A topological assessment of the electronic structure of mesoionic compounds

Mesoionic compounds belonging to the 1,3‐oxazol‐5‐one, 1,3‐diazole‐4‐thione and 1,3‐thiazole‐5‐thione rings have been evaluated by a combination of Density Functional Theory, Quantum Theory of Atoms in Molecules, Electron Localization Function, Natural Bond Orbitals and Geodesic Electrostatic Potential Charge calculations. Atomic, bond, and ring properties have been considered to describe the electronic structure of mesoionic compounds. The results show that not only the ring type, but also the substituent groups have great influence on these properties. In addition, there is a significant and heterogeneous π‐bonding contribution throughout the mesoionic rings. Finally, we conclude that some classical conceptions of charge localization and π‐bonding contribution in these compounds are misleading or incomplete. © 2015 Wiley Periodicals, Inc.     

Trace elements determination in red and white wines using total-reflection X-ray fluorescence

Several wines produced in different regions from south of Brazil and available in markets in Rio de Janeiro were analyzed for their contents of elements such as: P, S, Cl, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb and Sr. Multi-element analysis was possible with simple sample preparation and subsequent analysis by total-reflection X-ray fluorescence using synchrotron radiation. The measurement was carried at the X-ray fluorescence beamline in the Synchrotron Light Source Laboratory in Campinas, Brazil. The levels of the various elements obtained were lower in the Brazilian wines than the values generally found in the literature. The present study indicates the capability of multi-element analysis for determining the contents of various elements present in wines coming from Brazil vineyards by using a simple, sensitive and precise method.     

Synthesis of 1,2,3-triazole derivatives and in vitro antifungal evaluation on Candida strains

1,2,3-Triazoles have been extensively studied as compounds possessing important biological activities. In this work, we describe the synthesis of ten 2-(1-aryl-1H-1,2,3-triazol-4-yl)propan-2-ols via copper catalyzed azide alkyne cycloaddition (CuAAc or click chemistry). Next the in vitro antifungal activity of these ten compounds was evaluated using the microdilution broth method against 42 isolates of four different Candida species. Among all tested compounds, the halogen substituted triazole 2-[1-(4-chlorophenyl)-1H-(1,2,3)triazol-4-yl]propan-2-ol, revealed the best antifungal profile, showing that further modifications could be done in the structure to obtain a better drug candidate in the future.     

Characterization of carbonate rocks through X-ray microfluorescence and X-ray computed microtomography

Carbonate rocks play an important role in petroleum geology by acting as reservoir rocks, generators, and even hydrocarbon sealants, accounting for about half of the oil and gas reserves known in the world. The study of these carbonate rocks have become very important in the hydrocarbon exploration scene in Brazil because of they consist in analogous for reservoir rocks of the presalt interval. Thus, the objective of this research was to use X-ray microfluorescence (micro-XRF) and X-ray microtomography analysis, as complementary techniques, in order to characterize samples of carbonate rocks in respect to their structures, textures, mineralogy, and pores. The microtomographic analyses allowed the identification of the horizontal structures as parallel lamination, horizontal, and vertical fractures filled by calcite and biotic constituents (gastropods bioclasts). Different composition of minerals were also identified, as calcite, quartz, feldspars, iron sulfides, and oxides. The porosity (ranges <1 to17%), and the high-density elements could also be quantified, as well as their distribution in each sample. The micro-XRF analysis present a direct relationship with the distribution of minerals that compound carbonate rocks, highlighting some structures, as well as helping to identify trace and minor elements in the carbonates (Mn, Sr, and Mg).     

Behaviour of Low Molecular Weight Compounds,Iron and Copper of Wine Spirit Aged with Chestnut Staves under Different Levels of Micro-Oxygenation

Alternative technologies for a more sustainable wine spirits’ ageing have been studied but a lack of knowledge on the effect of oxygenation level remains. This work examined the behaviour of low molecular weight compounds, iron and copper of a wine spirit aged in 50 L demijohns with chestnut wood staves combined with three levels of micro-oxygenation or nitrogen. Compounds and mineral elements were quantified by HPLC and FAAS, respectively, in samples collected at 8, 21, 60, 180, 270 and 365 days of ageing. Results showed that most of the compounds underwent significant changes in their content over time and behave differently depending on the wine spirit’s oxygenation level: higher contents of gallic acid, syringic acid and vanillin were associated with lower micro-oxygenation level while higher contents of ellagic acid, syringaldehyde, coniferaldehyde and sinapaldehyde resulted from higher one; lowest contents of these compounds were found in the nitrogen modality. Weak correlation between copper and the studied compounds was evidenced whereas closer relationship between iron, vanillin, gallic, syringic and ellagic acids at end of ageing was observed. This study provides innovative information on the role of oxygen in wine spirit’s ageing, and on chestnut wood effect on wine spirit’s mineral composition.     

Crude oil analysis by X-ray scattering technique

Composed of hydrocarbons and other substances, petroleum is classified as a nonrenewable source of energy. In its unrefined form, it is called crude oil. Currently, its derivates are widely used in domestic and industrial environments, with the greatest exponent being motor fuels and lubricating oils. Due to the overwhelming demand, new oil wells in the presalt region of Brazil are going to be drilled, which will, in its turn, increase the demand for analysis and require the use of less costly technologies. The purpose of this paper is to present an experimental method that aims at characterizing crude oil samples through their X-ray scattering profiles without the need for any chemical preparation to be performed in advance, which will enable this method to be used for analyzing samples immediately after their extraction. For the experiment, a portable X-ray scattering system composed by an X-ray tube (silver anode) and a Si-PIN detector was used in order to analyze samples from different wells. The process consisted in establishing a linear relationship between the effective atomic number and the ratio between peak intensities of Compton and Rayleigh scattering from known samples. The linear function, verified experimentally, was then applied to samples of crude oil, and the results showed that it is possible to characterize them on the basis of the Rayleigh to Compton scattering ratio. After the analysis, a multiple comparison test performed on the samples proved that this methodology indeed allows to differentiate samples of different origins and to verify the compatibility of samples extracted from the same well.     

Evaluation of the structural characteristics and the fading effects of image plates

The photostimulated luminescence (PSL) is the basis for the digital image formation of image plates (IPs). However, the PSL decreases exponentially with the increasing of the elapsed time between the exposure and the IP scanning (t), and consequently, there is a fading of the digital image. The purpose of this paper is to investigate the relationship between IPs physical structure and elemental composition with the fading behavior. Three different types of IPs, with distinct resolutions, were analyzed. The fading behavior with the time, t, has been measured and correlated with their physical structure. Furthermore, micro X-ray fluorescence (μXRF) analysis was used to provide information on the elemental composition of this layer. The results showed that standard resolution plate have larger grains, thicker sensitive layer, and generate a bigger effect of image fading. The μXRF technique showed that, to compensate the low emission, the high-resolution IP has a higher concentration of Br and Sr.     

Disentangling the effects of phonation and articulation: Hemispheric asymmetries in the auditory N1m response of the human brain

Background  

The cortical activity underlying the perception of vowel identity has typically been addressed by manipulating the first and second formant frequency (F1 & F2) of the speech stimuli. These two values, originating from articulation, are already sufficient for the phonetic characterization of vowel category. In the present study, we investigated how the spectral cues caused by articulation are reflected in cortical speech processing when combined with phonation, the other major part of speech production manifested as the fundamental frequency (F0) and its harmonic integer multiples. To study the combined effects of articulation and phonation we presented vowels with either high (/a/) or low (/u/) formant frequencies which were driven by three different types of excitation: a natural periodic pulseform reflecting the vibration of the vocal folds, an aperiodic noise excitation, or a tonal waveform. The auditory N1m response was recorded with whole-head magnetoencephalography (MEG) from ten human subjects in order to resolve whether brain events reflecting articulation and phonation are specific to the left or right hemisphere of the human brain.