1,758 research outputs found
Trachoma and Ocular Chlamydial Infection in the Era of Genomics.
Trachoma is a blinding disease usually caused by infection with Chlamydia trachomatis (Ct) serovars A, B, and C in the upper tarsal conjunctiva. Individuals in endemic regions are repeatedly infected with Ct throughout childhood. A proportion of individuals experience prolonged or severe inflammatory episodes that are known to be significant risk factors for ocular scarring in later life. Continued scarring often leads to trichiasis and in-turning of the eyelashes, which causes pain and can eventually cause blindness. The mechanisms driving the chronic immunopathology in the conjunctiva, which largely progresses in the absence of detectable Ct infection in adults, are likely to be multifactorial. Socioeconomic status, education, and behavior have been identified as contributing to the risk of scarring and inflammation. We focus on the contribution of host and pathogen genetic variation, bacterial ecology of the conjunctiva, and host epigenetic imprinting including small RNA regulation by both host and pathogen in the development of ocular pathology. Each of these factors or processes contributes to pathogenic outcomes in other inflammatory diseases and we outline their potential role in trachoma
Bloch electron in a magnetic field and the Ising model
The spectral determinant det(H-\epsilon I) of the Azbel-Hofstadter
Hamiltonian H is related to Onsager's partition function of the 2D Ising model
for any value of magnetic flux \Phi=2\pi P/Q through an elementary cell, where
P and Q are coprime integers. The band edges of H correspond to the critical
temperature of the Ising model; the spectral determinant at these (and other
points defined in a certain similar way) is independent of P. A connection of
the mean of Lyapunov exponents to the asymptotic (large Q) bandwidth is
indicated.Comment: 4 pages, 1 figure, REVTE
Expansion of nanoplasmas and laser-driven nuclear fusion in single exploding clusters
The expansion of laser-irradiated clusters or nanodroplets depends strongly
on the amount of energy delivered to the electrons and can be controlled by
using appropriately shaped laser pulses. In this paper, a self-consistent
kinetic model is used to analyze the transition from quasineutral,
hydrodinamic-like expansion regimes to the Coulomb explosion (CE) regime when
increasing the ratio between the thermal energy of the electrons and the
electrostatic energy stored in the cluster. It is shown that a suitable
double-pump irradiation scheme can produce hybrid expansion regimes, wherein a
slow hydrodynamic expansion is followed by a fast CE, leading to ion overtaking
and producing multiple ion flows expanding with different velocities. This can
be exploited to obtain intracluster fusion reactions in both homonuclear
deuterium clusters and heteronuclear deuterium-tritium clusters, as also proved
by three-dimensional molecular-dynamics simulations.Comment: 9 pages, 3 figures, to appear in Plasma Physics and Controlled Fusio
Quantum Return Probability for Substitution Potentials
We propose an effective exponent ruling the algebraic decay of the average
quantum return probability for discrete Schrodinger operators. We compute it
for some non-periodic substitution potentials with different degrees of
randomness, and do not find a complete qualitative agreement with the spectral
type of the substitution sequences themselves, i.e., more random the sequence
smaller such exponent.Comment: Latex, 13 pages, 6 figures; to be published in Journal of Physics
Generic Continuous Spectrum for Ergodic Schr"odinger Operators
We consider discrete Schr"odinger operators on the line with potentials
generated by a minimal homeomorphism on a compact metric space and a continuous
sampling function. We introduce the concepts of topological and metric
repetition property. Assuming that the underlying dynamical system satisfies
one of these repetition properties, we show using Gordon's Lemma that for a
generic continuous sampling function, the associated Schr"odinger operators
have no eigenvalues in a topological or metric sense, respectively. We present
a number of applications, particularly to shifts and skew-shifts on the torus.Comment: 14 page
Anxiety in children attending a specialist inherited cardiac arrhythmia clinic: a questionnaire study
Objectives: Inherited cardiac arrhythmia syndromes are life-threatening conditions. There is a paucity of research examining the psychological impact of these conditions in children. This study had three main aims. The first was to explore how the Cardiac Anxiety Questionnaire (CAQ) performs in a child population. The second aim was to compare the level of anxiety of children with an inherited cardiac arrhythmia syndrome and children being screened due to a family history of an inherited cardiac arrhythmia syndrome to control children. The third aim was to examine associations between a sudden cardiac death in the immediate family and levels of anxiety. Method: 47 children with an inherited cardiac arrhythmia syndrome, 78 children with a family history and 75 control children completed the Revised Child Anxiety and Depression Scale (RCADS), the Cardiac Anxiety Questionnaire for Children (CAQ-C) and the Childhood Anxiety Sensitivity Index. Children were between the age of 8 and 16 years. Results: The study found the CAQ-C had promising psychometric properties. There were no significant differences in total anxiety scores (as measured by the RCADS) between the three groups. There were significant differences in cardiac-focused anxiety scores between the three groups. Conclusions: The CAQ has promising psychometric properties in a child population. However, further research is needed. Children attending specialist inherited cardiac arrhythmia clinics should be targeted for routine psychological screening and offered psychological intervention where necessary
The Ten Martini Problem
We prove the conjecture (known as the ``Ten Martini Problem'' after Kac and
Simon) that the spectrum of the almost Mathieu operator is a Cantor set for all
non-zero values of the coupling and all irrational frequencies.Comment: 31 pages, no figure
A test of the ability of current bulk optical models to represent the radiative properties of cirrus cloud across the mid-and far-infrared
Measurements of mid- to far-infrared nadir radiances obtained from the UK Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 aircraft during the Cirrus Coupled Cloud-Radiation Experiment (CIRCCREX) are used to assess the performance of various ice cloud bulk optical (single-scattering) property models. Through use of a minimisation approach, we find that the simulations can reproduce the observed spectra in the mid-infrared to within measurement uncertainty but are unable to simultaneously match the observations over the far-infrared frequency range. When both mid and far-infrared observations are used to minimise residuals, first order estimates of the flux differences between the best performing simulations and observations indicate a strong compensation effect between the mid and far infrared such that the absolute broadband difference is < 0.7 W m−2. However, simply matching the spectra using the mid-infrared observations in isolation leads to substantially larger discrepancies, with absolute differences reaching ~ 1.8 W m−2. These results highlight the benefit of far infrared observations for better constraining retrievals of cirrus cloud properties and their radiative impact, and provide guidance for the development of more realistic ice cloud optical models
The impact of a single round of community mass treatment with azithromycin on disease severity and ocular Chlamydia trachomatis load in treatment-naïve trachoma-endemic island communities in West Africa.
BACKGROUND: Trachoma, a neglected tropical disease, is caused by ocular infection with Chlamydia trachomatis (Ct). The World Health Organization (WHO) recommends three annual rounds of community mass drug treatment with azithromycin (MDA) if the prevalence of follicular trachoma in 1-9 year olds (TF1-9) exceeds 10% at district level to achieve an elimination target of district-level TF1-9 below 5% after. To evaluate this strategy in treatment-naïve trachoma-endemic island communities in Guinea Bissau, we conducted a cross-sectional population-based trachoma survey on four islands. The upper tarsal conjunctivae of each participant were clinically assessed for trachoma and conjunctival swabs were obtained (n = 1507). We used a droplet digital PCR assay to detect Ct infection and estimate bacterial load. We visited the same households during a second cross-sectional survey and repeated the ocular examination and obtained conjunctival swabs from these households one year after MDA (n = 1029). RESULTS: Pre-MDA TF1-9 was 22.0% (136/618). Overall Ct infection prevalence (CtI) was 18.6% (25.4% in 1-9 year olds). Post-MDA (estimated coverage 70%), TF1-9 and CtI were significantly reduced (7.4% (29/394, P < 0.001) and 3.3% (34/1029, P < 0.001) (6.6% in 1-9 year olds, P < 0.001), respectively. Median ocular Ct load was reduced from 2038 to 384 copies/swab (P < 0.001). Following MDA cases of Ct infection were highly clustered (Moran's I 0.27, P < 0.001), with fewer clusters of Ct infection overall, fewer clusters of cases with high load infections and less severe disease. CONCLUSIONS: Despite a significant reduction in the number of clusters of Ct infection, mean Ct load, disease severity and presence of clusters of cases of high load Ct infection suggesting the beginning of trachoma control in isolated island communities, following a single round of MDA we demonstrate that transmission is still ongoing. These detailed data are useful in understanding the epidemiology of ocular Ct infection in the context of MDA and the tools employed may have utility in determining trachoma elimination and surveillance activities in similar settings
Azbel-Hofstadter model on triangular lattice revisited
In the present paper, the mean of Lyapunov exponents for the Azbel-Hofstadter
model on the triangular lattice is calculated. It is recently proposed that
[Phys. Rev. Lett. {\bf 85}, 4920 (2000)], for the case of the square lattice,
this quantity can be related to the logarithm of the partition function of the
two dimensional Ising model and has a connection to the asymptotic bandwidth.
We find that the correspondence of this quantity to the logarithm of the
partition function of the two dimensional Ising model is not complete for the
triangular lattice. Moreover, the detailed connection between this quantity and
the asymptotic bandwidth is not valid. Thus the conclusions for the mean of
Lyapunov exponents suggested previously depend on the lattice geometry.Comment: RevTeX, 4 page, no figur
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