain waste during specific sleep stages, being blood pressure the motive force that propels the interstitial fluid through brain tissue to remove protein waste. Thus, the combination of severe sleep alterations, such as REM sleep behavioral disorder, and lack of the physiological nocturnal decrease of blood pressure due to severe dysautonomia may constitute the perfect storm for glymphatic failure, causing increased abnormal protein aggregation and spreading. In Lewy body disorders (Parkinson’s disease and dementia with Lewy bodies) the increment of intraneuronal alpha-synuclein and extracellular amyloid-β would lead to cognitive deterioration, while in multisystemic atrophy, increased pathology in oligodendroglia would relate to the faster and malignant motor progression. We present a research model that may help in developing studies aiming to elucidate the role of glymphatic function and associated factors mainly in alpha-synucleinopathies, but that could be relevant also for other protein accumulation-related neurodegenerative diseases. If the model is proven to be useful could open new lines for treatments targeting glymphatic function (for example through control of nocturnal blood pressure) with the objective to ameliorate cognitive and motor progression in alpha-synucleinopathies
EUROnu-WP6 2010 Report
This is a summary of the work done by the Working Package 6 (Physics) of the
EU project "EUROnu" during the second year of activity of the project.Comment: 82 pages, 51 eps figure
Visual processing speed in hemianopia patients secondary to acquired brain injury: a new assessment methodology
Producción CientíficaBackground: There is a clinical need to identify diagnostic parameters that objectively quantify and monitor the
effective visual ability of patients with homonymous visual field defects (HVFDs). Visual processing speed (VPS) is an
objective measure of visual ability. It is the reaction time (RT) needed to correctly search and/or reach for a visual
stimulus. VPS depends on six main brain processing systems: auditory-cognitive, attentional, working memory,
visuocognitive, visuomotor, and executive. We designed a new assessment methodology capable of activating
these six systems and measuring RTs to determine the VPS of patients with HVFDs.
Methods: New software was designed for assessing subject visual stimulus search and reach times (S-RT and R-RT
respectively), measured in seconds. Thirty-two different everyday visual stimuli were divided in four complexity
groups that were presented along 8 radial visual field positions at three different eccentricities (10o, 20o, and 30o).
Thus, for each HVFD and control subject, 96 S- and R-RT measures related to VPS were registered. Three additional
variables were measured to gather objective data on the validity of the test: eye-hand coordination mistakes
(ehcM), eye-hand coordination accuracy (ehcA), and degrees of head movement (dHM, measured by a head-tracker
system). HVFD patients and healthy controls (30 each) matched by age and gender were included. Each subject
was assessed in a single visit. VPS measurements for HFVD patients and control subjects were compared for the
complete test, for each stimulus complexity group, and for each eccentricity.
Results: VPS was significantly slower (p < 0.0001) in the HVFD group for the complete test, each stimulus
complexity group, and each eccentricity. For the complete test, the VPS of the HVFD patients was 73.0% slower
than controls. They also had 335.6% more ehcMs, 41.3% worse ehcA, and 189.0% more dHMs than the controls.
Conclusions: Measurement of VPS by this new assessment methodology could be an effective tool for objectively
quantifying the visual ability of HVFD patients. Future research should evaluate the effectiveness of this novel
method for measuring the impact that any specific neurovisual rehabilitation program has for these patients
Asymmetric Dark Matter and Dark Radiation
Asymmetric Dark Matter (ADM) models invoke a particle-antiparticle asymmetry,
similar to the one observed in the Baryon sector, to account for the Dark
Matter (DM) abundance. Both asymmetries are usually generated by the same
mechanism and generally related, thus predicting DM masses around 5 GeV in
order to obtain the correct density. The main challenge for successful models
is to ensure efficient annihilation of the thermally produced symmetric
component of such a light DM candidate without violating constraints from
collider or direct searches. A common way to overcome this involves a light
mediator, into which DM can efficiently annihilate and which subsequently
decays into Standard Model particles. Here we explore the scenario where the
light mediator decays instead into lighter degrees of freedom in the dark
sector that act as radiation in the early Universe. While this assumption makes
indirect DM searches challenging, it leads to signals of extra radiation at BBN
and CMB. Under certain conditions, precise measurements of the number of
relativistic species, such as those expected from the Planck satellite, can
provide information on the structure of the dark sector. We also discuss the
constraints of the interactions between DM and Dark Radiation from their
imprint in the matter power spectrum.Comment: 22 pages, 5 figures, to be published in JCAP, minor changes to match
version to be publishe
ANÁLISE COMPARATIVA DA PRODUTIVIDADE DOS PARES ORIENTADOR-ORIENTADO EM CIÊNCIA DA COMPUTAÇÃO
The increasing involvement of graduate students in scientific communication has been the subject of studies in many countries that have been discussing the role of doctoral studies in the research career. In this article we are interested on the study of the academic relationship between the advisor and the advisee for a group of PhD pairs in the Computer Science area, with curricula registered in the Lattes Platform. We analyze the main characteristics of the group and their coauthor relationships. In terms of co-authorship: (i) we observe that the duration that is established between advisor and advisee can extrapolate the formal period of supervision, and (ii) we show that the duration of the collaboration is correlated with both the number of articles published by the advisee and the ones published by the advisor. In this work we also present the advisee profile for researchers that worked in some of the graduate courses in Computer Science in Brazil in the triennium 2007-2009.A crescente participação dos pós-graduandos na comunicação científica das diversas áreas da ciência tem sido tema de estudos em diversos países que vêm discutindo o papel do doutoramento na carreira de pesquisa. Neste artigo é estudada a relação acadêmica temporal existente entre o aluno orientado e seu orientador para o conjunto de pares de doutores da área de Ciência da Computação com currículos cadastrados na plataforma Lattes. Analisamos as principais características do grupo e suas relações de coautoria. Em termos de coautoria: (i) observamos que o tempo de duração da parceria que se estabelece entre orientador e orientado pode extrapolar o período formal de orientação e (ii) mostramos que a duração do tempo de colaboração correlaciona-se com o número de artigos em periódicos publicados pelo orientado e o número de artigos publicados pelo orientador. Neste trabalho também apresentamos o perfil dos orientados para pesquisadores que atuaram como docentes de algum dos cursos de pós-graduação em Ciência da Computação no Brasil no triênio 2007-2009
Mass hierarchy, 2-3 mixing and CP-phase with Huge Atmospheric Neutrino Detectors
We explore the physics potential of multi-megaton scale ice or water
Cherenkov detectors with low ( GeV) threshold. Using some proposed
characteristics of the PINGU detector setup we compute the distributions of
events versus neutrino energy and zenith angle , and study
their dependence on yet unknown neutrino parameters. The
regions are identified where the distributions have the highest sensitivity to
the neutrino mass hierarchy, to the deviation of the 2-3 mixing from the
maximal one and to the CP-phase. We evaluate significance of the measurements
of the neutrino parameters and explore dependence of this significance on the
accuracy of reconstruction of the neutrino energy and direction. The effect of
degeneracy of the parameters on the sensitivities is also discussed. We
estimate the characteristics of future detectors (energy and angle resolution,
volume, etc.) required for establishing the neutrino mass hierarchy with high
confidence level. We find that the hierarchy can be identified at --
level (depending on the reconstruction accuracies) after 5 years of
PINGU operation.Comment: 39 pages, 21 figures. Description of Fig.3 correcte
Precision on leptonic mixing parameters at future neutrino oscillation experiments
We perform a comparison of the different future neutrino oscillation
experiments based on the achievable precision in the determination of the
fundamental parameters theta_{13} and the CP phase, delta, assuming that
theta_{13} is in the range indicated by the recent Daya Bay measurement. We
study the non-trivial dependence of the error on delta on its true value. When
matter effects are small, the largest error is found at the points where CP
violation is maximal, and the smallest at the CP conserving points. The
situation is different when matter effects are sizable. As a result of this
effect, the comparison of the physics reach of different experiments on the
basis of the CP discovery potential, as usually done, can be misleading. We
have compared various proposed super-beam, beta-beam and neutrino factory
setups on the basis of the relative precision of theta_{13} and the error on
delta. Neutrino factories, both high-energy or low-energy, outperform
alternative beam technologies. An ultimate precision on theta_{13} below 3% and
an error on delta of < 7^{\circ} at 1 sigma (1 d.o.f.) can be obtained at a
neutrino factory.Comment: Minor changes, matches version accepted in JHEP. 30 pages, 9 figure
Mapper of the IGM Spin Temperature (MIST): Instrument Overview
The observation of the global 21 cm signal produced by neutral hydrogen gas
in the intergalactic medium (IGM) during the Dark Ages, Cosmic Dawn, and Epoch
of Reionization requires measurements with extremely well-calibrated wideband
radiometers. We describe the design and characterization of the Mapper of the
IGM Spin Temperature (MIST), which is a new ground-based, single-antenna,
global 21 cm experiment. The design of MIST was guided by the objectives of
avoiding systematics from an antenna ground plane and cables around the
antenna, as well as maximizing the instrument's on-sky efficiency and
portability for operations at remote sites. We have built two MIST instruments,
which observe in the range 25-105 MHz. For the 21 cm signal, this frequency
range approximately corresponds to redshifts 55.5 > z > 12.5, encompassing the
Dark Ages and Cosmic Dawn. The MIST antenna is a horizontal blade dipole of
2.42 m in length, 60 cm in width, and 52 cm in height above the ground. This
antenna operates without a metal ground plane. The instruments run on 12 V
batteries and have a maximum power consumption of 17 W. The batteries and
electronics are contained in a single receiver box located under the antenna.
We present the characterization of the instruments using electromagnetic
simulations and lab measurements. We also show sample sky measurements from
recent observations at remote sites in California, Nevada, and the Canadian
High Arctic. These measurements indicate that the instruments perform as
expected. Detailed analyses of the sky measurements are left for future work.Comment: Comments welcom
Light Sterile Neutrinos: A White Paper
This white paper addresses the hypothesis of light sterile neutrinos based on
recent anomalies observed in neutrino experiments and the latest astrophysical
data
Neutrino Probes of the Nature of Light Dark Matter
Dark matter particles gravitationally trapped inside the Sun may annihilate
into Standard Model particles, producing a flux of neutrinos. The prospects of
detecting these neutrinos in future multi-\kton{} neutrino detectors designed
for other physics searches are explored here. We study the capabilities of a
34/100 \kton{} liquid argon detector and a 100 \kton{} magnetized iron
calorimeter detector. These detectors are expected to determine the energy and
the direction of the incoming neutrino with unprecedented precision allowing
for tests of the dark matter nature at very low dark matter masses, in the
range of 5-50 GeV. By suppressing the atmospheric background with angular cuts,
these techniques would be sensitive to dark matter - nucleon spin dependent
cross sections at the fb level, reaching down to a few ab for the most
favorable annihilation channels and detector technology.Comment: Minor changes and clarifications, matches JCAP versio
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