Screening of antioxidant properties of the apple juice using the front-face synchronous fluorescence and chemometrics

Fluorescence spectroscopy is gaining increasing attention in food analysis due to its higher sensitivity and selectivity as compared to other spectroscopic techniques. Synchronous scanning fluorescence technique is particularly useful in studies of multi-fluorophoric food samples, providing a further improvement of selectivity by reduction in the spectral overlapping and suppressing light-scattering interferences. Presently, we study the feasibility of the prediction of the total phenolics, flavonoids, and antioxidant capacity using front-face synchronous fluorescence spectra of apple juices. Commercial apple juices from different product ranges were studied. Principal component analysis (PCA) applied to the unfolded synchronous fluorescence spectra was used to compare the fluorescence of the entire sample set. The regression analysis was performed using partial least squares (PLS1 and PLS2) methods on the unfolded total synchronous and on the single-offset synchronous fluorescence spectra. The best calibration models for all of the studied parameters were obtained using the PLS1 method for the single-offset synchronous spectra. The models for the prediction of the total flavonoid content had the best performance; the optimal model was obtained for the analysis of the synchronous fluorescence spectra at Delta lambda = 110 nm (R (2) = 0.870, residual predictive deviation (RPD) = 2.7). The optimal calibration models for the prediction of the total phenolic content (Delta lambda = 80 nm, R (2) = 0.766, RPD = 2.0) and the total antioxidant capacity (Delta lambda = 70 nm, R (2) = 0.787, RPD = 2.1) had only an approximate predictive ability. These results demonstrate that synchronous fluorescence could be a useful tool in fast semi-quantitative screening for the antioxidant properties of the apple juices.info:eu-repo/semantics/publishedVersio

Nuclear astrophysics with radioactive ions at FAIR

The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process, β-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes

On the third-order coefficients of the tail of the direct correlation function: new computational direction

A practical scheme is here presented for the numerical calculation of the tail of the directcorrelation function. The procedure is shown to lead to accurate values for all the rootedcluster integrals in the tail function which are proportional to ρ3. The derived expressionsare shown to be correct and reliable at all temperatures by comparison with the knownanalytical results for the Gaussian potential function and certain irreducible clusterdiagrams that occur in the 5th virial coefficient

Group contribution method for estimating the critical pressures of C1C20 n-alkanes

To develop a new and useful method for evaluating and predicting the critical pressures ( Pc )of n-fatty acids and esters, logarithmic equations were developed that correlate, with goodagreement, the n-fatty acid and ester critical pressures with the corresponding n-alkanecritical pressure. The test with n-alkanes showed that even without the compressibility factor( ΔZb ), the error in estimated Pc was never more than about 20%. However, when ΔZb isestimated from an equation of state, the error is never more than 10%; indeed the majority of the values lie around 5%.Key Words: critical pressures, n-alkanes, enthalpies of vapourisation, Trouton’s rule,Clausius-Clapeyron equation

Extended integral-equation theories for Lennard-Jones fluids

19-29The Percus-Yervick (PY) integral-equation has been extended and used to determine structural and thermodynamic properties of a Lennard-Jones (LJ) fluid. The PY theory has been extended by calculating the coefficients, up to the thirdorder in density, of the tail function when the latter is expanded as a power series. For a LJ fluid , the resulting integralequation is exact at the level of the 5th virial coefficient. The properties obtained from the new procedure have been compared with a virial equation of state truncated after the 5th coefficient, computer simulation data and two empirical closures proposed by others. Excellent agreement has been obtained with simulation data for compression factor in the entire gas-phase region, excluding the critical region. The radial distribution function calculated from the method is in very good agreement with simulation data at supercritical temperatures and a density which is greater than the critical value by almost one-third. The tail functions which result from the approximate theories, at super-critical temperatures where data are available for comparison, compare poorly with simulation data at separations within the potential core and at long- range; there is only a fair agreement at intermediate separations at the lowest density examined