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.

[Chronic exposure to styrene and psychiatric symptomatology: a case-control descriptive study]. / Esposizione cronica a stirene e sintomatologia psichiatrica: studio descrittivo caso-controllo.

BACKGROUND: Although the acute psychiatric consequences exerted by Styrene and other aromatic hydrocarbons are abundantly described, the effects produced by a low-dosages chronic exposure are not known, in spite of the wide employment in the field of industrial production. The aim of this study is to evaluate the psychiatric symptoms in a group of subjects exposed to styrene in comparison with a control group, not exposed to the substance. SUBJECTS AND METHODS: Twenty two qualified workers, divided into 11 subjects in charge of welding and resin tapping exposed to styrene, and 11 not exposed to neurotoxic substances, were evaluated through the Symptom Check List Revised (SCL-90-R), a scale for the global self-evaluation of psychiatric symptomatology. RESULTS: The statistical tests, herein utilized, showed a significant prevalence for the dimensions somatization and psychoticism in the exposed subjects to styrene as compared to the non-exposed subjects. CONCLUSIONS: The results of this study, although limited by the paucity of the sample, emphasize the importance of an early diagnosis and evaluation of the clinical predictors in subjects exposed to styrene. The relatively low concentration levels of styrene in the working area of the subjects exposed underlines the opportunity to arrange preventive evaluation strategies for a prompt intervention in those cases with a clear syndromic presentation.

Complexity of time series associated to dynamical systems inferred from independent component analysis.

A not trivial problem for every experimental time series associated to a natural system is to individuate the significant variables to describe the dynamics, i.e., the effective degrees of freedom. The application of independent component analysis (ICA) has provided interesting results in this direction, e.g., in the seismological and atmospheric field. Since all natural phenomena can be represented by dynamical systems, our aim is to check the performance of ICA in this general context to avoid ambiguities when investigating an unknown experimental system. We show many examples, representing linear, nonlinear, and stochastic processes, in which ICA seems to be an efficacious preanalysis able to give information about the complexity of the dynamics.

Kinetic derivation of the hydrodynamic equations for capillary fluids.

Based on the generalized kinetic equation for the one-particle distribution function with a small source, the transition from the kinetic to the hydrodynamic description of many-particle systems is performed. The basic feature of this interesting technique to obtain the hydrodynamic limit is that the latter has been partially incorporated into the kinetic equation itself. The hydrodynamic equations for capillary fluids are derived from the characteristic function for the local moments of the distribution function. Fick's law appears as a consequence of the transformation law for the hydrodynamic quantities under time inversion.

Neural networks for blind-source separation of Stromboli explosion quakes.

Independent component analysis (ICA) is used to analyze the seismic signals produced by explosions of the Stromboli volcano. It has been experimentally proved that it is possible to extract the most significant components from seismometer recorders. In particular, the signal, eventually thought as generated by the source, is corresponding to the higher power spectrum, isolated by our analysis. Furthermore, the amplitude of the source signals has been found by using a simple trick and so overcoming, for this specific case, the classical problem of ICA regarding the amplitude loss of the separated signals.

Stochastic resonance mechanism in aerosol index dynamics.

We consider satellite time series concerning the atmospheric aerosol content. We prove that these time series are well described by a stochastic dynamical model. The principal peak in the power spectrum of these signals can be explained by stochastic resonance, linking variable external factors, such as Sun-Earth radiation budget and local insolation, to fluctuations on smaller spatial and temporal scale due to internal weather and antrophic components.

Field dependence and characteristics of conceptualization in identical twins.

This study falls in the areas of both differential psychology and twin psychology. Using the EFT and the WCST (computerized version), we examined 11 MZFF pairs between 18 and 35 years of age. The aim was to establish the genetic and/or environmental determination of global-analytical cognitive style as well as some characteristics of conceptualization linked to field dependence. The research strategy consisted of introducing three other groups of the same size to control the weight of environmental factors different from those determined by subject selection. The results seem to support the hypothesis of genetic determination of field dependence of the MZFFs, probably linked to the XX chromosome combination. The "couple effect" and the attitude of parents and others toward two identical female subjects may contribute to full expression of the genome. The characteristics of conceptualization revealed by the WCST show that MZFFs persevere in errors typical of a global approach to experience.