6,936 research outputs found
Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics
One way to incorporate systematic uncertainties into the calculation of
confidence intervals is by integrating over probability density functions
parametrizing the uncertainties. In this note we present a development of this
method which takes into account uncertainties in the prediction of background
processes, uncertainties in the signal detection efficiency and background
efficiency and allows for a correlation between the signal and background
detection efficiencies. We implement this method with the Feldman & Cousins
unified approach with and without conditioning. We present studies of coverage
for the Feldman & Cousins and Neyman ordering schemes. In particular, we
present two different types of coverage tests for the case where systematic
uncertainties are included. To illustrate the method we show the relative
effect of including systematic uncertainties the case of dark matter search as
performed by modern neutrino tel escopes.Comment: 23 pages, 10 figures, replaced to match published versio
New optical and near-infrared Surface Brightness Fluctuations models. A primary distance indicator ranging from Globular Clusters to distant galaxies?
We present new theoretical models for Surface Brightness Fluctuations (SBF)
both for optical and near-infrared bands in standard ground-based and Hubble
Space Telescope filter systems. Simple Stellar Population simulations are
adopted. Models cover the age and metallicity ranges from to and
from to 0.04 respectively. Effects due to the variation of the
Initial Mass Function and the stellar color-temperature relations are explored.
Particular attention is devoted to very bright stars in the color-magnitude
diagram and to investigate the effects of mass loss along the Red Giant Branch
(RGB) and the Asymptotic Giant Branch (AGB). It is found that and bands
SBF amplitudes are powerful diagnostics for the morphology of the Horizontal
Branch and the Post-AGB stars population. We point out that a careful treatment
of mass loss process along the RGB and AGB is fundamental in determining
reliable SBF evaluations. The SBF measurements are used to give robust
constraints on the evolution of AGB stars, suggesting that mass loss activity
on AGB stars should be twice more efficient than on the RGB stars. Our models
are able to reproduce the absolute SBF magnitudes of the Galactic Globular
Clusters and of galaxies, and their integrated colors. New calibrations of
absolute SBF magnitude in , , , and photometric filters are
provided, which appear reliable enough to directly gauge distances bypassing
other distance indicators. The SBF technique is also used as stellar population
tracer to derive age and metallicity of a selected sample of galaxies of known
distances. Finally, {\it SBF color} versus {\it integrated color} diagrams are
proposed as particularly useful in removing the well known {\it age-metallicity
degeneracy} affecting our knowledge of remote stellar systems.Comment: AJ accepted, 46 pages, 21 figures, 10 tables, uses aastex.cl
Optimizing ExoMars rover remote sensing multispectral science : cross-rover comparison using laboratory and orbital data
PMG, RBS, CRC, and EJA thank the UK Space Agency for support (grant ST/T001747/1). SM acknowledges a UK Science and Technology Facilities Council (STFC) PhD studentship (grant ST/R504961/1).Multispectral imaging instruments have been core payload components of Mars lander and rover missions for several decades. In order to place into context the future performance of the ExoMars Rosalind Franklin rover, we have carried out a detailed analysis of the spectral performance of three visible and near-infrared (VNIR) multispectral instruments. We have determined the root mean square error (RMSE) between the expected multispectral sampling of the instruments and high-resolution spectral reflectance data, using both laboratory spectral libraries and Mars orbital hyperspectral data. ExoMars Panoramic Camera (PanCam) and Mars2020 Perseverance Mastcam-Z instruments have similar values of RMSE, and are consistently lower than for Mars Science Laboratory Mastcam, across both laboratory and orbital remote sensing data sets. The performance across mineral groups is similar across all instruments, with the lowest RMSE values for hematite, basalt, and basaltic soil. Minerals with broader, or absent, absorption features in these visible wavelengths, such as olivine, saponite, and vermiculite have overall larger RMSE values. Instrument RMSE as a function of filter wavelength and bandwidth suggests that spectral parameters that use shorter wavelengths are likely to perform better. Our simulations of the spectral performance of the PanCam instrument will allow the future use of targeted filter selection during ExoMars 2022 Rosalind Franklin operations on Mars.Publisher PDFPeer reviewe
Particle Characteristics of Flake-Cut Meat
The size of flake-cut meat is an Important quality determinant of comminuted meat products which. potentially. depends upon a large number of factors. Temperature and whether or not the meat is pre-broken have a major Influence on the resulting particle size distribution, as does aperture size. Meat flaked at -7\u27C produced two to three times more flakes than at -3\u27 C. Under some conditions the particles produced were as little as 0.4 mm thick and characteristically were thicker at one end.
High speed photography, used to visualise the cutting action. Indicated that size reduction occurs In a controlled manner providing that the meat ts neither too cold . nor too warm. Above -1 C the meat merely deforms rather than being cut.
Single. discrete particles. examined using scanning electron microscopy (SEM) and cryoSEM. unexpectedly did not exhibit the usual features of cleanly-cut meat. The lack of ultrastructural detail was attributed to a smearing of sarcoplasmic fluid produced by a localised. transient rise In temperature during flaking
A New Nearby Candidate Star Cluster in Ophiuchus at d = 170 pc
The recent discoveries of nearby star clusters and associations within a few
hundred pc of the Sun, as well as the order of magnitude difference in the
formation rates of the embedded and open cluster populations, suggests that
additional poor stellar groups are likely to be found at surprisingly close
distances to the Sun. Here I describe a new nearby stellar aggregate found by
virtue of the parallel proper motions, similar trigonometric parallaxes, and
consistent color-magnitude distribution of its early-type members. The 120
Myr-old group lies in Ophiuchus at 170 pc, with its most massive
member being the 4th-magnitude post-MS B8II-III star Oph. The group may
have escaped previous notice due to its non-negligible extinction (
0.9 mag). If the group was born with a normal initial mass function,
and the nine B- and A-type systems represent a complete system of
intermediate-mass stars, then the original population was probably of order
200 systems. The age and space motion of the new cluster are very similar
to those of the Pleiades, Per cluster, and AB Dor Moving Group,
suggesting that these aggregates may have formed in the same star-forming
complex some yr ago.Comment: 23 pages, 3 figs., to appear in Nov. 2006 A
The Palomar Testbed Interferometer Calibrator Catalog
The Palomar Testbed Interferometer (PTI) archive of observations between 1998
and 2005 is examined for objects appropriate for calibration of optical
long-baseline interferometer observations - stars that are predictably
point-like and single. Approximately 1,400 nights of data on 1,800 objects were
examined for this investigation. We compare those observations to an
intensively studied object that is a suitable calibrator, HD217014, and
statistically compare each candidate calibrator to that object by computing
both a Mahalanobis distance and a Principal Component Analysis. Our hypothesis
is that the frequency distribution of visibility data associated with
calibrator stars differs from non-calibrator stars such as binary stars.
Spectroscopic binaries resolved by PTI, objects known to be unsuitable for
calibrator use, are similarly tested to establish detection limits of this
approach. From this investigation, we find more than 350 observed stars
suitable for use as calibrators (with an additional being
rejected), corresponding to sky coverage for PTI. This approach
is noteworthy in that it rigorously establishes calibration sources through a
traceable, empirical methodology, leveraging the predictions of spectral energy
distribution modeling but also verifying it with the rich body of PTI's on-sky
observations.Comment: 100 pages, 7 figures, 7 tables; to appear in the May 2008ApJS, v176n
The difference that tenure makes
This paper argues that housing tenures cannot be reduced to either production relations or consumption relations. Instead, they need to be understood as modes of housing distribution, and as having complex and dynamic relations with social classes. Building on a critique of both the productionist and the consumptionist literature, as well as of formalist accounts of the relations between tenure and class, the paper attempts to lay the foundations for a new theory of housing tenure. In order to do this, a new theory of class is articulated, which is then used to throw new light on the nature of class-tenure relations
Remote detection of past habitability at Mars-analogue hydrothermal alteration terrains using an ExoMars Panoramic Camera emulator
JKH is funded by a Birkbeck University of London Graduate Teaching Assistantship. CRC is funded by a Royal Society of Edinburgh Personal Research Fellowship co-funded by Marie Curie Actions. The Aberystwyth research leading to these results has been funded by the UK Space Agency, ExoMars Panoramic Camera (PanCam) Grant Nos. ST/G003114/1, ST/I002758/1, STL001454/1, and the UK Space Agency CREST2 PanCam-2020 research Grant No. ST/L00500X/1. Additional Aberystwyth funding has come from The European Community’s Seventh Framework Programme (FP7/2007-2013), Grant Agreement Nos. 21881 PRoVisG, 241523 PRoViScout, and Grant Agreement No. 312377 PRoViDE. PMG is funded by a UK Space Agency Aurora Fellowship (grants ST/J005215/1 and ST/L00254X/1).A major scientific goal of the European Space Agency’s ExoMars 2018 rover is to identify evidence of life within the martian rock record. Key to this objective is the remote detection of geological substrates that are indicative of past habitable environments, which will rely on visual (stereo wide-angle, and high resolution images) and multispectral (440–1000 nm) data produced by the Panoramic Camera (PanCam) instrument. We deployed a PanCam emulator at four hydrothermal sites in the Námafjall volcanic region of Iceland, a Mars-analogue hydrothermal alteration terrain. At these sites, sustained acidic–neutral aqueous interaction with basaltic substrates (crystalline and sedimentary) has produced phyllosilicate, ferric oxide, and sulfate-rich alteration soils, and secondary mineral deposits including gypsum veins and zeolite amygdales. PanCam emulator datasets from these sites were complemented with (i) NERC Airborne Research and Survey Facility aerial hyperspectral images of the study area; (ii) in situ reflectance spectroscopy (400–1000 nm) of PanCam spectral targets; (iii) laboratory X-ray Diffraction, and (iv) laboratory VNIR (350–2500 nm) spectroscopy of target samples to identify their bulk mineralogy and spectral properties. The mineral assemblages and palaeoenvironments characterised here are analogous to neutral–acidic alteration terrains on Mars, such as at Mawrth Vallis and Gusev Crater. Combined multispectral and High Resolution Camera datasets were found to be effective at capturing features of astrobiological importance, such as secondary gypsum and zeolite mineral veins, and phyllosilicate-rich substrates. Our field observations with the PanCam emulator also uncovered stray light problems which are most significant in the NIR wavelengths and investigations are being undertaken to ensure that the flight model PanCam cameras are not similarly affected.Publisher PDFPeer reviewe
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The identification of sulfide oxidation as a potential metabolism driving primary production on late Noachian Mars
The transition of the martian climate from the wet Noachian era to the dry Hesperian (4.1–3.0 Gya) likely resulted in saline surface waters that were rich in sulfur species. Terrestrial analogue environments that possess a similar chemistry to these proposed waters can be used to develop an understanding of the diversity of microorganisms that could have persisted on Mars under such conditions. Here, we report on the chemistry and microbial community of the highly reducing sediment of Colour Peak springs, a sulfidic and saline spring system located within the Canadian High Arctic. DNA and cDNA 16S rRNA gene profiling demonstrated that the microbial community was dominated by sulfur oxidising bacteria, suggesting that primary production in the sediment was driven by chemolithoautotrophic sulfur oxidation. It is possible that the sulfur oxidising bacteria also supported the persistence of the additional taxa. Gibbs energy values calculated for the brines, based on the chemistry of Gale crater, suggested that the oxidation of reduced sulfur species was an energetically viable metabolism for life on early Mar
Trumpler 20 - an old and rich open cluster
We show that the open cluster Trumpler 20, contrary to the earlier findings,
is actually an old Galactic open cluster. New CCD photometry and
high-resolution spectroscopy are used to derive the main parameters of this
cluster. At [Fe/H]=-0.11 for a single red giant star, the metallicity is
slightly subsolar. The best fit to the color-magnitude diagrams is achieved
using a 1.3 Gyr isochrone with convective overshoot. The cluster appears to
have a significant reddening at E(B-V)=0.46 (for B0 spectral type), although
for red giants this high reddening yields the color temperature exceeding the
spectroscopic T_eff by about 200 K. Trumpler 20 is a very rich open cluster,
containing at least 700 members brighter than M_V=+4. It may extend over the
field-of-view available in our study at 20'x20'.Comment: 7 pages, 5 figures; accepted for publication in MNRA
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