Ten per cent polarized optical emission from GRB 090102

The nature of the jets and the role of magnetic fields in gamma-ray bursts (GRB) remains unclear. In a baryon-dominated jet only weak, tangled fields generated in situ through shocks would be present. In an alternative model, jets are threaded with large scale magnetic fields that originate at the central engine and which accelerate and collimate the jets. The way to distinguish between the models is to measure the degree of polarization in early-time emission, however previous claims of gamma-ray polarization have been controversial. Here we report that the early optical emission from GRB 090102 was polarized at the level of P=10+/-1%, indicating the presence of large-scale fields originating in the expanding fireball. If the degree of polarization and its position angle were variable on timescales shorter than our 60-s exposure, then the peak polarization may have been larger than 10 per cent.Comment: 16 pages, 4 figures. Published in Nature (2009), Vol. 462, p767-76

Surgical treatment of zygomatic bone fracture using two points fixation versus three point fixation-a randomised prospective clinical trial

<p>Abstract</p> <p>Background</p> <p>The zygoma plays an important role in the facial contour for both cosmetic and functional reasons; therefore zygomatic bone injuries should be properly diagnosed and adequately treated. Comparison of various surgical approaches and their complications can only be done objectively using outcome measurements which in turn require protocol management and long-term follow up. The preference for open reduction and internal fixation of zygomatic fractures at three points has continued to grow in response to observations of inadequate results from two point and one point fixation techniques.</p> <p>The objectives of this study were to compare the efficacy of zygomatic bone after treatment with ORIF using 2 point fixation and ORIF using 3 point fixation and compare the outcome of two procedures.</p> <p>Methods</p> <p>100 patients were randomly divided equally into two groups. In group A, 50 patients were treated by ORIF using two point fixation by miniplates and in group B, 50 patients were treated by ORIF using three point fixation by miniplates. They were evaluated for their complications during and after surgery with their advantages and disadvantages and the difference between the two groups was observed.</p> <p>Results</p> <p>A total of 100 fractures were sustained. We found that postoperative complication like decreased malar height and vertical dystopia was more common in those patients who were treated by two point fixation than those who were treated with three point fixation.</p> <p>Conclusions</p> <p>Based on this study open reduction and internal fixation using three point fixation by miniplates is the best available method for the treatment zygomatic bone fractures.</p

SRG/ART-XC discovery of SRGA J204318.2+443815: Towards the complete population of faint X-ray pulsars

We report the discovery of the new long-period X-ray pulsar SRGA J204318.2+443815/SRGe J204319.0+443820 in a Be binary system. The source was found in the second all-sky survey by the Mikhail Pavlinsky ART-XC telescope on board the SRG mission. The followup observations with XMM-Newton, NICER, and NuSTAR allowed us to discover a strong coherent signal in the source light curve with a period of ~742 s. The pulsed fraction was found to depend on an increase in energy from ~20% in soft X-rays to >50% at high energies, as is typical for X-ray pulsars. The source has a quite hard spectrum with an exponential cutoff at high energies and a bolometric luminosity of Lx ≃ 4 x 1035 erg s-1. The X-ray position of the source is found to be consistent with the optical transient ZTF18abjpmzf, located at a distance of ~8.0 kpc. Dedicated optical and infrared observations with the RTT-150, NOT, Keck, and Palomar telescopes revealed a number of emission lines (Hα, He I, and the Paschen and Braket series) with a strongly absorbed continuum. According to the SRG scans and archival XMM-Newton data, the source flux is moderately variable (by a factor of 4-10) on timescales of several months and years. All this suggests that SRGA J204318.2+443815/SRGe J204319.0+443820 is a new quasipersistent low-luminosity X-ray pulsar in a distant binary system with a Be-star of the B0-B2e class. Thus the SRG observatory allowed us to unveil a hidden population of faint objects, including a population of slowly rotating X-ray pulsars in Be systems.</p

A Neuron-Glial Perspective for Computational Neuroscience

International audienceThere is growing excitement around glial cells, as compelling evidence point to new, previously unimaginable roles for these cells in information processing of the brain, with the potential to affect behavior and higher cognitive functions. Among their many possible functions, glial cells could be involved in practically every aspect of the brain physiology in health and disease. As a result, many investigators in the field welcome the notion of a Neuron-Glial paradigm of brain function, as opposed to Ramon y Cayal's more classical neuronal doctrine which identifies neurons as the prominent, if not the only, cells capable of a signaling role in the brain. The demonstration of a brain-wide Neuron-Glial paradigm however remains elusive and so does the notion of what neuron-glial interactions could be functionally relevant for the brain computational tasks. In this perspective, we present a selection of arguments inspired by available experimental and modeling studies with the aim to provide a biophysical and conceptual platform to computational neuroscience no longer as a mere prerogative of neuronal signaling but rather as the outcome of a complex interaction between neurons and glial cells

Keys to the insects of the European USSR. (Opredelitel nasekomykh Evropeiskoi chasti SSSR)

v. 3 pt

Highly polarized light from stable ordered magnetic fields in GRB 120308A

After the initial burst of prompt gamma rays that defines a Gamma Ray Burst (GRB), expanding ejecta collide with the circumburst medium and begin to decelerate at the onset of the afterglow, where – models predict – a forward shock travels outwards through the circumburst medium and a reverse shock propagates backwards into the oncoming flow. Light from the reverse shock should be highly polarized if the jet magnetic field is globally ordered and advected from the central engine, with a position angle predicted to remain stable in magnetized baryonic jet models or vary randomly with time if the magnetic field is produced locally by plasma or MHD instabilities. Optical linear polarization degrees P ~ 10% have previously been detected in the early afterglow, but the lack of temporal measurements prevented definitive tests of competing jet models. Hours to days after the GRB, polarization levels are low (P < 4%), when emission from the shocked ambient medium dominates15–17. Here we report the detection of P = 28 ± 4% in the immediate afterglow of Swift GRB 120308A, 240 sec after the trigger, decreasing to P = 16 +5 −4% over the subsequent 10 minutes. The polarization position angle remains stable, changing by no more than 15 degrees over this time, with a possible trend suggesting gradual rotation and ruling out plasma or MHD instabilities. Instead, the polarization properties of GRB 120308A show that GRBs contain magnetized baryonic jets with large-scale uniform magnetic fields that can survive for significant time after the initial explosion