31,781 research outputs found
Secular evolution in action: central values and radial trends in the stellar populations of boxy bulges
We determine central values and radial trends in the stellar populations of
the bulges of a sample of 28 edge-on S0-Sb disk galaxies, 22 of which are
boxy/peanut-shaped (and therefore barred). Our principal findings are the
following. (1) At a given velocity dispersion, the central stellar populations
of galaxies with boxy/peanut-shaped bulges are indistinguishable from those of
early-type (elliptical and S0) galaxies. Either secular evolution affects
stellar populations no differently to monolithic collapse or mergers, or
secular evolution is not important in the central regions of these galaxies,
despite the fact that they are barred. (2) The radial metallicity gradients of
boxy/peanut-shaped bulges are uncorrelated with velocity dispersion and are, on
average, shallower than those of unbarred early-type galaxies. This is
qualitatively consistent with chemodynamical models of bar formation, in which
radial inflow and outflow smears out pre-existing gradients.Comment: MNRAS Letters accepted. 5 page
Chandra and Far Ultraviolet Spectroscopic Explorer Observations of z~0 Warm-Hot Gas Toward PKS 2155-304
The X-ray bright z=0.116 quasar PKS 2155-304 is frequently observed as a
Chandra calibration source, with a total of 483 ksec of Low Energy Transmission
Grating (LETG) exposure time accumulated through May 2006. Highly-ionized metal
absorption lines, including numerous lines at z=0 and a putative OVIII K-alpha
line at z=0.055, have been reported in past Chandra studies of this source.
Using all available Chandra LETG spectra and analysis techniques developed for
such z=0 X-ray absorption along other sightlines, we revisit these previous
detections. We detect 4 absorption lines at >3\sigma significance (OVII
K-alpha/beta, OVIII K-alpha, and NeIX K-alpha), with OVII K-alpha being a
7.3\sigma detection. The 1\sigma ranges of z=0 OVII column density and Doppler
parameter are consistent with those derived for Mrk 421 and within 2\sigma of
the Mrk 279 absorption. Temperatures and densities inferred from the relative
OVII and other ionic column densities are found to be consistent with either
the local warm-hot intergalactic medium or a Galactic corona. Unlike the local
X-ray absorbers seen in other sightlines, a link with the low- or high-velocity
far-ultraviolet OVI absorption lines cannot be ruled out. The z=0.055 OVIII
absorption reported by Fang et al. is seen with 3.5\sigma confidence in the
ACIS/LETG spectrum, but no other absorption lines are found at the same
redshift.Comment: 11 pages, 9 figures; minor changes, accepted to Ap
Caryophyllaeid Cestodes from Four Species of Carpiodes (Teleostei: Catostomidae)
The caryophyllaeid cestode fauna of four species of carpsuckers was investigated. Four hundred and thirty hosts from Iowa, Minnesota, Wisconsin, and Nebraska were examined (Aug. 1967-Dec. 1968) and 260 (60%) were parasitized. Four species of caryophyllaeids were found, of which Spartoides wardi and Biacetabulum carpiodi were most abundant. B. carpiodi exhibits a definite seasonal periodicity in spring and early summer, but none appears to exist for S. wardi. Single infections of Glaridacris confusa and Monobothrium sp. were also encountered
Backbone and side chain H-1, N-15 and C-13 assignments for the oxidised and reduced forms of the oxidoreductase protein DsbA from Staphylococcus aureus
The function and dynamics of the thiol-disulfide oxidoreductase DsbA in the low-GC gram positive bacterium, Staphylococcus aureus, are yet to be elucidated. Here we report 13C, 15N and 1H assignments for the oxidised and reduced forms of SaDsbA as a prelude to further studies on the enzyme
Participant perceptions of physical activity-enhancing interventions for adults with disability: A meta-synthesis of qualitative research
The United Nations Convention on the Rights of Persons with Disabilities enshrines the rights of disabled people to access services in all areas of citizenship including participation in recreational, leisure and sport activities. Despite this protection, people with disabilities face multiple personal, environmental and social barriers to participation in physical activity (PA). As a result, disabled people are more likely to be inactive compared to the able bodied population and are at a greater risk of inactivity-related diseases. Thus, there is an urgent need for behaviour change interventions to increase PA by specifically addressing the situations of people with disabilities and their barriers to participation. This original meta-synthesis of qualitative research was undertaken to explore participants’ perceptions of PA-enhancing interventions for adults with physical disability. To identify published articles relevant to the meta-synthesis, a rigorous systematic search of electronic databases and hand search of relevant journals was undertaken. In total, 76 papers were read in full, and based on the inclusion criteria, 10 papers were included for review. Following a critical appraisal of the papers, methods of thematic synthesis were drawn upon to generate analytical themes through interpretation and conceptual synthesis. Seven interrelated analytical themes were constructed representing both components and outcomes of the interventions. These were: (i) social support; (ii) diversity; (iii) communication; (iv) behavioural strategies; (v) changing thoughts; (vi) knowledge; (vii) health and well-being. The results of this meta-synthesis provide significant new information that will help interventionists design more effective PA-enhancing interventions, and researchers to better identify and measure key mechanisms and outcomes associated with successful PA-enhancing interventions for people with disabilities
Using learning design as a framework for supporting the design and reuse of OER
The paper will argue that adopting a learning design methodology may provide a vehicle for enabling better design and reuse of Open Educational Resources (OERs). It will describe a learning design methodology, which is being developed and implemented at the Open University in the UK.
The aim is to develop a 'pick and mix' learning design toolbox of different resources and tools to help designers/teachers make informed decisions about creating new or adapting existing learning activities. The methodology is applicable for designers/teachers designing in a traditional context – such as creation of materials as part of a formal curriculum, but also has value for those wanting to create OERs or adapt and repurpose existing OERs. With the increasing range of OERs now available through initiatives as part of the Open Courseware movement, we believe that methodologies, such as the one we describe in this paper, which can help guide reuse and adaptation will become increasingly important and arguably are an important aspect of ensuring longer term sustainability and uptake of OERs. Our approach adopts an empirically based approach to understanding and representing the design process. This includes a range of evaluation studies (capturing of case studies, interviews with designers/teachers, in-depth course evaluation and focus groups/workshops), which are helping to develop our understanding of how designers/teachers go about creating new learning activities. Alongside this we are collating an extensive set of tools and resources to support the design process, as well as developing a new Learning Design tool that helps teachers articulate and represent their design ideas. The paper will describe how we have adapted a mind mapping and argumentation tool, Compendium, for this purpose and how it is being used to help designers and teachers create and share learning activities. It will consider how initial evaluation of the use of the tool for learning design has been positive; users report that the tool is easy to use and helps them organise and articulate their learning designs. Importantly the tool also enables them to share and discuss their thinking about the design process. However it is also clear that visualising the design process is only one aspect of design, which is complex and multi-faceted
The Nature of Nearby Counterparts to Intermediate Redshift Luminous Compact Blue Galaxies I. Optical/H I Properties and Dynamical Masses
We present single-dish H I spectra obtained with the Green Bank Telescope,
along with optical photometric properties from the Sloan Digital Sky Survey, of
20 nearby (D < 70 Mpc) Luminous Compact Blue Galaxies (LCBGs). These ~L*, blue,
high surface brightness, starbursting galaxies were selected with the same
criteria used to define LCBGs at higher redshifts. We find these galaxies are
gas-rich, with M(HI) ranging from 5*10^8 to 8*10^9 M_sun, and M(HI)/L_B ranging
from 0.2 to 2 M_sun/L_sun, consistent with a variety of morphological types of
galaxies. We find the dynamical masses (measured within R_25) span a wide
range, from 3*10^9 to 1*10^11 M_sun. However, at least half have dynamical
mass-to-light ratios smaller than nearby galaxies of all Hubble types, as found
for LCBGs at intermediate redshifts. By comparing line widths and effective
radii with local galaxy populations, we find that LCBGs are consistent with the
dynamical mass properties of Magellanic (low luminosity) spirals, and the more
massive irregulars and dwarf ellipticals, such as NGC 205.Comment: 33 pages, 8 figures, accepted by Ap
Ultrasonic NDT Prototype for the Inspection of Ducted Post Stressing Tendons in Concrete Beams
There is worldwide concern about concrete bridges which derive their strength from post stressed steel tendons in grouted ducts. Problems arise when grouting has not been carried out properly, since the combination of voided regions and moisture penetration can cause corrosion of the tendon and catastrophic failure of the structure [1]. Post tensioned bridges built during the middle of this century are particularly susceptible and there is a pressing need for a cost effective non destructive means of assessing the condition of the embedded ducts and tendons. In response to this problem, a track mounted ultrasonic scanning system ‘CANDI’ (Cable Analysis by Non Destructive Inspection) is currently under development in UMIST, and this work describes the CANDI prototype and results obtained
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