247 research outputs found
Polarized thermal emission by thin metal wires
We report new measurements of the linear polarization of thermal radiation
emitted by incandescent thin tungsten wires, with thicknesses ranging from five
to hundred microns. Our data show very good agreement with theoretical
predictions, based on Drude-type fits to measured optical properties of
tungsten.Comment: 12 pages, 4 encapsulated figures. This new version matches the one
published in New. J. Phys.. Improved presentation, more references added, and
one new figure include
Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF:Er
We present a detection scheme to search for QCD axion dark matter, that is
based on a direct interaction between axions and electrons explicitly predicted
by DFSZ axion models. The local axion dark matter field shall drive transitions
between Zeeman-split atomic levels separated by the axion rest mass energy . Axion-related excitations are then detected with an upconversion scheme
involving a pump laser that converts the absorbed axion energy (
hundreds of eV) to visible or infrared photons, where single photon
detection is an established technique. The proposed scheme involves rare-earth
ions doped into solid-state crystalline materials, and the optical transitions
take place between energy levels of electron configuration. Beyond
discussing theoretical aspects and requirements to achieve a cosmologically
relevant sensitivity, especially in terms of spectroscopic material properties,
we experimentally investigate backgrounds due to the pump laser at temperatures
in the range K. Our results rule out excitation of the upper Zeeman
component of the ground state by laser-related heating effects, and are of some
help in optimizing activated material parameters to suppress the
multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure
Inflation in Multidimensional Quantum Cosmology
We extend to multidimensional cosmology Vilenkin's prescription of tunnelling
from nothing for the quantum origin of the observable Universe. Our model
consists of a -dimensional spacetime of topology , with a scalar field (``chaotic inflaton'') for the
matter component. Einstein gravity and Casimir compactification are assumed.
The resulting minisuperspace is 3--dimensional. Patchwise we find an
approximate analytic solution of the Wheeler--DeWitt equation through which we
discuss the tunnelling picture and the probability of nucleation of the
classical Universe with compactifying extra dimensions. Our conclusion is that
the most likely initial conditions, although they do not lead to the
compactification of the internal space, still yield (power-law) inflation for
the outer space. The scenario is physically acceptable because the inner space
growth is limited to in 100 e-foldings of inflation, starting
from the Planck scale.Comment: RevTeX, 30 pages, 4 figures available via fax on request to
[email protected], submitted to Phys. Rev.
Testing the neutrality of matter by acoustic means in a spherical resonator
New measurements to test the neutrality of matter by acoustic means are
reported. The apparatus is based on a spherical capacitor filled with gaseous
SF excited by an oscillating electric field. The apparatus has been
calibrated measuring the electric polarizability. Assuming charge conservation
in the decay of the neutron, the experiment gives a limit of
for the electron-proton charge
difference, the same limit holding for the charge of the neutron. Previous
measurements are critically reviewed and found incorrect: the present result is
the best limit obtained with this technique
Measurement of the Casimir force between parallel metallic surfaces
We report on the measurement of the Casimir force between conducting surfaces
in a parallel configuration. The force is exerted between a silicon cantilever
coated with chromium and a similar rigid surface and is detected looking at the
shifts induced in the cantilever frequency when the latter is approached. The
scaling of the force with the distance between the surfaces was tested in the
0.5 - 3.0 m range, and the related force coefficient was determined at the
15% precision level.Comment: 4 Figure
Infrared emission spectrum and potentials of and states of Xe excimers produced by electron impact
We present an investigation of the Xe excimer emission spectrum
observed in the near infrared range about 7800 cm in pure Xe gas and in
an Ar (90%) --Xe (10%) mixture and obtained by exciting the gas with energetic
electrons. The Franck--Condon simulation of the spectrum shape suggests that
emission stems from a bound--free molecular transition never studied before.
The states involved are assigned as the bound state with atomic limit and the dissociative state with limit. Comparison with the spectrum simulated by using theoretical
potentials shows that the dissociative one does not reproduce correctly the
spectrum features.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let
Cascade Birth of Universes in Multidimensional Spaces
The formation mechanism of universes with distinctly different properties is
considered within the framework of pure gravity in a space of D > 4 dimensions.
The emergence of the Planck scale and its relationship to the inflaton mass are
discussed.Comment: 10 p., minor correction
Hysteroscopy in the management of endometrial hyperplasia and cancer in reproductive aged women: new developments and current perspectives
Over the last twenty years, the incidence of early endometrial cancer (EC) and atypical endometrial hyperplasia (AEH) among women of reproductive age is increasing rapidly, likely due to a combination of factors including increased prevalence of obesity and delayed of childbirths. Regarding preoperative diagnosis of endometrial neoplasia, it is still debated which is the most accurate and reliable method to obtain endometrial histopathological samples with fractional dilatation and curettage (D&C) having been considered, for a long time, as the method of choice. Nowadays, the advent of in-office endometrial biopsy with or without hysteroscopy has radically changed the approach, giving the opportunity to perform the endometrial biopsy under direct visualization. However, the lack of agreement about its diagnostic accuracy is still relevant. Since a significant number of women with AEH and/or EC are of childbearing age, a fertility-sparing diagnostic and therapeutic approach should be considered in all cases. The feasibility, safety and efficacy of fertility-sparing strategies involving hysteroscopic focal resections in conjunction with hormonal therapies have been evaluated and beneficial effects have been confirmed in several studies and one meta-analysis. Both local and systemic administration of hormonal therapies are currently used. Oral progestin, including medroxyprogesterone acetate (MPA) and megestrol acetate, are the most commonly used therapies. Nowadays, new therapeutic approaches, such as levonorgestrel intrauterine systems (LNG-IUS), gonadotropin-releasing hormone (GnRH) agonists, combined megestrol acetate and metformin, and other combinations of therapies are also used as first line therapies or after the hysteroscopic resection of the lesion. However, it is still unclear which approach provides higher clinical response with lower relapse rate, in addition to preserving fertility in women desiring to conceive. The aim of this narrative review is to summarize the available evidence regarding the evaluation and management with fertility-sparing treatments options of women with AEC and EC
Proposal to produce long-lived mesoscopic superpositions through an atom-driven field interaction
We present a proposal for the production of longer-lived mesoscopic
superpositions which relies on two requirements: parametric amplification and
squeezed vacuum reservoir for cavity-field states. Our proposal involves the
interaction of a two-level atom with a cavity field which is simultaneously
subjected to amplification processes.Comment: 12 pages, title changed, text improved and refences adde
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