Social and epidemiological aspects of dengue were evaluated in an important metropolitan area in southern Brazil, from August 2012 to September 2014. Demographic, clinical, serological data were collected from patients with acute dengue symptoms treated at public health system units (HSUs). A systematic approach to analyze the spatial and temporal distribution of cases was developed, considering the temporal cross-correlation between dengue and weather, and the spatial correlation between dengue and income over the city’s census tracts. From the 878 patients with suggestive symptoms, 249 were diagnosed as positive dengue infection (28%). Considering the most statistically significant census tracts, a negative correlation was found between mean income and dengue (r = −0.65;p = 0.02; 95% CI: −0.03 to −0.91). The occurrence of dengue followed a seasonal distribution, and it was found to be three and four months delayed in relation to precipitation and temperature, respectively. Unexpectedly, the occurrence of symptomatic patients without dengue infection followed the same seasonal distribution, however its spatial distribution did not correlate with income. Through this methodology, we have found evidence that suggests a relation between dengue and poverty, which enriches the debate in the literature and sheds light on an extremely relevant socioeconomic and public health issue.

A combined and sequential use of Monte Carlo simulations and quantum mechanical calculations is made to analyze the spectral shift of the lowest π–π* transition of phenol in water. The solute polarization is included using electrostatic embedded calculations at the MP2/aug-cc-pVDZ level giving a dipole moment of 2.25 D, corresponding to an increase of 76% compared to the calculated gas-phase value. Using statistically uncorrelated configurations sampled from the MC simulation, first-principle size-extensive calculations are performed to obtain the solvatochromic shift. Analysis is then made of the origin of the blue shift. Results both at the optimized geometry and in room-temperature liquid water show that hydrogen bonds of water with phenol promote a red shift when phenol is the proton-donor and a blue shift when phenol is the proton-acceptor. In the case of the optimized clusters the calculated shifts are in very good agreement with results obtained from mass-selected free jet expansion experiments. In the liquid case the contribution of the solute–solvent hydrogen bonds partially cancels and the total shift obtained is dominated by the contribution of the outer solvent water molecules. Our best result, including both inner and outer water molecules, is 570 ± 35 cm⁻¹, in very good agreement with the small experimental shift of 460 cm⁻¹ for the absorption maximum.

Etched fiber Bragg grating (EFBG) was coated with diphenilalanine nanotubes (DNT) to produce sensors capable of detecting methanol in methanol-ethanol blend vapors. The DNT was studied in two phases, hexagonal and orthorhombic, which were observed by Raman spectroscopy and scanning electron microscopy (SEM). The temperature transition between the phases was determined through small angle x-ray scattering (SAXS). Considering the methanol concentration in the vapor, the orthorhombic phase showed a sensitivity of -7.3 ± 0.8pm / (%v/v), which was 33 times greater than that observed for the hexagonal phase, with approximately the same response time. The maximum wavelength shift measured was -0.98 ± 0.02nm. Additionally, we proposed a mathematical model to describe the sensor's response, and we hypothesized the mechanisms that could lead to its nonlinear behavior.

This work presents the results of the production and characterization of etched saturated fiber Bragg gratings (ESFBG) functionalized with gold nanoparticles (AuNPs) as a refractive index sensor. Saturated fiber Bragg gratings are produced by directly exposing the phase mask to the laser beam to generate the interference pattern in a hydrogenated fiber. An iris with variable diameter is used to select the central portion of the laser beam; 2mm and 4mm diameters are used to inscribe the gratings. ESFBG exhibits sensitivity over a broader range of refractive indices and a reflection spectrum with greater intensity, even after the deposition of AuNPs on the fiber, and coupling to the HE ₁₂ mode with greater sensitivity. The results show that the ESFBG inscribed with the iris opening of 4mm presented the greatest range of refractive indices possible to be measured. These characteristics show that the ESFBG is a good option for refractive index sensors in which power loss is a limiting factor.

In this paper, we propose a simple nonlinear equation to describe the cross-sensitivity between temperature and refractive index in fiber Bragg grating refractometers. A numerical analysis using Comsol Multiphysics software was performed to understand how the effective index changes with the temperature and refractive index. The sensor response to refractive index (from 1.33 to 1.45) and temperature (from 15 degrees C to 45 degrees C) was fitted using a surface equation. Even though the refractive index range considered being significantly large, and the sensor response being nonlinear, proper concordance between computer simulations and experiments point out that this multivariable equation is suitable to describe the Bragg wavelengths as a function of temperature and refractive index. When applied to multimode fiber Bragg gratings, the proposed equation can be used to construct a system of equations to calculate temperature and refractive index from the measured Bragg wavelengths.