799 research outputs found
Universal Tunnelling Time in photonic Barriers
Tunnelling transit time for a frustrated total internal reflection in a
double-prism experiment was measured using microwave radiation. We have found
that the transit time is of the same order of magnitude as the corresponding
transit time measured either in an undersized waveguide (evanescent modes) or
in a photonic lattice. Moreover we have established that in all such
experiments the tunnelling transit time is approximately equal to the
reciprocal 1/f of the corresponding frequency of radiation.Comment: 8 pages, 4 figures, 1 tabl
Cerenkov's Effect and Neutrino Oscillations in Loop Quantum Gravity
Bounds on the scale parameter {\cal L} arising in loop quantum gravity theory
are derived in the framework of Cerenkov's effect and neutrino oscillations.
Assuming that {\cal L} is an universal constant, we infer {\cal L}>
10^{-18}eV^{-1}, a bound compatible with ones inferred in different physical
context.Comment: 6 pages, no figures, in print on MPL
Sex hormones in allergic conjunctivitis: altered levels of circulating androgens and estrogens in children and adolescents with vernal keratoconjunctivitis
PURPOSE:
Vernal keratoconjunctivitis (VKC) is a chronic allergic disease mainly affecting boys in prepubertal age and usually recovering after puberty. To evaluate a possible role of sex hormones in VKC, serum levels of sex hormones in children and adolescents with VKC were assessed.
METHODS:
12 prepubertal and 7 early pubertal boys with active VKC and 6 male patients with VKC in remission phase at late pubertal age and 48 healthy age and sex-matched subjects were included. Serum concentration of estrone, 17 beta-estradiol, dehydroepiandrosterone-sulfate, total testosterone and free testosterone, dihydrotestosterone (DHT), cortisol, delta-4-androstenedione, follicle-stimulating hormone, luteinizing hormone, and sex-hormones binding globuline (SHBG) were evaluated.
RESULTS:
Serum levels of Estrone were significantly increased in all groups of patients with VKC when compared to healthy controls (P < 0.001). Prepubertal and early pubertal VKC showed a significant decrease in DHT (P = 0.007 and P = 0.028, resp.) and SHBG (P = 0.01 and P = 0.002, resp.) when compared to controls and serum levels of SHBG were increased in late pubertal VKC in remission phase (P = 0.007).
CONCLUSIONS AND RELEVANCE:
VKC patients have different circulating sex hormone levels in different phases of the disease and when compared to nonallergic subjects. These findings suggest a role played by sex hormones in the pathogenesis and/or activity of VKC
Maximal Acceleration Corrections to the Lamb Shift of Muonic Hydrogen
The maximal acceleration corrections to the Lamb shift of muonic hydrogen are
calculated by using the relativistic Dirac wave functions. The correction for
the transition is meV and is higher than the accuracy of
present QED calculations and of the expected accuracy of experiments in
preparation.Comment: LaTex file, 9 pages, to be published in Il Nuovo Cimento
Nutritional Pearls and Pitfalls of Gastrointestinal Diseases
Since ancient times, food has been considered a possible therapy for treating a wide range of diseases [...]
A review of the role of ultrasound biomicroscopy in glaucoma associated with rare diseases of the anterior segment
Ultrasound biomicroscopy is a non-invasive imaging technique, which allows high-resolution evaluation of the anatomical features of the anterior segment of the eye regardless of optical media transparency. This technique provides diagnostically significant information in vivo for the cornea, anterior chamber, chamber angle, iris, posterior chamber, zonules, ciliary body, and lens, and is of great value in assessment of the mechanisms of glaucoma onset. The purpose of this paper is to review the use of ultrasound biomicroscopy in the diagnosis and management of rare diseases of the anterior segment such as mesodermal dysgenesis of the neural crest, iridocorneal endothelial syndrome, phakomatoses, and metabolic disorders
Probing the Brans-Dicke Gravitational Field by Cerenkov Radiation
The possibility that a charged particle propagating in a gravitational field
described by Brans-Dicke theory of gravity could emit Cerenkov radiation is
explored. This process is kinematically allowed depending on parameters
occurring in the theory. The Cerenkov effect disappears as the BD parameter
omega tends to inftinity, i.e. in the limit in which the Einstein theory is
recovered, giving a signature to probe the validity of the Brans-Dicke theory.Comment: 8 pages, no figure
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