Evaluation of a Brazilian ion chromatography interlaboratory study

This paper describes a Brazilian interlaboratory program study on anion measurement in synthetic water. The program described is promoted regularly since 2007 and recommended the use of ion chromatography as analytical technique for all participant laboratories. Two samples (X and Y) with different anion (fluoride, chloride, nitrite-N, nitrate-N, sulfate and phosphate-P) concentration levels were twice distributed in 2011. Each sample on each round had the homogeneity, and the stability tested for a period of 15 days. Upon ensuring the homogeneity and stability, the samples were distributed to 39 laboratories located around the country. The aim of this study was to verify the laboratories’ precision and to establish the measurement comparability among Brazilian laboratories that routinely use ion chromatography for water sample analysis. It was also possible to identify the most frequent sources of systematic and random errors for each measured anion, related to the ion chromatography technique. Some specific metrological issues related to the geographical region are discussed.     

ASBR Applied to the Treatment of Biodiesel Production Effluent: Effect of Organic Load and Fill Time on Performance and Methane Production

The effect of organic matter and fill time on anaerobic sequencing batch reactor (5 L, 30°C, 8-h cycles, 50 rpm) efficiency has been analyzed. Organic matter was increased by the influent concentration. Fill times investigated were in the batch mode and fed-batch followed by batch. In the batch mode organic matter removal were 93%, 81%, and 66% for influent concentration of 500, 1,000, and 2,000 mgCOD/L (0.6, 1.29, and 2.44 gCOD/L.d), respectively. At 3,000 mgCOD/L (3.82 gCOD/L.d) operational stability could not be achieved. Removal efficiency was improved by increasing the fill time, and was 85% for the 1,000 mgCOD/L condition and fill times of 2 and 4 h, and 80 and 77% for the 2,000 mgCOD/L condition and fill times of 2 and 4 h, respectively. Hence, gradual feeding seemed to improve and to smooth the profiles of organic matter and volatile acids along the cycle with 78 to 96 NmLCH₄/gCOD.     

Biocompatible and fluorescent polycaprolactone/silk electrospun nanofiber yarns loaded with carbon quantum dots for biotextiles

Carbon quantum dots (CDs) are attractive nanoparticles for several applications, due to inherent properties such as excitation dependent photoluminescence emission and chemical stability. In the present work, we synthesized CDs from silk (Bombyx Mori) by a microwave‐assisted method. The resultant spherical nanoparticles with high fluorescence under UV light were incorporated into PCL/silk matrix and electrospun into continuous nanofiber yarns (NF‐Ys) by a one‐step method. Besides granting yarns fluorescence, CD inclusion contributed to a decrease in fiber diameter and an increase in strength by 2.7‐fold. Cell viability studies with mammalian lung cell lines show viability above 80%, suggesting good biocompatibilty. Such yarns show the potential to be assembled into larger structures such as biotextiles, with possible multifunctionalities such as antiviral, antibacterial, and biosensing applications.     

Uncertainty measurement evaluation of WDXRF and EDXRF techniques for the Si and U<Subscript>total</Subscript> determination in U<Subscript>3</Subscript>Si<Subscript>2</Subscript> nuclear fuel

Uranium silicide (U₃Si₂), 20% ²³⁵U enriched powder, is an intermetallic compound used as nuclear fuel material, which is the state-of-the-art among nuclear fuel materials used in modern research reactors. It is produced by IPEN and used as nuclear fuel of the IEA-R1 reactor (IPEN/CNEN, São Paulo, Brazil); U₃Si₂ has 92.3 wt% U_total and 7.7 wt% Si. The qualification of this material requires chemical and physical tests such as Si and U_total content, isotope ratio, impurities, density, specific surface area and particle size determination. The Si and U_total were determined by gravimetric and volumetric procedures. Usually, these classical methods require a long time for analyses and are expensive. The objective of this study was to establish a fast and efficient analytical method to meet ISO/IEC 17025:2005 requirements in the Si and U_total determination. The X-ray fluorescence techniques (XRF) were chosen to allow a direct and non-destructive analysis, what is the main advantage compared to other instrumental techniques, since previous chemical treatments are not necessary. In this study, the performance of the wavelength dispersive (WDXRF) and energy dispersive (EDXRF) X-ray fluorescence techniques was evaluated. Furthermore, two different sample preparation procedures, plain powdered and pressed powdered, were evaluated. Statistical tools were used to evaluate the results and a comparison between these results and the conventional methods was done.     

Sub-Doppler optical one-photon spectroscopy of binary mixtures of neutral,mutually interacting gases with lasers: dispersion spectra

We consider in this paper the optical, sub-Doppler high resolution dispersion spectra for one-photon transitions of a mixture of two different interacting gases. The gases are supposed to be neutral and each molecule of the mixture interacts with molecules of the same kind and with molecules of different kinds, via hard collisions. Those interactions are restricted to binary collisions treated in the so-called impact approximation. We calculate the dispersion optical sub-Doppler spectra of a weak laser beam in the presence of a strong, saturating, counterpropagating laser one. The optical fields of both lasers are supposed to be travelling electromagnetic plane monochromatic waves. The angular frequencies ω₁ and ω₂ of those waves are taken, in general as different. An appropriate parametrizing procedure of all the physical quantities involved for treating this problem is taken.     

Differential sub-Doppler,one-photon,optical absorption spectroscopy of gases,and vapors with lasers

We consider in this work a high resolution, Doppler-free, one-photon, optical absorption differential spectroscopy of a mixture of two different mutually interacting gases or vapors in order to display the effects of this interaction directly in the optical spectra. Those interactions are restricted to binary collisions and they are treated in the so-called impact approximation (hard collisions). Usually, the high resolution, Doppler-free optical spectra are observed when two counterpropagating laser beams pass through the gas cell. One beam is strong enough to saturate the optical transition to several different degrees. The other beam is a weak probe absorbed by the saturated atomic or molecular pair of energy levels (a two-energy level system with angular frequency ω₀). The laser beams are supposed to have different angular frequencies and to be linearly polarized. In order to achieve the Doppler-free differential optical absorption one-photon spectra, a convenient geometrical experimental set up is proposed.     

Chemical and microstructural characterization of remelted Zircaloy by X-ray fluorescence techniques and metallographic analysis

Brazilian nuclear power reactor (PWR type) use, as nuclear fuel, sintered UO₂ pellets with Zircaloy cladding. The cladding material has to present high mechanical strength and corrosion resistance, which are related to the material chemical composition and microstructural characteristics. Zircaloy machining scraps were remelted using VAR process, resulting in a billet, and its elemental composition was determined. The major elements Zr, Sn, Fe, Cr and Ni were determined by EDXRFS; Hf and contaminants were determined by WDXRFS. The chemical analysis did not show changes in the alloy elemental composition, except for Fe and Cr, which their out-off content can be attributed to contamination from steel scraps. The found Cu contamination may be related to the contact of the melted Zircaloy droplets with copper crucible. The billet microstructure was evaluated using optical and scanning electron microscopy and showed the typical zirconium alloy microstructures (needle and plates) resulting from the high cooling rate and thermal gradients, present during the solidification.     

Modulation of the pharmacological activities of secretory phospholipase A2 from Crotalus durissus cascavella induced by naringin

In this work we have characterized the action of the naringin, a flavonoid found in grapefruit and known for its various pharmacological effects, which include antioxidant blood lipid lowering and anticancer activity, on the structure and biochemical activities of a secretory phospholipase A (sPLA2) from Crotalus durissus cascavella, an important protein involved in the releasinge of arachidonic acid in phospholipid membranes. sPLA2 was incubated with naringin (mol:mol) at 37 °C and a discrete reduction in the UV scanning signal and a modification of the circular dichroism spectra were observed after treatment with naringin, suggesting modifications of the secondary structure of the protein. This flavonoid was able to decrease enzymatic activity and some pharmacological effects, such as myonecrosis, platelet aggregation, and neurotoxic activity caused by sPLA2, however, the inflammatory effect was not affected by naringin. In addition, small angle X-ray scattering (SAXS) data were collected for sPLA2 and naringin-treated sPLA2 to evaluate possible modifications of the protein structure. These structural investigations have shown that sPLA2 is an elongated dimer in solution and after treatment with naringin a conformational change in the dimeric configuration was observed. Our results suggest that structural modification may be correlated with the loss of enzymatic activity and alterations in pharmacological properties.     

Cytotoxicity of active ingredients extracted from plants of the Brazilian "Cerrado"

Cytotoxicity assays are needed for the screening of natural products with potential anti-inflammatory. The purpose of this study was to compare the basal cytotoxicity of active ingredients extracted from plants of the Brazilian "cerrado". The viability was assayed with the neutral red uptake assay in Mac Coy cells after 24h of exposition. The dose evaluated was 50 microg/microL. The test substances were: cinnamic acid, p-coumaric acid, chlorogenic acid, syringic acid, vannilic acid, homogentisic acid, scandenin, palustric acid, diosgenin, cabraleone. Studies of cytotoxicity demonstrated that all active compounds evaluated have low toxicity in vitro. The substances showed cell viability above 60% for the concentration used. However, the cinnamic acid, sacandenin and palustric acid showed highest toxicity with a 50% reduction in cell viability for the dose of 50 microg/microL. Cytotoxic screening results are useful to estimate the best concentrations of those compounds with potential anti-inflammatory without their cause cell death.     

Application of multivariate calibration for simultaneous determination of major and minor constituents in U3Si2 by WDXRF technique

The aim of this work was to implement and to validate the multivariate calibration for simultaneous determination of major and minor constituents in uranium nuclear fuel by WDXRF technique. The method is nondestructive and involves no chemical treatments thus is possible to perform fast chemical analysis and produces no hazardous waste. The precision and accuracy achieved are statistically comparable to others sensitive techniques like ICP-OES for impurities determination.