1,054 research outputs found
Sensorimotor processing for balance in spinocerebellar ataxia type 6.
We investigated whether balance impairments caused by cerebellar disease are associated with specific sensorimotor processing deficits that generalize across all sensory modalities. Experiments focused on the putative cerebellar functions of scaling and coordinate transformation of balance responses evoked by stimulation of single sensory channels. Vestibular, visual, and proprioceptive sensory channels were stimulated in isolation using galvanic vestibular stimulation, moving visual scenery, and muscle vibration, respectively, in 16 subjects with spinocerebellar ataxia type 6 (SCA6) and 16 matched healthy controls. Two polarities of each stimulus type evoked postural responses of similar form in the forward and backward directions. Disease severity was assessed using the Scale for Assessment and Rating of Ataxia. Impaired balance of SCA6 subjects during unperturbed stance was reflected in faster than normal body sway (P = 0.009), which correlated with disease severity (r = 0.705, P < 0.001). Sensory perturbations revealed a sensorimotor processing abnormality that was specific to response scaling for the visual channel. This manifested as visually evoked postural responses that were approximately three times larger than normal (backward, P < 0.001; forward P = 0.005) and correlated with disease severity (r = 0.543, P = 0.03). Response direction and habituation properties were no different from controls for all three sensory modalities. Cerebellar degeneration disturbs the scaling of postural responses evoked by visual motion, possibly through disinhibition of extracerebellar visuomotor centers. The excessively high gain of the visuomotor channel without compensatory decreases in gains of other sensorimotor channels provides a potential mechanism for instability of the balance control system in cerebellar disease. © 2015 International Parkinson and Movement Disorder Society
Reactor Fuel Fraction Information on the Antineutrino Anomaly
We analyzed the evolution data of the Daya Bay reactor neutrino experiment in
terms of short-baseline active-sterile neutrino oscillations taking into
account the theoretical uncertainties of the reactor antineutrino fluxes. We
found that oscillations are disfavored at with respect to a
suppression of the reactor antineutrino flux and at
with respect to variations of the and
fluxes. On the other hand, the analysis of the rates of the
short-baseline reactor neutrino experiments favor active-sterile neutrino
oscillations and disfavor the suppression of the flux at
and variations of the and fluxes
at . We also found that both the Daya Bay evolution data and the
global rate data are well-fitted with composite hypotheses including variations
of the or fluxes in addition to
active-sterile neutrino oscillations. A combined analysis of the Daya Bay
evolution data and the global rate data shows a slight preference for
oscillations with respect to variations of the and
fluxes. However, the best fits of the combined data are given
by the composite models, with a preference for the model with an enhancement of
the flux and relatively large oscillations.Comment: 9 page
Episodic ataxias: Faux or real?
The term Episodic Ataxias (EA) was originally used for a few autosomal dominant diseases, characterized by attacks of cerebellar dysfunction of variable duration and frequency, often accompanied by other ictal and interictal signs. The original group subsequently grew to include other very rare EAs, frequently reported in single families, for some of which no responsible gene was found. The clinical spectrum of these diseases has been enormously amplified over time. In addition, episodes of ataxia have been described as phenotypic variants in the context of several different disorders. The whole group is somewhat confused, since a strong evidence linking the mutation to a given phenotype has not always been established. In this review we will collect and examine all instances of ataxia episodes reported so far, emphasizing those for which the pathophysiology and the clinical spectrum is best defined
Mitochondrial Dysfunction in Friedreich Ataxia
Friedreich’s Ataxia (FRDA) is the commonest hereditary form of ataxia affecting the Western European population. FRDA is an autosomal recessive neurodegenerative disorder caused by an intronic GAA repeat expansion within the FXN gene; the 96% of the patients are homozygous, while the remaining 4% are compound heterozygous carrying the GAA repeat mutation on one allele and point mutations on the other one. FRDA first symptoms appear at young age during the firsts two decades of life. The clinical features include progressive gait and limb ataxia, dysarthria, muscle weakness, peripheral sensory neuropathy, pes cavus, and scoliosis. FRDA is a multi-systemic disorder; therefore, patients develop non-neurological signs, such as hypertrophic cardiomyopathy, diabetes, and urological problems
Gopi: compiling linear and static channels in go
PTDC/CCI-COM/32166/2017We identify two important features to enhance the design of communication protocols specified in the pi-calculus, that are linear and static channels, and present a compiler, named GoPi, that maps high level specifications into executable Go programs. Channels declared as linear are deadlock-free, while the scope of static channels, which are bound by a hide declaration, does not enlarge at runtime; this is enforced statically by means of type inference, while specifications do not include annotations. Well-behaved processes are transformed into Go code that supports non-deterministic synchronizations and race-freedom. We sketch two main examples involving protection against message forwarding, and forward secrecy, and discuss the features of the tool, and the generated code. We argue that GoPi can support academic activities involving process algebras and formal models, which range from the analysis and testing of concurrent processes for research purposes to teaching formal languages and concurrent systems.publishersversionpublishe
Probing Sterile Neutrino Parameters with Double Chooz, Daya Bay and RENO
In this work, we present a realistic analysis of the potential of the
present-day reactor experiments Double Chooz, Daya Bay and RENO for probing the
existence of sterile neutrinos. We present exclusion regions for sterile
oscillation parameters for each of these experiments, using simulations with
realistic estimates of systematic errors and detector resolutions, and compare
the sterile parameter sensitivity regions we obtain with the existing bounds
from other reactor experiments. We find that these experimental set-ups give
significant bounds on the parameter \Theta_{ee} especially in the low sterile
oscillation region 0.01 < \Delta m_{41}^2 < 0.05 eV^2. These bounds can add to
our understanding of the sterile neutrino sector since there is still a tension
in the allowed regions from different experiments for sterile parameters.Comment: 12 pages, 5 figure
What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly
We investigate how the anticipated neutral current rate from will
sharpen our understanding of the solar neutrino anomaly. Quantitative analyses
are performed with representative values of this rate in the expected range of
. This would provide a signal for transition
into a state containing an active neutrino component. Assuming this state to be
purely active one can estimate both the neutrino flux and the
survival probability to a much higher precision than currently possible.
Finally the measured value of the rate will have profound implications for
the mass and mixing parameters of the solar neutrino oscillation solution.Comment: Brief discussion on the first NC result from SNO added; final version
to be published in the MPL
nu_e Disappearance in MiniBooNE
The anomalous excess of low-energy nu_e events measured in the MiniBooNE
experiment is explained through a renormalization of the absolute neutrino flux
and a simultaneous disappearance of the nu_e's in the beam, which is compatible
with that indicated by the results of Gallium radioactive source experiments.
We present the results of the fit of MiniBooNE data (P(nu_e->nu_e) = 0.64 +0.08
-0.07) and the combined fit of MiniBooNE data and the nu_e disappearance
measured in the Gallium radioactive source experiments, which gives
P(nu_e->nu_e) = 0.82 +- 0.04. We show that our interpretation of the data is
also compatible with an old indication in favor of nu_e disappearance found
from the analysis of the results of beam-dump experiments, leading to
P(nu_e->nu_e) = 0.80 +0.03 -0.04.Comment: 17 pages. Final version published in Phys. Rev. D 77, 093002 (2008
Light sterile neutrino production in the early universe with dynamical neutrino asymmetries
Light sterile neutrinos mixing with the active ones have been recently
proposed to solve different anomalies observed in short-baseline oscillation
experiments. These neutrinos can also be produced by oscillations of the active
neutrinos in the early universe, leaving possible traces on different
cosmological observables. Here we perform an updated study of the neutrino
kinetic equations in (3+1) and (2+1) oscillation schemes, dynamically evolving
primordial asymmetries of active neutrinos and taking into account for the
first time CP-violation effects. In the absence of neutrino asymmetries,
eV-mass scale sterile neutrinos would be completely thermalized creating a
tension with respect to the CMB, LSS and BBN data. In the past literature,
active neutrino asymmetries have been invoked as a way to inhibit the sterile
neutrino production via the in-medium suppression of the sterile-active mixing
angle. However, neutrino asymmetries also permit a resonant sterile neutrino
production. We find that if the active species have equal asymmetries L, a
value |L|=10^{-3} is required to start suppressing the resonant sterile
production, roughly an order of magnitude larger than what previously expected.
When active species have opposite asymmetries the sterile abundance is further
enhanced, requiring an even larger |L|\simeq 10^{-2} to start suppressing their
production. In the latter case, CP-violation (naturally expected) further
exacerbates the phenomenon. Some consequences for cosmological observables are
briefly discussed: for example, it is likely that moderate suppressions of the
sterile species production are associated with significant spectral distortions
of the active neutrino species, with potentially interesting phenomenological
consequences especially for BBN.Comment: (v2: 22 pages, 10 eps figures. Revised version. Typos removed,
reference updated. Matches the version published on PRD.
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