Pressure-sensitive platform based on multiplexed in-series macro-bend optical fiber sensors.

This work shows a pressure-sensitive platform instrumented with a set of five in-series macro-bend optical fiber sensors. The structure of 20×20cm is divided into sixteen 5×5cm sensing cells. Sensing is based on the wavelength-dependent intensity changes in the array transmission visible spectrum, which carries information about the pressure acting on the structure. Data analysis uses principal component analysis to reduce spectral data to 12 principal components that explain 99% of the data variance and k-nearest neighbors classification and support vector regression methods. The capability of pressure detection with fewer sensors than the number of monitored cells was demonstrated with an accuracy of 94% for predicting the pressure location and a mean absolute error of 0.31 kPa within 3.74-9.98 kPa range.

Spectroscopic Detection of Glyphosate in Water Assisted by Laser-Ablated Silver Nanoparticles.

Glyphosate is one of the most widely used herbicides in the world. Its safety for both human health and aquatic biomes is a subject of wide debate. There are limits to glyphosate's presence in bodies of water, and it is usually detected through complex analytical procedures. In this work, the presence of glyphosate is detected directly through optical interrogation of aqueous solution. For this purpose, silver nanoparticles were produced by pulsed laser ablation in liquids. Limits of detection of 0.9 mg/L and 3.2 mg/L were obtained with UV-Vis extinction and Surface Enhanced Raman spectroscopies, respectively. The sensing mechanism was evaluated in the presence of potential interferents as well as with commercial glyphosate-based herbicides.

Matching long-period grating modes and localized plasmon resonances: effect on the sensitivity of the grating to the surrounding refractive index.

The sensitivity and dynamical range of an optical-fiber transducer consisting of a long-period grating coated with gold nanoparticles is investigated. For a grating with an 80 µm spatial periodicity, the resonances close to the turning point lie within the 450-900 nm spectral range. Employing a bottom-up production route, the localized surface plasmon resonance of gold nanoparticles is matched to the grating resonances; it is shown that this results in an increase in the refractive index sensitivity of the device. The device also shows increased dynamic range and enhanced refractive index sensitivity in water.

Plasmonic optical fiber sensors: enhanced sensitivity in water-based environments.

In this work, we demonstrate a refractometric fiber sensor with improved sensitivity for refractive indices ranging from 1.3629 to 1.4479. The device relies on the coupling between a long period grating (LPG) transducer and a localized surface plasmon resonance (LSPR). Sensor operation is based on the transference of energy from LPG cladding modes at the visible spectral range to the LSPR. The transducer consists of a long period grating 3.15-mm-long covered with 2-7 nm gold nanoparticles. The sensor is intensity coded at a 568 nm wavelength, presenting sensitivity of 208%/unit of refractive index for a refractive index of 1.39 and resolution better than 0.0003 for the dynamic range of refractive indices from 1.3629 to 1.4479.

Geographic patterns of distribution and ecological niche of the snake-necked turtle genus Hydromedusa.

Biotic and abiotic factors play a crucial role in determining the distribution of species. These factors dictate the conditions that must be met for a species to thrive in a particular area. Sister species that present some degree of niche overlap can shed light on how they are distributed and coexist in their environment. This study aims to investigate the geographical distribution and ecological niche of the sister species of snake-necked turtles Hydromedusa maximiliani and H. tectifera. By analyzing their niche overlap, we aim to obtain a better understanding of how these two species coexist and which variables are determining their occurences. We applied species distribution modeling and compared the niches using the niche equivalence and similarity tests. Our findings show that the distribution of H. maximiliani is most influenced by temperature seasonality and isothermality, while H. tectifera is most affected by the temperature seasonality, precipitation of warmest quarter and mean diurnal range. In addition, our results suggest that the niche expressed by H. maximiliani retained ecological characteristics that can accurately predict the H. tectifera distribution, but the inverse is not true. In this sense, differences are not solely due to the geographic availability of environmental conditions but can reflect niche restrictions, such as competition.

Tailoring fiber grating sensors for assessment of highly refractive fuels.

Three approaches that allow the tailoring of long period gratings based refractometric sensors for concentration measurement in fuel blends are employed to assess the fuel quality in biodiesel and biodiesel-petrodiesel blend. To allow the analysis of fuel samples with refractive index higher than fiber cladding one, the samples refractive indices were changed by thermo-optic effect and by dilution in a standard substance with low refractive index. The obtained results show the sensor can detect oil concentration in biodiesel samples with resolution as better as 0.07% and biodiesel concentration in biodiesel-petrodiesel samples with average resolution of 0.09%.

Fiber Bragg grating sensor to monitor stress kinetics in drying process of commercial latex paints.

In this paper, we report a study about the application of packaged fiber Bragg gratings used as strain sensors to monitor the stress kinetics during the drying process of commercial latex paints. Three stages of drying with distinct mechanical deformation and temporal behaviors were identified for the samples, with mechanical deformation from 15 µm to 21 µm in the longitudinal film dimension on time intervals from 370 to 600 minutes. Drying time tests based on human sense technique described by the Brazilian Technical Standards NBR 9558 were also done. The results obtained shows that human sense technique has a limited perception of the drying process and that the optical measurement system proposed can be used to characterize correctly the dry-through stage of paint. The influence of solvent (water) addition in the drying process was also investigated. The paint was diluted with four parts paint and one part water (80% paint), and one part paint and one part water (50% paint). It was observed that the increase of the water ratio mixed into the paint decreases both the mechanical deformation magnitude and the paint dry-through time. Contraction of 5.2 µm and 10.4 µm were measured for concentrations of 50% and 80% of paint in the mixture, respectively. For both diluted paints the dry-through time was approximately 170 minutes less than undiluted paint. The optical technique proposed in this work can contribute to the development of new standards to specify the drying time of paint coatings.

Influence of surrounding media refractive index on the thermal and strain sensitivities of long-period gratings.

A detailed study of the thermal and strain sensitivities of a long-period grating when the device is immersed in different external media is presented. The range of refractive indices analyzed are within 1.000 to 1.447, corresponding to samples of air, water, ethanol, naphtha, thinner, turpentine, and kerosene. Within the same range of refractive indices, the strain sensitivity is between (-0.24 +/- 0.03) and (-0.94 +/- 0.11) pm/microepsilon. For the grating immersed in these fluids, the refractive index sensitivity ranges from -3 to -1035.6 nm per refractive index units. The coupling thermo-optic coefficients and the strain-optic coefficients are also measured, resulting in the range from (2.45 +/- 0.04)x10(-5) to (15.89 +/- 0.82)x10(-5) deg C(-1) and (-1.15 +/- 0.04) to (-1.61 +/- 0.04) microepsilon(-1), respectively. A noticeable nonlinear behavior of the thermal sensitivity is found for external media with refractive indices higher than 1.430.

Prevalência e adequaçäo do uso de antimicrobianos no hospital de clínicas de Porto Alegre / Prevalence and adequacy of antibiotic use in hospital de clinicas de Porto Alegre

Durante o dia 30 de julho de 1987, foram estudados alguns aspectos envolvendo o uso de antibióticos no Hospital de Clínicas de Porto Alegre. De 432 pacientes internados, 182 (42%) estavam utilizando antibióticos, e destes, 42% recebiam a medicaçäo de forma inadequada. Dos antibióticos usados terapeuticamente, os mais prescritos foram ampicilina, penicilina, cefalosporinas e amicacina. Entre os usados profilaticamente, destacram-se cefalosporinas, gentamicina e ampicilina. O trabalho sugere que o controle do uso de antibióticos pode reduzir a adoçäo inapropriada destes agentes