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Determinação da polarização ferroelétrica do PVDF estirado biaxialmente utilizando a técnica de corrente constante.; Determination of the biaxially stretched PVDF ferroelectric polarization using constant current technique.

Moura, Walterley Araujo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/07/1998 PT
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Foi desenvolvido um novo método para a determinação da polarização ferroelétrica de polímeros ferroelétricos, em particular do PVDF estirado biaxialmente. A técnica consiste em manter constante a corrente através da amostra e medir a evolução da tensão (V versus t) entre os eletrodos da mesma. As medidas foram realizadas em ambiente com atmosfera de ar superseco o que permite desprezar a condução elétrica das amostras, simplificando sobremaneira as equações do problema. Considera-se a existência de dois tipos de polarização: a ferroelétrica, com tempo de chavamento desprezível, e uma polarização elétrica foram realizados em duas situações distintas: com chaveamento e sem chaveamento ferroelétrico. O procedimento permite avaliar a dependência da polarização ferroelétrica com o campo, determinada a partir da equação geral da corrente. Para se descrever a resposta da polarização elétrica dependente do tempo, usa-se o princípio da superposição e assume-se que ela está em fase com o campo elétrico aplicado (processo lento). Será mostrado que é possível determinar a polarização ferroelétrica do polímero PVDF estirado biaxialmente sem a necessidade de determinar a formas funcionais da polarização dependente do tempo e de se conhecer o valor da capacitância da amostra.; In this work a novel method was developed for the determination of the ferroelectric polarization of ferroelectric polymers...

QBER Estimation in QKD Systems With Polarization Encoding

Muga, Nelson; Ferreira, Mário; Pinto, Armando
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
ENG
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A model for quantum BER estimation in polarization encoded quantum key distribution systems is presented. Both TDM and WDM based polarization control schemes are analyzed. It is shown that TDM presents some important advantages when compared with the WDM control scheme. In WDM, the polarization decorrelation between the reference and data signals is an intrinsic and very limitative impairment. This effect has a contribution to quantum BER that increases with the propagation distance, and is highly dependent on the fiber polarization mode dispersion. In the TDM control scheme, the polarization decorrelation is less critical and other issues, like the single photon detector and feedback polarization control system performance tend to dominate. We show that for long distances the fiber losses represent the main contribution to the total quantum BER. Nevertheless, for distances shorter than 70 km and frequencies higher than 5 MHz the after pulse detections provide an important contribution to the total quantum BER.

Evolution of the degree of co-polarization in high-birefringence fibers

Muga, Nelson J.; Silva, Nuno A.; Ferreira, Mário F. S.; Pinto, Armando N.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
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An analytical model accurately describing the evolution of the relative state of polarization between two signals in high-birefringence fibers is presented. The degree of co-polarization is calculated as a function of the angle between the principal axes of the fiber and the state of polarization of the two input signals, for two different input polarization schemes. It is shown that for small fiber lengths or narrow wavelength separation, launching the two signals with orthogonal polarizations can present a higher degree of co-polarization along the propagation: for large wavelength separation or long distances, the degree of co-polarization for the parallel scheme is always equal or higher than for the orthogonal case. The model for the degree of co-polarization is compared with theoretical and experimental four-wave mixing results in a dispersion shifted high-birefringence fiber. (C) 2010 Elsevier B.V. All rights reserved.

Polarization scattering property of cascaded polarization controllers

Muga, Nelson J.; Ferreira, Mário F.; Pinto, Armando Nolasco
Fonte: Electronics and Telecommunications Research Institute (ETRI) Publicador: Electronics and Telecommunications Research Institute (ETRI)
Tipo: Artigo de Revista Científica
ENG
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The relation between the allowed range of variation of polarization controller wave-plates angles and the respective polarization scattering properties is investigated It is demonstrated that a nearly uniform polarization scattering over the Poincare sphere is obtained using a concatenation of three polarization controllers with angles randomly changed between -pi/4 and pi/4. It is also shown that an improvement of the scattering properties is obtained if the configuration angles are allowed to change between -pi/2 and pi/2.

Uniform polarization scattering with fiber-coil-based polarization controllers

Muga, Nelson J.; Pinto, Armando Nolasco; Ferreira, Mário F. S.; da Rocha, José R. Ferreira
Fonte: IEEE Publicador: IEEE
Tipo: Artigo de Revista Científica
ENG
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A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions

Vancomycin monitoring in term newborns: comparison of peak and trough serum concentrations determined by high performance liquid chromatography and fluorescence polarization immunoassay

Feferbaum,Rubens; Machado,José Kleber Kobol; Diniz,Edna Maria de Albuquerque; Okay,Thelma S.; Santos,Silvia R. C. J.; Ceccon,Maria Esther J.R.; Krebs,Vera L. J.; Araújo,Maria C. K. de; Vaz,Flávio Adolfo Costa
Fonte: Faculdade de Medicina / Universidade de São Paulo - FM/USP Publicador: Faculdade de Medicina / Universidade de São Paulo - FM/USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2001 EN
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INTRODUCTION: Peak and trough serum concentrations of vancomycin were determined in term newborn infants with confirmed or suspected Staphylococcus sp sepsis by high performance liquid chromatography and flourescence polarization immunoassay. OBJECTIVE: To statistically compare the results of the high performance liquid chromatography and flourescence polarization immunoassay techniques for measuring serum vancomycin concentrations. METHODS: Eighteen peak and 20 trough serum samples were assayed for vancomycin concentrations using high performance liquid chromatography and flourescence polarization immunoassay from October 1995 to October 1997. RESULTS: The linear correlation coefficients for high performance liquid chromatography and flourescence polarization immunoassay were 0.27 (peak, P = 0.110) and 0.26 (trough, P = 0.1045) respectively, which were not statistically significant. CONCLUSION: There was wide variation in serum vancomycin concentrations determined by high performance liquid chromatography as compared with those determined by flourescence polarization immunoassay. There was no recognizable pattern in the variability; in an apparently random fashion, the high performance liquid chromatography measurement was sometimes substantially higher than the flourescence polarization immunoassay measurement...

Polarization and coherence-engineered illumination with applications in imaging

Brown, Dean Patterson (1981 - ); Brown, Thomas G.
Fonte: University of Rochester. Publicador: University of Rochester.
Tipo: Tese de Doutorado Formato: Number of Pages:xxvi, 176 leaves
ENG
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Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2010.; In image formation, the coherence properties of the illumination source are of great importance. At the same time, the polarization properties of an optical system also play a role in the quality of an imaging system, particularly those of high numerical aperture (NA). Polarization-dependent coherence is therefore an important area of study for any imaging system. In the past few years, while there has been a unification of the ability to use coherence theory to describe vectorial fields through the use of a construct called a correlation matrix, very little has been done experimentally predicting or measuring the coherence properties of an illumination system comprised of vectorial fields. In the work that follows, we explore several arrangements in which a polarization vortex mode converter was placed in the pupil plane of an illumination system. In these arrangements, we study both theoretically and experimentally the spatially dependent coherence properties using a vectorial treatment of optical coherence. Those properties were applied to imaging systems that then results in an improvement in image contrast using polarization- and orientation-dependent coherence properties of the illumination. In this work...

Polarization sensitivity of rainbow trout (Oncorhynchus mykiss) under natural photic conditions

Hauser, Frances E
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
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The underwater photic environment provides spectral and polarization visual cues that fish use to guide their behaviour. Variation in the spectrum of underwater light affects how polarization stimuli are detected. Rainbow trout (Oncorhynchus mykiss) detect the polarization of light through the use of the UVS and LWS cone mechanisms – two differentially sensitive polarization detectors that overlap in the ultraviolet spectral region. However, since polarization sensitivity was previously measured under artificial background lighting, polarization sensitivity under natural lighting conditions has not yet been examined. Using compound action potential recordings from the optic nerve, I assessed the spectral sensitivity of juvenile rainbow trout under background lighting conditions that simulated a natural photic environment of rainbow trout, and found that this condition activated the UVS and LWS cone mechanisms. To define the spectral range over which polarization sensitivity is possible under natural lighting, I presented plane-polarized stimuli at a number of wavelengths that extend into the long wavelength region of the spectrum. I found that a plane-polarized ultraviolet stimulus activated both detector mechanisms, resulting in a “W”-shaped polarization sensitivity function. The activation of two differentially sensitive polarization detectors indicates the potential for discrimination between polarized stimuli in the natural environment. Contrary to our current understanding of the spectral limits of polarization sensitivity...

Ontogeny and topography of retinal polarization sensitivity in rainbow trout (Oncorhynchus mykiss).

Habib-Nayany, Maheen
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN
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Smoltification induces physiological and behavioural changes in salmonids to prepare them for subsequent changes in diet and habitat. One such change that distinguishes parr (fry) from smolts (juveniles) involves the loss of ultraviolet-sensitive (UVS) cones from the ventral retinal region. Rainbow trout (Oncorhynchus mykiss) can discriminate between different states of polarized light, and can utilize these signals in orientation, navigation, and foraging. Polarization sensitivity is mediated by the UVS (vertical polarization sensitivity), and the medium wavelength/long wavelength sensitive (MWS/LWS, horizontal polarization sensitivity) mechanisms. It is unknown how the loss of UVS cones in the smolt ventral retina affects the ability to detect polarized light. First, spectral sensitivity was measured for both parr and smolts to assess the expression of each cone class in either the ventral or dorsal retinal regions. There was no difference in UV spectral sensitivity between the parr dorsal and ventral retina. In smolts, there was a decrease in UV sensitivity in the ventral region compared to dorsal. As well, there was an increase in long wavelength sensitivity in the ventral region under both background conditions and life stages. Then...

First Time Measurements of Polarization Observables for the Charged Cascade Hyperon in Photoproduction

Bono, Jason S
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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The parity violating weak decay of hyperons offers a valuable means of measuring their polarization, providing insight into the production of strange quarks and the matter they compose. Jefferson Lab’s CLAS collaboration has utilized this property of hyperons, publishing the most precise polarization measurements for the Λ and Σ in both photoproduction and electroproduction to date. In contrast, cascades, which contain two strange quarks, can only be produced through indirect processes and as a result, exhibit low cross sections thus remaining experimentally elusive. At present, there are two aspects in cascade physics where progress has been minimal: characterizing their production mechanism, which lacks theoretical and experimental developments, and observation of the numerous excited cascade resonances that are required to exist by flavor SU(3)F symmetry. However, CLAS data were collected in 2008 with a luminosity of 68 pb−1 using a circularly polarized photon beam with energies up to 5.45 GeV, incident on a liquid hydrogen target. This dataset is, at present, the world’s largest for meson photoproduction in its energy range and provides a unique opportunity to study cascade physics with polarization measurements. The current analysis explores hyperon production through the γp → K+K+Ξ− reaction by providing the first ever determination of spin observables P...

A polarization survey of bright extragalactic AT20G sources

Massardi, Marcella; Burke-Spolaor, S. G.; Murphy, T.; Ricci, R.; López-Caniego Alcarria, Marcos; Negrello, Mattia; Chhetri, R.; De Zotti, Gianfranco; Ekers, R. D.; Partridge, R. B.; Sadler, E. M.
Fonte: Oxford University Press; Royal Astronomical Society Publicador: Oxford University Press; Royal Astronomical Society
Tipo: info:eu-repo/semantics/article; publishedVersion
ENG
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We present polarization data for 180 extragalactic sources extracted from the Australia Telescope 20 GHz (AT20G) survey catalogue and observed with the Australia Telescope Compact Array during a dedicated, high sensitivity run (σP ∼ 1 mJy). For the sake of completeness, we extracted the polarization information for seven extended sources from the 9 yr Wilkinson Microwave Anisotropy Probe co-added maps at 23 GHz. The full sample of 187 sources constitutes a ≃99 per cent complete sample of extragalactic sources brighter than S20GHz = 500 mJy at the selection epoch with declination δ < −30°. The sample has a 91.4 per cent detection rate in polarization at ∼20 GHz (94 per cent if considering the subsample of point-like sources). We have measurements also at 4.8 and 8.6 GHz within ∼1 month of the 20 GHz observations for 172 sources to reconstruct the spectral properties of the sample in total intensity and in polarization: 143 of them have a polarization detection at all three frequencies. We find that there is no statistically significant evidence of a relationship either between the fraction of polarization and frequency or between the fraction of polarization and the total intensity flux density. This indicates that Faraday depolarization is not very important above 4.8 GHz and that the magnetic field is not substantially more ordered in the regions dominating the emission at higher frequencies (up to 20 GHz). We estimate the distribution of the polarization fraction and the polarized flux density source counts at ∼20 GHz.

Uniform polarization scattering with fiber-coil-based polarization controllers

Muga, Nelson J.; Pinto, Armando Nolasco; Ferreira, Mário F. S.; Ferreira da Rocha, José R.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PC's can be used to emulate both, first- and second-order polarization- mode dispersions.

Ocular aberrations with ray tracing and Shack–Hartmann wave-front sensors: Does polarization play a role?

Marcos, Susana; Díaz-Santana, Luis; Llorente, Lourdes; Dainty, Chris
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artículo Formato: 1083176 bytes; application/pdf
ENG
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10 pages, 9 figures.-- OCIS codes: 330.5370, 260.5430.-- PMID: 12049343 [PubMed].; Ocular aberrations were measured in 71 eyes by using two reflectometric aberrometers, employing laser ray tracing (LRT) (60 eyes) and a Shack–Hartmann wave-front sensor (S–H) (11 eyes). In both techniques a point source is imaged on the retina (through different pupil positions in the LRT or a single position in the S–H). The aberrations are estimated by measuring the deviations of the retinal spot from the reference as the pupil is sampled (in LRT) or the deviations of a wave front as it emerges from the eye by means of a lenslet array (in the S–H). In this paper we studied the effect of different polarization configurations in the aberration measurements, including linearly polarized light and circularly polarized light in the illuminating channel and sampling light in the crossed or parallel orientations. In addition, completely depolarized light in the imaging channel was obtained from retinal lipofuscin autofluorescence. The intensity distribution of the retinal spots as a function of entry (for LRT) or exit pupil (for S–H) depends on the polarization configuration. These intensity patterns show bright corners and a dark area at the pupil center for crossed polarization...

Social Polarization: Introducing distances between and within groups

Permanyer, Iñaki
Fonte: Conselho Superior de Investigações Científicas Publicador: Conselho Superior de Investigações Científicas
Tipo: Documento de trabajo Formato: 274952 bytes; application/pdf
ENG
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37 pages, 7 figures.; The measurement of social polarization has received little attention from the literature. The only social polarization index that has been used to measure religious or ethnic polarization (the RQ index) has several shortcomings that are critically discussed in the paper. In particular, that index is not taking into account the existing distance between and within different groups. A couple of axiomatically characterized social polarization indices that overcome these limitations are presented. In the empirical section we show that the rankings of countries according to the levels of polarization change to a great extent when we replace the RQ index by the indices presented in this paper.; Peer reviewed

Mask induced polarization effects at high NA

Estroff, Andrew; Fan, Yongfa; Bourov, Anatoly; Smith, Bruce; Foubert, Philippe; Leunissen, L.; Philipsen, Vicky; Aksenov, Yuri
Fonte: SPIE Publicador: SPIE
Tipo: Proceedings
EN_US
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It is important to understand how a photomask will polarize incident radiation. This paper presents data collected on binary mask and various attenuated phase shifting mask materials, feature sizes, duty ratios, and illumination schemes via rigorous coupled wave analysis, extinction spectroscopy, and 193nm lithographic evaluation. Additionally, the result of polarization effects due to the photomask on imaging has been studied. It was found that in the majority of the cases, higher NA led to greater polarization effects. All mask materials predominantly pass the TM polarization state for the 0 order, whereas different materials and duty ratios affect the polarization of the first diffracted orders differently. The polarization effects contributed by mask materials being considered for use in high NA imaging systems need to be examined. The degree of polarization as a function of n and k is presented, providing an introduction to the desirable properties of future mask materials. Materials with higher refractive indices and lower extinction coefficients tend to pass more of the TM polarization state, which is undesirable. Materials with lower indices and relatively wide range of extinction coefficients pass more TE polarized radiation. The duty ratio...

Characterization of dichroism and linear polarization effects on colorimetric properties of plastic transmitting materials

Riffel, Richard W.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
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Polarization is not a new phenomenon. However, in some applications polarization can be a contributing factor to colorimetric mismatch between samples When investigating polarization effects, most work has centered on the application of circular polarization on absorption spectroscopy in organic molecules. However, little if any colorimetric research on plastic materials has been done. Given the fact that linear polarization is a naturally occurring phenomenon, the dichroic effect is further highlighted in some end-user applications. The current research defines a technique for characterizing the linear-polarization-induced dichroic effect in a transmitting plastics application. Included in the work is the description of a polar-spectrophotometer capable of defined illumination and collection polarization states. Sample measurements and data analysis techniques are also discussed.

Polarimetric remote sensing system analysis: Digital Imaging and Remote Sensing Image Generation (DIRSIG) model validation and impact of polarization phenomenology on material discriminability

Devaraj, Chabitha
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Dissertação
EN_US
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In addition to spectral information acquired by traditional multi/hyperspectral systems, passive electro optical and infrared (EO/IR) polarimetric sensors also measure the polarization response of different materials in the scene. Such an imaging modality can be useful in improving surface characterization; however, the characteristics of polarimetric systems have not been completely explored by the remote sensing community. Therefore, the main objective of this research was to advance our knowledge in polarimetric remote sensing by investigating the impact of polarization phenomenology on material discriminability. The first part of this research focuses on system validation, where the major goal was to assess the fidelity of the polarimetric images simulated using the Digital Imaging and Remote Sensing Image Generation (DIRSIG) model. A theoretical framework, based on polarization vision models used for animal vision studies and industrial defect detection applications, was developed within which the major components of the polarimetric image chain were validated. In the second part of this research, a polarization physics based approach for improved material discriminability was proposed. This approach utilizes the angular variation in the polarization response to infer the physical characteristics of the observed surface by imaging the scene in three different view directions. The usefulness of the proposed approach in improving detection performance in the absence of apriori knowledge about the target geometry was demonstrated. Sensitivity analysis of the proposed system for different scene related parameters was performed to identify the imaging conditions under which the material discriminability is maximized. Furthermore...

Enzyme Polarization of Substrates of Dihydrofolate Reductase by Different Theoretical Methods

Greatbanks, S; Gready, Jill; Limaye, Ajay; Rendell, Alistair
Fonte: Wiley-Liss Inc Publicador: Wiley-Liss Inc
Tipo: Artigo de Revista Científica
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We have investigated the importance of polarization by the enzyme dihydrofolate reductase (DHFR) on its substrates, folate and dihydrofolate, using a series of quantum mechanical (QM) techniques (Hartree-Fock (HF), Moller-Plesset second-order perturbation theory (MP2), local density approximation (LDA) and generalized gradient approximation (GGA) density functional theory (DFT) calculations) in which the bulk enzyme is included in the calculations as point charges. Polarization, in terms of both charges on components (residues) of the folate and dihydrofolate molecules and changes in the electron density, particularly of the pterin ring of the substrates, and the implications for the catalytic reduction are discussed. Significant differences in polarization behavior are observed for the different theoretical methods employed. The consequences of this, particularly for choosing an appropriate model for quantum mechanical/molecular mechanical (QM/MM) calculations, are pointed out. The HF and MP2 QM methods show small polarizations (~0.04 electrons) of the pterin ring but quite large polarizations with both LDA and GGA DFT methods (0.3-0.5 electrons). This large difference in polarization for both folate and dihydrofolate arises as a result of substantial differences between the charge distributions for the gas-phase DFT and HF calculations...

Monitorização do vale e pico sérico de vancomicina em recém-nascidos de termo: comparação entre as técnicas de cromatografia líquida de alta eficácia e imunoensaio por fluorescência polarizada; Vancomycin monitoring in term newborns: comparison of peak and trough serum concentrations determined by high performance liquid chromatography and fluorescence polarization immunoassay

Feferbaum, Rubens; Machado, José Kleber Kobol; Diniz, Edna Maria de Albuquerque; Okay, Thelma S.; Santos, Silvia R. C. J.; Ceccon, Maria Esther J.R.; Krebs, Vera L. J.; Araújo, Maria C. K. de; Vaz, Flávio Adolfo Costa
Fonte: Universidade de São Paulo. Faculdade de Medicina Publicador: Universidade de São Paulo. Faculdade de Medicina
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/10/2001 ENG
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INTRODUÇÃO: Foi realizada monitorização dos níveis séricos de vancomicina em recém-nascidos de termo com sepse ou suspeita de sepse Staphylococcus sp., através da cromatografia líquida de alta eficácia (HPLC) e imunoensaio por fluorescência polarizada (FPIA). OBJETIVO: Verificar a existência de correlação estatística entre os resultados obtidos pelas duas técnicas. MÉTODO E CASUÍSTICA: Foram obtidas dezoito e vinte concentrações séricas de vancomicina no pico e vale respectivamente, em recém-nascidos de termo, no período de outubro de 1995 a outubro de 1997. RESULTADO: O coeficiente de correlação linear para pico sérico foi de 0,27, p=0,110 e para vale sérico 0,26, p= 0,1045 não sendo estatisticamente significativo, não sendo estatisticamente significativo. CONCLUSÃO: Apesar da pequena casuística, não houve correlação estatisticamente significante entre os resultados obtidos pelos duas técnicas.; INTRODUCTION: Peak and trough serum concentrations of vancomycin were determined in term newborn infants with confirmed or suspected Staphylococcus sp sepsis by high performance liquid chromatography and flourescence polarization immunoassay. OBJECTIVE: To statistically compare the results of the high performance liquid chromatography and flourescence polarization immunoassay techniques for measuring serum vancomycin concentrations. METHODS: Eighteen peak and 20 trough serum samples were assayed for vancomycin concentrations using high performance liquid chromatography and flourescence polarization immunoassay from October 1995 to October 1997. RESULTS: The linear correlation coefficients for high performance liquid chromatography and flourescence polarization immunoassay were 0.27 (peak...

A simple method for changing the state of polarization from elliptical into circular

Montoya,M.; Paez,G.; Malacara-Hernández,D.; García-Márquez,J.
Fonte: Sociedad Mexicana de Física Publicador: Sociedad Mexicana de Física
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2005 EN
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Changes of polarization occur as a consequence of the interaction of light and the various optical elements through which it passes. A circularly polarized light beam may change its state to slightly elliptically polarized for many reasons. To correct this is not always easy but we show a very simple method for correcting circular polarization that has changed slightly into elliptic polarization. In this paper we propose to restore the circular state of polarization of an elliptically polarized light beam back to circular by means of a glass plate properly oriented while polarization is being measured. The basic idea is to modulate the transmittances of the electric field in both the major and minor axes of the ellipse of polarization. It is done by means of glass plates at non-normal incidence. Experimental results are consistent with theory.