8,238 research outputs found
Analytical computation of the off-axis Effective Area of grazing incidence X-ray mirrors
Focusing mirrors for X-ray telescopes in grazing incidence, introduced in the
70s, are characterized in terms of their performance by their imaging quality
and effective area, which in turn determines their sensitivity. Even though the
on-axis effective area is assumed in general to characterize the collecting
power of an X-ray optic, the telescope capability of imaging extended X-ray
sources is also determined by the variation in its effective area with the
off-axis angle. [...] The complex task of designing optics for future X-ray
telescopes entails detailed computations of both imaging quality and effective
area on- and off-axis. Because of their apparent complexity, both aspects have
been, so far, treated by using ray-tracing routines aimed at simulating the
interaction of X-ray photons with the reflecting surfaces of a given focusing
system. Although this approach has been widely exploited and proven to be
effective, it would also be attractive to regard the same problem from an
analytical viewpoint, to assess an optical design of an X-ray optical module
with a simpler calculation than a ray-tracing routine. [...] We have developed
useful analytical formulae for the off-axis effective area of a
double-reflection mirror in the double cone approximation, requiring only an
integration and the standard routines to calculate the X-ray coating
reflectivity for a given incidence angle. [...] Algebraic expressions are
provided for the mirror geometric area, as a function of the off-axis angle.
Finally, the results of the analytical computations presented here are
validated by comparison with the corresponding predictions of a ray-tracing
code.Comment: 12 pages, 11 figures, accepted for publication in "Astronomy &
Astrophysics", section "Instruments, observational techniques, and data
processing". Updated version after grammatical revision and typos correctio
Is arrhythmogenic right ventricular cardiomyopathy a paediatric problem too?
Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a heart muscle disease
that is often familial, characterized by arrhythmias of right ventricular origin, due to
transmural fatty or fibrofatty replacement of atrophic myocardium. ARVC is usually
diagnosed in the clinical setting between 20 and 40 years of age. The disease is
seldom recognised in infancy or under the age of 10, probably because the clinical
expression of the disease is normally postponed to youth and adulthood. This review
focuses its attention to the pediatric age, defined as the period of life raging from birth
to 18 years. During this span of life, ARVC is not so rare as previously supposed and
can be identified by applying the same diagnostic criteria proposed for the adult.
Ventricular arrhythmias range from isolated ventricular arrhythmias to sustained
ventricular tachycardia and fibrillation. Children and adolescents with ARVC must be
carefully evaluated and followed-up especially when a family positive history is
present, taking into account the high probability during this life-period that
asymptomatic affected patients become symptomatic or that arrhythmias worsen
during follow-up. The recent identification of the first defective gene opens new
avenues for the early identification of affected subjects even when asymptomatic.peer-reviewe
Drell-Yan phenomenology in the color dipole picture revisited
An extensive phenomenological study of the Drell-Yan (DY) process in
collisions at various energies is performed in the color dipole framework.
Besides previously studied production we have also included the
contribution relevant at large dilepton invariant masses. We investigate
the DY cross section differential in invariant mass, rapidity and transverse
momentum of the dilepton pair in collisions at RHIC and LHC. We consider
three different phenomenological models for the dipole cross section and found
a reasonable agreement with the available data. As a further test of the color
dipole formalism, we also study the correlation function in azimuthal angle
between the dilepton pair and a forward pion for different
energies, dilepton rapidites and invariant masses. The characteristic
double-peak structure of the correlation function around found for very forward pions and low-mass dilepton pairs is sensitive to
the saturation effects and can be tested by future DY measurements in
collisions.Comment: 16 pages, 12 figures; typos corrected, references added, conclusions
unchange
Joint Attention in the Child with Autism: An Appropriate Play Intervention for Children with Autism Spectrum Disorder
The effects of an Appropriate Play Intervention program, given to three children diagnosed with Autism Spectrum Disorder, were evaluated through a multiple-baseline design across subjects. The research targeted two main skills, appropriate play and joint attention engagement, through the use of an Appropriate Play Intervention program. Children were taught the appropriate use of toys in play behavior with another individual, and measurements collected pre- and post-treatment were used to assess their progress. Upon introduction to the intervention, children showed a rapid increase in their acquisition of appropriate play skills and joint attention engagements, revealing a new perspective from which researchers can approach the deficiencies of joint attention skills in children with low-functioning Autism Spectrum Disorder
Scaling function in AdS/CFT from the O(6) sigma model
Asymptotic behavior of the anomalous dimensions of Wilson operators with high
spin and twist is governed in planar N=4 SYM theory by the scaling function
which coincides at strong coupling with the energy density of a two-dimensional
bosonic O(6) sigma model. We calculate this function by combining the two-loop
correction to the energy density for the O(n) model with two-loop correction to
the mass gap determined by the all-loop Bethe ansatz in N=4 SYM theory. The
result is in agreement with the prediction coming from the thermodynamical
limit of the quantum string Bethe ansatz equations, but disagrees with the
two-loop stringy corrections to the folded spinning string solution.Comment: 25 pages, 2 figure
Photon and Pomeron -- induced production of Dijets in , and collisions
In this paper we present a detailed comparison of the dijet production by
photon -- photon, photon -- pomeron and pomeron -- pomeron interactions in
, and collisions at the LHC energy. The transverse
momentum, pseudo -- rapidity and angular dependencies of the cross sections are
calculated at LHC energy using the Forward Physics Monte Carlo (FPMC), which
allows to obtain realistic predictions for the dijet production with two
leading intact hadrons. We obtain that \gamma \pom channel is dominant at
forward rapidities in collisions and in the full kinematical range in the
nuclear collisions of heavy nuclei. Our results indicate that the analysis of
dijet production at the LHC can be useful to test the Resolved Pomeron model as
well as to constrain the magnitude of the absorption effects.Comment: 11 pages, 6 figures, 1 table. Improved and enlarged version published
in European Physical Journal
Cusp anomalous dimension in maximally supersymmetric Yang-Mills theory at strong coupling
We construct an exact analytical solution to the integral equation which is
believed to describe logarithmic growth of the anomalous dimensions of high
spin operators in planar N=4 super Yang-Mills theory and use it to determine
the strong coupling expansion of the cusp anomalous dimension.Comment: 5 pages. v3: minor corrections, references and important note adde
Longitudinal spin Seebeck coefficient: heat flux vs. temperature difference method
The determination of the longitudinal spin Seebeck effect (LSSE) coefficient
is currently plagued by a large uncertainty due to the poor reproducibility of
the experimental conditions used in its measurement. In this work we present a
detailed analysis of two different methods used for the determination of the
LSSE coefficient. We have performed LSSE experiments in different laboratories,
by using different setups and employing both the temperature difference method
and the heat flux method. We found that the lack of reproducibility can be
mainly attributed to the thermal contact resistance between the sample and the
thermal baths which generate the temperature gradient. Due to the variation of
the thermal resistance, we found that the scaling of the LSSE voltage to the
heat flux through the sample rather than to the temperature difference across
the sample greatly reduces the uncertainty. The characteristics of a single
YIG/Pt LSSE device obtained with two different setups was Vm/W and Vm/W with the heat flux method
and V/K and V/K
with the temperature difference method. This shows that systematic errors can
be considerably reduced with the heat flux method.Comment: PDFLaTeX, 10 pages, 6 figure
Direct calorimetric measurements of isothermal entropy change on single crystal W-type hexaferrites at the spin reorientation transition
We report on the magnetic field induced isothermal entropy change, \Delta
s(Ha, T), of W-type ferrite with CoZn substitution. Entropy measurements are
performed by direct calorimetry. Single crystals of the composition
BaCoZnFeO, prepared by the flux method, are measured at
different fixed temperatures under an applied field perpendicular and parallel
to the c axis. At 296 K one deduces a value of K = 8.7 \times 10^{4} J
m for the first anisotropy constant, which is in good agreement with the
literature. The spin reorientation transition temperature is estimated to take
place between 200 and 220 K
J Acquir Immune Defic Syndr
We describe HIV-1 evolutionary dynamics in the 4 participants from the TDF2-PrEP trial who became HIV-1 infected while prescribed emtricitabine and tenofovir disoproxil fumarate (FTC/TDF). At seroconversion, virus diversity in the 2 participants with detectable drug was only 0.05% (95% confidence intervals: 0.04 to 0.06) and 0.07% (0.06 to 0.08) compared with 2.25% (1.95 to 2.6) and 0.42% (0.36 to 0.49) in those with no detectable drug and 0.07%-0.69% in 5 placebo recipients (P > 0.5). At 10 months, diversity in adherent participants was only 0.37% (0.31 to 0.41) and 0.86% (0.82 to 0.90) compared with 0.5%-1.7% among participants who did not take FTC/TDF (P > 0.5). Although limited by the small number of infections that reduced the power to detect differences, we found that sequences from seroconverters with detectable drug were more homogeneous than those from placebo or nonadherent seroconverters.26689970PMC487657
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