2,265 research outputs found
The effects of narrowband ultraviolet B (311 nm) phototherapy on epidermal barrier and differentiation markers in polymorphic light eruption
Aberrant expression of the epidermal tight junction protein Claudin-1 in polymorphic light eruption
Redshift and Shear Calibration: Impact on Cosmic Shear Studies and Survey Design
The cosmological interpretation of weak lensing by large-scale structures
requires knowledge of the redshift distribution of the source galaxies. Current
lensing surveys are often calibrated using external redshift samples which span
a significantly smaller sky area in comparison to the lensing survey, and are
thus subject to sample variance. Some future lensing surveys are expected to be
calibrated in the same way, in particular the fainter galaxy populations where
the entire color coverage, and hence photometric redshift estimate, could be
challenging to obtain. Using N-body simulations, we study the impact of this
sample variance on cosmic shear analysis and show that, to first approximation,
it behaves like a shear calibration error 1+/-epsilon. Using the Hubble Deep
Field as a redshift calibration survey could therefore be a problem for current
lensing surveys. We discuss the impact of the redshift distribution sampling
error and a shear calibration error on the design of future lensing surveys,
and find that a lensing survey of area Theta square degrees and limiting
magnitude m_lim}, has a minimum shear and redshift calibration accuracy
requirements given by epsilon = epsilon_0 10^{beta(m_lim-24.5)} / sqrt(Theta/
200). Above that limit, lensing surveys would not reach their full potential.
Using the galaxy number counts from the Hubble Ultra-Deep Field, we find
(epsilon_0,beta)=(0.015,-0.18) and (epsilon_0,beta)=(0.011,-0.23) for ground
and space based surveys respectively. Lensing surveys with no or limited
redshift information and/or poor shear calibration accuracy will loose their
potential to analyse the cosmic shear signal in the sub-degree angular scales,
and therefore complete photometric redshift coverage should be a top priority
for future lensing surveys.Comment: Accepted version to Astroparticle Physic
Ferromagnetic order in U(Rh,Co)Ge
We report the variation of ferromagnetic order in the pseudo-ternary
compounds URh_{1-x}Co_{x}Ge (0 \leq x \leq 1). Magnetization and transport data
taken on polycrystalline samples show that the Curie temperature T_{C}
gradually increases with increasing Co content from a value of 9.5 K for URhGe
to a maximum value of 20 K for x = 0.6 and then steadily decreases to 3 K for
UCoGe. The magnetic interaction strength varies smoothly across the series. For
all samples the electrical resistivity for T < T_{C} follows the behaviour \rho
= \rho_{0} + AT^2. The A coefficient is dominated by scattering at spin waves
and is strongly enhanced for x = 0 and 1.Comment: 12 pages (4 figures), submitted to SS
Pre-freezing of multifractal exponents in Random Energy Models with logarithmically correlated potential
Boltzmann-Gibbs measures generated by logarithmically correlated random
potentials are multifractal. We investigate the abrupt change ("pre-freezing")
of multifractality exponents extracted from the averaged moments of the measure
- the so-called inverse participation ratios. The pre-freezing can be
identified with termination of the disorder-averaged multifractality spectrum.
Naive replica limit employed to study a one-dimensional variant of the model is
shown to break down at the pre-freezing point. Further insights are possible
when employing zero-dimensional and infinite-dimensional versions of the
problem. In particular, the latter version allows one to identify the pattern
of the replica symmetry breaking responsible for the pre-freezing phenomenon.Comment: This is published version, 11 pages, 1 figur
Investigating the impact of nicotine on executive functions using a novel virtual reality assessment
Aims Nicotine is known to enhance aspects of cognitive functioning in abstinent smokers but the effects on specific areas of executive functions, and in non-smokers are inconclusive. This may be due in part to the poor sensitivity of tests used to assess executive functions. This study used a new virtual reality assessment of executive functions known as JEF (the Jansari assessment of Executive Functions) to address this issue. Design 2x2 design manipulating group (smokers and never-smokers) and drug (nicotine [4mg for smokers; 2mg for never smokers] vs placebo gum). Setting School of Psychology; University of East LondonParticipants 72 participants (aged 18 to 54). 36 minimally-deprived (2 hr) smokers and 36 never-smokers.Measurements Components of executive function were measured using the virtual reality paradigm JEF, which assesses eight cognitive constructs simultaneously as well as providing an overall performance measure. Results Univariate ANOVAs revealed that nicotine improved overall JEF performance, time-based prospective memory and event-based prospective memory in smokers (p < 0.01) but not in never-smokers. Action-based prospective memory was enhanced in both groups (p < 0.01) and never-smokers out-performed smokers on selective thinking and adaptive thinking (p < 0.01). Conclusions. Overall executive functioning and prospective memory can be enhanced by nicotine gum in abstinent smokers. That smokers were only minimally deprived suggests that JEFis a sensitive measure of executive functioning and that prospective memory is particularly susceptible to disruption by abstinence
Statistical Mechanics of Logarithmic REM: Duality, Freezing and Extreme Value Statistics of Noises generated by Gaussian Free Fields
We compute the distribution of the partition functions for a class of
one-dimensional Random Energy Models (REM) with logarithmically correlated
random potential, above and at the glass transition temperature. The random
potential sequences represent various versions of the 1/f noise generated by
sampling the two-dimensional Gaussian Free Field (2dGFF) along various planar
curves. Our method extends the recent analysis of Fyodorov Bouchaud from the
circular case to an interval and is based on an analytical continuation of the
Selberg integral. In particular, we unveil a {\it duality relation} satisfied
by the suitable generating function of free energy cumulants in the
high-temperature phase. It reinforces the freezing scenario hypothesis for that
generating function, from which we derive the distribution of extrema for the
2dGFF on the interval. We provide numerical checks of the circular and
the interval case and discuss universality and various extensions. Relevance to
the distribution of length of a segment in Liouville quantum gravity is noted.Comment: 25 pages, 12 figures Published version. Misprint corrected,
references and note adde
Holistic processing, contact, and the other-race effect in face recognition
Face recognition, holistic processing, and processing of configural and featural facial information are known to be influenced by face race, with better performance for own- than other-race faces. However, whether these various other-race effects (OREs) arise from the same underlying mechanisms or from different processes remains unclear. The present study addressed this question by measuring the OREs in a set of face recognition tasks, and testing whether these OREs are correlated with each other. Participants performed different tasks probing (1) face recognition, (2) holistic processing, (3) processing of configural information, and (4) processing of featural information for both own- and other-race faces. Their contact with other-race people was also assessed with a questionnaire. The results show significant OREs in tasks testing face memory and processing of configural information, but not in tasks testing either holistic processing or processing of featural information. Importantly, there was no cross-task correlation between any of the measured OREs. Moreover, the level of other-race contact predicted only the OREs obtained in tasks testing face memory and processing of configural information. These results indicate that these various cross-race differences originate from different aspects of face processing, in contrary to the view that the ORE in face recognition is due to cross-race differences in terms of holistic processing
The angular correlations of galaxies in the COSMOS field
We present measurements of the two-point galaxy angular correlation function
w(\theta) in the COSMOS field. Independent determinations of w(\theta) as a
function of magnitude limit are presented for both the HST ACS catalog and also
for the ground-based data from Subaru and the CFHT. Despite having
significantly different masks, these three determinations agree well. At bright
magnitudes (IAB<22), our data generally match very well with existing
measurements and with mock catalogs based on semi-analytic galaxy formation
calculations of Kitzbichler and White from the Millennium Simulation. The
exception is that our result is at the upper end of the expected cosmic
variance scatter for \theta > 10 arcmin, which we attribute to a particularly
rich structure known to exist at z~0.8. For fainter samples, however, the level
of clustering is somewhat higher than reported by some previous studies: in all
three catalogues we find w(\theta=1')~0.014 at a median IAB magnitude of 24. At
these very faintest magnitudes, our measurements agree well with the latest
determinations from the Canada-France Legacy Survey. This level of clustering
is approximately double what is predicted by the semi-analytic catalogs (at all
angles). The semi-analytic results allow an estimate of cosmic variance, which
is too small to account for the discrepancy. We therefore conclude that the
mean amplitude of clustering at this level is higher than previously estimated.Comment: Six pages, five figures. Accepted for publication in the ApJS COSMOS
special issue, Sept. 200
Cosmic Shear Statistics and Cosmology
We report a measurement of cosmic shear correlations using an effective area
of 6.5 sq. deg. of the VIRMOS deep imaging survey in progress at the
Canada-France-Hawaii Telescope. We measured various shear correlation
functions, the aperture mass statistic and the top-hat smoothed variance of the
shear with a detection significance exceeding 12 sigma for each of them. We
present results on angular scales from 3 arc-seconds to half a degree. The
consistency of different statistical measures is demonstrated and confirms the
lensing origin of the signal through tests that rely on the scalar nature of
the gravitational potential. For Cold Dark Matter models we find at the 95% confidence level. The
measurement over almost three decades of scale allows to discuss the effect of
the shape of the power spectrum on the cosmological parameter estimation. The
degeneracy on sigma_8-Omega_0 can be broken if priors on the shape of the
linear power spectrum (that can be parameterized by Gamma) are assumed. For
instance, with Gamma=0.21 and at the 95% confidence level, we obtain
0.60.65 and
Omega_0<0.4 for flat (Lambda-CDM) models. From the tangential/radial modes
decomposition we can set an upper limit on the intrinsic shape alignment, which
was recently suggested as a possible contribution to the lensing signal. Within
the error bars, there is no detection of intrinsic shape alignment for scales
larger than 1'.Comment: 13 pages, submitted to A&
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