ElecSus: Extension to arbitrary geometry magneto-optics

We present a major update to ElecSus, a computer program and underlying model to calculate the electric susceptibility of an alkali-metal atomic vapour. Knowledge of the electric susceptibility of a medium is essential to predict its absorptive and dispersive properties. In this version we implement several changes which significantly extend the range of applications of ElecSus, the most important of which is support for non-axial magnetic fields (i.e. fields which are not aligned with the light propagation axis). Supporting this change requires a much more general approach to light propagation in the system, which we have now implemented. We exemplify many of these new applications by comparing ElecSus to experimental data. In addition, we have developed a graphical user interface front-end which makes the program much more accessible, and have improved on several other minor areas of the program structure

Simultaneous two-photon resonant optical laser locking (STROLLing) in the hyperfine Paschen-Back regime

We demonstrate a technique to lock simultaneously two laser frequencies to each step of a two-photon transition in the presence of a magnetic field sufficiently large to gain access to the hyperfine Paschen–Back regime. A ladder configuration with the 5S1/2, 5P3/2, and 5D5/2 terms in a thermal vapor of Rb87 atoms is used. The two lasers remain locked for more than 24 h. For the sum of the laser frequencies, which represents the stability of the two-photon lock, we measure a frequency instability of less than the Rb D2 natural linewidth of 6 MHz for nearly all measured timescales

Single-photon interference due to motion in an atomic collective excitation

We experimentally demonstrate the generation of heralded bi-chromatic single photons from an atomic collective spin excitation (CSE). The photon arrival times display collective quantum beats, a novel interference effect resulting from the relative motion of atoms in the CSE. A combination of velocity-selective excitation with strong laser dressing and the addition of a magnetic field allows for exquisite control of this collective beat phenomenon. The present experiment uses a diamond scheme with near-IR photons that can be extended to include telecommunications-wavelengths or modified to allow storage and retrieval in an inverted-Y scheme

Quantitative optical spectroscopy of 87^{87}Rb vapour in the Voigt geometry in DC magnetic fields up to 0.4T

We present a detailed spectroscopic investigation of a thermal ⁸⁷Rb atomic vapour in magnetic fields up to 0.4T in the Voigt geometry. We fit experimental spectra with our theoretical model ElecSus and find excellent quantitative agreement, with RMS errors of backsim0.3%. We extract the magnetic field strength and the angle between the polarisation of the light and the magnetic field from the atomic signal and find excellent agreement to within backsim1% with a commercial Hall probe. Finally, we present an investigation of the relative sensitivity of this technique to variations in the field strength and angle with a view to enabling atom-based high-field vector magnetometry

REDRISK: reduction of the virus risk in shellfish harvesting areas

Filter feeding bivalve shellfish can accumulate human pathogenic bacteria and viruses if grown in sewage-contaminated waters. Current consumer protection legislation relies on classification of harvesting areas based on their sanitary quality, using E coli as an indicator of sewage contamination. Advances in viral monitoring have shown that E coli can underestimate the extent of the contamination. The most common cause of gastroenteritis associated with shellfish is norovirus, commonly known as winter vomiting virus. The REDRISK project was undertaken to investigate the main environmental factors that cause viral contamination in shellfish. The REDRISK project is part of a EU research pillar with parallel research being undertaken in the UK, France and Spain. A recently developed technique to quantify norovirus in shellfish, real-time PCR, has been used in the REDRISK project. Clew Bay, in Co. Mayo was chosen as the study area in Ireland. The bay is generally considered to have good water quality but with certain areas subject to intermittent sewage contamination. The cooperation of local producers and organisations such as the Clew Bay Marine Forum and the Native Oyster Co-op greatly helped the project. The project was divided into a two-phased approach. Phase one involved the identification of contamination sources impacting the bay through a sanitary survey and selection of appropriate sites for further study. Results of the first phase of this study were presented previously at this forum (Keaveney, et al 2006) and the characteristics of the sites selected for study and locations within the bay are shown in table 1 and figure 1 respectively. The second phase of the project focused on monitoring environmental conditions and microbiological levels in shellfish to identify environmental conditions leading to viral contamination. This paper reports the finding of this monitoring

Detection of human viruses in shellfish and update on REDRISK research project, Clew Bay, Co. Mayo

This paper describe the progress in norovirus detection methods and initial results from the REDRISK study

Preliminary results from a survey of oyster production areas in Ireland for norovirus

A survey of 18 oyster production areas in Ireland for norovirus (NoV) contamination was initiated in August 2006. The findings presented are the preliminary results from the first seven months of the survey. Prior to the survey commencing, a simple desk bask sanitary survey of each area was undertaken. This provided an assessment enabling each site to be ranked into 3 categories (low, medium and high) on the basis of the risk of NoV contamination. Samples were collected on a monthly basis and tested for the presence of NoV using semi-quantitative real-time PCR allowing relative quantitation of NoV levels. A correlation was observed between occurrence and levels of NoV detected and the risk categories ascribed to each production area. To date NoV was detected in 60.7, 30.0 and 2.5 percent of samples from the high, medium and low risk categorised areas, respectively. A strong seasonal bias towards increased winter contamination was observed with NoV detected in 15.5 and 50 % of samples in August and February, respectively. The preliminary results from this survey indicate that it may be possible to predict the relative risk of NoV contamination in a shellfish harvesting area. This in conjunction with targeted NoV monitoring using real-time PCR could aid the further development of risk management procedures in shellfisheries

Management of health risks associated with oysters harvested from a norovirus contaminated area, Ireland, February–March 2010

Copyright © 2010 B. Doré et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Peer reviewed.Oysters from a harvesting area responsible for outbreaks of gastroenteritis were relaid at a clean seawater site and subsequently depurated in tanks of purified seawater at elevated temperatures. This combined treatment reduced norovirus levels to those detected prior to the outbreak. On the basis of norovirus monitoring the sale of treated oysters was permitted although the harvest area remained closed for direct sale of oysters. No reports of illness have been associated with the consumption of treated oysters