CEDR: Contextualized Embeddings for Document Ranking

Although considerable attention has been given to neural ranking architectures recently, far less attention has been paid to the term representations that are used as input to these models. In this work, we investigate how two pretrained contextualized language modes (ELMo and BERT) can be utilized for ad-hoc document ranking. Through experiments on TREC benchmarks, we find that several existing neural ranking architectures can benefit from the additional context provided by contextualized language models. Furthermore, we propose a joint approach that incorporates BERT's classification vector into existing neural models and show that it outperforms state-of-the-art ad-hoc ranking baselines. We call this joint approach CEDR (Contextualized Embeddings for Document Ranking). We also address practical challenges in using these models for ranking, including the maximum input length imposed by BERT and runtime performance impacts of contextualized language models

'If I cannot access services then there is no reason for me to test': the impact of health service charges on HIV testing and treatment amongst migrants in England

Policy governing entitlement to access government health care for foreign nationals in England is a subject of debate, controversy and confusion. Of particular concern to health providers has been the impact of National Health Service charges on delaying HIV testing and anti-retroviral treatment uptake and adherence amongst certain migrant groups. Data obtained through focus groups with 70 migrants from southern Africa, suggest that confusion over health care entitlements exists amongst those seeking health care and is reported amongst health service providers. This confusion, as well as financial difficulties and fears over deportation facing some migrants, can in turn be a factor influencing their decisions to avoid formal health services, resort to alternative and often ineffective or potentially adverse forms of therapy, and delay HIV testing and treatment uptake

Coordinating International Standards: The Formation of the ISO

In the article on “Standardization” in the 14th edition of the Encyclopædia Britannica, Paul Gough Agnew, the long-time Secretary of the American Standards Association (ASA), argued: In the flow of products from farm, forest, mine, and sea through processing and fabricating plants, and through wholesale and retail markets to the ultimate consumer, most difficulties are met at the transition points––points at which the product passes from department to department within a company, or is sold by one company to another or to an individual. The main function of standards is to facilitate the flow of products through these transition points. Standards are thus both facilitators and integrators. In smoothing out points of difficulty, or “bottlenecks,” they provide the evolutionary adjustments which are necessary for industry to keep pace with technical advances. They do this in the individual plant, in particular industries, and in industry at large. They are all the more effective as integrators in that they proceed by simple evolutionary steps, albeit inconspicuously.2 Albeit inconspicuous, standard setting has been among the nuts and bolts of globalizing industrial capitalism since its beginning, assuring that things needing to work together fit from product to product, industry to industry, and country to country. The foci of the first two of the now 229 “technical committees” of the non-specialized international standards organizations that emerged after the two world wars—the interwar International Standards Association [ISA] and the post-World War II International Organization for Standardization [ISO]—are iconic: “Screw Threads” and “Bolts, Nuts and Accessories.” Over the past two decades, voluntary standardization processes, invented by turn-of-the-twentieth-century engineers working in national and international technical committees, have increasingly been 1 We would like to thank Madame Beatrice Frey at ISO for her help in providing us access to original documents from UNSCC and ISO, and Stacy Leistner at ANSI for his help in providing access to the minutes from AESC and ASA meetings. 2 Quoted as epigraph of Dickson Reck, ed., National Standards in a Modern Economy, (New York, 1956), v. 3 applied to issues that have little in common with those of fitting one mechanical part to another, such as work processes (ISO 9000), environmental pollution (ISO 14,000), and human rights (SA 8000 and the planned ISO 26000)

Prediction of transonic flutter for a supercritical wing by modified strip analysis and comparison with experiment

Use of a supercritical airfoil can adversely affect wing flutter speeds in the transonic range. As adequate theories for three dimensional unsteady transonic flow are not yet available, the modified strip analysis was used to predict the transonic flutter boundary for the supercritical wing. The steady state spanwise distributions of section lift curve slope and aerodynamic center, required as input for the flutter calculations, were obtained from pressure distributions. The calculated flutter boundary is in agreement with experiment in the subsonic range. In the transonic range, a transonic bucket is calculated which closely resembles the experimental one with regard to both shape and depth, but it occurs at about 0.04 Mach number lower than the experimental one

Whistler mode waves upstream of Saturn

Whistler-mode waves are generated within and can propagate upstream of collisionless shocks. They are known to play a role in electron thermodynamics/acceleration and, under certain conditions, are markedly observed as wave trains preceding the shock ramp. In this paper, we take advantage of Cassini's presence at ~10 AU to explore the importance of whistler-mode waves in a parameter regime typically characterized by higher Mach number (median of ~14) shocks, as well as a significantly different IMF structure, compared to near Earth. We identify electromagnetic precursors preceding a small subset of bow shock crossings with properties which are consistent with whistler-mode waves. We find these monochromatic, low-frequency, circularly-polarized waves to have a typical frequency range of 0.2 - 0.4 Hz in the spacecraft frame. This is due to the lower ion and electron cyclotron frequencies near Saturn, between which whistler waves can develop. The waves are also observed as predominantly right-handed in the spacecraft frame, the opposite sense to what is typically observed near Earth. This is attributed to the weaker Doppler shift, owing to the large angle between the solar wind velocity and magnetic field vectors at 10 AU. Our results on the low occurrence of whistler waves upstream of Saturn also underpins the predominantly supercritical bow shock of Saturn.Comment: Published in Journal of Geophysical Research: Space Physics (January 2017) 21 pages, 4 figure

Analysis of nuclear waste disposal in space, phase 3. Volume 1: Executive summary of technical report

The objectives, approach, assumptions, and limitations of a study of nuclear waste disposal in space are discussed with emphasis on the following: (1) payload characterization; (2) safety assessment; (3) health effects assessment; (4) long-term risk assessment; and (5) program planning support to NASA and DOE. Conclusions are presented for each task