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

Optical Observations of GRB 050401 Afterglow : A case for Double Jet Model

The afterglow of GRB 050401 presents several novel and interesting features : [1] An initially faster decay in optical band than in X-rays. [2] A break in the X-ray light curve after $\sim$ 0.06 day with an unusual slope after the break. [3] The X-ray afterglow does not show any spectral evolution across the break while the R band light curve does not show any break. We have modeled the observed multi-band evolution of the afterglow of GRB 050401 as originating in a two component jet, interpreting the break in X-ray light curve as due to lateral expansion of a narrow collimated outflow which dominates the X-ray emission. The optical emission is attributed to a wider jet component. Our model reproduces all the observed features of multi-band afterglow of GRB 050401. We present optical observations of GRB 050401 using the 104-cm Sampurnanand Telescope at ARIES, Nainital. Results of the analysis of multi-band data are presented and compared with GRB 030329, the first reported case of double jet.Comment: 8 pages, 2 figures and 4 tables. To appear in MNRA

The effectiveness of Nurse Practitioners working at a GP cooperative: a study protocol

Contains fulltext : 109803.pdf (publisher's version ) (Open Access)ABSTRACT: BACKGROUND: In many countries out-of-hours care faces serious challenges, including shortage of general practitioners, a high workload, reduced motivation to work out of hours, and increased demand for out-of-hours care. One response to these challenges is the introduction of nurse practitioner as doctor substitutes, in order to maintain the (high) accessibility and safety of out of hours care. Although nurse practitioners have proven to provide equally safe and efficient care during daytime primary care, it is unclear whether substitution is effective and efficient in the more complex out of hours primary care. This study aims to assess the effects of substitution of care from general practitioners to nurse practitioners in an out of hours primary care setting. DESIGN: A quasi experimental study is undertaken at one "general practitioner cooperative" to offer out-of-hours care for 304.000 people in the South East of the Netherlands. In the experimental condition patient care is provided by a team of one nurse practitioner and four general practitioners; where the nurse practitioner replaces one general practitioner during one day of the weekend from 10 am to 5 pm. In the control condition patient care is provided by a team of five general practitioners during the other day of the weekend, also from 10 am to 5 pm. The study period last 15 months, from April 2011 till July 2012. METHODS: Data will be collected on number of different outcomes using a range of methods. Our primary outcome is substitution of care. This is calculated using the number and characteristics of patients that have a consultation at the GP cooperative. We compare the number of patients seen by both professionals, type of complaints, resource utilization (e.g. prescription, tests, investigations, referrals) and waiting times in the experimental condition and control condition. This data is derived from patient electronic medical records. Secondary outcomes are: patient satisfaction; general practitioners workload; quality and safety of care and barriers and facilitators. DISCUSSION: The study will provide evidence whether substitution of care in out-of-hours setting is safe and efficient and give insight into barriers and facilitators related to the introduction of nurse practitioners in out-of-hours setting. TRIAL REGISTRATION: ClinicalTrials.gov ID NCT01388374