268 research outputs found
Optical pulsations from a transitional millisecond pulsar
Weakly magnetic, millisecond spinning neutron stars attain their very fast
rotation through a 1E8-1E9 yr long phase during which they undergo
disk-accretion of matter from a low mass companion star. They can be detected
as accretion-powered millisecond X-ray pulsars if towards the end of this phase
their magnetic field is still strong enough to channel the accreting matter
towards the magnetic poles. When mass transfer is much reduced or ceases
altogether, pulsed emission generated by particle acceleration in the
magnetosphere and powered by the rotation of the neutron star is observed,
preferentially in the radio and gamma-ray bands. A few transitional millisecond
pulsars that swing between an accretion-powered X-ray pulsar regime and a
rotationally-powered radio pulsar regime in response to variations of the mass
in-flow rate have been recently identified. Here we report the detection of
optical pulsations from a transitional pulsar, the first ever from a
millisecond spinning neutron star. The pulsations were observed when the pulsar
was surrounded by an accretion disk and originated inside the magnetosphere or
within a few hundreds of kilometres from it. Energy arguments rule out
reprocessing of accretion-powered X-ray emission and argue against a process
related to accretion onto the pulsar polar caps; synchrotron emission of
electrons in a rotation-powered pulsar magnetosphere seems more likely.Comment: 32 pages, 7 figures. The first two authors contributed equally to
this wor
Multi-band high resolution spectroscopy rules out the hot Jupiter BD+20 1790b - First data from the GIARPS Commissioning
Context. Stellar activity is currently challenging the detection of young
planets via the radial velocity (RV) technique. Aims. We attempt to
definitively discriminate the nature of the RV variations for the young active
K5 star BD+20 1790, for which visible (VIS) RV measurements show divergent
results on the existence of a substellar companion. Methods. We compare VIS
data with high precision RVs in the near infrared (NIR) range by using the
GIANO - B and IGRINS spectrographs. In addition, we present for the first time
simultaneous VIS-NIR observations obtained with GIARPS (GIANO - B and HARPS -
N) at Telescopio Nazionale Galileo (TNG). Orbital RVs are achromatic, so the RV
amplitude does not change at different wavelengths, while stellar activity
induces wavelength-dependent RV variations, which are significantly reduced in
the NIR range with respect to the VIS. Results. The NIR radial velocity
measurements from GIANO - B and IGRINS show an average amplitude of about one
quarter with respect to previously published VIS data, as expected when the RV
jitter is due to stellar activity. Coeval multi-band photometry surprisingly
shows larger amplitudes in the NIR range, explainable with a mixture of cool
and hot spots in the same active region. Conclusions. In this work, the claimed
massive planet around BD+20 1790 is ruled out by our data. We exploited the
crucial role of multi- wavelength spectroscopy when observing young active
stars: thanks to facilities like GIARPS that provide simultaneous observations,
this method can reach its maximum potential.Comment: 12 pages, 7 figure
A pilot study on the Spanish version of the Psychosocial Adjustment to Illness Scale (PAISâSR) with carers of people with Parkinson's disease
Aim: To report the cross-cultural adaptation and pilot study of the ongoing validation of the Spanish version of the Psychosocial Adjustment to Illness Scale with carers of people with Parkinson's disease.
Design: Cross-cultural adaptation and pilot study with a cross-sectional validation design of the Spanish version of the Psychosocial Adjustment to Illness Scale - Carers.
Methods: Twenty-one carers of people with Parkinson's disease from a Primary Care practice in Spain were recruited and completed the PAIS-Carers, the SF-36 Health Survey, the Brief COPE Inventory and an assessment form. SPSS 23.0 was used to determine viability/acceptability and preliminary aspects of internal consistency of the instrument.
Results: Five of the seven domains presented floor effect (71.42%), and only one presented ceiling effect (14.28%). The internal consistency of the scale and domains showed acceptable values (over 0.7). The content validity of the Spanish version seemed satisfactory with positive comments in general from participants
18F-FDG-PET Imaging Patterns in Autoimmune Encephalitis: Impact of Image Analysis on the Results
Brain positron emission tomography imaging with 18Fluorine-fluorodeoxyglucose
(FDG-PET) has demonstrated utility in suspected autoimmune encephalitis. Visual and/or
assisted image reading is not well established to evaluate hypometabolism/hypermetabolism.
We retrospectively evaluated patients with autoimmune encephalitis between 2003 and 2018.
Patients underwent EEG, brain magnetic resonance imaging (MRI), cerebrospinal fluid (CSF)
sampling and autoantibodies testing. Individual FDG-PET images were evaluated by standard
visual reading and assisted by voxel-based analyses, compared to a normal database. For the
latter, three different methods were performed: two based on statistical surface projections (Siemens
syngo.via Database Comparison, and 3D-SSP Neurostat) and one based on statistical parametric
mapping (SPM12). Hypometabolic and hypermetabolic findings were grouped to identify specific
patterns. We found six cases with definite diagnosis of autoimmune encephalitis. Two cases had
anti-LGI1, one had anti-NMDA-R and two anti-CASPR2 antibodies, and one was seronegative.
18F-FDG-PET metabolic abnormalities were present in all cases, regardless of the method of analysis.
Medialâtemporal and extra-limbic hypermetabolism were more clearly depicted by voxel-based
analyses. We found autoantibody-specific patterns in line with the literature. Statistical surface
projection (SSP) methods (Neurostat and syngo.via Database Comparison) were more sensitive
and localized larger hypermetabolic areas. As it may lead to comparable and accurate results,
visual analysis of FDG-PET studies for the diagnosis of autoimmune encephalitis benefits from
voxel-based analysis, beyond the approach based on MRI, CSF sample and EEG
A Protein Standard That Emulates Homology for the Characterization of Protein Inference Algorithms
Proteomic
GIARPS: commissioning and first scientific results
GIARPS (GIAno \& haRPS) is a project devoted to have on the same focal
station of the Telescopio Nazionale Galileo (TNG) both high resolution
spectrographs, HARPS-N (VIS) and GIANO-B (NIR), working simultaneously. This
could be considered the first and unique worldwide instrument providing
cross-dispersed echelle spectroscopy at a resolution of 50,000 in the NIR range
and 115,000 in the VIS and over in a wide spectral range (m)
in a single exposure. The science case is very broad, given the versatility of
such an instrument and its large wavelength range. A number of outstanding
science cases encompassing mainly extra-solar planet science starting from
rocky planets search and hot Jupiters to atmosphere characterization can be
considered. Furthermore both instruments can measure high precision radial
velocities by means the simultaneous thorium technique (HARPS-N) and absorbing
cell technique (GIANO-B) in a single exposure. Other science cases are also
possible. GIARPS, as a brand new observing mode of the TNG started after the
moving of GIANO-A (fiber fed spectrograph) from Nasmyth-A to Nasmyth-B where it
was re-born as GIANO-B (no more fiber feed spectrograph). The official
Commissioning finished on March 2017 and then it was offered to the community.
Despite the work is not finished yet. In this paper we describe the preliminary
scientific results obtained with GIANO-B and GIARPS observing mode with data
taken during commissioning and first open time observations.Comment: 10 pages, 11 figures, Telescopes and Astronomical instrumentation,
SPIE Conf. 201
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Common folate gene variant, MTHFR C677T, is associated with brain structure in two independent cohorts of people with mild cognitive impairmentâ
A commonly carried C677T polymorphism in a folate-related gene, MTHFR, is associated with higher plasma homocysteine, a well-known mediator of neuronal damage and brain atrophy. As homocysteine promotes brain atrophy, we set out to discover whether people carrying the C677T MTHFR polymorphism which increases homocysteine, might also show systematic differences in brain structure. Using tensor-based morphometry, we tested this association in 359 elderly Caucasian subjects with mild cognitive impairment (MCI) (mean age: 75 ± 7.1 years) scanned with brain MRI and genotyped as part of Alzheimer's Disease Neuroimaging Initiative. We carried out a replication study in an independent, non-overlapping sample of 51 elderly Caucasian subjects with MCI (mean age: 76 ± 5.5 years), scanned with brain MRI and genotyped for MTHFR, as part of the Cardiovascular Health Study. At each voxel in the brain, we tested to see where regional volume differences were associated with carrying one or more MTHFR âTâ alleles. In ADNI subjects, carriers of the MTHFR risk allele had detectable brain volume deficits, in the white matter, of up to 2â8% per risk T allele locally at baseline and showed accelerated brain atrophy of 0.5â1.5% per T allele at 1 year follow-up, after adjusting for age and sex. We replicated these brain volume deficits of up to 5â12% per MTHFR T allele in the independent cohort of CHS subjects. As expected, the associations weakened after controlling for homocysteine levels, which the risk gene affects. The MTHFR risk variant may thus promote brain atrophy by elevating homocysteine levels. This study aims to investigate the spatially detailed effects of this MTHFR polymorphism on brain structure in 3D, pointing to a causal pathway that may promote homocysteine-mediated brain atrophy in elderly people with MCI
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