16,735 research outputs found
Barriers for highly qualified A8 immigrants in the UK labour market
The number of migrants arriving in the UK from the EU accession countries has been higher than projected. The evidence indicates that they have been over-represented in low-paid and low-skilled jobs. This is arguably transitory and there should be good prospects of upward mobility. Over-qualification among A8 migrants, measured using the Annual Population Survey data, is examined in this article. The findings show that A8 migrants have been subject to migration penalties at the high end of the UK labour market. There are persistent labour market disadvantages for A8 migrants in the UK and their over-qualification may be a long-term concern
Clustering of the Diffuse Infrared Light from the COBE DIRBE maps. III. Power spectrum analysis and excess isotropic component of fluctuations
The cosmic infrared background (CIB) radiation is the cosmic repository for
energy release throughout the history of the universe. Using the all-sky data
from the COBE DIRBE instrument at wavelengths 1.25 - 100 mic we attempt to
measure the CIB fluctuations. In the near-IR, foreground emission is dominated
by small scale structure due to stars in the Galaxy. There we find a strong
correlation between the amplitude of the fluctuations and Galactic latitude
after removing bright foreground stars. Using data outside the Galactic plane
() and away from the center () we extrapolate
the amplitude of the fluctuations to cosec. We find a positive intercept
of nW/m2/sr at 1.25, 2.2,3.5 and 4.9 mic
respectively, where the errors are the range of 92% confidence limits. For
color subtracted maps between band 1 and 2 we find the isotropic part of the
fluctuations at nW/m2/sr. Based on detailed numerical and
analytic models, this residual is not likely to originate from the Galaxy, our
clipping algorithm, or instrumental noise. We demonstrate that the residuals
from the fit used in the extrapolation are distributed isotropically and
suggest that this extra variance may result from structure in the CIB. For
2\deg< \theta < 15^\deg, a power-spectrum analysis yields firm upper limits
of (\theta/5^\deg) \times\delta F_{\rm rms} (\theta) < 6, 2.5, 0.8, 0.5
nW/m2/sr at 1.25, 2.2, 3.5 and 4.9 mic respectively. From 10-100 mic, the upper
limits <1 nW/m2/sr.Comment: Ap.J., in press. 69 pages including 24 fig
Adapted digital music players for individuals with severe impairments
This is the peer reviewed version of the following article: Saunders, M. D., Questad, K. A., Cullinan, T. B., & Saunders, R. R. (2011). Adapted Digital Music Players for Individuals with Severe Impairments. Behavioral Interventions : Theory & Practice in Residential & Community-Based Clinical Programs, 26(2), 10.1002/bin.327. http://doi.org/10.1002/bin.327, which has been published in final form at doi.org/10.1002/bin.327. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingPortable music production devices, such as radios, cassette players and MP3 players have characteristics that make them less than ideal for teaching the cause-and-effect relationships that would enable children and adults with severe impairments to control them independently and appropriately. Even when adapted for control with adaptive switches, the relationship between switch closure and on-off operation results in contingency characteristics that can inhibit learning. Some solutions to these problems are described, and for those individuals who can learn with complex contingencies, some promising products are reviewed
Annotating Synapses in Large EM Datasets
Reconstructing neuronal circuits at the level of synapses is a central
problem in neuroscience and becoming a focus of the emerging field of
connectomics. To date, electron microscopy (EM) is the most proven technique
for identifying and quantifying synaptic connections. As advances in EM make
acquiring larger datasets possible, subsequent manual synapse identification
({\em i.e.}, proofreading) for deciphering a connectome becomes a major time
bottleneck. Here we introduce a large-scale, high-throughput, and
semi-automated methodology to efficiently identify synapses. We successfully
applied our methodology to the Drosophila medulla optic lobe, annotating many
more synapses than previous connectome efforts. Our approaches are extensible
and will make the often complicated process of synapse identification
accessible to a wider-community of potential proofreaders
Southern Sky Redshift Survey: Clustering of Local Galaxies
We use the two-point correlation function to calculate the clustering
properties of the recently completed SSRS2 survey. The redshift space
correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85
h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best
estimate for the real space correlation function is xi(r) = (r/5.36 h-1
Mpc)^{-1.86}. Both are comparable to previous measurements using surveys of
optical galaxies over much larger and independent volumes. By comparing the
correlation function calculated in redshift and real space we find that the
redshift distortion on intermediate scales is small. This result implies that
the observed redshift-space distribution of galaxies is close to that in real
space, and that beta = Omega^{0.6}/b < 1, where Omega is the cosmological
density parameter and b is the linear biasing factor for optical galaxies. We
also use the SSRS2 to study the dependence of xi on the internal properties of
galaxies. We confirm earlier results that luminous galaxies (L>L*) are more
clustered than sub-L* galaxies and that the luminosity segregation is
scale-independent. We find that early types are more clustered than late types,
but that in the absence of rich clusters, the relative bias between early and
late types in real space, is not as strong as previously estimated.
Furthermore, both morphologies present a luminosity-dependent bias, with the
early types showing a slightly stronger dependence on luminosity. We also find
that red galaxies are significantly more clustered than blue ones, with a mean
relative bias stronger than that seen for morphology. Finally, we find that the
relative bias between optical and iras galaxies in real space is b_o/b_I
1.4.Comment: 43 pages, uses AASTeX 4.0 macros. Includes 8 tables and 16 Postscript
figures, updated reference
The IRAS 1-Jy Survey of Ultraluminous Infrared Galaxies: I. The sample and Luminosity Function
A complete flux-limited sample of 118 ultraluminous infrared galaxies (ULIGs)
has been identified from the IRAS Faint Source Catalog (FSC). The selection
criteria were a 60 micron flux density greater than 1 Jy in a region of the sky
delta > -40 deg, |b| > 30 deg. All sources were subsequently reprocessed using
coadded IRAS maps in order to obtain the best available flux estimates in all
four IRAS wavelength bands. The maximum observed infrared luminosity is L_ir =
10^{12.90} L_{sun}, and the maximum redshift is z = 0.268. The luminosity
function for ULIGs over the decade luminosity range L_ir = 10^{12} - 10^{13}
L_{sun} can be approximated by a power law Phi (L) ~= L^{-2.35} Mpc^{-3}
mag^{-1}. In the local Universe z < 0.1, the space density of ULIGs appears to
be comparable to or slightly larger than that of optically selected QSOs at
comparable bolometric luminosities. A maximum likelihood test suggests strong
evolution for our sample; assuming density evolution proportional to
(1+z)^{alpha} we find alpha = 7.6+/-3.2. Examination of the two-point
correlation function shows a barely significant level of clustering, xi (r) =
1.6 +/- 1.2, on size scales r ~= 22 h^{-1} Mpc.Comment: 18 pages of text, 10 pages of figures 1 to 6, 6 pages of tables 1 to
3, ApJS accepte
Electronic structure of the molecule based magnet Cu PM(NO3)2 (H2O)2
We present density functional calculations on the molecule based S=1/2
antiferromagnetic chain compound Cu PM(NO3)2 (H2O)2; PM = pyrimidine. The
properties of the ferro- and antiferromagnetic state are investigated at the
level of the local density approximation and with the hybrid functional B3LYP.
Spin density maps illustrate the exchange path via the pyrimidine molecule
which mediates the magnetism in the one-dimensional chain. The computed
exchange coupling is antiferromagnetic and in reasonable agreement with the
experiment. It is suggested that the antiferromagnetic coupling is due to the
possibility of stronger delocalization of the charges on the nitrogen atoms,
compared to the ferromagnetic case. In addition, computed isotropic and
anisotropic hyperfine interaction parameters are compared with recent NMR
experiments
Negative oxygen vacancies in HfO as charge traps in high-k stacks
We calculated the optical excitation and thermal ionization energies of
oxygen vacancies in m-HfO using atomic basis sets, a non-local density
functional and periodic supercell. The thermal ionization energies of
negatively charged V and V centres are consistent with values
obtained by the electrical measurements. The results suggest that negative
oxygen vacancies are the likely candidates for intrinsic electron traps in the
hafnum-based gate stack devices.Comment: 3 pages, 2 figure
Recovering the Primordial Density Fluctuations: A comparison of methods
We present a comparative study of six different methods for reversing the
gravitational evolution of a cosmological density field to recover the
primordial fluctuations: linear theory, the Gaussianization mapping scheme, two
different quasi-linear dynamical schemes based on the Zel'dovich approximation,
a Hybrid dynamical-Gaussianization method and the Path Interchange Zel'dovich
Approximation (PIZA). The final evolved density field from an N-body simulation
constitutes our test case. We use a variety of statistical measures to compare
the initial density field recovered from it to the true initial density field,
using each of the six different schemes. These include point-by-point
comparisons of the density fields in real space, the individual modes in
Fourier space, as well as global statistical properties such as the genus, the
PDF of the density, and the distribution of peak heights and their shapes. We
find linear theory to be the most inaccurate of all the schemes. The
Gaussianization scheme is the least accurate after linear theory. The two
quasi-linear dynamical schemes are more accurate than Gaussianization, although
they break down quite drastically when used outside their range of validity -
the quasi-linear regime. The complementary beneficial aspects of the dynamical
and the Gaussianization schemes are combined in the Hybrid method. We find this
Hybrid scheme to be more accurate and robust than either Gaussianization or the
dynamical method alone. The PIZA scheme performs substantially better than the
others in all point-by-point comparisons. However, it produces an oversmoothed
initial density field, with a smaller number of peaks than expected, but
recovers the PDF of the initial density with impressive accuracy on scales as
small as 3Mpc/h.Comment: 39 pages, including 13 Figures, submitted to Ap
Synthesis of luminescent silicon clusters by spark ablation
The synthesis of luminescent nanometer-scale Si clusters by spark ablation from a crystalline Si substrate is described. The cluster source, described in the text, generates clusters in a flowing Ar stream at atmospheric pressure. Electron microscopy reveals that the clusters have diameters in the 2-4 nm size range. The luminescence spectra of the clusters, similar to that of porous Si, are presented
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