12,841 research outputs found
The Gaia white dwarf population within 100 pc of the Sun
No full textThe recent Gaia Data Release 2 has provided an
unprecedented sample of the local white dwarf
population. The high astrometric resolution and
the photometry provided by Gaia allows to build a
clean magnitude-color diagram that, with the aid
of the most updated population synthesis simulator,
permit us to select the sample of white dwarf
candidates. Our analysis shows that Gaia has virtually
identified all white dwarfs within 100 pc from
the Sun. Additionally, we use the Virtual Observatory
tool VOSA to derive effective temperatures and
luminosities for our sources by fitting their spectral
energy distributions. The Gaia 100 pc white dwarf
population is clearly dominated by cool ( 8,000
K) objects and reveals a significant population of
massive (M 0:8M ) white dwarfs, of which
no more than 30 ¿ 40% can be attributed to
hydrogen-deficient atmospheres. Preliminary results
including white dwarf mergers seem not to
explain this excess unless some ad hoc hypothesis
are adopted. Finally, we use an Intelligent Artificial
algorithm based on the Random Forest method to
disentangle the different Galactic components of
the white dwarf population. Our results show that
the thin, thick and halo ratio in the 100 pc sample
is 89:11:1, identifying 97 halo white dwarf candidates.Peer ReviewedPostprint (published version
An improved thick-film piezoelectric material by powder blending and enhanced processing parameters
No full textThis paper details improvements of the d33 coefficient for thick-film lead zirconate titanate (PZT) layers. In particular, the effect of blending ball and attritor milled powders has been investigated. Mathematical modeling of the film structure has produced initial experimental values for powder combination percentages. A range of paste formulations between 8:1 and 2:1 ball to attritor milled PZT powders by weight have been mixed into a screen-printable paste. Each paste contains 10% by weight of lead borosilicate glass and an appropriate quantity of solvent to formulate a screen printable thixotropic paste. A d33 of 63.5 pC/N was obtained with a combination of 4:1 ball milled to attritor milled powder by weight. The improved paste combines the high d33 values of ball and the consistency of attritor milled powder. The measured d33 coefficient was further improved to 131 pC/N by increasing the furnace firing pro-file to 100
The Gaia 20 pc white dwarf sample
No full textUsing Gaia DR2 data, we present an up-to-date sample of white dwarfs within 20 pc of the Sun. In total we identified 139 systems in Gaia DR2, nine of which are new detections, with the closest of these located at a distance of 13.05 pc. We estimated atmospheric parameters for all stellar remnants based on the Gaia parallaxes and photometry. The high precision and completeness of the Gaia astrometry allowed us to search for wide binary companions. We re-identified all known binaries where both components have accurate DR2 astrometry, and established the binarity of one of the nine newly identified white dwarfs. No new companions were found to previously known 20 pc white dwarfs. Finally, we estimated the local white dwarf space-density to be (4.49 ± 0.38) × 10-3 pc-3, having given careful consideration to the distance-dependent Gaia completeness, which misses known objects at short distances, but is close to complete for white dwarfs near 20 pc
The Gaia 20 pc white dwarf sample
No full textUsing Gaia DR2 data, we present an up-to-date sample of white dwarfs within 20 pc of the Sun. In total we identified 139 systems in Gaia DR2, nine of which are new detections, with the closest of these located at a distance of 13.05 pc. We estimated atmospheric parameters for all stellar remnants based on the Gaia parallaxes and photometry. The high precision and completeness of the Gaia astrometry allowed us to search for wide binary companions. We re-identified all known binaries where both components have accurate DR2 astrometry, and established the binarity of one of the nine newly identified white dwarfs. No new companions were found to previously known 20 pc white dwarfs. Finally, we estimated the local white dwarf space-density to be (4.49 ± 0.38) × 10−3 pc−3, having given careful consideration to the distance-dependent Gaia completeness, which misses known objects at short distances, but is close to complete for white dwarfs near 20 pc
A PC parallel port button box provides millisecond response time accuracy under Linux
No full textFor psychologists, it is sometimes necessary to measure people's reaction times to the nearest millisecond. This article describes how to use the PC parallel port to receive signals from a button box to achieve millisecond response time accuracy. The workings of the parallel port, the corresponding port addresses, and a simple Linux program for controlling the port are described. A test of the speed and reliability of button box signal detection is reported. If the reader is moderately familiar with Linux, this article should provide sufficient instruction for him or her to build and test his or her own parallel port button box. This article also describes how the parallel port could be used to control an external apparatus
The 40 pc sample of white dwarfs from Gaia
No full textWe present a comprehensive overview of a volume-complete sample of white dwarfs located within 40 pc of the Sun, a significant proportion of which were detected in Gaia Data Release 3 (DR3). Our DR3 sample contains 1076 spectroscopically confirmed white dwarfs, with just five candidates within the volume remaining unconfirmed (> 99 per cent spectroscopic completeness). Additionally, 28 white dwarfs were not in our initial selection from Gaia DR3, most of which are in unresolved binaries. We use Gaia DR3 photometry and astrometry to determine a uniform set of white dwarf parameters, including mass, effective temperature, and cooling age. We assess the demographics of the 40 pc sample, specifically magnetic fields, binarity, space density, and mass distributions
White working-class neighbourhoods:common themes and policy suggestions
No full textWhat does it mean to be white and working class in modern Britain? The Joseph Rowntree Foundation’s studies of traditionally white estates in Bradford, London, Coventry and Birmingham are part of a growing body of research into ‘white identities’. This paper: • identifies common findings from JRF research into traditionally white estates, in the context of other similar work; • suggests how issues of white identity can be better understood and makes recommendations for policy and practice. Key points: • Profound economic and social change has increased isolation and fear in traditionally white estates. Residents often claim that things were better in the past. • ‘Estatism’ refers to specific social dynamics associated with council estates and prejudice towards residents based on where they live. This can result in lowered self-esteem and reluctance to participate in community campaigns. • People on traditionally white estates often feel they are not listened to by outside agencies. Consultations can raise hopes but ultimately reinforce disengagement. Initiatives to ensure equality have become associated with political correctness (‘PC’). • White working-class people feel they are bound by values of hard work, reciprocity and support. They are frustrated by the closure and lack of access to community facilities. The social class system simultaneously disadvantages the working class while giving advantage to other classes. • There is a strong desire for allocation of resources to be fair, with a widespread perception that minorities are given preference. Blaming incomers for decline is common, with the target of blame differing between sites. Participants did not want to be considered racist and felt that labelling ideas as racist prevents discussion. Similarly, the term ‘PC’ can also be used to shut down debate. • Recommendations include community-twinning, new ways of accessing local authorities, involvement from the private sector in disadvantaged areas and local panels to define and develop the ‘Big Society’. Initiatives aimed solely at white working-class people are unlikely to be successful
Where’s Morningside? Locating bro’Town in the ethnic genealogy of New Zealand/Aotearoa
No full textThis article uses discourse analysis to locate animated primetime cartoon comedy bro'Town in terms of ethnicity and identification in both a local New Zealand/Aotearoa (NZ) and a global, postmodern, postcolonial media environment. It analyses and problematises the polarisation of local ethnic discourse between conservative assimilationist and bicultural "politically correct" viewpoints by situating the text in global postmodern media environment and demonstrating the discursive interdependence of such binary oppositions. Finally it looks at the degree to which bro'Town's self-proclaimed status as "hilariously anti-PC" comedy works to both exploit and undermine polarities of ethnic representation through employing "reverse discourse". The overall aim of the paper is not to present a close reading or textual analysis, but to situate the text in larger discursive frameworks and thus offer a number of possible theoretical approaches
PC-based single-vessel flow velocity (CBFv) mapping.
No full text(A) Representative 2D MGE slices (yellow boxes) from a deep layer of the primary forepaw somatosensory cortex (first frame) at different TEs, as indicated. (B) The 2D A–V map (yellow box) derived from the images with different TEs in panel A, arterioles, and venules appear as bright and dark voxels, respectively. The expanded views (red boxes) show individual venules, i.e., black voxels marked in blue, and arterioles, i.e., white voxels marked in red. (C) The vectorized flow velocity map (blue box) from the same 2D MGE slice in panel B. The expanded views (green boxes) show the individual venules, i.e., white dots with positive velocity, and arterioles, i.e., black dots with negative velocity. Note that 2 bright dots are caused by the “overflowed” velocity beyond the maximal velocity, i.e., the Venc parameter, defined in the PC-MRI sequence, which could be not correctly estimated. (D) Scatter plot of the flow velocities from individual arterioles and venules as the function of the normalized signal intensities of each vessel in the A–V map of panel B, data from 11 rats as indicated. Insert shows the blood flow direction of arterioles and venules in the forepaw somatosensory cortical region. The lower panel shows the histogram of the blood velocity distribution across arterioles and venules, as well as the bar graph to show the mean velocity. The data underlying this figure can be found in S2 Data. A–V, arteriole–venule; CBFv, cerebral blood flow–related velocity; MGE, multi-gradient echo; PC, phase contrast; ROI, region of interest; Venc, velocity encoding; TE, echo time.</p
The white dwarf population within 40 pc of the Sun
No full text© 2016 ESO. Context. The white dwarf luminosity function is an important tool to understand the properties of the solar neighborhood, like its star formation history, and its age. Aims. Here we present a population synthesis study of the white dwarf population within 40 pc from the Sun, and compare the results of this study with the properties of the observed sample. Methods. We use a state-of-the-art population synthesis code based on Monte Carlo techniques, which incorporates the most recent and reliable white dwarf cooling sequences, an accurate description of the Galactic neighborhood, and a realistic treatment of all the known observational biases and selection procedures. Results. We find a good agreement between our theoretical models and the observed data. In particular, our simulations reproduce a previously unexplained feature of the bright branch of the white dwarf luminosity function, which we argue is due to a recent episode of star formation. We also derive the age of the solar neighborhood employing the position of the observed cut-off of the white dwarf luminosity function, to obtain ~8.9 ± 0.2 Gyr. Conclusions. We conclude that a detailed description of the ensemble properties of the population of white dwarfs within 40 pc of the Sun allows us to obtain interesting constraints on the history of the Solar neighborhood.Peer ReviewedPostprint (published version
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