6,477 research outputs found
Lesser or just different? Capturing children''s voices in consumer research
Child research has been conducted 'on' rather than 'with' children, and has often used parental proxies or opinion to account for the views of the child. Due to this the voice of the child has been unheard. Once access and ethical concerns have been addressed the adult researcher then has to decide which role to take when conducting research with children. Children are largely seen in one of three ways, and each perspective has an impact on the role the adult researcher could adopt. The first claims that children are entirely different from adults, and fosters the notion that they are unreliable and contaminated data sources. The second perspective views children as being entirely the same as adults, and the third views children as being similar to adults but as having different (although not necessarily inferior) competencies. The latter perspective has received most support and is the favoured view of the child respondent
Superfluid instability of r-modes in "differentially rotating" neutron stars
Superfluid hydrodynamics affects the spin-evolution of mature neutron stars,
and may be key to explaining timing irregularities such as pulsar glitches.
However, most models for this phenomenon exclude the global instability
required to trigger the event. In this paper we discuss a mechanism that may
fill this gap. We establish that small scale inertial r-modes become unstable
in a superfluid neutron star that exhibits a rotational lag, expected to build
up due to vortex pinning as the star spins down. Somewhat counterintuitively,
this instability arises due to the (under normal circumstances dissipative)
vortex-mediated mutual friction. We explore the nature of the superfluid
instability for a simple incompressible model, allowing for entrainment
coupling between the two fluid components. Our results recover a previously
discussed dynamical instability in systems where the two components are
strongly coupled. In addition, we demonstrate for the first time that the
system is secularly unstable (with a growth time that scales with the mutual
friction) throughout much of parameter space. Interestingly, large scale
r-modes are also affected by this new aspect of the instability. We analyse the
damping effect of shear viscosity, which should be particularly efficient at
small scales, arguing that it will not be sufficient to completely suppress the
instability in astrophysical systems.Comment: RevTex, 11 figure
Single-Step Quantum Search Using Problem Structure
The structure of satisfiability problems is used to improve search algorithms
for quantum computers and reduce their required coherence times by using only a
single coherent evaluation of problem properties. The structure of random k-SAT
allows determining the asymptotic average behavior of these algorithms, showing
they improve on quantum algorithms, such as amplitude amplification, that
ignore detailed problem structure but remain exponential for hard problem
instances. Compared to good classical methods, the algorithm performs better,
on average, for weakly and highly constrained problems but worse for hard
cases. The analytic techniques introduced here also apply to other quantum
algorithms, supplementing the limited evaluation possible with classical
simulations and showing how quantum computing can use ensemble properties of NP
search problems.Comment: 39 pages, 12 figures. Revision describes further improvement with
multiple steps (section 7). See also
http://www.parc.xerox.com/dynamics/www/quantum.htm
Euro-American discussion document on entry and advanced level practice in nuclear medicine
The European Association of Nuclear Medicine Technologist Committee (EANMTC) and the Society of Nuclear Medicine Technologist Section (SNMTS) meet biannually to consider matters of mutual importance. These meetings are held during the SNM and EANM annual conferences. For several years, within these meetings, EANMTC and SNMTS have considered the value of having a Euro-American initiative in defining entry-level and advanced practice competencies for nuclear medicine radiographers (NMRs) and nuclear medicine technologists (NMTs). In June 2009, during the SNM annual conference in Toronto, it was agreed that a Euro-American working party would be established to consider advanced practice. It was recognized that any consideration of a definition for advanced practice would be predicated on an understanding or definition of entry-level practice. As a result, both types of practice would have to be considered. This discussion document outlines some of the background issues associated with advanced practice generally and specifically within nuclear medicine. The primary purpose of this document is to stimulate debate, on a Euro-American level, about the perceived value of advanced practice for NMRs and NMTs within nuclear medicine and to develop an internationally accepted list of entry-level competencies and scope of practice for NMRs and NMTs within nuclear medicine
A List of Wisconsin Springtails With New Records and Annotations (Hexapoda: Parainsecta: Collembola)
Twenty Collembola species new to Wisconsin were collected from soil at two agricultural sites in southern Wisconsin, including an undescribed species of Isotomidae. The state faunal list now contains 52 species representing seven families
Interleukin-12 p40 secretion by cutaneous CD11c(+) and F4/80(+) cells is a major feature of the innate immune response in mice that develop Th1-mediated protective immunity to Schistosoma mansoni
Radiation-attenuated (RA) schistosome larvae are potent stimulators of innate immune responses at the skin site of exposure (pinna) that are likely to be important factors in the development of Th1-mediated protective immunity. In addition to causing an influx of neutrophils, macrophages, and dendritic cells (DCs) into the dermis, RA larvae induced a cascade of chemokine and cytokine secretion following in vitro culture of pinna biopsy samples. While macrophage inflammatory protein 1alpha and interleukin-1beta (IL-1beta) were produced transiently within the first few days, the Th1-promoting cytokines IL-12 and IL-18 were secreted at high levels until at least day 14. Assay of C3H/HeJ mice confirmed that IL-12 secretion was not due to lipopolysaccharide contaminants binding Toll-like receptor 4. Significantly, IL-12 p40 secretion was sustained in pinnae from vaccinated mice but not in those from nonprotected infected mice. In contrast, IL-10 was produced from both vaccinated and infected mice. This cytokine regulates IL-12-associated dermal inflammation, since in vaccinated IL-10(-/-) mice, pinna thickness was greatly increased concurrent with elevated levels of IL-12 p40. A significant number of IL-12 p40(+) cells were detected as emigrants from in vitro-cultured pinnae, and most were within a population of rare large granular cells that were Ia(+), consistent with their being antigen-presenting cells. Labeling of IL-12(+) cells for CD11c, CD205, CD8alpha, CD11b, and F4/80 indicated that the majority were myeloid DCs, although a proportion were CD11c(-) F4/80(+), suggesting that macrophages were an additional source of IL-12 in the skin
Cosmology with liquid mirror telescopes
Liquid mirrors provide an exciting means to obtain large optical telescopes for substantially lower costs than conventional technologies. The liquid mirror concept has been demonstrated in the lab with the construction of a diffraction limited 1.5 m mirror. The mirror surface, using liquid mercury, forms a perfect parabolic shape when the mirror cell is rotated at a uniform velocity. A liquid mirror must be able to support a heavy mercury load with minimal flexure and have a fundamental resonant frequency that is as high as possible, to suppress the amplitude of surface waves caused by small vibrations transmitted to the mirror. To minimize the transmission of vibrations to the liquid surface, the entire mirror rests on an air bearing. This necessitates the mirror cell being lightweight, due to the limited load capabilities of the air bearing. The mirror components must also have physical characteristics which minimize the effects of thermal expansion with ambient temperature fluctuations in the observatory. In addition, the 2.7 m mirror construction is designed so that the techniques used may be readily extended to the construction of large mirrors. To attain the goals of a lightweight, rigid mirror, a composite laminant construction was used. The mirror consists of a foam core cut to the desired parabolic shape, with an accuracy of a few mm. An aluminum hub serves as an anchor for the foam and skin, and allows precise centering of the mirror on the air bearing and drive system. Several plys of Kevlar, covered in an epoxy matrix, are then applied to the foam. A final layer of pure epoxy is formed by spin casting. This final layer is parabolic to within a fraction of a mm. An aluminum ring bonded to the circumference of the mirror retains the mercury, and incorporates stainless-steel hard-points for the attachment of balance weights
A maximum-likelihood method for improving faint source flux and color estimates
Flux estimates for faint sources or transients are systematically biased high
because there are far more truly faint sources than bright. Corrections which
account for this effect are presented as a function of signal-to-noise ratio
and the (true) slope of the faint-source number-flux relation. The corrections
depend on the source being originally identified in the image in which it is
being photometered. If a source has been identified in other data, the
corrections are different; a prescription for calculating the corrections is
presented. Implications of these corrections for analyses of surveys are
discussed; the most important is that sources identified at signal-to-noise
ratios of four or less are practically useless.Comment: 9 pp., accepted for publication in PAS
Using microsimulation feedback for trip adaptation for realistic traffic in Dallas
This paper presents a day-to-day re-routing relaxation approach for traffic
simulations. Starting from an initial planset for the routes, the route-based
microsimulation is executed. The result of the microsimulation is fed into a
re-router, which re-routes a certain percentage of all trips. This approach
makes the traffic patterns in the microsimulation much more reasonable.
Further, it is shown that the method described in this paper can lead to strong
oscillations in the solutions.Comment: Accepted by International Journal of Modern Physics C. Complete
postscript version including figures in
http://www-transims.tsasa.lanl.gov/research_team/papers
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