Can Multi-threaded Flux Tubes in Coronal Arcades Support a Magnetohydrodynamic Avalanche?

Magnetohydrodynamic (MHD) instabilities allow energy to be released from stressed magnetic fields, commonly modelled in cylindrical flux tubes linking parallel planes, but, more recently, also in curved arcades containing flux tubes with both footpoints in the same photospheric plane. Uncurved cylindrical flux tubes containing multiple individual threads have been shown to be capable of sustaining an MHD avalanche, whereby a single unstable thread can destabilise many. We examine the properties of multi-threaded coronal loops, wherein each thread is created by photospheric driving in a realistic, curved coronal arcade structure (with both footpoints of each thread in the same plane). We use three-dimensional MHD simulations to study the evolution of single- and multi-threaded coronal loops, which become unstable and reconnect, while varying the driving velocity of individual threads. Experiments containing a single thread destabilise in a manner indicative of an ideal MHD instability and consistent with previous examples in the literature. The introduction of additional threads modifies this picture, with aspects of the model geometry and relative driving speeds of individual threads affecting the ability of any thread to destabilise others. In both single- and multi-threaded cases, continuous driving of the remnants of disrupted threads produces secondary, aperiodic bursts of energetic release.

Flux Rope Formation Due to Shearing and Zipper Reconnection.

Zipper reconnection has been proposed as a mechanism for creating most of the twist in the flux tubes that are present prior to eruptive flares and coronal mass ejections. We have conducted a first numerical experiment on this new regime of reconnection, where two initially untwisted parallel flux tubes are sheared and reconnected to form a large flux rope. We describe the properties of this experiment, including the linkage of magnetic flux between concentrated flux sources at the base of the simulation, the twist of the newly formed flux rope, and the conversion of mutual magnetic helicity in the sheared pre-reconnection state into the self-helicity of the newly formed flux rope.

A quarterly update on food- and waterborne diseases in Europe--summary of data for the third quarter of 2007.

This paper highlights findings from the first quarterly report on food- and waterborne diseases produced by the European Centre for Disease Prevention and Control (ECDC). In the past such reports had been generated by Enter-net, a Europe-based international surveillance network for the enteric infections. The quarterly reports are an important surveillance tool for the network participants and other public health professionals to use in order to identify emerging trends and changes taking place in a shorter interval than one year.

An outbreak due to peanuts in their shell caused by Salmonella enterica serotypes Stanley and Newport--sharing molecular information to solve international outbreaks.

Salmonellosis is a global problem caused by the international movement of foods and high incidence in exporting countries. In September 2001, in an outbreak investigation Australia isolated Salmonella Stanley from imported peanuts, which resulted in a wider investigation in Canada, England & Wales and Scotland. Patients infected with Salmonella serotypes known to be isolated from peanuts and reported to surveillance systems were interviewed to determine exposure histories. Tagged image file format (TIFF) images of pulsed-field gel electrophoresis (PFGE) patterns of Salmonella isolates were shared electronically amongst laboratories. Laboratories tested packets of 'Brand X' peanuts from various lots and product lines. In total, 97 cases of S. Stanley and 12 cases of S. Newport infection were found. Seventy-three per cent (71/97) of S. Stanley cases were in persons of Asian ethnicity. Twenty-eight per cent of cases recalled eating Brand X peanuts and a further 13% had peanuts in their house in the previous month or had eaten Asian-style peanuts. Laboratories isolated S. Stanley, S. Newport, S. Kottbus, S. Lexington and S. Unnamed from Brand X peanuts. Isolates of S. Stanley from peanuts and human patients were indistinguishable by PFGE. This international outbreak resulted from a product originating from one country affecting several others. Rapid sharing of electronic DNA images was a crucial factor in delineating the outbreak; multinational investigations would benefit from a harmonized approach.

Fluorescent amplified fragment length polymorphism genotyping of Salmonella Enteritidis: a method suitable for rapid outbreak recognition.

OBJECTIVE: To perform fluorescent amplified fragment length polymorphism (FAFLP) analysis on phage type (PT) reference strains of Salmonella enterica subsp. enterica serotype Enteritidis (S. Enteritidis), and S. Enteritidis PT 6 and 6a recent clinical isolates to determine its usefulness for primary characterization of clinical S. Enteritidis isolates, and then to determine whether FAFLP is suitable for rapid characterization of strains in an outbreak situation. METHODS: Twenty-five PT reference strains of S. Enteritidis and 20 S. Enteritidis PT 6 and 6a clinical isolates were subjected to FAFLP analysis using the selective primer combinations Eco + 0-Mse + T and Eco + 0-Mse + TA. RESULTS: FAFLP successfully separated each one of the 25 S. Enteritidis PT strains into distinct profiles, while macrorestriction and PFGE using XbaI identified 20 pulsed-field profiles. FAFLP also resolved cases and outbreaks due to S. Enteritidis PTs 6 and 6a. CONCLUSIONS: The resolving power of FAFLP was higher than that of PFGE. FAFLP is a highly discriminatory genotyping method and, in conjunction with phage typing for primary subdivision of S. Enteritidis, provides a rapid and powerful tool for strain differentiation, both for outbreak investigation and for epidemiologic surveillance.

The effects of road traffic accidents on driving behaviour.

Questionnaires about the effects of accidents on subsequent driving behaviour were sent to 869 people admitted consecutively to a general hospital as a result of involvement in road traffic accidents 4-6 years previously. There were 418 (48 per cent) replies, 67 per cent of delivered questionnaires. One-fifth of the motorcyclists had stopped using a motorcycle. Nearly one-half the motorcyclists and vehicle drivers reported that they now drove more slowly and that they were more cautious. A considerable proportion of replies described emotional distress, avoidance and limitation of activities. Lack of confidence in driving was common immediately after the accident. After 4-6 years, one-third of respondents reported that they still suffered specific anxiety about the place of the accident and about situations similar to the accident. Many people were anxious about being passengers. The findings have implications for road safety, for the recognition and management of a common, and often disabling, clinical problem, and for the assessment of disabilities in medical reports for compensation proceedings.