The spectrum of the continuous Laplacian on a graph

We study the spectrum of the continuous Laplacian on a countable connected locally finite graph without self-loops, whose edges have suitable positive conductances and are identified with copies of segments [0, 1], with the condition that the sum of the weighted normal exterior derivatives is 0 at every node (Kirchhoff-type condition). In particular, we analyse the relation-between the spectrum of the operator and the spectrum of the discrete Laplacian (I-P) defined on the vertices of .     

Opposite CD curves in chromophoric derivatives of 3-substituted 5-and 6-membered cyclic amines

Absolute configuration was assigned to 3-isopropylpyrrolidine by chemical correlation with R-3-isopropylsuccinic acid. The comparison between CD curves of 3-substituted piperidines, morpholines and pyrrolidine having the same chirality shows that the chiroptical properties of these five and six-membered cyclic amine derivatives are opposite.     

Pharmacokinetic measurements of IDN 5390 using electrospray ionization tandem mass spectrometry: structure characterization and quantification in dog plasma

In this report, electrospray ionization tandem mass spectrometry (ESI-MS/MS) for a pharmacokinetic study of IDN 5390, a novel C-seco taxane derivative, which is under preclinical evaluation, has been investigated. Our results showed that IDN 5390 and other taxanes including paclitaxel and IDN 5109 could ionize well in not only positive-, but also in negative-ion mode. Under collision-induced dissociation (CID) conditions, these compounds could fragment into similar M- (molecular), T- (taxane ring) and S- (side chain) series ions. In positive-ion ESI, the formation of both T- and S-series ions involved the breaking of the C-13 ester bond. In negative-ion ESI, however, while the formation mechanism of S-series ions remained the same, the breaking of the C-1' carboxylic ester bond resulted in T-series ions. At optimum collision energy (CE) values, M-, T- and S-series ions of IDN 5390 in both positive- and negative-ion ESI-MS/MS spectra had good intensity. This phenomenon makes both positive- and negative-ion ESI-MS/MS good methods for IDN 5390 metabolite structural characterization, i.e. to reveal the location of modification groups in IDN 5390 metabolites versus IDN 5390 either on the side chain or the taxane ring. A liquid chromatography (LC)/ESI-MS/MS method using the multiple-reaction monitoring (MRM) technique was thereafter developed to quantify IDN 5390 in dog plasma using paclitaxel as internal standard. The method was validated using a concentration range between 5 and 1000 ng/mL and had a limit of detection of 1 ng/mL. The inter-day %CV (%coefficient of variation) of the calibration standards ranged between 4.36 and 9.64%, the intra-day %CV of the calibration standards between 0.61 and 13.44%, and the mean % accuracy of the quality control samples at the low, middle and high end of the concentration curves were 12.5, 6.8 and 9.6%, respectively.     

Epoxidation of Polyunsaturated Fatty Acid Double Bonds by Dioxirane Reagent: Regioselectivity and Lipid Supramolecular Organization

The use of dimethyldioxirane (DMD) as the epoxidizing agent for polyunsaturated fatty acids was investigated. With fatty acid methyl esters, this is a convenient method for avoiding acidic conditions, using different solvents, and simplifying the isolation procedures, with less contamination due to by‐products. The reagent was also tested with free fatty acids in water. In this case, the supramolecular organization of fatty acids influenced the reaction outcome, and the epoxidation showed interesting regioselective features. The C?C bonds closest to the aqueous‐micelle interface is the most favored for the interaction with dimethyldioxirane. The preferential epoxidation of linoleic acid (= (9Z,12Z)‐octadeca‐9,12‐dienoic acid) to the 9,10‐monoepoxy derivative was achieved, with a high yield and 65% regioselectivity. In case of arachidonic acid (= (5Z,8Z,11Z,14Z)‐eicosa‐5,8,11,14‐tetraenoic acid) micelles, the regioselective outcome with formation of the four possible monoepoxy isomers was studied under different conditions. It resulted to be a convenient synthesis of ‘cis‐5,6‐epoxyeicosatrienoic acid’ (= 3‐[(2Z,5Z,8Z)‐tetradeca‐2,5,8‐trienyl]oxiran‐2‐butanoic acid), whereas in reverse micelles, epoxidation mostly gave ‘cis‐14,15‐epoxyeicosatrienoic acid (= (5Z,8Z,11Z)‐13‐(3‐pentyloxiran‐2‐yl)trideca‐5,8,11‐trienoic acid).     

Wheat lipids to discriminate species, varieties, geographical origins and crop years

The knowledge of lipid components of wheat finds a precious information in order to differentiate between Triticum durum (TD) and Triticum aestivum (TA). The determination of the percentages of methyl esters of the differently unsaturated fatty acids with 18-carbon atoms (C₁₈), of sterol fraction and of the other components is of particular weight. In this paper, the classification methods of linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) were applied in order to measure the classification and prediction abilities of the determined (percentages of the) components of the lipid fraction of wheat in differentiating among species, origins, varieties and crops. By univariate feature selection method (Fisher weights (FW)) and linear discriminant analysis, it was found that the only oleate is able to distinguish between the two species with a prediction rate of 100%. Inside the species Triticum durum, it was obtained a prediction rate of 83.9% while discriminating between the different origins, a prediction rate of 82.2% while discriminating among varieties and a prediction rate of 94.3% among crop years.     

Inelastic scattering of fast electrons from simple closed shell atoms. I. He,Be

The inelastic collision of fast electrons with ground state closed shell atoms is investigated within the context of First Born Approximation and Random Phase Approximation. Generalized oscillator strengths and total cross sections for 1¹ S n ¹ D transitions in He and 1¹ S n ¹ S in Be are evaluated and discussed.Work supported by Consiglio Nazionale delle Richerche (C.N.R.) through its Istituto di Chimica Quantistica ed Energetica Molecolare in Pisa.     

Morphological and structural characterization of polypropylene/conductive graphite nanocomposites

The structure and morphology of polypropylene/conductive graphite (PP/CG) composites were studied by wide angle X-ray diffraction, small-angle X-ray scattering and scanning electron microscopy. An effect of graphite on the crystallization behavior was observed and the opposite influences of enhanced thermal conductivity and hinder of chain mobility on the formation of the γ-phase of PP were discussed.     

[3]Pseudorotaxanes based on the cryptand/monopyridinium salt recognition motif

The first cryptand/monopyridinium salt [3]pseudorotaxanes were prepared from two cryptand hosts and two bispyridinium guests as confirmed by proton NMR characterization, electrospray ionization mass spectrometry, and X-ray analysis. It was found that the two monopyridinium binding sites are independent of each other for the formation of one [3]pseudorotaxane.     

Antimicrobial activity of spices essential oils and its effectiveness on mature biofilms of human pathogens

Abstract

The antibacterial activity of Pimpinella anisum L., Cinnamomum zeylanicum, Syzygium aromaticum, and Cuminum cyminum L. essential oils (EOs) against some common pathogenic microorganisms (Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 14990, Enterococcus faecalis ATCC 29212, Streptococcus pyogenes ATCC 1915, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Aeromonas hydrophila ATCC 7966, Proteus mirabilis ATCC 10005, Klebsiella pneumoniae ATCC 13883, and Candida albicans ATCC 10231) and their biofilms was studied. The EOs inhibitory effects were evaluated by both Agar Well Diffusion assay and Minimum Inhibitory Concentration (MIC) determination. The most active EOs, cinnamon and cloves, were also tested on 18, 24, 48, 72?hours mature biofilms. Cinnamon and cloves exhibited the best results showing a significant activity against all the tested bacteria. Concerning biofilm, results suggest that Cinnamomum zeylanicum oil may be a useful approach to impair the biofilm produced by the tested Gram-negative bacteria.      

The mobility and ion structure of protonated aminoazoles

The reduced mobility of protonated pyrazole derivatives was measured by ion mobility spectrometry (IMS) in air, nitrogen, and carbon dioxide, at temperatures between 150 and 250°C. It was found that the mobility of protonated 5-amino-1-phenylpyrazole was higher than that of its 3- and 4-isomers. This was attributed to the fact that in the 5-isomer the preferred site of protonation is on the endocyclic nitrogen, which leads to delocalization of the ionic charge, and thus to a diminished interaction with the drift gas molecules. On the other hand, protonated 5-amino-1-methylpyrazole has a slightly lower mobility than its isomers, which is indicative of a different protonation mechanism.