Swings between rotation and accretion power in a binary millisecond pulsar.

It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.

Memory and executive functions in aneurysms of the anterior communicating artery.

The cognitive outcome of three groups of patients, who had undergone surgery for repair of a single ruptured intracranial aneurysm, was evaluated. We assessed performance on tests of executive functions and memory in a group of 15 patients tested at least 3 months after an aneurysm of the anterior communicating artery (ACoA) and in a group of 12 patients tested in the first month after the same pathology. Acute patients were more impaired overall than chronic ones, but the two groups significantly differed on two executive and one memory test. The performance of the ACoA patients was also compared to the performance of a group of 10 patients who had undergone surgery for an aneurysm located on the posterior communicating artery (PCoA) at least 3 months before the examination. Chronic ACoA and PCoA patients significantly differed in two memory and in two executive tests performance, with posterior patients being more impaired than anterior. An unexpected finding was the impairment of semantic memory in ACoA patients.

Analysis of some physical and seismological parameters as earthquakes precursors

A summary of the results of research carried out in the past, and a description of current activity on the subject of the title is given. The b value of the Gutemberg Ritcher formula (log N=a -bM) and the changes in seismic wave velocity were examined. Recording of the earth self-potential for correlation with seismicity was attempted by the istallation of two perpendicular arrays in Friuli at Colloredo di Faedis. The work, which is about to be finished, deals with seismic gaps in the Friuli area in the periods before those earthquakes slightly stronger than average. Finally we are preparing to begin correlations between well-water level changes and the seismicity of the zone.(AU)