An apparently normal gamma-ray burst with an unusually low luminosity

Much of progress in gamma-ray bursts has come from the studies of distant events (redshift z~1). The brightest GRBs are the most collimated events and seen across the Universe due to their brilliance. It has long been suspected that nearest (and most common) events have been missed because they are not so collimated or under-energetic or both. Here we report soft gamma-ray observations of GRB 031203, the nearest event to date (z=0.106). This event with a duration of 40 s and peak energy of >190 keV appears to be a typical long duration GRB. However, the isotropic gamma-ray energy <~10^50 erg, about three orders of magnitude smaller than the cosmological population. This event as well as the other nearby but somewhat controversial event GRB 980425 are clear outliers for the much discussed isotropic-energy peak-energy relation and luminosity spectral-lag relations. Radio calorimetry shows that both these events are under-energetic explosions. We conclude that there does indeed exist a large population of under-energetic events.Comment: 11 pages, 3 figure

An optical supernova associated with the X-ray flash XRF 060218

Long-duration gamma-ray bursts (GRBs) are associated with type Ic supernovae that are more luminous than average and that eject material at very high velocities. Less-luminous supernovae were not hitherto known to be associated with GRBs, and therefore GRB-supernovae were thought to be rare events. Whether X-ray flashes - analogues of GRBs, but with lower luminosities and fewer gamma-rays - can also be associated with supernovae, and whether they are intrinsically 'weak' events or typical GRBs viewed off the axis of the burst, is unclear. Here we report the optical discovery and follow-up observations of the type Ic supernova SN 2006aj associated with X-ray flash XRF 060218. Supernova 2006aj is intrinsically less luminous than the GRB-supernovae, but more luminous than many supernovae not accompanied by a GRB. The ejecta velocities derived from our spectra are intermediate between these two groups, which is consistent with the weakness of both the GRB output and the supernova radio flux. Our data, combined with radio and X-ray observations, suggest that XRF 060218 is an intrinsically weak and soft event, rather than a classical GRB observed off-axis. This extends the GRB-supernova connection to X-ray flashes and fainter supernovae, implying a common origin. Events such as XRF 060218 are probably more numerous than GRB-supernovae.Comment: Final published versio

An investigation of the phase locking index for measuring of interdependency of cortical source signals recorded in the EEG

The phase locking index (PLI) was introduced to quantify in a statistical sense the phase synchronization of two signals. It has been commonly used to process biosignals. In this article, we investigate the PLI for measuring the interdependency of cortical source signals (CSSs) recorded in the Electroencephalogram (EEG). To this end, we consider simple analytical models for the mapping of simulated CSSs into the EEG. For these models, the PLI is investigated analytically and through numerical simulations. An evaluation is made of the sensitivity of the PLI to the amount of crosstalk between the sources through biological tissues of the head. It is found that the PLI is a useful interdependency measure for CSSs, especially when the amount of crosstalk is small. Another common interdependency measure is the coherence. A direct comparison of both measures has not been made in the literature so far. We assess the performance of the PLI and coherence for estimation and detection purposes based on, respectively, a normalized variance and a novel statistical measure termed contrast. Based on these performance measures, it is found that the PLI is similar or better than the CM in most cases. This result is also confirmed through analysis of EEGs recorded from epileptic patients

Development of Peasant Farms in Central Russia

The article looks at peasant farms in Tambov Oblast, a typical Central Russian region, discussing the legal framework for private farming, the regional land policies, and the socio-economic factors that encourage or inhibit the development of peasant farms. The data collected in an ongoing original survey are used to analyse the growth of peasant farms, the use of inputs, the activity portfolio, the level of commercialisation, and the efficiency of production during 1992–2002. The conclusion is that, under the prevailing conditions, individual farming cannot be expected to expand beyond its limited present scope by attracting broader strata of the rural population. Comparative Economic Studies (2005) 47, 101–114. doi:10.1057/palgrave.ces.8100079