Resonant nonlinear magneto-optical effects in atoms

In this article, we review the history, current status, physical mechanisms, experimental methods, and applications of nonlinear magneto-optical effects in atomic vapors. We begin by describing the pioneering work of Macaluso and Corbino over a century ago on linear magneto-optical effects (in which the properties of the medium do not depend on the light power) in the vicinity of atomic resonances, and contrast these effects with various nonlinear magneto-optical phenomena that have been studied both theoretically and experimentally since the late 1960s. In recent years, the field of nonlinear magneto-optics has experienced a revival of interest that has led to a number of developments, including the observation of ultra-narrow (1-Hz) magneto-optical resonances, applications in sensitive magnetometry, nonlinear magneto-optical tomography, and the possibility of a search for parity- and time-reversal-invariance violation in atoms.Comment: 51 pages, 23 figures, to appear in Rev. Mod. Phys. in Oct. 2002, Figure added, typos corrected, text edited for clarit

Stakeholder perspectives on shale gas fracking: A Q-method study of environmental discourses

The rapid expansion of shale gas exploration worldwide is a significant source of environmental controversy. Successful shale gas policymaking is dependent upon a clear understanding of the dynamics of competing stakeholder perspectives on these issues, and so methods are needed to delineate the areas of agreement and conflict that emerge. This empirical study, based in the United Kingdom, examines emergent perspectives on a range of environmental, health and socio-economic impacts associated with shale gas fracking using Q- methodology: a combined qualitative-quantitative approach. The analysis reveals three typologies of perspectives amongst key industry, civil society and non-affiliated citizen stakeholders; subsequently contextualised in relation to Dryzek’s typology of environmental discourses. These are labelled A) “Don’t trust the fossil fuels industry: campaign for renewables” (mediating between sustainable development and democratic pragmatism discourses); B) “Shale gas is a bridge fuel: economic growth and environmental scepticism” (mediating between economic rationalism and ecological modernisation discourses); and C) “Take place protective action and legislate in the public interest” (reflecting a discourse of administrative rationalism). The implications of these competing discourses for nascent shale gas policy in the UK are discussed in light of recent Government public consultation on changes to national planning policy

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Heat transfer experiments in rod bundles cooled by lead-bismuth uutectic (LBE)

Heavy liquid metals (HLMs), such as lead-bismuth eutectic (LBE) and pure lead are prominent candidate coolants for critical assemblies and accelerator-driven systems based on fast neutrons. With a strong focus on safety, key thermal-hydraulic aspects of these systems must be considered. The main challenge for modeling the heat transfer in liquid metals is given by their characteristically low Prandtl number (Pr << 1), separating the scales of turbulent transfer of momentum and heat. For that reason, specific experimental investigations are required for validating according models, particularly for complex geometries such as rod bundles. This work presents the experimental evaluation of two tests sections, both consisting of electrically-heated 19-pin hexagonal bundles, although with different characteristics. The setup #1 has grid spacers and a relatively large pitch-to-diameter ratio P/D=1.4. In this recently completed experimental campaign, extensive heat transfer and pressure drop information was obtained at typical reactor conditions of temperature (up to 450 °C), power density (up to 1.0 MW m ) and bulk velocity (2.2 m s ). With a good repeatability, these results agree well with information available in literature and are a suitable source of data for the validation of predicting models. The setup #2 is a similar bundle, with wire spacers and P/D=1.28. It is currently in the last stages of construction and commissioning. Its main characteristics, instrumentation and envisaged experiments are presented in this work

EXPERIMENTAL INVESTIGATION OF LEAD-BISMUTH-EUTECTIC FLOW AND HEAT TRANSFER IN HEXAGONAL-LATTICE ROD BUNDLES WITH GRID SPACERS

Heavy liquid metals are proposed as coolants for subcritical assemblies such as accelerator-driven systems. Particularly lead- bismuth eutectic is a superior candidate due to its low melting temperature. In that context, fluid- and geometry-specific thermal-hydraulic experiments play a major role for the design and operation of such systems. In this work a bundle with 19 rods (8.2 mm in diameter) in a hexagonal lattice with a pitch-to-diameter ratio P/D = 1.4 was tested in the existing THEADES loop at Karlsruhe Liquid Metal Laboratory of KIT. This vertical test section (870 mm heated length) includes three grid spacers, where localized instrumentation for both temperature and pressure drop is mounted. For this geometry and with reactor-representative operating conditions (temperature, velocity, heat flux) forced-convective tests applying a heat power density up to 100 W/cm2 have been performed. Based on these results, it can be concluded that within acceptable engineering accuracy, the heat transfer performance for this case can be well predicted by existing dimensionless correlations originally developed for other fluids, mainly sodium