410 research outputs found
Correction of moisture effects on near infrared calibration for the analysis of phenol content in eucalyptus wood extracts
Les méthodes basées sur la spectroscopie proche infrarouge pour estimer les propriétés du bois sont sensibles aux variations des paramètres physiques (température, granulométrie. . . ). Le bois étant un matériau hygroscopique sensible, l'influence de l'humidité sur l'absorbance et l'étalonnage proche infrarouge a été étudiée afin de mieux considérer les possibilités d'applications dans des conditions réelles.Un étalonnage de référence de la quantité de polyphénols présents dans les extraits a été établi à partir de spectres d'une collection de bois d'hybrides d'Eucalyptus urophylla × E. grandis à humidité constante fixée. D'autres spectres ont été obtenus sur des échantillons de même provenance mais à 8 teneurs en eau couvrant une large plage de variation. L'influence de l'humidité sur l'absorbance proche infrarouge puis sur l'estimation par le modèle de référence a été analysée. / Methods based on near infrared spectroscopy used to assess wood properties are susceptible to variations in physical parameters (temperature, grain size, etc). As wood is a hygroscopically sensitive material, we studied the effects of moisure on near infrared absorbance and calibration to accurately determine the application potential of this technique under routine. A collection of Eucalyptus urophylla x E. grandis hybrid wood pieces were analysed to obtain reference calibration of polyphenol contents in wood extracts via NIR spectra acquired under constant moisture conditions.Others specimens from the same source were assessed to obtain spectra for eight moisture contents spanning a broad variation range. The effects of moisture on absorption and on estimates based on a reference model were analysed. An increase in moisture content prompteda rise in near infrared absorption over the entire spectrum and the water O-H absorption bands. The polyphenol content estimates obtained by assessing specimens against the reference calibration at variable moisture contents revealed prediction bias. Five correction methods were then tested on enhance the robustness relative to moisture. In-depth calibration and external parameter orthogonalization were found to be the most efficient methods for offsetting this factor
Oakscan: procédé de mesure rapide et non destructif des polyphénols du bois de chêne de tonnellerie
Les polyphénols extractibles contenus dans le bois de chêne des barriques de tonnellerie sont des composés très importants car ils ont une influence sur la couleur et sur les propriétés organoleptiques des vins qu'ils enrichissent. Les analyses chimiques de laboratoire qui permettent de les mesurer sont réalisées sur des extractions, nécessitent un délai de réalisation très long et ne permettent d'analyser que des lots de matière par échantillonnage. Le procédé de mesure rapide et non destructif Oakscan® a été développé par la tonnellerie Radoux. Il se fonde sur la spectrométrie proche infrarouge et permet de mesurer la teneur en polyphénols en quelques secondes, directement sur le bois massif. Le contenu polyphénolique de chaque douelle est alors mesuré, permettant une meilleure maitrise de la matière première entrant dans la composition des fûts
Flavonoids in phylloclades discriminate endemic Semele androgyna chemotypes from Madeira
Thirty-five randomly-collected Semele androgyna Kunth
samples were screened by RP-HPLC for their phenolic
composition. Fraction analysis allowed the detection of
17 different compounds. According to their retention
times and UV spectra obtained by diode array analysis,
these phenolics represent three classes: phenolic
acids, flavones and flavonols. Co-chromatography with
specific standards enabled identification of quercetin,
rutin and quercitrin in Semele tissues for the first time.
Polymorphism based on phenolic composition was
evaluated using multivariate analysis and showed four
distinct S. androgyna clusters. This polymorphism was
not associated with morphological diversity or different
in ambient light intensities. Biochemical differentiation
is thus present in this species. The application of
multivariate analysis techniques to RP-HPLC data has
allowed the classification of samples into two groups,
previously proposed on the basis of morphological and
cytotaxonomical information. Therefore, the use of
phenolics as chemotaxonomic markers in Semele is
highly recommended because of its diagnostic value,
even at a subspecies level. Discriminant canonical
analysis and Mahalanobis distances confirmed these
clusters as recognisable chemosystematic units.
However, these units do not support the separation of S.
pterygophora.The Portuguese Foundation for Science and
Technology (FCT) funded this work through the Centre of Macaronesian
Studies (CEM). The authors are grateful to the Madeiran Centre of
Science and Technology (CITMA), the Berardo Foundation and
European Social Funding for financial assistance given during execution
of this work. The assistance rendered by Mr Rogério Correia during field
collection is gratefully acknowledged.info:eu-repo/semantics/publishedVersio
Search for composite and exotic fermions at LEP 2
A search for unstable heavy fermions with the DELPHI detector at LEP is
reported. Sequential and non-canonical leptons, as well as excited leptons and
quarks, are considered. The data analysed correspond to an integrated
luminosity of about 48 pb^{-1} at an e^+e^- centre-of-mass energy of 183 GeV
and about 20 pb^{-1} equally shared between the centre-of-mass energies of 172
GeV and 161 GeV. The search for pair-produced new leptons establishes 95%
confidence level mass limits in the region between 70 GeV/c^2 and 90 GeV/c^2,
depending on the channel. The search for singly produced excited leptons and
quarks establishes upper limits on the ratio of the coupling of the excited
fermio
Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using
data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000.
The corresponding integrated luminosity is 650 pb^{-1}. The values of the
cross-section obtained are found to be in agreement with QED predictions.
Limits on the anomalous magnetic and electric dipole moments of the tau lepton
are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.
Evidence for an Excess of Soft Photons in Hadronic Decays of Z^0
Soft photons inside hadronic jets converted in front of the DELPHI main
tracker (TPC) in events of qqbar disintegrations of the Z^0 were studied in the
kinematic range 0.2 < E_gamma < 1 GeV and transverse momentum with respect to
the closest jet direction p_T < 80 MeV/c. A clear excess of photons in the
experimental data as compared to the Monte Carlo predictions is observed. This
excess (uncorrected for the photon detection efficiency) is (1.17 +/- 0.06 +/-
0.27) x 10^{-3} gamma/jet in the specified kinematic region, while the expected
level of the inner hadronic bremsstrahlung (which is not included in the Monte
Carlo) is (0.340 +/- 0.001 +/- 0.038) x 10^{-3} gamma/jet. The ratio of the
excess to the predicted bremsstrahlung rate is then (3.4 +/- 0.2 +/- 0.8),
which is similar in strength to the anomalous soft photon signal observed in
fixed target experiments with hadronic beams.Comment: 37 pages, 9 figures, Accepted by Eur. Phys. J.
Study of Inclusive J/psi Production in Two-Photon Collisions at LEP II with the DELPHI Detector
Inclusive J/psi production in photon-photon collisions has been observed at
LEP II beam energies. A clear signal from the reaction gamma gamma -> J/psi+X
is seen. The number of observed N(J/psi -> mu+mu-) events is 36 +/- 7 for an
integrated luminosity of 617 pb^{-1}, yielding a cross-section of
sigma(J/psi+X) = 45 +/- 9 (stat) +/- 17 (syst) pb. Based on a study of the
event shapes of different types of gamma gamma processes in the PYTHIA program,
we conclude that (74 +/- 22)% of the observed J/psi events are due to
`resolved' photons, the dominant contribution of which is most probably due to
the gluon content of the photon.Comment: 13 pages, 8 figures, Accepted by Phys. Lett.
CP asymmetry in in a general two-Higgs-doublet model with fourth-generation quarks
We discuss the time-dependent CP asymmetry of decay in an
extension of the Standard Model with both two Higgs doublets and additional
fourth-generation quarks. We show that although the Standard Model with
two-Higgs-doublet and the Standard model with fourth generation quarks alone
are not likely to largely change the effective from the decay of
, the model with both additional Higgs doublet and
fourth-generation quarks can easily account for the possible large negative
value of without conflicting with other experimental
constraints. In this model, additional large CP violating effects may arise
from the flavor changing Yukawa interactions between neutral Higgs bosons and
the heavy fourth generation down type quark, which can modify the QCD penguin
contributions. With the constraints obtained from processes
such as and , this model can lead to the
effective to be as large as in the CP asymmetry of .Comment: 13 pages, 5 figures, references added, to appear in Eur.Phys.J.
Energy dependence of Cronin momentum in saturation model for and collisions
We calculate dependence of Cronin momentum for and
collisions in saturation model. We show that this dependence is consistent with
expectation from formula which was obtained using simple dimentional
consideration. This can be used to test validity of saturation model (and
distinguish among its variants) and measure dependence of saturation
momentum from experimental data.Comment: LaTeX2e, 12 pages, 8 figure
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