Pseudo 1-homogeneous distance-regular graphs

Let Γ be a distance-regular graph of diameter d≥2 and a ₁≠0. Let θ be a real number. A pseudo cosine sequence for θ is a sequence of real numbers σ ₀,…,σ _d such that σ ₀=1 and c _i σ _i−1+a _i σ _i +b _i σ _i+1=θ σ _i for all i∈{0,…,d−1}. Furthermore, a pseudo primitive idempotent for θ is E _θ =s ∑ _i=0 ^d σ _i A _i , where s is any nonzero scalar. Let be the characteristic vector of a vertex v∈VΓ. For an edge xy of Γ and the characteristic vector w of the set of common neighbours of x and y, we say that the edge xy is tight with respect to θ whenever θ≠k and a nontrivial linear combination of vectors , and Ew is contained in . When an edge of Γ is tight with respect to two distinct real numbers, a parameterization with d+1 parameters of the members of the intersection array of Γ is given (using the pseudo cosines σ ₁,…,σ _d , and an auxiliary parameter ε). Let S be the set of all the vertices of Γ that are not at distance d from both vertices x and y that are adjacent. The graph Γ is pseudo 1-homogeneous with respect to xy whenever the distance partition of S corresponding to the distances from x and y is equitable in the subgraph induced on S. We show Γ is pseudo 1-homogeneous with respect to the edge xy if and only if the edge xy is tight with respect to two distinct real numbers. Finally, let us fix a vertex x of Γ. Then the graph Γ is pseudo 1-homogeneous with respect to any edge xy, and the local graph of x is connected if and only if there is the above parameterization with d+1 parameters σ ₁,…,σ _d ,ε and the local graph of x is strongly regular with nontrivial eigenvalues a ₁ σ/(1+σ) and (σ ₂−1)/(σ−σ ₂).     

Synthesis and characterisation of luminescent fluorinated organoboron compounds

The reaction of 8-hydroxyquinoline (HQ) with B(C(6)F(5))(3) leads to the formation of the zwitterionic compound (C(6)F(5))(3)BQH (1), involving a proton migration from O to N. Compound 1 can be converted thermally to (C(6)F(5))(2)BQ (2), which can also be prepared from (C(6)F(5))(2)BCl and HQ. The reaction of HQ with (C(6)F(5))B(OC(6)F(5))(2) generates initially (C(6)F(5))(OC(6)F(5))BQ (3), which easily hydrolyses to give the diboron compound ((C(6)F(5))BQ)(2)O (4). Compounds 1, 2 and 4 have been fully characterised, including X-ray analysis. The spectroscopic properties of these compounds, including photoluminescence (PL) have been investigated and compared with the non-fluorinated luminescent boron compound (C(6)H(5))(2)BQ and also with AlQ(3). The changes in luminescent behaviour upon fluorination of these boron quinolinate compounds have been rationalised using computational studies.     

Preparation of magnesium hydroxide from nitrate aqueous solution

Nucleation of Mg(OH)₂ was investigated by measuring the electrical conductivity and pH of the Mg(NO₃)₂ reaction solution to which ammonia containing different amounts of NH₄NO₃ was added. NH₄NO₃ increases solubility and slows down precipitation of Mg(OH)₂ in the system. Data are presented on the influence of NH₄NO₃ on the solubility of Mg(OH)₂ at 25°C. The phenomena observed can be explained by the solvation effect of nitrate ions brought to the system with the addition of ammonium nitrate, which was proved by NMR spectroscopy. When the mass fraction of NH₄NO₃ exceeds 15 %, homogeneous nucleation does not proceed. It was found that seeding of the system with Mg(OH)₂ crystals only influenced the rate of Mg(OH)₂ crystallisation, not the size and shape of the crystals. Primary crystals are smaller than 0.1 μm. The large difference in the surface energy of individual crystal planes leads to oriented agglomeration. This process is accelerated in a pressure reactor at 130°C. The resulting polycrystals are hexagonal plates 0.2 μm thin with a diameter of 1–2 μm. Under variable reaction conditions, agglomerates as big as 30 μm can be prepared.     

Low-Flammable Parahydrogen-Polarized MRI Contrast Agents

Many MRI contrast agents formed with the parahydrogen-induced polarization (PHIP) technique exhibit biocompatible profiles. In the context of respiratory imaging with inhalable molecular contrast agents, the development of nonflammable contrast agents would nonetheless be highly beneficial for the biomedical translation of this sensitive, high-throughput and affordable hyperpolarization technique. To this end, we assess the hydrogenation kinetics, the polarization levels and the lifetimes of PHIP hyperpolarized products (acids, ethers and esters) at various degrees of fluorine substitution. The results highlight important trends as a function of molecular structure that are instrumental for the design of new, safe contrast agents for in vivo imaging applications of the PHIP technique, with an emphasis on the highly volatile group of ethers used as inhalable anesthetics.     

Quantitative Compositional Analyses of Calcareous Rocks for Lime Industry Using LIBS

Here, the potential of laser-induced breakdown spectroscopy (LIBS) in grading calcareous rocks for the lime industry was investigated. In particular, we developed a system equipped with non-intensified detectors operating in scanning mode, defined a suitable data acquisition protocol, and implemented quantitative data processing using both partial least squares regression (PLS-R) and a multilayer perceptron (MLP) neural network. Tests were carried out on 32 samples collected in various limestone quarries, which were preliminarily analyzed using traditional laboratory X-ray fluorescence (XRF); then, they were divided into two groups for calibration and validation. Particular attention was dedicated to the development of LIBS methodology providing a reliable basis for precise material grading. The congruence of the results achieved demonstrates the capability of the present approach to precisely quantify major and minor geochemical components of calcareous rocks, thus disclosing a concrete application perspective within the lime industry production chain.     

Novel Lipophilic Fluorophores with Highly Acidity-Dependent Two-Photon Response

Lipophilic fluorophores are widely implemented in nonlinear microscopy; however, few existing membrane-specific probes combine the high brightness of two-photon excited fluorescence (2PEF) with pH sensitivity. Herein we describe four novel two-photon excited fluorophores, based on a coumarin 151 core structure, where lipophilicity is induced by a covalently attached phosphazene moiety. Changing the environmental acidity using trifluoromethanesulfonic (triflic) acid leads to profound changes in the linear fluorescence and 2PEF characteristics, due to chromophores’ switching between neutral- and protonated forms. We characterize this dependence by measuring the two-photon absorption (2PA) spectra over the region λ_2PA=550–1000 nm, observing 2PA cross sections of σ_2PA=10–20 GM, with an associated 2PEF brightness of 10–13 GM, in neutral solutions of both acetonitrile and n-octanol. Although quantum chemical modelling and NMR measurements show that, at high chromophore concentrations, protonation may be accompanied by a dimerization process, these dimers likely do not form at the lower concentrations used in optical spectroscopy.     

Quality Assessment of Two Spectrophotometric Procedures for Polyphenol Determination and Application in Moltkia petraea Species

A comparison study of quality of two spectrophotometric procedures: Schneider’s (T‐Sch) and 4‐aminoantipyrine (T‐AAP) procedures for total polyphenols determination was carried out using informative prevalidation strategy. Good quality of the measurements at the lower analyte level, excellent resolution of signals, homogenous data material, ideal linear calibration and analytical evaluation functions, very low limit of quantitation (0.13 μg/mL), and high precision (from ±0.60 % to ±3.43 %) and accuracy (from ?4.26 % to +4.00 %) confirmed the high quality of the T‐Sch procedure. Although favorable performance characteristics of T‐AAP procedure were obtained, the signal resolution, sensitivity, precision and accuracy are somewhat lower than in T‐Sch procedure. Both prevalidated procedures were successfully applied to determine total polyphenols in leaves, stems, and flowers in three populations of endemic Illyric? Balkan species Moltkia petraea (Tratt.) Griseb. growing in Croatia. Total concentrations of polyphenols obtained by T‐Sch procedure in all plant organs of all populations were somewhat lower than determined by T‐AAP procedure. However, the relative abundance of polyphenols obtained by both methods is the same. Prevalidation results demonstrated the reliability of the T‐AAP and T‐Sch procedures as valuable tools in polyphenols analysis and their application provided new information regarding phytochemical characterization of endemic M. petraea.     

The cross sections for the binary and ternary fission of thorium induced by 14, 18, and 23 GeV protons

In this work the cross sections for the binary and ternary fission of thorium induced by 14, 18, and 23 GeV protons were determined. A polycarbonate (macrofol) was used as the detector of fission fragments.     

Adsorption of SO2 on alumina

The adsorption of SO₂ on alumina used in the aluminium industry, the so-called smelter-grade alumina, was studied in the temperature range 15–120°C. It was found that at temperatures lower than 40°C, sulphur dioxide was bonded to alumina reversibly by physical forces, and the adsorption could be described satisfactorily by the Langmuir adsorption isotherm. The heat of adsorption was estimated to be −33 kJ mol⁻¹. At temperatures ranging from 80°C to 120°C, which prevail in dry scrubbers in the aluminium industry, the heat of adsorption was determined to be −56 kJ mol⁻¹. When SO₂ was adsorbed at temperatures higher than 80°C, about 30 % of the SO₂ could not be desorbed even if the samples were heated up to 250°C. In the presence of SO₂ and oxygen, the formation of sulphate was observed at temperatures above 90°C.     

Ein Beitrag zur Kenntnis der Biogenese der Sialinsäure

Zusammenfassung Die Konzentrationen der Brenztraubensäure und der Eiweißzuckerkomponenten wurden in 150 Seren, deren Struktur im Sinne eines deutlichen Anstiegs der-Globulinfraktionen verändert war, ohne Rücksicht auf die Ätiologie dieser Dysprotoeinämien, ermittelt.Aus den Resultaten ist ersichtlich, daß sich am Stoffwechsel der Kohlenhydratkomponenten der Eiweißzucker auch die Brenztraubensäure beteiligt. Aus einem Vergleich der Mittelwerte der genannten Konzentrationen bzw. deren Indices geht hervor, daß zwischen dem Anstieg der Konzentration der Brenztraubensäure und des Hexosamins einerseits, der der Sialinsäure anderseits eine Beziehung besteht. Dies bekräftigt die Annahme, daß auch die Biosynthese der Sialinsäure über die Brenztraubensäure und das Hexosamin ablaufen könnte.

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Summary The concentrations of pyruvic acid and the protein sugar components were determined in 150 sera, whose structure was altered in the sense of a pronounced increase in the-globulin fractions, without consideration of the etiology of these dysproteinemias.It can be seen from the findings that pyruvic acid is also a participant in the metabolism of the carbohydrate components of the protein sugars. From a comparison of the mean values of the cited concentrations or their indices it may be concluded that a relation exists between the rise in the concentration of the pyruvic acid and of the hexosamine on one hand and that of the sialinic acid on the other. This supports the assumption that the biosynthesis of the sialinic acid also can proceed via pyruvic acid and hexosamine.

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Résumé On a déterminé les concentrations en acide pyruvique et en glucoprotéides de 150 sérums dont la structure était altérée par une augmentation importante en-globulines, sans prendre en considération l'étiologie de ces dysprotéinémies.Les résultats montrent clairement que l'acide pyruvique participe aussi à l'assimilation des constituants hydrocarbonés des glucoprotéides. La comparaison des valeurs moyennes des concentrations en question met en évidence une relation entre l'augmentation de la concentration en acide pyruvique et en hexosamine d'une part et celle de l'acide sialinique d'autre part. Ceci renforce l'hypothèse que la biosynthèse de l'acide sialinique pourrait aussi découler via l'acide pyruvique et à l'hexosamine.

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Herrn Prof. Dr. Ing.Fritz Feigl zum 70. Geburtstag gewidmet.