Istituto Universitario Di Studi Superiori Di Pavia

About: Istituto Universitario Di Studi Superiori Di Pavia is a education organization based out in Pavia, Italy. It is known for research contribution in the topics: Pulsar & Neutron star. The organization has 162 authors who have published 566 publications receiving 22605 citations.

A biomarker study in long-lasting amnestic mild cognitive impairment

Abstract: Mild cognitive impairment (MCI) is a heterogeneous syndrome resulting from Alzheimer’s disease (AD) as well as to non-AD and non-neurodegenerative conditions. A subset of patients with amnestic MCI (aMCI) present with an unusually long-lasting course, a slow rate of clinical neuropsychological progression, and evidence of focal involvement of medial temporal lobe structures. In the present study, we explored positron emission tomography (PET) and cerebrospinal fluid (CSF) biomarkers in a sample of subjects with aMCI with such clinical features in order to provide in vivo evidence to improve disease characterisation in this subgroup. Thirty consecutive subjects with aMCI who had long-lasting memory impairment (more than 4 years from symptom onset) and a very slow rate of cognitive progression were included. All subjects underwent fluorodeoxyglucose-positron emission tomography (FDG-PET) metabolic imaging. A measure of cerebral amyloid load, by PET and/or CSF, was obtained in 26 of 30 subjects. The mean clinical follow-up was 58.3 ± 10.1 months. No patient progressed to dementia during the follow-up. The typical AD FDG-PET pattern of temporoparietal hypometabolism was not present in any of the subjects. In contrast, a selective medial temporal lobe hypometabolism was present in all subjects, with an extension to frontolimbic regions in some subjects. PET imaging showed absent or low amyloid load in the majority of samples. The values were well below those reported in prodromal AD, and they were slightly elevated in only two subjects, consistent with the CSF β-amyloid (1–42) protein values. Notably, no amyloid load was present in the hippocampal structures. FDG-PET and amyloid-PET together with CSF findings questioned AD pathology as a unique neuropathological substrate in this aMCI subgroup with long-lasting disease course. The possibility of alternative pathological conditions, such as argyrophilic grain disease, primary age-related tauopathy or age-related TDP-43 proteinopathy, known to spread throughout the medial temporal lobe and limbic system structures should be considered in these patients with MCI.

Hubble Space Telescope Multiepoch Imaging of the PSR B0540–69 System Unveils a Highly Dynamic Synchrotron Nebula

Abstract: PSR B0540-69 is the Crab twin in the Large Magellanic Cloud. The age and energetic and overall behavior of the two pulsars are very similar. The same is true for the general appearance of their pulsar wind nebulae (PWNe). Analysis of Hubble Space Telescope images spanning 10 yr unveiled significant variability in the PWN surrounding PSR B0540-69, with a hot spot moving at ~0.04c. Such behavior, reminiscent of the variability observed in the Crab Nebula along the counterjet direction, may suggest an alternative scenario for the geometry of the system. The same data were used to assess the pulsar proper motion. The null displacement recorded over 10 yr allowed us to set a 3 σ upper limit of 290 km s-1 to the pulsar velocity.

HST and VLT observations of the neutron star 1E 1207.4–5209

Abstract: The peculiar central compact object 1E1207.4−5209 in the G296.5+10.0 supernova remnant has been proposed to be an “antimagnetar” ‐ a young neutron star born with a weak dipole field. Accretion, possibly of supernova fallback material, has also been invoked to explain a large surface temperature anisotropy as well as the generation of peculiar cyclotron absorption features superimposed on its thermal spectrum. Interestingly enough, a faint optical/infrared source was proposed as a possible counterpart to 1E1207.4−5209, but later questioned, based on coarse positional coincidence. On the basis of the large offset of 1E1207.4−5209 with respect to the center of its host supernova remnant, the source should move at ∼70 mas yr −1 . Thus, we tested the association by measuring the proper motion of the proposed optical counterpart. Using Hubble Space Telescope (HST) observations spanning 3.75 years, we computed a 3σ upper limit of 7 mas yr −1 . Absolute astrometry on the same HST data set also places the optical source significantly off the 99% confidence Chandra position. This allows us to safely rule out the association. Using the HST data set, coupled to ground-based observations collected at the ESO/Very Large Telescope (VLT), we set the deepest limits ever obtained on the optical/infrared emission from 1E1207.4−5209. By combining these limits with the constraints derived from X-ray timing, we rule out accretion as the source of the thermal anisotropy of the neutron star.