Use of chemometrics to characterize tropical wines from different vintages and grape cultivars according to the 1H NMR spectroscopy data.

Resumo

Use of chemometrics to characterize tropical wines from different vintages and grape cultivars according to the 1H NMR spectroscopy data.

Tropical wines have been produced in Northeast of Brazil since 1980's, between the 8° and 9° S latitude, in a region called Sub-rniddle São Francisco river Valley. This area presents an intra-annual climate variability and wines can be elaborated in different months of the year, according to the winery, with different analytical characteristics due to the climatic conditions. NMR spectroscopy is an interesting tool that allows to determine in a single analysis many analytical compounds of the wines. PCA and PLS rnultivariate statistical analyses applied on NMR data allow to discriminate samples and to identify the responsible compounds for the clustering. The aim of this work was to use chemometrics, PCA and PLS, applied on IH NMR spectroscopy data, to characterize tropical wines from different vintages and grape cultivars, in Northeast of Brazil. Wines were elaborated by using traditional winemaking process with control of the fermentations temperature and use of antioxidants. Before statistical analyses, IHNMR spectra were segmented, normalized, converted to Excel software format and further processed for PCA and PLS analyses. Statistical analyses applied on NMR spectra data were not satisfactory to discriminate between different vintages of white and red wines together, but they were able to separate each one according to different vintages and cultivars. Metabolic compounds were found to explain wine clusters, and fingerprints are discussed

Metabolic profiles of Brazilian tropical wines determined by H NMR spectroscopy and chemometrics.

Tropical wines are a new concept of vitiviniculture that is being developped principally in Brazil

Simulating data envelopment analysis using neural networks: a new paradigm of efficiency measurement.

This article studies the creation of efficiency measurement structures of Decision-Making Units (DMUs) by using high-speed optimisation modules, inspired in the idea of an unconventional Artificial Neural Network (ANN) and numerical methods. In addition, the Linear Programming Problem (LPP) inherent in the Data Envelopment Analysis (DEA) methodology is transformed into an optimisation problem without constraints, by using a pseudo-cost function, including a penalty term, causing high cost every time one of the constraints is violated. The LPP is converted into a differential equations system. A non-standard ANN implements a numerical solution based on the gradient method

Unified description of the dc conductivity of monolayer and bilayer graphene at finite densities based on resonant scatterers

We show that a coherent picture of the dc conductivity of monolayer and bilayer graphene at finite electronic densities emerges upon considering that strong short-range potentials are the main source of scattering in these two systems. The origin of the strong short-range potentials may lie in adsorbed hydrocarbons at the surface of graphene. The equivalence among results based on the partial-wave description of scattering, the Lippmann-Schwinger equation, and the T-matrix approach is established. Scattering due to resonant impurities close to the neutrality point is investigated via a numerical computation of the Kubo formula using a kernel polynomial method. We find that relevant adsorbate species originate impurity bands in monolayer and bilayer graphene close to the Dirac point. In the midgap region, a plateau of minimum conductivity of about $e^2/h$ (per layer) is induced by the resonant disorder. In bilayer graphene, a large adsorbate concentration can develop an energy gap between midgap and high-energy states. As a consequence, the conductivity plateau is supressed near the edges and a "conductivity gap" takes place. Finally, a scattering formalism for electrons in biased bilayer graphene, taking into account the degeneracy of the spectrum, is developed and the dc conductivity of that system is studied.Comment: 25 pages, 13 figures. published version: appendixes improved, references added, abstract and title slightly changed, plus other minor revision

Astrometry of the main satellites of Uranus: 18 years of observations

We determine accurate positions of the main satellites of Uranus: Miranda, Ariel, Umbriel, Titania, and Oberon. Positions of Uranus, as derived from those of these satellites, are also determined. The observational period spans from 1992 to 2011. All runs were made at the Pico dos Dias Observatory, Brazil. We used the software called Platform for Reduction of Astronomical Images Automatically (PRAIA) to minimise (digital coronography) the influence of the scattered light of Uranus on the astrometric measurements and to determine accurate positions of the main satellites. The positions of Uranus were then indirectly determined by computing the mean differences between the observed and ephemeris positions of these satellites. A series of numerical filters was applied to filter out spurious data. These filters are mostly based on the comparison between the positions of Oberon with those of the other satellites and on the offsets as given by the differences between the observed and ephemeris positions of all satellites. We have, for the overall offsets of the five satellites, -29 (+/-63) mas in right ascension and -27 (+/-46) mas in declination. For the overall difference between the offsets of Oberon and those of the other satellites, we have +3 (+/-30) mas in right ascension and -2 (+/-28) mas in declination. Ephemeris positions for the satellites were determined from DE432+ura111. Comparisons using other modern ephemerides for the solar system -INPOP13c- and for the motion of the satellites -NOE-7-2013- were also made. They confirm that the largest contribution to the offsets we find comes from the motion of the barycenter of the Uranus system around the barycenter of the solar system, as given by the planetary ephemerides. Catalogues with the observed positions are provided.Comment: 13 pages, 21 figure