A new algorithm to handle finite nuclear mass effects in electronic calculations: the ISOTOPE program

We report the development of a simple algorithm to modify quantum chemistry codes based on the LCAO procedure, to account for the isotope problem in electronic structure calculations. No extra computations are required compared to standard Born-Oppenheimer calculations. An upgrade of the Gamess package called ISOTOPE is presented, and its applicability is demonstrated in some examples.     

Instrumental factors influencing absorption measurements for fluid food color determination

The differences in color coordinates obtained from the use of different spectral features in the calculation are studied. Seven groups of food (olive oil, vanilla milkshake, brandy, honey, grape juice, vinegar, and orange juice) and an anthocyanin petunidin solution (natural pigment present in several vegetables) with different pH values were selected. Tristimulus values were calculated by considering the different sources of errors (truncation, abridgement, or different bandwidths). Results obtained were corrected by using the methods recommended (see References). These methods of abridgment work well in general, although in some circumstances (20 nm bandwidth or larger), specific spectral weighting functions have to be used to obtain a negligible error. Therefore, it is interesting to know how much difference can be expected from those factors in order to avoid confusion between color differences attributable to instruments and those attributable to actual color changes.     

New high-nuclearity Ni-Pt carbonyl clusters: synthesis and X-ray structure of the ordered [HNi24Pt17(CO)46]5- and the substitutionally Ni/Pt disordered [Ni32Pt24(CO)56]6- cluster anions

Condensation between preformed Ni-Pt and Pt carbonyl clusters leads to the new [H(6-n)Ni(24)Pt(17)(CO)(46)](n-)(n= 5, 6) and the substitutionally Ni/Pt disordered [Ni(24)(Ni(12-x)Pt(x))Pt(20)(CO)(56)](6-) (x = 4) carbonyl clusters, the latter of which represents the highest nuclearity homoleptic carbonyl cluster anion so far reported.     

A new Ru complex capable of catalytically oxidizing water to molecular dioxygen

We have prepared three new dinuclear ruthenium complexes having the formulas [Ru2II(bpp)(trpy)2(mu-L)]2+ (L = Cl, 1; L = AcO, 2) and [Ru2II(bpp)(trpy)2(H2O)2]3+ (3). The three complexes have been characterized through the usual spectroscopic and electrochemical techniques and, in the cases of 1 and 2, the X-ray crystal structures have been solved. In aqueous acidic solution, the acetato bridge of 2 is replaced by aqua ligands, generating the bis(aqua) complex 3 which, upon oxidation to its RuIVRuIV state, has been shown to catalytically oxidize water to molecular oxygen. The measured pseudo-first-order rate constant for the O2-evolving process is 1.4 x 10-2 s-1, more than 3 times larger than the higher one previously reported for Ru-O-Ru type catalysts. This new water-splitting catalyst also has improved stability with regard to any previously described, achieving a total of 18.6 metal cycles.     

Comparison of different calibration methods for the determination by FT-NIR spectroscopy of the hydroxyl number in polyester resins

Different calibration methods have been applied for the determination of the Hydroxyl Number in polyester resins, namely Partial Least Squares (PLS), Principal Component Regression (PCR), Ordinary Least Squares with selection of the variables by genetic algorithm (OLS-GEN) and back-propagation Artificial Neural Networks (BP-ANN). The predictive ability of the regression models was estimated by splitting the dataset in training and test sets by application of the Kohonen self-organising maps. The linear methods (OLS-GEN, PLS and PCR) showed comparable results while artificial neural networks provided the best results both in fitting and prediction.     

Total reflection X-ray fluorescence polymer spectra: classification by taxonomy statistic tools

The aim of this work is to explore the use of chemometric tools for the classification of synthetic and natural polymers with a mean molecular weight greater than 10(6). Total Reflection X-Ray Fluorescence (TXRF) spectra were obtained and analyzed in order to retrieve matrix information and to illustrate the calibration procedure. The intensities of the coherent and incoherent scattered peaks were specially selected for this purpose. The polymers studied were aqueous solutions of scleroglucan, polyacrilamide, polyoxyethylene oxide, glucomannan, 2,3,6-tri-o-ethylamylose and xhantan, in concentrations upto 1% (m/m). matlab software was used for numerical calculations. Using a combination of principal component analysis and cluster analysis, the differences in composition of various analyzed polymers can be visualized.     

Inexpensive isolation of beta-D-glucopyranosidase from alpha-L-arabinofuranosidase,alpha-L-rhamnopyranosidase,and o-acetylesterase

β-d-Glucopyranosidase (βG, EC 3.2.1.21) has been isolated from some collateral activities, α-l-arabinofuranosidase (Ara, EC3.2.1.55), α-l-rhamnopyranosidase (Rha, EC 3.2.1.40), and o-acetylesterase (Est, EC 3.1.1.53), using a commercial enzyme preparation and a simple method economically sustainable for the food industry. The procedure comprises precipitation of extraneous substances by adding ethanol and CaCl₂, ultrafiltration, and adsorption, first on bentonite and then on chitosan. The results obtained were the complete isolation of βG from the above-mentioned activities, a drastic reduction in extraneous compounds, such as brown substances and polysaccharides, and a slight increase in purification.     

Hydrophobicity of peritoneal tissues in the rat

In this study, an inventory of the hydrophobicity of peritoneal tissues in the living rat was made. Peritoneal tissues were divided into mesentery (i.e., omentum) and parietal and visceral peritoneum and their hydrophobicity was determined by the sessile drop method. All peritoneal tissues were hydrophilic with water contact angles varying from 0 degrees to 61 degrees. Mesentery and visceral peritoneum covering the intestines were significantly more hydrophilic than parietal and other visceral peritoneal tissues. In general, visceral peritoneum was the most hydrophobic tissue, and visceral peritoneum covering the kidneys (61 degrees) and the stomach (54 degrees) was less hydrophilic than that covering the rest of the organs, i.e., spleen (49 degrees), liver (45 degrees), and bladder (41 degrees). In summary, peritoneal tissues involved in adsorptive and exchange functions and requiring lubrication are more hydrophilic than tissues with more important and protective functions.     

Finite Element Matrix Sequences: the Case of Rectangular Domains

In the present paper, we consider a preconditioning strategy for Finite Element (FE) matrix sequences {A _n (a)} _n discretizing the elliptic problem $$\left\{ \begin{gathered} A_a u \equiv ( - )^k \nabla ^k [a(x,y)\nabla ^k u(x,y)] = f(x,y),{ }(x,y) \in \Omega = (0,1)^2 , \hfill \\ \left. {\left( {\frac{{\partial ^s }}{{\partial v^s }}u(x,y)} \right)} \right|_{\partial \Omega } \equiv 0,{ }s = 0,...,k - 1,{ }^{^{^{^{^{^{(1)} } } } } } \hfill \\ \end{gathered} \right.$$ with a(x,y) being a uniformly positive function and ν denoting the unit outward normal direction. More precisely, in connection with preconditioned conjugate gradient (PCG) like methods, we define the preconditioning sequence: {P _n (a)} _n , P _n (a):= $$\widetilde D$$ _n ^1/2(a)A _n (1) $$\widetilde D$$ _n ^1/2(a), where $$\widetilde D$$ _n (a) is the suitable scaled main diagonal of A _n (a). In fact, under the mild assumption of Lebesgue integrability of a(x), the weak clustering at the unity of the corresponding preconditioned sequence is proved. Moreover, if a(x,y) is regular enough and if a uniform triangulation is considered, then the preconditioned sequence shows a strong clustering at the unity so that the sequence {P _n (a)} _n turns out to be a superlinear preconditioning sequence for {A _n (a)} _n . The computational interest is due to the fact that the computation with A _n (a) is reduced to computations involving diagonals and two-level Toeplitz structures {A _n (1)} _n with banded pattern. Some numerical experimentations confirm the efficiency of the discussed proposal.