The Angular Distribution of Photoneutrons From O16

The relative importance of competing reaction channels in the photo-excitation of the giant resonance in O16 has been studied by measurement of the angular distribution of the emitted photo-neutrons through the corresponding energy range using a multi-angle neutron time of flight spectrometer installed at the Kelvin Laboratory of the University of Glasgow. Design factors for the spectrometer are discussed with regard to optimisation of energy resolution and counting rates under the constraints of the source, and the obtainable accuracy of normalisation between neutron detectors at different angles has been measured, A reliable method of calibration of the neutron energy scale at each angle is described and corrections to the neutron spectra for absorption by materials in the flight path have been made. The energy dependent efficiency of the neutron detectors is calculated in an appendix by a Monte Carlo technique using a new measurement of the scintillation response curve for recoil protons. Angular distributions of photoneutrons from the D2 (gamma,n)p reaction with 26.9 MeV bremsstrahlung have been measured and are found to agree with previously published results and theoretical predictions to within the expected accuracy. This is taken as confirmation of good angular normalisation in the system. Measurements by the author of the angular distributions of photo-neutrons from 26.9 MeV bremsstrahlung on O16 are presented and absolute cross sections have been obtained with respect to that known for deuterium. Photoproton data from other authors is analysed in a similar way for comparison with the photoneutron results. In the E1 approximation, the relative intensity of s/d wave admixture is found to follow the resonance structure for both protons and neutrons and the corresponding phase difference is found to vary about the value expected from optical model predictions. The E2 cross section has been extracted from the data and is found to rest mainly in two broad states centred at about 23 MeV and 24.7 MeV, while a Barker-Mann analysis shows the isospin impurity in the O16 giant resonance to be small and to be mainly associated with the regions of E2 strength. The pure 1p1h dipole approximation fails to describe these features and the observed splitting of the giant resonance in O16 but the presence of more complicated excitations is shown to be more consistent with experiment

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

Community-Initiated Urban Development: An Ecological Intervention

Neglected urban environments have been linked to social isolation, depression, and other health problems. In Portland, OR in 2003, an intervention was implemented and evaluated in three neighborhoods with the objective of promoting community participation in urban renewal and engaging residents in the construction of attractive urban places. Municipal officials approved and permitted community-designed street murals, public benches, planter boxes, information kiosks with bulletin boards, trellises for hanging gardens, all positioned in the public right-of-way. Residents within a two-block radius of the three sites were systematically sampled and interviewed before (N = 325) and after (N = 349) the intervention, of which, 265 individuals completed both surveys of the panel study. After the intervention, multivariate results revealed improvements in mental health (p = 0.03), increased sense of community (p < 0.01), and an overall expansion of social capital (p = 0.04). Through community empowerment, participation, and collective action, the strategy successfully engaged residents in restoring neighborhoods, with direct benefits to community well-being

Neutronic analysis of JET external neutron monitor response

The power output of fusion devices is measured in terms of the neutron yield which relates directly to the fusion yield. JET made a transition from Carbon wall to ITER-Like Wall (Beryllium/Tungsten/Carbon) during 2010–11. Absolutely calibrated measurement of the neutron yield by JET neutron monitors was ensured by direct measurements using a calibrated 252Cf neutron source (NS) deployed by the in-vessel remote handling system (RHS) inside the JET vacuum vessel. Neutronic calculations were required in order to understand the neutron transport from the source in the vacuum vessel to the fission chamber detectors mounted outside the vessel on the transformer limbs of the tokamak. We developed a simplified computational model of JET and the JET RHS in Monte Carlo neutron transport code MCNP and analyzed the paths and structures through which neutrons reach the detectors and the effect of the JET RHS on the neutron monitor response. In addition we performed several sensitivity studies of the effect of substantial massive structures blocking the ports on the external neutron monitor response. As the simplified model provided a qualitative picture of the process only, some calculations were repeated using a more detailed full 3D model of the JET tokamak

Radiation damage and nuclear heating studies in selected functional materials during the JET DT campaign

A new Deuterium-Tritium campaign (DTE2) is planned at JET in the next years, with a proposed 14MeV neutron budget of 1.7×1021, which is nearly an order of magnitude higher than any previous DT campaigns. The neutron and gamma ray fields inside the JET device during DT plasma operations at specific locations have previously been evaluated. It is estimated that a total neutron fluence on the first wall of JET of up to 1020 n/m2 could be achieved, which is comparable to the fluence occurring in ITER at the end of life in the rear part of the port plug, where several diagnostic components will be located.The purpose of the present work is to evaluate the radiation damage and nuclear heating in selected functional materials to be irradiated at JET during DT plasma operation. These quantities are calculated with the use of the MCNP6 code and the FISPACT II code. In particular the neutron and gamma ray fields at specific locations inside the JET device, dedicated to material damage studies, were characterized. The emphasis is on a potential long term irradiation station located close to the first wall at outboard midplane, offering the opportunity to irradiate samples of functional materials used in ITER diagnostics, to assess the degradation of the physical properties. The radiation damage and the nuclear heating were calculated for selected materials irradiated in these positions and for the neutron flux and fluence expected in DTE2. The studied candidate functional materials include, among others, Sapphire, YAG, ZnS, Spinel, Diamond. In addition the activation of the internal irradiation holder itself was calculated with FISPACT. Damage levels in the range of 10-5 dpa were found