8,809 research outputs found
Analytical results for a Bessel function times Legendre polynomials class integrals
When treating problems of vector diffraction in electromagnetic theory, the
evaluation of the integral involving Bessel and associated Legendre functions
is necessary. Here we present the analytical result for this integral that will
make unnecessary numerical quadrature techniques or localized approximations.
The solution is presented using the properties of the Bessel and associated
Legendre functions.Comment: 4 page
Ion-ion correlations: an improved one-component plasma correction
Based on a Debye-Hueckel approach to the one-component plasma we propose a
new free energy for incorporating ionic correlations into Poisson-Boltzmann
like theories. Its derivation employs the exclusion of the charged background
in the vicinity of the central ion, thereby yielding a thermodynamically stable
free energy density, applicable within a local density approximation. This is
an improvement over the existing Debye-Hueckel plus hole theory, which in this
situation suffers from a "structuring catastrophe". For the simple example of a
strongly charged stiff rod surrounded by its counterions we demonstrate that
the Poisson-Boltzmann free energy functional augmented by our new correction
accounts for the correlations present in this system when compared to molecular
dynamics simulations.Comment: 5 pages, 2 figures, revtex styl
Una propuesta : enseñar física a niños de grados elementales
With the purpose of doing a previous presentation on Physics issues to children in their school initial steps, we intend to discuss a proposition using the scope of some tales as an appropriate tool to reach that objective. Our paper deals with two experiences. We have presented and established some comments in two of our municipality of Rio de Janeiro schools. In one of them, a public school which deals with students of a lower economic class and another one, a private school dealing with students of a middle economic class. In order to assist achvely in the process of Physics teaching, as a sequence of our proposition, we are describing one of our experiences, which is being developed with educators responsible for students of these levels
Orbital Exenteration for Eyelid Skin Carcinoma
Exenteration of the orbit is a disfiguring and destructive procedure; it is generally performed for orbital malignancies and often provides a significant reconstructive
challenge. Our purpose was to evaluate the clinical indications for orbital exenteration in a tertiary referral
center and to assess the reconstructive options employed. A retrospective nonrandomized analysis was performed,
selecting all patients undergoing orbital exenteration over a 5-year period, between January 2005 and January 2010.
Patient demographics, tumor characteristics, and reconstructive techniques used were evaluated. Twenty patients with a mean age of 76.5 years underwent total orbital
exenteration. Basal cell carcinoma was the main operative indication (45%), followed by squamous cell carcinoma (15%). Reconstructive techniques included cover of the raw orbital cavity with a temporal muscular flap in all cases followed with split skin grafting (25%), bilaterally pedicle V-Y advancement flap (10%) and a fasciocutaneous island flap of the retroauricular region (65%). Twenty percent of patients had local complications and all were treated in a satisfactory fashion. Eyelid skin tumors remain an important
cause of orbital exenteration. Temporal muscle flap is a reliable and stable reconstructive solution after orbital
exenteration and additional aid is supplied with skin grafts or local flaps. This technique ensures a good aesthetic
outcome and better situation for later complementary treatments and minimal associated donor site morbidity
Accretion Signatures from Massive Young Stellar Objects
High resolution (lambda / Delta-lambda = 50,000) K-band spectra of massive,
embedded, young stellar objects are presented. The present sample consists of
four massive young stars located in nascent clusters powering Galactic giant H
II regions. Emission in the 2.3 micron 2--0 vibrational--rotational bandhead of
CO is observed. A range of velocity broadened profiles seen in three of the
objects is consistent with the emission arising from a circumstellar disk seen
at various inclination angles. Br gamma spectra of the same spectral and
spatial resolution are also presented which support an accretion disk or torus
model for massive stars. In the fourth object, Br emission suggesting a
rotating torus is observed, but the CO profile is narrow, indicating that there
may be different CO emission mechanisms in massive stars and this is consistent
with earlier observations of the BN object and MWC 349. To--date, only young
massive stars of late O or early B types have been identified with clear
accretion disk signatures in such embedded clusters. Often such stars are found
in the presence of other more massive stars which are revealed by their
photospheric spectra but which exhibit no disk signatures. This suggests the
timescale for dissipating their disks is much faster than the less massive OB
stars or that the most massive stars do not form with accretion disks.Comment: 28 pages, 10 Figures, accepted for publication in the Astrophysical
Journa
A redução da mortalidade embrionária - estratégia hormonal para otimizar a função luteínica em bovinos
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