Introduction to special section : U.S. GLOBEC : physical processes on Georges Bank (GLOBEC)

Author Posting. © American Geophysical Union, 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 108, C11 (2003): 8000, doi:10.1029/2003JC002165.Support for the guest editors was provided by NSF grant OCE 02-27679 (RB), the Bedford Institute of Oceanography (PS), and NSF grant OCE 01-07946 (CL)

The FHD/ε\boldsymbol{\varepsilon}ppsilon Epoch of Reionization Power Spectrum Pipeline

Epoch of Reionization data analysis requires unprecedented levels of accuracy in radio interferometer pipelines. We have developed an imaging power spectrum analysis to meet these requirements and generate robust 21 cm EoR measurements. In this work, we build a signal path framework to mathematically describe each step in the analysis, from data reduction in the FHD package to power spectrum generation in the $\varepsilon$ppsilon package. In particular, we focus on the distinguishing characteristics of FHD/$\varepsilon$ppsilon: highly accurate spectral calibration, extensive data verification products, and end-to-end error propagation. We present our key data analysis products in detail to facilitate understanding of the prominent systematics in image-based power spectrum analyses. As a verification to our analysis, we also highlight a full-pipeline analysis simulation to demonstrate signal preservation and lack of signal loss. This careful treatment ensures that the FHD/$\varepsilon$ppsilon power spectrum pipeline can reduce radio interferometric data to produce credible 21 cm EoR measurements.Comment: 21 pages, 10 figures, accepted by PAS

A Case of Back to The Future: Paediatric Abdominal Pain. Thorough History, Examination And Senior Clinician Involvement Remain Imperative For Successful Management

INTRODUCTION: The inherent variability of the history and exam in paediatrics make acute abdominal pain a diagnostic challenge. Investigations such as white-cell-count (WCC), C-reactive-protein and radiological studies have been advocated to help objectify management. Whilst Computed Tomography is accurate, the amount of radiation involved renders it unacceptable and thus many view ultrasonographyas an acceptable alternative. But do these tests add value? METHODS: Retrospective review between 2002–2012. Data was collected for children under sixteen with acute abdominal pain undergoing investigation with ultrasound and haematological testing. For 2005,a retrospective review was conducted for children presenting with abdominal pain to obtain data on demographics, history and examination findings. Analysis for diagnostic accuracy was undertaken. RESULTS: 5000 records were reviewed, and 1744 records included. 6% of children developed appendicitis. Findings of worsening pain, associated with nausea or vomiting yielded moderate sensitivities and specificities (combined values over 70%). Fever was non-specific. Localised tenderness is the most sensitive exam finding and rebound tenderness is the most specific, both having values over 90%. WCC and CRP offer similar sensitivities and specificities, both producing results under 80%. Only 30% of ultrasounds visualised the appendix, significantly dampening the sensitivity below 75%. The incidence of appendicitis in the non-visualised group was 8%. Conclusion No test is useful for ruling out appendicitis. Given that the incidence of appendicitis is higher in the non-visualised group, this is especially so with ultrasonography. Clinical examination with senior input is the most sensible strategy for managing children with acute abdominal pain

Automatic 3D model construction for turn-table sequences

As virtual worlds demand ever more realistic 3D models, attention is being focussed on systems that can acquire graphical models from real objects. This paper describes a system which, given a sequence of images of an object rotating about a single axis, generates a textured 3D model fully automatically. In contrast to previous approaches, the technique described here requires no prior information about the cameras or scene, and does not require that the turntable angles be known (or even constant through the sequence). From an analysis of the projective geometry of the situation, it is shown that the rotation angles may be determined unambiguously, and that camera calibration, camera positions and 3D structure may be determined to within a two parameter family. An algorithm has been implemented to compute this reconstruction fully automatically. The two parameter reconstruction ambiguity may be removed by specifying, for example, camera aspect ratio and parallel scene lines. Examples are presented on four turn-table sequences

The Completely Hackable Amateur Radio Telescope (CHART) Project

We present the Completely Hackable Amateur Radio Telescope (CHART), a project that provides hands-on radio instrumentation and design experience to undergraduates while bringing accessible radio astronomy experiments to high school students and teachers. Here we describe a system which can detect 21-cm emission from the Milky Way which is optimized for cost and simplicity of construction. Software, documentation, and tutorials are all completely open source to improve the user experience and facilitate community involvement. We demonstrate the design with several observations which we compare with state-of-the-art surveys. The system is shown to detect galactic 21-cm emission in both rural and urban settings

Studies of the Canadian Arctic Archipelago water transport and its relationship to basin-local forcings : results from AO-FVCOM

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 4392–4415, doi:10.1002/2016JC011634.A high-resolution (up to 2 km), unstructured-grid, fully coupled Arctic sea ice-ocean Finite-Volume Community Ocean Model (AO-FVCOM) was employed to simulate the flow and transport through the Canadian Arctic Archipelago (CAA) over the period 1978–2013. The model-simulated CAA outflow flux was in reasonable agreement with the flux estimated based on measurements across Davis Strait, Nares Strait, Lancaster Sound, and Jones Sounds. The model was capable of reproducing the observed interannual variability in Davis Strait and Lancaster Sound. The simulated CAA outflow transport was highly correlated with the along-strait and cross-strait sea surface height (SSH) difference. Compared with the wind forcing, the sea level pressure (SLP) played a dominant role in establishing the SSH difference and the correlation of the CAA outflow with the cross-strait SSH difference can be explained by a simple geostrophic balance. The change in the simulated CAA outflow transport through Davis Strait showed a negative correlation with the net flux through Fram Strait. This correlation was related to the variation of the spatial distribution and intensity of the slope current over the Beaufort Sea and Greenland shelves. The different basin-scale surface forcings can increase the model uncertainty in the CAA outflow flux up to 15%. The daily adjustment of the model elevation to the satellite-derived SSH in the North Atlantic region outside Fram Strait could produce a larger North Atlantic inflow through west Svalbard and weaken the outflow from the Arctic Ocean through east Greenland.NSF Grant Numbers: OCE-1203393, PLR-1203643; National Natural Science Foundation of China Grant Number: 41276197; Shanghai Pujiang Program Grant Number: 12PJ1404100; Shanghai Shuguang Program2016-12-2

Ocean variability contributing to basal melt rate near the ice front of Ross Ice Shelf, Antarctica

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 119 (2014): 4214–4233, doi:10.1002/2014JC009792.Basal melting of ice shelves is an important, but poorly understood, cause of Antarctic ice sheet mass loss and freshwater production. We use data from two moorings deployed through Ross Ice Shelf, ∼6 and ∼16 km south of the ice front east of Ross Island, and numerical models to show how the basal melting rate near the ice front depends on sub-ice-shelf ocean variability. The moorings measured water velocity, conductivity, and temperature for ∼2 months starting in late November 2010. About half of the current velocity variance was due to tides, predominantly diurnal components, with the remainder due to subtidal oscillations with periods of a few days. Subtidal variability was dominated by barotropic currents that were large until mid-December and significantly reduced afterward. Subtidal currents were correlated between moorings but uncorrelated with local winds, suggesting the presence of waves or eddies that may be associated with the abrupt change in water column thickness and strong hydrographic gradients at the ice front. Estimated melt rate was ∼1.2 ± 0.5 m a−1 at each site during the deployment period, consistent with measured trends in ice surface elevation from GPS time series. The models predicted similar annual-averaged melt rates with a strong annual cycle related to seasonal provision of warm water to the ice base. These results show that accurately modeling the high spatial and temporal ocean variability close to the ice-shelf front is critical to predicting time-dependent and mean values of meltwater production and ice-shelf thinning.The Woods Hole Oceanographic Institution (WHOI) participation in the ANDRILL Coulman High Program was supported by the National Science Foundation Office of Polar Programs (NSF ANT-0839108) through a subcontract from the University of Nebraska, Lincoln (UNL 25-0550-0004-004). I. Arzeno was supported as a 2011 WHOI Summer Student Fellow through the NSF Research Experiences for Undergraduates program (OCE- 0649139). L. Padman and S. Springer were supported by NASA grant NNX10AG19G to Earth & Space Research (ESR). M. Williams and C. Stewart were supported by the New Zealand National Institute of Water and Atmosphere (NIWA) core funding under the National Climate Centre, and the Ministry of Business, Innovation, and Employment (Contract CO5X1001).2015-01-0