131 research outputs found
The Peculiar Velocities of Local Type Ia Supernovae and their Impact on Cosmology
We quantify the effect of supernova Type Ia peculiar velocities on the
derivation of cosmological parameters. The published distant and local Ia SNe
used for the Supernova Legacy Survey first-year cosmology report form the
sample for this study. While previous work has assumed that the local SNe are
at rest in the CMB frame (the No Flow assumption), we test this assumption by
applying peculiar velocity corrections to the local SNe using three different
flow models. The models are based on the IRAS PSCz galaxy redshift survey, have
varying beta = Omega_m^0.6/b, and reproduce the Local Group motion in the CMB
frame. These datasets are then fit for w, Omega_m, and Omega_Lambda using
flatness or LambdaCDM and a BAO prior. The chi^2 statistic is used to examine
the effect of the velocity corrections on the quality of the fits. The most
favored model is the beta=0.5 model, which produces a fit significantly better
than the No Flow assumption, consistent with previous peculiar velocity
studies. By comparing the No Flow assumption with the favored models we derive
the largest potential systematic error in w caused by ignoring peculiar
velocities to be Delta w = +0.04. For Omega_Lambda, the potential error is
Delta Omega_Lambda = -0.04 and for Omega_m, the potential error is Delta
Omega_m < +0.01. The favored flow model (beta=0.5) produces the following
cosmological parameters: w = -1.08 (+0.09,-0.08), Omega_m = 0.27 (+0.02,-0.02)
assuming a flat cosmology, and Omega_Lambda = 0.80 (+0.08,-0.07) and Omega_m =
0.27 (+0.02,-0.02) for a w = -1 (LambdaCDM) cosmology.Comment: 4 pages, 2 figures, 1 table, accepted for publication in ApJ Letter
Vibration Alert Bracelet for Notification of the Visually and Hearing Impaired
This paper presents the prototype of an electronic vibration bracelet designed to help the visually and hearing impaired to receive and send emergency alerts. The bracelet has two basic functions. The first function is to receive a wireless signal and respond with a vibration to alert the user. The second function is implemented by pushing one button of the bracelet to send an emergency signal. We report testing on a prototype system formed by a mobile application and two bracelets. The bracelets and the application form a complete system intended to be used in retirement apartment communities. However, the system is flexible and could be expanded to add new features or to serve as a research platform for gait analysis and location services. The medical and professional potential of the proposed system is that it offers a simple, modular, and cost-effective alternative to all the existing medical devices with similar functionality currently on the market. The proposed system has an educational potential as well: it can be used as a starting point for capstone projects and demonstration purposes in schools to attract students to STEM disciplines
Predicted and observed evolution in the mean properties of Type Ia supernovae with redshift
Recent studies indicate that Type Ia supernovae (SNe Ia) consist of two
groups - a "prompt" component whose rates are proportional to the host galaxy
star formation rate, whose members have broader lightcurves and are
intrinsically more luminous, and a "delayed" component whose members take
several Gyr to explode, have narrower lightcurves, and are intrinsically
fainter. As cosmic star formation density increases with redshift, the prompt
component should begin to dominate. We use a two-component model to predict
that the average lightcurve width should increase by 6% from z=0-1.5. Using
data from various searches we find an 8.1% +/- 2.7% increase in average
lightcurve width for non-subluminous SNe Ia from z=0.03 - 1.12, corresponding
to an increase in the average intrinsic luminosity of 12%. To test whether
there is any bias after supernovae are corrected for lightcurve shape we use
published data to mimic the effect of population evolution and find no
significant difference in the measured dark energy equation of state parameter,
w. However, future measurements of time-variable w will require standardization
of SN Ia magnitudes to 2% up to z=1.7, and it is not yet possible to assess
whether lightcurve shape correction works at this level of precision. Another
concern at z=1.5 is the expected order of magnitude increase in the number of
SNe Ia that cannot be calibrated by current methods.Comment: 5 pages, 3 figures, accepted to ApJ Letters, addressed referee's
comments, table adde
Results from the Supernova Photometric Classification Challenge
We report results from the Supernova Photometric Classification Challenge
(SNPCC), a publicly released mix of simulated supernovae (SNe), with types (Ia,
Ibc, and II) selected in proportion to their expected rate. The simulation was
realized in the griz filters of the Dark Energy Survey (DES) with realistic
observing conditions (sky noise, point-spread function and atmospheric
transparency) based on years of recorded conditions at the DES site.
Simulations of non-Ia type SNe are based on spectroscopically confirmed light
curves that include unpublished non-Ia samples donated from the Carnegie
Supernova Project (CSP), the Supernova Legacy Survey (SNLS), and the Sloan
Digital Sky Survey-II (SDSS-II). A spectroscopically confirmed subset was
provided for training. We challenged scientists to run their classification
algorithms and report a type and photo-z for each SN. Participants from 10
groups contributed 13 entries for the sample that included a host-galaxy
photo-z for each SN, and 9 entries for the sample that had no redshift
information. Several different classification strategies resulted in similar
performance, and for all entries the performance was significantly better for
the training subset than for the unconfirmed sample. For the spectroscopically
unconfirmed subset, the entry with the highest average figure of merit for
classifying SNe~Ia has an efficiency of 0.96 and an SN~Ia purity of 0.79. As a
public resource for the future development of photometric SN classification and
photo-z estimators, we have released updated simulations with improvements
based on our experience from the SNPCC, added samples corresponding to the
Large Synoptic Survey Telescope (LSST) and the SDSS, and provided the answer
keys so that developers can evaluate their own analysis.Comment: accepted by PAS
Portal technologies for patient-centred integrated care
Integrated care pathways (ICP) are increasingly used in clinical settings to provide more effective care to patients. ICPs form part of local working agreements to assist co-ordination of multi-disciplinary teams to deliver evidence-based care plans to individual patients. They also document the expected progress of specific patient groups as part of clinical records. To anticipate increased use of ICPs, we have developed Healthcare@Home, a research-phase demonstrator for improving integration of information along the patient path. Healthcare@Home includes support for at-home, in-clinic and mobile wireless sensor devices feeding patient-proximal data hubs, timeline-based physiological trend analysis, data aggregation/dashboarding and individualised risk stratification. These and other decision support tools are embedded in portal designs supporting 'end-to-end' workflows as focused by the composite needs of a National Service Framework (NSF) for patients with diabetes. Healthcare@Home thus represents a scaleable, extensible personalised healthcare information system driven directly from national policy on disease early detection and prevention. Individual portlets have been mapped to stages in the ICP. The portal technologies employed, running on PCs, mobile phones or TVs are capable of highly cost-effective 'end-to-end, anywhere-to-anywhere' information integration
Respiratory Health and Related Quality of Life in Patients with Congenital Agammaglobulinemia in the Northern Region of the UK
Towards a Cosmological Hubble Diagram for Type II-P Supernovae
We present the first high-redshift Hubble diagram for Type II-P supernovae
(SNe II-P) based upon five events at redshift up to z~0.3. This diagram was
constructed using photometry from the Canada-France-Hawaii Telescope Supernova
Legacy Survey and absorption line spectroscopy from the Keck observatory. The
method used to measure distances to these supernovae is based on recent work by
Hamuy & Pinto (2002) and exploits a correlation between the absolute brightness
of SNe II-P and the expansion velocities derived from the minimum of the Fe II
516.9 nm P-Cygni feature observed during the plateau phases. We present three
refinements to this method which significantly improve the practicality of
measuring the distances of SNe II-P at cosmologically interesting redshifts.
These are an extinction correction measurement based on the V-I colors at day
50, a cross-correlation measurement for the expansion velocity and the ability
to extrapolate such velocities accurately over almost the entire plateau phase.
We apply this revised method to our dataset of high-redshift SNe II-P and find
that the resulting Hubble diagram has a scatter of only 0.26 magnitudes, thus
demonstrating the feasibility of measuring the expansion history, with present
facilities, using a method independent of that based upon supernovae of Type
Ia.Comment: 36 pages, 16 figures, accepted for publication in Ap
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