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- De Simone, M., et al.
(författare)
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Glycolaldehyde in Perseus young solar analogs
- 2017
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 599
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Tidskriftsartikel (refereegranskat)abstract
- © ESO 2017. Context. The earliest evolutionary stages of low-mass protostars are characterised by the so-called hot-corino stage, when the newly born star heats the surrounding material and enrich the gas chemically. Studying this evolutionary phase of solar protostars may help understand the evolution of prebiotic complex molecules in the development of planetary systems. Aims. In this paper we focus on the occurrence of glycolaldehyde (HCOCH 2 OH) in young solar analogs by performing the first homogeneous and unbiased study of this molecule in the Class 0 protostars of the nearby Perseus star forming region. Methods. We obtained sub-arcsec angular resolution maps at 1.3 mm and 1.4 mm of glycolaldehyde emission lines using the IRAM Plateau de Bure (PdB) interferometer in the framework of the CALYPSO IRAM large program. Results. Glycolaldehyde has been detected towards 3 Class 0 and 1 Class I protostars out of the 13 continuum sources targeted in Perseus: NGC1333-IRAS2A1, NGC1333-IRAS4A2, NGC1333-IRAS4B1, and SVS13-A. The NGC1333 star forming region looks particularly glycolaldehyde rich, with a rate of occurrence up to 60%. The glycolaldehyde spatial distribution overlaps with the continuum one, tracing the inner 100 au around the protostar. A large number of lines (up to 18), with upper-level energies E u from 37 K up to 375 K has been detected. We derived column densities ≥10 15 cm -2 and rotational temperatures T rot between 115 K and 236 K, imaging for the first time hot-corinos around NGC1333-IRAS4B1 and SVS13-A. Conclusions. In multiple systems glycolaldehyde emission is detected only in one component. The case of the SVS13-A+B and IRAS4-A1+A2 systems support that the detection of glycolaldehyde (at least in the present Perseus sample) indicates older protostars (i.e. SVS13-A and IRAS4-A2), evolved enough to develop the hot-corino region (i.e. 100 K in the inner 100 au). However, only two systems do not allow us to firmly conclude whether the primary factor leading to the detection of glycolaldehyde emission is the environments hosting the protostars, evolution (e.g. low value of L submm /L int ), or accretion luminosity (high L int ).
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- Oliveira, F., et al.
(författare)
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Data driven diagnostic classification in Alzheimer's disease based on different reference regions for normalization of PiB-PET images and correlation with CSF concentrations of A beta species
- 2018
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Ingår i: Neuroimage-Clinical. - : Elsevier BV. - 2213-1582. ; 20, s. 603-610
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Tidskriftsartikel (refereegranskat)abstract
- Positron emission tomography (PET) neuroimaging with the Pittsburgh Compound_B (PiB) is widely used to assess amyloid plaque burden. Standard quantification approaches normalize PiB-PET by mean cerebellar gray matter uptake. Previous studies suggested similar pons and white-matter uptake in Alzheimer's disease (AD) and healthy controls (HC), but lack exhaustive comparison of normalization across the three regions, with data-driven diagnostic classification. We aimed to compare the impact of distinct reference regions in normalization, measured by data-driven statistical analysis, and correlation with cerebrospinal fluid (CSF) amyloid beta (A beta) species concentrations. 243 individuals with clinical diagnosis of AD, HC, mild cognitive impairment (MCI) and other dementias, from the Biomarkers for Alzheimer's/Parkinson's Disease (BIOMARKAPD) initiative were included. PiB-PET images and CSF concentrations of A beta(38), A beta(40) and A beta(42) were submitted to classification using support vector machines. Voxel-wise group differences and correlations between normalized PiB-PET images and CSF A beta concentrations were calculated. Normalization by cerebellar gray matter and pons yielded identical classification accuracy of AD (accuracy-96%, sensitivity-96%, specificity-95%), and significantly higher than A beta concentrations (best accuracy 91%). Normalization by the white-matter showed decreased extent of statistically significant multivoxel patterns and was the only method not outperforming CSF biomarkers, suggesting statistical inferiority. A beta(38) and A beta(40) correlated negatively with PiB-PET images normalized by the white-matter, corroborating previous observations of correlations with non-AD-specific subcortical changes in white-matter. In general, when using the pons as reference region, higher voxel-wise group differences and stronger correlation with A beta(42), the A beta(42)/A beta(40) or A beta(42)/A beta(38) ratios were found compared to normalization based on cerebellar gray matter.
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