228 research outputs found
Understanding interference experiments with polarized light through photon trajectories
Bohmian mechanics allows to visualize and understand the quantum-mechanical
behavior of massive particles in terms of trajectories. As shown by
Bialynicki-Birula, Electromagnetism also admits a hydrodynamical formulation
when the existence of a wave function for photons (properly defined) is
assumed. This formulation thus provides an alternative interpretation of
optical phenomena in terms of photon trajectories, whose flow yields a
pictorial view of the evolution of the electromagnetic energy density in
configuration space. This trajectory-based theoretical framework is considered
here to study and analyze the outcome from Young-type diffraction experiments
within the context of the Arago-Fresnel laws. More specifically, photon
trajectories in the region behind the two slits are obtained in the case where
the slits are illuminated by a polarized monochromatic plane wave. Expressions
to determine electromagnetic energy flow lines and photon trajectories within
this scenario are provided, as well as a procedure to compute them in the
particular case of gratings totally transparent inside the slits and completely
absorbing outside them. As is shown, the electromagnetic energy flow lines
obtained allow to monitor at each point of space the behavior of the
electromagnetic energy flow and, therefore, to evaluate the effects caused on
it by the presence (right behind each slit) of polarizers with the same or
different polarization axes. This leads to a trajectory-based picture of the
Arago-Fresnel laws for the interference of polarized light.Comment: 36 pages, 6 figure
Should particle trajectories comply with the transverse momentum distribution?
The momentum distributions associated with both the wave function of a
particle behind a grating and the corresponding Bohmian trajectories are
investigated and compared. Near the grating, it is observed that the former
does not depend on the distance from the grating, while the latter changes with
this distance. However, as one moves further apart from the grating, in the far
field, both distributions become identical.Comment: 10 pages, 7 figure
The Effective Dynamic Ranges for Glaucomatous Visual Field Progression With Standard Automated Perimetry and Stimulus Sizes III and V.
Purpose: It has been shown that threshold estimates below approximately 20 dB have little effect on the ability to detect visual field progression in glaucoma. We aimed to compare stimulus size V to stimulus size III, in areas of visual damage, to confirm these findings by using (1) a different dataset, (2) different techniques of progression analysis, and (3) an analysis to evaluate the effect of censoring on mean deviation (MD). Methods: In the Iowa Variability in Perimetry Study, 120 glaucoma subjects were tested every 6 months for 4 years with size III SITA Standard and size V Full Threshold. Progression was determined with three complementary techniques: pointwise linear regression (PLR), permutation of PLR, and linear regression of the MD index. All analyses were repeated on "censored'' datasets in which threshold estimates below a given criterion value were set to equal the criterion value. Results: Our analyses confirmed previous observations that threshold estimates below 20 dB contribute much less to visual field progression than estimates above this range. These findings were broadly similar with stimulus sizes III and V. Conclusions: Censoring of threshold values < 20 dB has relatively little impact on the rates of visual field progression in patients with mild to moderate glaucoma. Size V, which has lower retest variability, performs at least as well as size III for longitudinal glaucoma progression analysis and appears to have a larger useful dynamic range owing to the upper sensitivity limit being higher
PAL2 ATTRIBUTES FOR PREFERENCE OF NEW FAST DISSOLVING TABLET (FDT) FORMULATION OF EBASTINE IN PATIENTS WITH ALLERGY
Electromagnetic energy flow lines as possible paths of photons
Motivated by recent experiments where interference patterns behind a grating
are obtained by accumulating single photon events, here we provide an
electromagnetic energy flow-line description to explain the emergence of such
patterns. We find and discuss an analogy between the equation describing these
energy flow lines and the equation of Bohmian trajectories used to describe the
motion of massive particles.Comment: 8 pages, 3 figure
Understanding chemical reactions within a generalized Hamilton-Jacobi framework
Reaction paths and classical and quantum trajectories are studied within a
generalized Hamilton-Jacobi framework, which allows to put on equal footing
topology and dynamics in chemical reactivity problems. In doing so, we show how
high-dimensional problems could be dealt with by means of Caratheodory plots or
how trajectory-based quantum-classical analyses reveal unexpected
discrepancies. As a working model, we consider the reaction dynamics associated
with a Mueller-Brown potential energy surface, where we focus on the
relationship between reaction paths and trajectories as well as on reaction
probability calculations from classical and quantum trajectories.Comment: 22 pages, 5 figures, 1 tabl
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Visual Field Progression in Glaucoma What Is the Specificity of the Guided Progression Analysis?
Purpose: To estimate the specificity of the Guided Progression Analysis (GPA) (Carl Zeiss Meditec, Dublin, CA) in individual patients with glaucoma.
Design: Observational cohort study.
Participants: Thirty patients with open-angle glaucoma.
Methods: In 30 patients with open-angle glaucoma, 1 eye (median mean deviation [MD], −2.5 decibels [dB]; interquartile range, −4.4 to −1.3 dB) was tested 12 times over 3 months (Humphrey Field Analyzer, Carl Zeiss Meditec; SITA Standard, 24-2). “Possible progression” and “likely progression” were determined with the GPA. These analyses were repeated after the order of the tests had been randomly rearranged (1000 unique permutations).
Main Outcome Measures: Rate of false-positive alerts of “possible progression” and “likely progression” with the GPA.
Results: On average, the specificity of the GPA “likely progression” alert was high—for the entire sample, the mean rate of false-positive alerts after 10 follow-up tests was 2.6%. With “possible progression,” the specificity was considerably lower (false-positive rate, 18.5%). Most important, the cumulative rate of false-positive alerts varied substantially among patients, from 0.31, P≤0.10).
Conclusions: On average, progression criteria currently used in the GPA have high specificity, but some patients are more likely to show false-positive alerts than others. This is a natural consequence of population-based change criteria and may not matter in clinical trials and studies in which large groups of patients are compared. However, it must be considered when the GPA is used in clinical practice where specificity needs to be controlled for individual patients
Características citopatológicas del carcinoma de células acinares (CCA) de glándula salival: a propósito de cuatro observaciones
Objetivo: Presentar las características citopatológicas del carcinoma
acinar (CCA), así como su correlación cito-histológica,
comentando los problemas de diagnóstico diferencial de esta
entidad en base a cuatro observaciones estudiadas mediante
PAAF.
Casos clínicos: Dos varones de 52 y 53 años, una mujer de
79 años, y una niña de 12 años que presentaron tumoraciones
localizadas en territorio parotídeo (casos 1, 2 y 4), y a nivel
laterocervical (caso 3).
En tres pacientes, la PAAF fue, junto a los estudios de imagen,
la primera aproximación diagnóstica; correspondiendo el caso
3 a una punción de adenopatías laterocervicales metastásicas en
una paciente con antecedentes de CCA de parótida.
Hallazgos citológicos: Las extensiones citológicas mostraron
abundante celularidad tumoral dispuesta en pequeñas placas
monocapa, formando estructuras acinares, o como células aisladas.
Es de destacar la abundancia de núcleos desnudos en el
fondo de los frotis, y la ausencia de grasa y de epitelio ductal.
Las células poseían núcleos monomorfos redondeados u ovales,
nucleólo poco evidente y abundante citoplasma granular o
finamente vacuolado.
Discusión: La PAAF proporciona información esencial en la
actuación diagnóstico-terapeútica de las tumoraciones de la
glándula salival, resultando esta metodología muy sensible
en su eficacia diagnóstica. La identificación de los CCA frecuentemente
presenta dificultades, debido a la gran similitud citológica de las células tumorales con el componente acinar
normal propio de la glándula salival. El diagnóstico diferencial
se plantea, fundamentalmente, con carcinomas de células claras,
con carcinomas mucoepidermoides, con el tumor de Warthin
y con los oncocitomas. Nuestras observaciones confirman la
validez de la PAAF en una primera aproximación diagnóstica
de estas lesiones tumorales accesibles a la punción directa.Objective: To present the cytopathological characteristics of
acinic cell carcinoma (ACC) as well as its cyto-histological
correlation, commenting on the differential diagnostic problems
of this entity based on four observations studied using fine-needle
aspiration biopsy (FNAB).
Clinical Cases: Two males of 52 and 53 years of age, one 79
year-old woman and a girl of 12 years of age, who presented
tumors located in the parotid area (cases 1, 2 and 4) and at the
laterocervical level (case 3).
In 3 patients, the FNAB was, together with the image studies,
the first diagnostic indication; case 3 corresponding to a puncture
of metastatic laterocervical adenopathies in a patient with
a history of parotid ACC.
Cytological findings: The cytologic smears revealed abundant
tumoral cellularity arranged in small monolayered sheets,
forming acinar structures or isolated cells. The abundance of
bare nuclei at the background of the smears, and the absence of
adipose tissue and ductal epithelium are highlighted. The cells
possessed round or oval monomorphic nuclei, few nucleoli and
abundant granular or finely vacuolate cytoplasm.
Discussion: FNAB provides essential information on the diagnostic-
therapeutic management of salivary gland tumors; this
methodology is highly sensitive in its diagnostic efficacy. The
diagnosis of ACCs frequently presents difficulties, owing to
the great cytologic similarity of the tumor cells with the normal
acinar component of the salivary gland. The differential diag-nosis is considered, fundamentally, with clear cell carcinomas,
mucoepidermoid carcinomas, Warthin's tumor, and oncocytomas.
Our observations confirm the validity of FNAB in a first
diagnostic approximation for those lesions accessible to direct
puncture
Diagnóstico citológico de las recidivas tumorales de ameloblastoma: presentación de dos casos clínicos
Introducción: Los ameloblastomas son los tumores odontogénicos
más frecuentes del maxilar. A pesar de su aspecto citohistológico
de benignidad, se comportan como tumores invasivos,
recidivantes y con posibilidad de metastatizar.
La P.A.A.F. es una prueba rápida e incruenta que proporciona
un diagnóstico prequirúrgico evitando, en ocasiones, tomas
biópsicas destinadas al diagnóstico.
Presentamos las características citológicas de dos casos de
recidiva yugal de ameloblastoma de rama mandibular diagnosticados
por PAAF, así como su correlación citohistológica.
Casos clínicos: Dos pacientes, una mujer de 36 años y un varón
de 62 años, que acuden por tumoración mandibular de escasos
meses de evolución. En ambos casos, la primera aproximación
diagnóstica fue junto a los estudios radiológicos el estudio
histológico de la masa tumoral. Tras la extirpación terapeútica,
ambos casos recidivaron. El diagnóstico de las recidivas fue
establecido citológicamente mediante PAAF.
Las extensiones citológicas mostraron un fondo granular con
aislados macrófagos y células multinucleadas gigantes y una
abundante celularidad epitelial de aspecto basaloide dispuesta
en grupos cohesivos configurando imágenes de empalizada
periférica, así como pequeños grupos de células de metaplasia
escamosa.
Discusión: La PAAF se considera como un método diagnóstico rápido, incruento y fiable en el diagnóstico del ameloblastoma.
La citología de estos tumores revela los componentes de la lesión
que, en general, son suficientes para llegar al diagnóstico de
ameloblastoma, especialmente en casos de recidiva.Introduction: Ameloblastomas are the most frequent odontogenic
tumors of the maxilla. In spite of their benign cytohistological
appearance, they behave as invasive recurring tumors, with the
possibility of metastasis.
FNAB is a rapid, bloodless test that provides a pre-surgical
diagnosis, thus, on occasions avoiding the need for diagnostic
biopsies.
We present the cytological characteristics of two cases of jugal
recurrences of mandibular ameloblastomas diagnosed by FNAB,
as well as their cytohistological correlation.
Clinical cases: Two patients, a 36-year-old woman, and a 62-
year-old male who both attended with mandibular swelling
of a few months evolution. In both cases the first diagnostic
approximation was the histological study of the tumoral mass,
together with the radiological studies. Following therapeutic
extirpation both cases recurred. The diagnosis of the recurrences
was established cytologically by means of FNAB.
The cytologic smears revealed a granular background with isolated
macrophages and giant multinucleate cells and an abundant
epithelial cellularity of basaloid appearance arranged in cohesive
groups forming images of peripheral palidasing, as well as small
groups of squamous metaplastic cells.
Discussion: FNAB is considered to be a rapid, bloodless and reliable
method for the diagnosis of ameloblastoma. The cytology of these tumors reveals components of the lesion that, in general,
are sufficient for the diagnosis of ameloblastoma, especially in
cases of recurrence
O Impacto de Capital Humano, Capital Social e Práticas Gerenciais na Sobrevivência de Empresas Nascentes: um Estudo com Dados de Pequenas Empresas no Estado de São Paulo
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