Crowded-Field Astrometry with the Space Interferometry Mission - I. Estimating the Single-Measurement Astrometric Bias Arising from Confusion

The accuracy of position measurements on stellar targets with the future Space Interferometry Mission (SIM) will be limited not only by photon noise and by the properties of the instrument (design, stability, etc.) and the overall measurement program (observing strategy, reduction methods, etc.), but also by the presence of other "confusing" stars in the field of view (FOV). We use a simple "phasor" model as an aid to understanding the main effects of this "confusion bias" in single observations with SIM. This analytic model has been implemented numerically in a computer code and applied to a selection of typical SIM target fields drawn from some of the Key Projects already accepted for the Mission. We expect that less than 1% of all SIM targets will be vulnerable to confusion bias; we show that for the present SIM design, confusion may be a concern if the surface density of field stars exceeds 0.4 star/arcsec^2. We have developed a software tool as an aid to ascertaining the possible presence of confusion bias in single observations of any arbitrary field. Some a priori knowledge of the locations and spectral energy distributions of the few brightest stars in the FOV is helpful in establishing the possible presence of confusion bias, but the information is in general not likely to be available with sufficient accuracy to permit its removal. We discuss several ways of reducing the likelihood of confusion bias in crowded fields. Finally, several limitations of the present semi-analytic approach are reviewed, and their effects on the present results are estimated. The simple model presented here provides a good physical understanding of how confusion arises in a single SIM observation, and has sufficient precision to establish the likelihood of a bias in most cases.Comment: 28 pages, 20 figures, 1 table; to appear in December 2007 issue of PAS

Comparison of energy estimates in chronic kidney disease using doubly-labelled water

This is the peer reviewed version of the following article: S. Sridharan, J. Wong, E. Vilar, and K. Farrington, ‘Comparison of energy estimates in chronic kidney disease using doubly-labelled water’, Journal of Human Nutrition and Dietetics, Vol. 29 (1): 59-66, February 2016, which has been published in final form at https://doi.org/10.1111/jhn.12326. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. © 2015 The British Dietetic Association Ltd.BACKGROUND: Total energy expenditure (TEE) is estimated in clinical practice as a combined measure of resting energy expenditure and physical activity level. Commonly available questionnaires to estimate physical activity level have not been validated in patients with kidney disease using the doubly-labelled water method. METHODS: This prospective, cross-sectional study was conducted on 40 patients with chronic kidney disease stages 1-5 with the objective of validating two physical activity questionnaires: the Recent Physical Activity Questionnaire (RPAQ) and the Stanford 7-day recall questionnaire. TEE was measured using doubly-labelled water technique. TEE was also estimated using predicted resting energy expenditure and estimated physical activity measures from the questionnaires. RESULTS: Measured TEE correlated better with TEE estimated from RPAQ compared to that from the Stanford questionnaire. In Bland-Altman analysis, TEE estimated from RPAQ had the least bias and narrower limits of agreement compared to the measured TEE. A metabolic equivalent of task value of 1.3 for the unaccounted time in RPAQ provided the best approximation of estimated TEE to the measured TEE. CONCLUSIONS: RPAQ is an acceptable questionnaire tool for assessing physical activity level in patients with chronic kidney disease.Peer reviewedFinal Accepted Versio

The workings of the single member plurality electoral system in India and the need for reform

India uses single member plurality system (SMPS) to elect the members of the lower house of its national parliament and the state assemblies. Under SMPS, elections are conducted for separate geographical areas, known as constituencies or districts, and the electors cast one vote each for a candidate with the winner being the candidate who gets the plurality of votes. SMPS is traditionally defended primarily on the grounds of simplicity and its tendency to produce winning candidates, which promotes a link between constituents and their representatives. It tends to provide a clear-cut choice for voters between two main parties, and is expected to gives rise to single-party rather than coalition governments. It also has the benefit of excluding extremist parties from gaining representation, unless their support is geographically concentrated

Rotational Structure and Outflow in the Infrared Dark Cloud 18223-3

We examine an Infrared Dark Cloud (IRDC) at high spatial resolution as a means to study rotation, outflow, and infall at the onset of massive star formation. Submillimeter Array observations combined with IRAM 30 meter data in 12CO(2--1) reveal the outflow orientation in the IRDC 18223-3 region, and PdBI 3 mm observations confirm this orientation in other molecular species. The implication of the outflow's presence is that an accretion disk is feeding it, so using high density tracers such as C18O, N2H+, and CH3OH, we looked for indications of a velocity gradient perpendicular to the outflow direction. Surprisingly, this gradient turns out to be most apparent in CH3OH. The large size (28,000 AU) of the flattened rotating object detected indicates that this velocity gradient cannot be due solely to a disk, but rather from inward spiraling gas within which a Keplerian disk likely exists. From the outflow parameters, we derive properties of the source such as an outflow dynamical age of ~37,000 years, outflow mass of ~13 M_sun, and outflow energy of ~1.7 x 10^46 erg. While the outflow mass and energy are clearly consistent with a high-mass star forming region, the outflow dynamical age indicates a slightly more evolved evolutionary stage than previous spectral energy distribution (SED) modeling indicates. The calculated outflow properties reveal that this is truly a massive star in the making. We also present a model of the observed methanol velocity gradient. The rotational signatures can be modeled via rotationally infalling gas. These data present evidence for one of the youngest known outflow/infall/disk systems in massive star formation. A tentative evolutionary picture for massive disks is discussed.Comment: 11 pages, 9 figures. Accepted for publication in A&A. Figures 2,3,6, and 9 are available at higher resolution by email or in the journal publicatio

High Mass Starless Cores

We report the identification of a sample of potential High-Mass Starless Cores (HMSCs). The cores were discovered by comparing images of the fields containing candidate High-Mass Protostellar Objects (HMPOs) at 1.2mm and mid-infrared (8.3um; MIR) wavelengths. While the HMPOs are detected at both wavelengths, several cores emitting at 1.2mm in the same fields show absorption or no emission at the MIR wavelength. We argue that the absorption is caused by cold dust. The estimated masses of a few 10^2Msun - 10^3 Msun and the lack of IR emission suggests that they may be massive cold cores in a pre-stellar phase, which could presumably form massive stars eventually. Ammonia (1,1) and (2,2) observations of the cores indicate smaller velocity dispersions and lower rotation temperatures compared to HMPOs and UCHII regions suggesting a quiescent pre-stellar stage. We propose that these newly discovered cores are good candidates for the HMSC stage in high-mass star-formation. This sample of cores will allow us to study the high-mass star and cluster formation processes at the earliest evolutionary stages.Comment: 7 pages, 3 figures, 1 table, to be published in ApJL, author names replaced with comma separatio

Clinical perception of effectiveness of virtual appointments and comparison with appointment outcomes at a specialist children's hospital

Introduction: A transition from face-to-face to virtual consultations occurred in response to the COVID-19 pandemic. Evaluation of outcome data is essential for future healthcare modelling. Methods: Clinicians at a children's hospital evaluated perceptions of face-to-face video and telephone appointments by questionnaire. Responses were compared with operational outcomes from June 2019 and June 2020. Results: Ninety-three clinicians responded from 28 subspecialties. Virtual consultations increased from 6% (2019) to 67% (2020). No differences were found between appointment types for recording a medical and social history; a significant difference (p<0.001) was seen for the perceived ability to detect clinical signs, organise investigations and make a diagnosis. The proportion of appointments resulting in discharge compared with face-to-face visits was unchanged. The proportion of patients requiring further contact increased from 35% (32% face-to-face and 3% telephone) to 46% (14% face-to-face; 21% telephone and 11% video; chi-squared 426; p<0.0001). The percentage of patients offered an appointment following two ‘was not brought’ appointments increased from 71% (2019) to 81% (2020) and was most common following telephone appointments (20% face-to-face, 43% telephone and 18% video; chi-squared 474; p<0.0001). Conclusion: The perception of clinicians is that virtual appointments enabled continuity of paediatric care with improved clinical assessment capability and attendance during video consultations compared with telephone consultations

Mission planning for space based satellite surveillance experiments with the MSX

The Midcourse Space Experiment is a BMDO-sponsored scientific satellite set for launch within the year. The satellite will collect phenomenology data on missile targets, plumes, earth limb backgrounds and deep space backgrounds in the LWIR, visible and ultra-violet spectral bands. It will also conduct functional demonstrations for space-based space surveillance. The Space-Based Visible sensor, built by Lincoln Laboratory, Massachusetts Institute of Technology, is the primary sensor on board the MSX for demonstration of space surveillance. The SBV Processing, Operations and Control Center (SPOCC) is the mission planning and commanding center for all space surveillance experiments using the SBV and other MSX instruments. The guiding principle in the SPOCC Mission Planning System was that all routine functions be automated. Manual analyst input should be minimal. Major concepts are: (I) A high level language, called SLED, for user interface to the system; (2) A group of independent software processes which would generally be run in a pipe-line mode for experiment commanding but can be run independently for analyst assessment; (3) An integrated experiment cost computation function that permits assessment of the feasibility of the experiment. This paper will report on the design, implementation and testing of the Mission Planning System