Prediction of properties of biodiesel-diesel blends using spectrofluorimetry and multivariate calibration

Regressions based on fluorescence spectroscopy were developed to provide relatively inexpensive and rapid measurements of the concentration, viscosity, and specific gravity of biodiesel-diesel blends. The methods involved obtaining a mathematical model from spectrofluorimetric data and data from a given property (concentration, dynamic viscosity, or specific gravity) using partial least squares (PLS) regression, which was then applied as a model for predicting properties of interest. The predicted concentrations, dynamic viscosities, and specific gravities of the biodiesel-diesel blends were compared with actual values and agreed reasonably well with the obtained results. The models showed high correlation between real and predicted values. The R-square values near 1 indicated excellent model accuracy for predicting concentrations, specific gravities, and dynamic viscosities of biodiesel-diesel blends. The residual distribution did not follow a trend with respect to the predicted variables, indicating an excellent fit to the data.      

Nb/BiSCCO point conctact junctions

Summary Preparation procedure and sample characterization of 112 BiSCCO pellets exhibiting high-T _c superconductivity are discussed. TypicalI–V and dV/dI curves of Nb/BiSCCO point conctact junctions at various temperatures are presented.     

Photochemical and pharmacological aspects of nitric oxide release from some nitrosyl ruthenium complexes entrapped in sol–gel and silicone matrices

The entrapped [Ru(terpy)(L)NO](PF₆)₃, where terpy = 2,2′:6′,2″-terpyridine and L = 2,2′-bipyridine (bpy) and 3,4-diiminebenzoic acid (NH · NHq) complexes into sol–gel processed polysiloxane and silicone matrices, shows NO release characteristics when submitted to light irradiation at 355 and 532 nm, as judged by NO measurement using a NO-sensor electrode. The pharmacological properties of doped matrix showed vasodilator characteristics by visible light irradiation, which is of great interest because the target delivery system can avoid the occurrence of side effects possibly by the aquo ruthenium species. All matrices obtained showed to be amorphous materials. The scanning electron micrographs of the matrices showed irregularly shaped particles, with a broad size of 1000 μm for both matrices and homogeneous distribution.     

Measurement ofD meson production in 200 GeV π−-Be interactions

We have measured the differential and total cross sections ofD meson production in 200 GeV π^?-beryllium interactions, using a sample of 48 fully reconstructed and nearly background-freeD mesons in the decay channelsK ^?π^±,K ^?π^±π^± andK ^?π^?π^±π^±. A single electron trigger has been used to select events containing a pair of charmed particles. A vertex telescope of 6 silison microstrip detectors allowed the reconstruction of tracks of charged secondaries and the reconstruction of primary and decay vertices with high precision. The ratio of branching fractions for \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \pm \) to \(\mathop {D^0 }\limits^{( - )} \to K^ \mp \pi ^ \mp \pi ^ \pm \pi ^ \pm \) , and an upper limit for \(D^0 - \bar D^0 \) mixing are presented.     

Effect of the type of linkage between phenyl groups on the structure and photochemical properties of 2,2-diaryl-substituted pyridoannelated [2H]-chromenes

Three 2,2-diaryl-substituted pyridoannelated [2H]-chromenes have been studied by X-ray diffraction analysis. Bonding of the benzene rings through bridges of different nature and with different length affects substantially the orientation of the benzene rings, steric interactions at the C center, the conformation of the molecule, and the C−O bond length. A correlation between the photocolorability of chromenes under study and the orientation of the benzene rings with respect to the C−O bond, which provides different prerequisites to stabilization of the C(1)-centered, cation formed upon cleavage of the C−O bond, was established. The effect of the orientation of the benzene rings on the dark reaction of ring closure was found. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1129–1135, June, 1998.     

Elastin-Hyaluronan Bioconjugate as Bioactive Component in Electrospun Scaffolds

Hyaluronic acid or hyaluronan (HA) and elastin-inspired peptides (EL) have been widely recognized as bioinspired materials useful in biomedical applications. The aim of the present work is the production of electrospun scaffolds as wound dressing materials which would benefit from synergic action of the bioactivity of elastin peptides and the regenerative properties of hyaluronic acid. Taking advantage of thiol-ene chemistry, a bioactive elastin peptide was successfully conjugated to methacrylated hyaluronic acid (MAHA) and electrospun together with poly-D,L -lactide (PDLLA). To the best of our knowledge, limited reports on peptide-conjugated hyaluronic acid were described in literature, and none of these was employed for the production of electrospun scaffolds. The conformational studies carried out by Circular Dichroism (CD) on the bioconjugated compound confirmed the preservation of secondary structure of the peptide after conjugation while Scanning Electron Microscopy (SEM) revealed the supramolecular structure of the electrospun scaffolds. Overall, the study demonstrates that the bioconjugation of hyaluronic acid with the elastin peptide improved the electrospinning processability with improved characteristics in terms of morphology of the final scaffolds.     

Theoretical and experimental studies of cationized uracil complexes in the gas phase

Cationized uracil clusters were generated in the gas phase by electrospray ionization (ESI). Mass spectrometry experiments showed that with particular experimental conditions, decameric uracil clusters are magic number clusters. MS/MS experiments demonstrated that the structure of these decameric uracil clusters depends substantially on the size and the charge of the cation. On the basis of the ab initio and density functional theory (DFT) quantum chemistry calculations, structures for these decameric clusters were proposed. These structures are in agreement with the experimental mass spectra of modified nucleobases. Theoretical calculations showed that complexes experimentally observed using ESI-MS techniques, are not naturally the most stable in the gas phase.     

Energy-dependent dissociation of benzylpyridinium ions in an ion-trap mass spectrometer

Benzylpyridinium ions, generated via electrospray ionization of dilute solutions of their salts in acetonitrile/water, are probed by collisional activation in an ion-trap mass spectrometer. From the breakdown diagrams obtained, phenomenological appearance energies of the fragment ions are derived. Comparison of the appearance energies with calculated reaction endothermicities shows a reasonably good correlation for this particular class of compounds. In addition, the data indirectly indicate that at threshold the dissociation of almost all of the benzylpyridinium ions under study leads to the corresponding benzylium ions, rather than the tropylium isomers. Substituent effects on the fragmentation for a series of benzylpyridinium ions demonstrate that neither mass effects nor differences in density of states seriously affect the energetics derived from the ion-trap experiments.     

Crown-containing spirooxazines and spiropyrans

Methods for the synthesis of new spironaphthooxazines containing an aza-15-crown-5 fragment in two different positions (5′ and 9′) were developed. The spectral and photochemical properties of these compounds suggest that two competitive complexation processes occur with alkaline-earth or rare-earth metal cations differing in efficiency and selectivity. A metal cation occupies the optimum position in the crown-ether cavity with respect to the donor oxygen atom of the merocyanine form of the dye and thus can affect more strongly its spectral and photochemical properties than in the case of intermolecular interaction. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1974–1983, October, 1999.