2,238 research outputs found
Developing a Raspberry Pi magnetometer for schools in the UK
We describe our efforts to build a magnetic field sensor to be deployed in schools across the United Kingdom, adding to the existing variometer network from AuroraWatch set up by the University of Lancaster (Figure 1). The aim is to encourage students from 14-18 years old to look at how sensors can be used to collect geophysical data and integrate it together to give a wider understanding of physical phenomena. A second aim is to provide useful data on the spatial variation of the magnetic field for analysis of geomagnetic storms, alongside data from the BGS observatory and SAMNET variometer network. The system uses a Raspberry Pi computer as a logging and data transfer device, connected to a set of miniature fluxgate magnetometers. The system has a nominal sensitivity of around 1 nT RMS (~1 part in 50,000) in each component and is relatively low-cost at about ÂŁ250 per unit. We intend to build 10 systems initially. In this poster we show results from the build and testing of the sensor and examples of recorded horizontal field
Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters
We present the result of a wide-field survey of globular clusters (GCs) in
M31 covering a 3deg x 3deg field c. We have searched for GCs on CCD images
taken with Washington CMT1 filters at the KPNO 0.9 m telescope using steps: (1)
inspection of morphological parameters given by the SExtractor package such as
stellarity, full maximum, and ellipticity; (2) consulting the spectral types
and radial velocities obtained from spectra takena spectrograph at the WIYN 3.5
m telescope; and (3) visual inspection of the images of each object. We have
and GC candidates, of which 605 are newly found GCs and GC candidates and 559
are previously known GCs. Amoects there are 113 genuine GCs, 258 probable GCs,
and 234 possible GCs, according to our classification critee known objects
there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total
there are 496 genprobable GCs and 301 possible GCs. Most of these newly found
GCs have T1 magnitudes of 17.5 - 19.5 mag, [17.9 < V < 19.9 mag assuming (C-T1)
~ 1.5], and (C-T1) colors in the range 1 - 2.Comment: accepted by AJ, using emulateapj.cl
Cool White Dwarfs in the Sloan Digital Sky Survey
A reduced proper motion diagram utilizing Sloan Digital Sky Survey (SDSS)
photometry and astrometry and USNO-B plate astrometry is used to separate cool
white dwarf candidates from metal-weak, high-velocity main sequence Population
II stars (subdwarfs) in the SDSS Data Release 2 imaging area. Follow-up
spectroscopy using the Hobby-Eberly Telescope, the MMT, and the McDonald 2.7m
Telescope is used to demonstrate that the white dwarf and subdwarf loci
separate cleanly in the reduced proper motion diagram, and that the
contamination by subdwarfs is small near the cool white dwarf locus. This
enables large statistically complete samples of white dwarfs, particularly the
poorly understood cool white dwarfs, to be created from the SDSS imaging
survey, with important implications for white dwarf luminosity function
studies. SDSS photometry for our sample of cool white dwarfs is compared to
current white dwarf models.Comment: AJ accepted, 36 pages, 11 figures (Figure 1 low-rez version
The Extreme Hosts of Extreme Supernovae
We use GALEX ultraviolet (UV) and optical integrated photometry of the hosts
of seventeen luminous supernovae (LSNe, having peak M_V < -21) and compare them
to a sample of 26,000 galaxies from a cross-match between the SDSS DR4 spectral
catalog and GALEX interim release 1.1. We place the LSNe hosts on the galaxy
NUV-r versus M_r color magnitude diagram (CMD) with the larger sample to
illustrate how extreme they are. The LSN hosts appear to favor low-density
regions of the galaxy CMD falling on the blue edge of the blue cloud toward the
low luminosity end. From the UV-optical photometry, we estimate the star
formation history of the LSN hosts. The hosts have moderately low star
formation rates (SFRs) and low stellar masses (M_*) resulting in high specific
star formation rates (sSFR). Compared with the larger sample, the LSN hosts
occupy low-density regions of a diagram plotting sSFR versus M_* in the area
having higher sSFR and lower M_*. This preference for low M_*, high sSFR hosts
implies the LSNe are produced by an effect having to do with their local
environment. The correlation of mass with metallicity suggests that perhaps
wind-driven mass loss is the factor that prevents LSNe from arising in
higher-mass, higher-metallicity hosts. The massive progenitors of the LSNe
(>100 M_sun), by appearing in low-SFR hosts, are potential tests for theories
of the initial mass function that limit the maximum mass of a star based on the
SFR.Comment: 8 pages, 3 figures, 2 tables, accepted to ApJ, amended references and
updated SN designation
Crop Updates 2005 Oilseeds
This session covers fifteen papers from different authors:
1. ACKNOWLEDGEMENTS, Douglas Hamilton, FARMING SYSTEMS DEVELOPMENT OFFICER
CROP AGRONOMY AND NUTRITION
2. Canola workshop at Crop Updates 2005, Oilseeds WA, John Duff, EXECUTIVE OFFICER OILSEEDS WA
3. Comparison of IT and TT canola varieties in geographic zones of WA, 2003-4, Graham Walton and Hasan Zaheer, Department of Agriculture
4. Farmer scale canola variety trials in WA, 2004, Graham Walton, John Duff, Neil Harris and Heather Cosgriff, Oilseeds WA
5. Oilseed crops for industrial uses, Margaret C. Campbell, Centre for Legumes in Mediterranean Agriculture (CLIMA), Graham Walton,Department of Agriculture
6. Weed control opportunities with GM canola, Bill Crabtree, Independent
Consultant, Northam
7. Soil and tissue tests for the sulfur requirements of canola, R.F. Brennan and M.D.A. Bolland, Department of Agriculture
8. Tests to predict the potassium requirements of canola, R.F. Brennan and M.D.A. Bolland, Department of Agriculture
9. Genotypic variation in potassium efficiency of canola, P.M. Damon and Z. Rengel, Faculty of Natural and Agricultural Sciences, UWA
10. Atrazine contamination of groundwater in the agricultural region of Western Australia, Russell Speed1, Neil Rothnie2, John Simons1, Ted Spadek2 and John Moore1;1Department of Agriculture, 2Chemistry Centre (WA)
PESTS AND DISEASES
11. Controlling aphids and Beet western yellows virus in canola using imidacloprid seed dressing, Brenda Coutts and Roger Jones; Department of Agriculture
12. Managing sclerotinia in canola, Neil Harris, Dovuro Seeds Western Australia
13. Slugs, the trail of destruction in canola, Neil Harris, Dovuro Seeds Western Australia
14. Blackleg risk assessment and strategies for risk management in canola during 2005 and beyond, Moin Salam, Ravjit Khanguraand Art Diggle, Department of Agriculture
15. Modelling: BRAT – Blackleg Risk Appraisal Tool, Moin Salam, Ravjit KhanguraDepartment of Agricultur
The White Dwarf Luminosity Function from Sloan Digital Sky Survey Imaging Data
A sample of white dwarfs is selected from the Sloan Digital Sky Survey (SDSS) Data Release 3 using their reduced proper motions, based on improved proper motions from combined SDSS and USNO-B data. Numerous SDSS and follow-up spectra (Kilic and coworkers) are used to quantify completeness and contamination of the sample; kinematicsmodels are used to understand and correct for velocity-dependent selection biases.A luminosity function is constructed covering the range 7 \u3c Mbol \u3c 16, and its sensitivity to various assumptions and selection limits is discussed. The white dwarf luminosity function based on 6000 stars is remarkably smooth and rises nearly monotonically to Mbol=15.3. It then drops abruptly, although the small number of low-luminosity stars in the sample and their unknown atmospheric composition prevent quantitative conclusions about this decline. Stars are identified that may have high tangential velocities, and a preliminary luminosity function is constructed for them
Schindler’s legacy : from eutrophic lakes to the phosphorus utilization strategies of cyanobacteria
David Schindler and his colleagues pioneered studies in the 1970s on the role of phosphorus in stimulating cyanobacterial blooms in North American lakes. Our understanding of the nuances of phosphorus utilization by cyanobacteria has evolved since that time. We review the phosphorus utilization strategies used by cyanobacteria, such as use of organic forms, alternation between passive and active uptake, and luxury storage. While many aspects of physiological responses to phosphorus of cyanobacteria have been measured, our understanding of the critical processes that drive species diversity, adaptation and competition remains limited. We identify persistent critical knowledge gaps, particularly on the adaptation of cyanobacteria to low nutrient concentrations. We propose that traditional discipline-specific studies be adapted and expanded to encompass innovative new methodologies and take advantage of interdisciplinary opportunities among physiologists, molecular biologists, and modellers, to advance our understanding and prediction of toxic cyanobacteria, and ultimately to mitigate the occurrence of blooms
The White Dwarf Luminosity Function from SDSS Imaging Data
A sample of white dwarfs is selected from SDSS DR3 imaging data using their
reduced proper motions, based on improved proper motions from SDSS plus USNO-B
combined data. Numerous SDSS and followup spectra (Kilic et al. 2005) are used
to quantify completeness and contamination of the sample; kinematic models are
used to understand and correct for velocity-dependent selection biases. A
luminosity function is constructed covering the range 7 < M_bol < 16, and its
sensitivity to various assumptions and selection limits is discussed. The white
dwarf luminosity function based on 6000 stars is remarkably smooth, and rises
nearly monotonically to M_bol = 15.3. It then drops abruptly, although the
small number of low-luminosity stars in the sample and their unknown
atmospheric composition prevent quantitative conclusions about this decline.
Stars are identified that may have high tangential velocities, and a
preliminary luminosity function is constructed for them.Comment: Accepted for AJ (Jan 2006). 35 pages (includes 10 figures
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