2,553 research outputs found
Translations and dynamics
We analyze the role played by local translational symmetry in the context of
gauge theories of fundamental interactions. Translational connections and
fields are introduced, with special attention being paid to their universal
coupling to other variables, as well as to their contributions to field
equations and to conserved quantities.Comment: 22 Revtex pages, no figures. Published version with minor correction
Electromagnetic wave scattering by a superconductor
The interaction between radiation and superconductors is explored in this
paper. In particular, the calculation of a plane standing wave scattered by an
infinite cylindrical superconductor is performed by solving the Helmholtz
equation in cylindrical coordinates. Numerical results computed up to
of Bessel functions are presented for different wavelengths
showing the appearance of a diffraction pattern.Comment: 3 pages, 3 figure
Poynting's theorem for planes waves at an interface: a scattering matrix approach
We apply the Poynting theorem to the scattering of monochromatic
electromagnetic planes waves with normal incidence to the interface of two
different media. We write this energy conservation theorem to introduce a
natural definition of the scattering matrix S. For the dielectric-dielectric
interface the balance equation lead us to the energy flux conservation which
express one of the properties of S: it is a unitary matrix. For the
dielectric-conductor interface the scattering matrix is no longer unitary due
to the presence of losses at the conductor. However, the dissipative term
appearing in the Poynting theorem can be interpreted as a single absorbing mode
at the conductor such that a whole S, satisfying flux conservation and
containing this absorbing mode, can be defined. This is a simplest version of a
model introduced in the current literature to describe losses in more complex
systems.Comment: 5 pages, 3 figures, submitted to Am. J. Phy
The role of angular momentum in the construction of electromagnetic multipolar fields
Multipolar solutions of Maxwell's equations are used in many practical
applications and are essential for the understanding of light-matter
interactions at the fundamental level. Unlike the set of plane wave solutions
of electromagnetic fields, the multipolar solutions do not share a standard
derivation or notation. As a result, expressions originating from different
derivations can be difficult to compare. Some of the derivations of the
multipolar solutions do not explicitly show their relation to the angular
momentum operators, thus hiding important properties of these solutions. In
this article, the relation between two of the most common derivations of this
set of solutions is explicitly shown and their relation to the angular momentum
operators is exposed.Comment: 13 pages, 2 figure
Патогенез ренальных дисфункций при метаболическом синдроме
Анализируются патофизиологические механизмы возникновения и развития ренальных дисфункций в условиях метаболического синдрома (МС). Рассматриваются результаты популяционных клинических исследований деятельности почек у лиц с МС, а также механизмы, вызывающие нарушения гомеостатических функций почек в
условиях течения МС. Проведен обзор литературы о роли
ренин-ангиотензиновой системы и оксида азота в патогенезе ренальных дисфункций при МС.Analysis of pathophisiological mechanisms of renal dysfunctions development was carried out during metabolic syndrome. Results of clinic researches of renal activity in patients
with metabolic syndrome (MS) and disturbances of homeostatic renal functions during MS were established. The literature review about research of renin-angiotensin system’s role
and nitric oxide in pathogenesis of renal functions during
MS was conducted
Multipole structure and coordinate systems
Multipole expansions depend on the coordinate system, so that coefficients of
multipole moments can be set equal to zero by an appropriate choice of
coordinates. Therefore, it is meaningless to say that a physical system has a
nonvanishing quadrupole moment, say, without specifying which coordinate system
is used. (Except if this moment is the lowest non-vanishing one.) This result
is demonstrated for the case of two equal like electric charges. Specifically,
an adapted coordinate system in which the potential is given by a monopole term
only is explicitly found, the coefficients of all higher multipoles vanish
identically. It is suggested that this result can be generalized to other
potential problems, by making equal coordinate surfaces coincide with the
potential problem's equipotential surfaces.Comment: 2 figure
Mutational Analysis in Pediatric Thyroid Cancer and Correlations with Age, Ethnicity, and Clinical Presentation.
BackgroundWell-differentiated thyroid cancer (WDTC) incidence in pediatrics is rising, most being papillary thyroid carcinoma (PTC). The objective of the study was to assess the prevalence of different mutations in pediatric WDTC and correlate the genotype with the clinical phenotype.MethodsThis is a single-center retrospective study. Thyroid tissue blocks from 42 consecutive pediatric WDTC patients who underwent thyroidectomy between 2001 and 2013 were analyzed at Quest Diagnostics for BRAF(V600E), RAS mutations (N,K,H), and RET/PTC and PAX8/PPARγ rearrangements, using validated molecular methods. Thyroid carcinomas included PTC, follicular thyroid carcinoma (FTC), and follicular variant of PTC (FVPTC).ResultsThirty-nine samples (29 females) were genotyped. The mean age at diagnosis was 14.7 years (range 7.9-18.4 years), and most were Hispanic (56.4%) or Caucasian (35.9%). The mean follow-up period was 2.9 years. Mutations were noted in 21/39 (53.8%), with both BRAF(V600E) (n = 9), and RET/PTC (n = 6) detected only in PTC. Mutations were detected in 2/5 FTC (PAX8/PPARγ and NRAS) and 3/6 FVPTC cases (PAX8/PPARγ). Of 28 PTC patients, 57.1% had mutations: 32.1% with BRAF(V600E), 21.4% with RET/PTC, and 3.6% with NRAS. Of patients with BRAF(V600E), 77.8% were Hispanic and 88.9% were >15 years, while all RET/PTC-positive patients were ≤15 years (p = 0.003). Tumor size, lymph node involvement, and distant metastasis at diagnosis (or soon after (131)I ablation) did not vary significantly based on the mutation.ConclusionsBRAF(V600E) was the most common mutation, especially in older and Hispanic adolescents. A larger, ethnically diverse pediatric cohort followed long term will enable the genotypic variability, clinical presentation, and response to therapy to be better assessed
Electromagnetically induced transparency in cold 85Rb atoms trapped in the ground hyperfine F = 2 state
We report electromagnetically induced transparency (EIT) in cold 85Rb atoms,
trapped in the lower hyperfine level F = 2, of the ground state 5
(Tiwari V B \textit{et al} 2008 {\it Phys. Rev.} A {\bf 78} 063421). Two steady
state -type systems of hyperfine energy levels are investigated using
probe transitions into the levels F = 2 and F = 3 of the
excited state 5 in the presence of coupling transitions F = 3
F = 2 and F = 3 F = 3, respectively. The
effects of uncoupled magnetic sublevel transitions and coupling field's Rabi
frequency on the EIT signal from these systems are studied using a simple
theoretical model.Comment: 12 pages, 7 figure
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