The smallest Hosoya index in (<Emphasis Type="Italic">n</Emphasis>, <Emphasis Type="Italic">n</Emphasis> + 1)-graphs

A (n, n + 1)-graph G is a connected simple graph with n vertices and n + 1 edges. In this paper, we determine the lower bound for the Hosoya index in (n, n + 1)-graphs in terms of the order n, and characterize the (n, n + 1)-graph with the smallest Hosoya index.     

Infrared reststrahlen revisited: commonly disregarded optical details related to <Emphasis Type="Italic">n</Emphasis><1

Spectral ellipsometry has developed into a routine method applicable to the infrared spectral range. It can give both the refractive index (n) and the absorption index (k), which has so far only been determined for a limited number of compounds. It turns out that vibrations that have a dispersion with an interval of n<1 are by no means restricted to crystals, but occur with numerous compounds including polymers and liquids. In conventional infrared spectroscopy, one usually is not aware of such a situation and so the consequences are disregarded. These include the so-called reststrahlen (residual rays) bands and specific phenomena that occur when n matches the absorption index (the Berreman effect) or the refractive index of ambient air (vanishing reflection, the Christiansen effect). These and some typical applications are discussed, including model calculations and experimental data.Dedicated to the memory of Wilhelm Fresenius     

Excess Isentropic Compressibilities for 1,3-Dioxolane or 1,4-Dioxane <Emphasis Type="Italic">+</Emphasis> Water <Emphasis Type="Italic">+</Emphasis> Formamide or N,N-Dimethylformamide Ternary Mixtures at 308.15 K

Speeds of sound, u_ijk, of 1,3-dioxolane or 1,4-dioxane (i) + water (j) + formamide or dimethylformamide (k) ternary mixtures and of their binary subsystems, u_ij, of 1,3-dioxolane or 1,4-dioxane (i) + formamide or dimethylformamide (j), and water (i) + formamide or dimethylformamide (j) have been measured over the entire composition range at 308.15 K. The experimental data have been used to evaluate the excess isentropic compressibilities of binary (κ_s^E)_ij and ternary (κ_s^E)_ijk mixtures using their densities calculated from molar excess volume data. The Moelwyn-Huggins concept [M. L. Huggins, Polymer 12, 389 (1971)] of interaction between the surfaces of components of a binary mixture has been employed to evaluate the excess isentropic compressibilities (using the concept of connectivity parameter of third degree of a molecule, ³ξ, which in turn depends on its topology) of binary mixtures, and this method has been extended to predict excess compressibilities of ternary mixtures. Values of (κ_s^E)_ij and (κ_s^E)_ijk have also been calculated by the Flory theory. It was observed that (κ_s^E)_ij and (κ_s^E)_ijk predicted by the Moelwyn-Huggins approach compare well with calculated and experimental values.     

Isothermal solubility of individual light fullerenes in the homologous series of <Emphasis Type="Italic">n</Emphasis>-alkanes, <Emphasis Type="Italic">n</Emphasis>-alkanols, <Emphasis Type="Italic">n</Emphasis>-alkylcarboxylic acids,and arenes

Available published data on isothermal solubility (at 20°C) of individual light fullerenes in a homologous series of n-alkanes, n-alkanols, n-alkylcarboxylic acids, and arenas were systematized. A correlation between the parameter of Hildebrand’s cohesion and the logarithm of the mole fraction of the fullerene in the saturated solution was revealed.     

Calculation of the viscosity of <Emphasis Type="Italic">n</Emphasis>-heptane-methanol solutions at low <Emphasis Type="Italic">n</Emphasis>-heptane concentrations

The molar heat capacity C _p of the methanol-n-heptane system was measured at low concentrations of n-heptane and 298.15 K. The dynamic viscosity η of the system at 298.15 K was calculated from data on the molar heat capacity of methanol-n-heptane solutions within the framework of the Flory theory and the theory of free volume with regard to the molecular association. Based on the experimental data and calculation results, it was concluded that the viscosity of the methanol-n-heptane system exhibits an anomalous behavior.     

Speciation studies of nitric acid and U(VI) third phases in <Emphasis Type="Italic">n</Emphasis>,<Emphasis Type="Italic">n</Emphasis>-dialkyl amides/<Emphasis Type="Italic">n</Emphasis>-dodecane systems

Conventionally composition of the actinide-extractant solvate is assumed to be the same in the unpartitioned organic phase and the formed third phase. For example, if a m:n solvate has formed during extraction, the solvate is expected to be in the same state even during the third phase condition. However contemporary analysis, based on the spectroscopy measurements and empirical observations, has indicated the presence of an extended solvate. In this article, the proposed speciation in nitric acid and U(VI) third phase formation in n–n dialkyl amide/dodecane-nitric acid systems has been modeled with empirical correlations.     

Radiothermoluminescence of <Emphasis Type="Italic">n</Emphasis>-eicosane mixtures with <Emphasis Type="Italic">n</Emphasis>-tetracosane: Effect of mixture composition

Radiothermoluminescence (RTL) curves of mixtures of C20 and C24 n-alkanes have been deconvoluted into the curves of crystalline and disordered regions, and their change depending on the mixture composition has been analyzed. The shape of the total RTL curve of the mixture regardless of the its composition is fundamentally different from that shape of the sum of the curves of the individual components taken in the relevant ratios. The difference becomes noticeable at as low a C20 amount in the mixture as 2% and is manifested in the disappearance of the intense RTL peaks of the individual components and appearance of new intense peaks in temperature intervals other than those of the RTL peaks of the components. It has been shown that these changes correlate with changes of the crystalline structure of the mixture: a new crystalline structure other than the structure of any of the individual components emerges and the mixture becomes amorphous. High selectivity of charge trapping in disordered regions of the mixture has been revealed: the contribution of RTL of the disordered regions to the total curve is many times higher than their volume fraction in the mixture. This selectivity might be due to an increase in concentration of defects in the unordered regions of the mixture in comparison with their concentration in the pure alkanes. These defects are traps for electrons that are accessible to acceptors introduced into the mixture.     

Calculation of the anisotropy of molecular polarizability of liquid <Emphasis Type="Italic">n</Emphasis>-alkanes and <Emphasis Type="Italic">n</Emphasis>-alcohols

Light scattering from liquid n-alkanes and n-alcohols in a strong electric field is measured by a photoelectric colorimeter at various wavelengths. The anisotropy of molecular polarizability of the substances is calculated by the Rayleigh formula.     

Liquid-liquid equilibrium in the-<Emphasis Type="Italic">n</Emphasis>-heptane-<Emphasis Type="Italic">n</Emphasis>-perfluorohexane system

The shape of the liquid-liquid coexistence curve in the C₇H₁₆-C₆F₁₄ system in the molar concentration-temperature coordinates close to the critical solution point was studied by narrow-beam gamma-raying of two-phase samples. The molar volumes of the coexisting liquid phases and critical point coordinates (critical temperature T _c = 316.266 ± 0.03 K and critical concentration x _c = 39.0 ± 0.4 mol % C₆F₁₄) were determined. The critical index β of the coexistence curve was found to be 0.322 ± 0.005. The diameter of the coexistence curve did not obey the classic “rectilinear diameter rule.”     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Structural transformations in a water-<Emphasis Type="Italic">n</Emphasis>-octane + chloroform-sodium dodecyl sulfate-<Emphasis Type="Italic">n</Emphasis>-pentanol microemulsion

Conductivity, viscosity, and water and oil solubilization are measured, and the parameter of hydrophilic-lipophilic balance is calculated for stable water-n-octane + chloroform-n-pentanol-sodium dodecyl sulfate microemulsions (Winsor Type IV system) at a water content of 2.5–56 vol %. Domains of the most probable existence of globular and bicontinuous structures and the boundaries of the transitions between the following states of the system are determined: reverse micelles containing solubilized water, a water-in-oil microemulsion, a microemulsion with a continuous structure, an oil-in-water microemulsion, and normal micelles containing solubilized oil. Peculiarities of the bicontinuous structure of the microemulsions and the relation between parameter R of the Winsor theory and the parameter of the hydrophilic-lipophilic balance of microemulsion, which the authors have determined, are discussed.     

A new stilbene glycoside from the <Emphasis Type="Italic">n</Emphasis>-butanol fraction of <Emphasis Type="Italic">Veratrum dahuricum</Emphasis>

A new stilbene glycoside, 5-methylresveratrol-3,4′-O-β-D-diglucopyranoside (1), was isolated from the n-butanol fraction of the rhizomes of Veratrum dahuricum, together with five known stilbenoids: resveratrol-3-O-β-D-glycoside (2), 4′-methylresveratrol-3-O-β-D-glycoside (3), oxyresveratrol-4′-O-β-D-glycoside (4), oxyresveratrol-3-O-β-D-glycoside (5), and oxyresveratrol-3,4′-O-β-D-diglycoside (6), and found for the first time in the investigated plant. The structures of six isolates were identified on the basis of 1D and 2D NMR data. Compounds 1–6 showed platelet aggregation inhibition, and compound 1 had an IC₅₀ value of 383.6 μM against platelet aggregation induced by AA. Published in Khimiya Prirodnykh Soedinenii, No. 3, pp. 279–282, May–June, 2009.     

Quantum-chemical investigation of structure and stability of [<Emphasis Type="Italic">n</Emphasis>]-prismanes and [<Emphasis Type="Italic">n</Emphasis>]-asteranes

The study by DFT [B3LYP/6-311G(2df,p)] method of structural and energy characteristics peculiar to [n]-prismanes and [n]-asteranes demonstrated that prismanes of n = 3–10 and asteranes of n = 3–7 possessed a stable structure of D_nh-symmetry; the D_nh-geometry was distorted in the subsequent terms of the series.     

The <Emphasis Type="Italic">pVT</Emphasis> properties and phase equilibria in the <Emphasis Type="Italic">n</Emphasis>-pentane-water binary system

The pVT properties of the 0.075 n-C₅H₁₂ + 0.925H₂O binary system were studied experimentally. Thermal properties were measured along nine different isochores over the density and temperature ranges 87–698 kg/m³ and 303–684 K at pressures up to 60 MPa. Measurements were performed using a constant-volume piezometer. Inflection and break points of the p(T) dependences were used to construct phase equilibrium curves, which were described by scaling equations.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

The solubility of fullerenes in <Emphasis Type="Italic">n</Emphasis>-alkanols-1

The isothermal and polythermal solubility of C₆₀ and fullerene mixture (60% C₆₀, 39% C₇₀, and 1% C_76–90) in unbranched saturated alcohols C₁–C₁₁ was studied over the temperature range 20–80°C. The isotherms and polytherms of solubility are presented and characterized.     

Synthesis and properties of maleopimaric <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">n</Emphasis>-alkyl)imides

Method of synthesis of maleopimaric N-(n-alkyl)imides by the reaction of maleopimaric acid with primary aliphatic amines in melt was developed. On the basis of the obtained compounds allyl esters were synthesized. Thermal stability of the synthesized compounds was evaluated by the method of derivatography.     

Analysis of <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> PAO1 Biofilm Protein Profile After Exposure to <Emphasis Type="Italic">n</Emphasis>-Butanolic <Emphasis Type="Italic">Cyclamen coum</Emphasis> Extract Alone and in Combination with Ciprofloxacin

Pseudomonas aeruginosa biofilm-related infections are the major cause of premature death in cystic fibrosis patients. Strategies to induce biofilm dispersal are of interest, because of their potential in preventing biofilm-related infections. Our previous work demonstrated that n-butanolic Cyclamen coum extract with ciprofloxacin could eliminate 1- and 3-day-old P. aeruginosa PAO1 biofilms. To gain new insights into the role of C. coum extract and its synergistic effect with ciprofloxacin in eliminating P. aeruginosa PAO1 biofilms, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry-based protein identification were used. Changes in the bacterial protein expression were analyzed when 3-day-old biofilm cells were exposed to the C. coum extract alone and in combination with ciprofloxacin. Proteins involved in alginate biosynthesis, quorum sensing, adaptation/protection, carbohydrate and amino acid metabolism showed a weaker expression in the C. coum extract-ciprofloxacin-treated biofilm cells compared to those in the untreated cells. Interestingly, the proteome of C. coum extract-ciprofloxacin-treated biofilm revealed more resemblance to the planktonic phenotype than to the biofilm phenotype. It appears that saponin extract in combination with ciprofloxacin causes biofilm disruption due to several mechanisms such as motility induction, cell envelope integrity perturbation, stress protein expression reduction, and more importantly, signal transduction perturbation. In conclusion, exposure to a combination of biofilm dispersal such as saponin extract and antimicrobial agents may offer a novel strategy to control preestablished, persistent P. aeruginosa biofilms and biofilm-related infections.     

Excess Volumetric and Spectroscopic Properties of Mixtures of Some <Emphasis Type="Italic">n</Emphasis>-Alkoxyethanols and of Some Polyethers with 2-Pyrrolidinone and <Emphasis Type="Italic">N</Emphasis>-Methyl-2-Pyrrolidinone at 298.15 K

Excess molar volumes V_m^E for binary liquid mixtures of n-alkoxyethanols or polyethers + 2-pyrrolidinone or N-methyl-2-pyrrolidinone have been measured with a continuous dilution dilatometer at 298.15 K and atmospheric pressure as a function of composition. The alkoxyethanols are diethylene glycol monomethylether, 2-(2-methoxyethoxy) ethanol, CH₃(OC₂H₄)₂OH; diethylene glycol monoethylether, 2-(2-ethoxyethoxy) ethanol, C₂H₅(OC₂H₄)₂OH; and diethylene glycol monobutylether, 2-(2-butoxyethoxy) ethanol, C₄H₉(OC₂H₄)₂OH; whereas the polyethers are diethylene glycol dimethylether, bis(2-methoxyethyl)ether, CH₃(OC₂H₄)₂OCH₃; diethylene glycol diethylether, bis(2-ethoxyethyl)ether, C₂H₅(OC₂H₄)₂OC₂H₅; and diethylene glycol dibutylether, bis(2-butoxyethyl)ether, C₄H₉(OC₂H₄)₂OC₄H₉. In all mixtures the excess molar volumes are negative and symmetric across the entire composition range. The excess volumes are fitted to the Redlich–Kister polynomial equation to obtain the binary coefficients and the standard errors. The experimental results have also been discussed on the basis of IR measurements.