Quasi-hereditary algebras with two simple modules and fibonacci numbers

Let K be an algebraically closed field. In [10] Happel showed that number-theoretic properties of the Fibonacci numbers are related to ho-mological properties of a family of finite-dimensional Ji-algebras An. In particular he showed that at least for n > 3 odd, An is not derived equiv alent to a quasi-hereditary algebra.Using well-known properties that are shared by two rings that are derived equivalent and deeper properties of the Fibonacci numbers we are able to show that for all n > 3, the algebra A_n is not derived equivalent to a quasi-hereditary algebra.     

Anomalous reactivity of radical cations produced by photosensitized oxidation of 4-methoxybenzyl alcohol derivatives: role of the sensitizer

Steady-state and nanosecond laser flash photolysis measurements of 4-methoxybenzyl alcohol (1a), 4-methoxy-alpha-methylbenzyl alcohol (1b), 4,4'-dimethoxydiphenylmethanol (1c) and 4-methoxy-alpha,alpha'-dimethylbenzyl alcohol (1d) were carried out in air-equilibrated CH(2)Cl(2) and CH(3)CN solutions, in the presence of 9,10-dicyanoanthracene (DCA) and N-methylquinolinium tetrafluoroborate (NMQ(+)BF(4)(-)) as sensitizers. In particular, steady-state irradiation with DCA produced carbonyl compounds and, with NMQ(+)BF(4)(-), carbonyl compounds, ethers (substrates 1a-c ) and styrene (substrate 1d ) while time-resolved investigations gave evidence of charged species produced upon irradiation. The effect of solvent polarity on the reactivity was investigated; in the case of DCA, the reactivity increased with the solvent polarity, while the opposite was obtained when NMQ(+)BF(4)(-) was used. Quantum mechanical calculations at semiempirical (INDO/1-CI) and DFT (B3LYP/6-311G(d)) levels were used to support transient assignments and to obtain the charge and spin density distributions, respectively. The different photooxidation mechanisms operative with the neutral and charged sensitizer were rationalized in terms of the reactivity of free and complexed radical cations, respectively.     

Molecular structure, vibrational spectra, quantum chemical calculations and photochemistry of picolinamide and isonicotinamide isolated in cryogenic inert matrixes and in the neat low-temperature solid phases

Picolinamide (PA) and isonicotinamide (INA), two structural isomers of pyridinecarboxamide, have been investigated by matrix isolation and low-temperature solid-state infrared spectroscopy, combined with UV (lambda > 235 nm) photoexcitation and density functional theory and ab initio (MP2) theoretical studies. In consonance with the theoretical data, both PA and INA were found to exist in a single conformation in cryogenic rare gas matrixes. Comparison between the experimental spectra of the matrix-isolated compounds with those theoretically predicted allowed for full assignment of the experimental spectra. In situ UV (lambda > 235 nm) irradiation of the matrixes showed that only PA reacts, with production of isocyanic acid and pyridine, the first photoproduct further reacting to yield CO + NH and cyanic acid. The different photochemical behavior of the two compounds was explained taking into consideration their different structures. The infrared spectra of (i) the low-temperature glassy state resulting from fast deposition of vapors of the compounds onto a substrate cooled to 10 K, (ii) the crystal resulting from the annealed amorphous film of the compound, and (iii) the room-temperature crystals (alpha-phase) of the studied compounds were also obtained, fully assigned and correlated with intermolecular interactions present in the condensed phases, in particular H-bond interactions, showing that these latter are stronger in INA than in PA.     

Matrix isolation FTIR spectroscopic and theoretical study of 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243)

The molecular structure and infrared spectrum of the atmospheric pollutant 3,3-dichloro-1,1,1-trifluoropropane (HCFC-243) were characterized experimentally and theoretically. The theoretical calculations show the existence of two conformers, with the gauche (G) and trans (T) orientation around the HCCC dihedral angle. Conformer G was calculated to be more stable than form T by more than 10 kJ mol (-1). In consonance with the large predicted relative energy of conformer T, only the G form was identified spectroscopically in cryogenic argon (10 K) and xenon (20 K) matrices prepared from room-temperature equilibrium vapor of the compound. The observed infrared spectra of the matrix-isolated HCFC-243 were interpreted with the aid of high-level density functional theory calculations and normal coordinate analysis. For experimental identification of the weakest IR absorption bands, the spectrum of HCFC-243 in the neat solid state at 145 K was obtained. This spectrum also confirmed the sole presence of the G conformer in the sample. Natural bond orbital and atomic charge analyses were carried out for the two conformers to shed light on the most important intramolecular interactions in the two conformers, in particular those responsible for their relative stability.     

Structure of Isolated 1,4-Butanediol: Combination of MP2 Calculations, NBO Analysis, and Matrix-Isolation Infrared Spectroscopy

Theoretical calculations at the MP2 level, NBO and AIM analysis, and matrix-isolation infrared spectroscopy have been used to investigate the structure of the isolated molecule of 1,4-butanediol (1,4-BDO). Sixty-five structures were found to be minima on the potential energy surface, and the three most stable forms are characterized by a folded backbone conformation leading to the formation of an intramolecular H-bond. To better characterize the intramolecular interactions and particularly the hydrogen bonds, natural bond orbital analysis (NBO) was performed for the four most stable conformers, and was further complemented with an atoms-in-molecules (AIM) topological analysis. Infrared spectra of 1,4-BDO isolated in low-temperature argon and xenon matrixes show a good agreement with a population-weighted mean theoretical spectrum, and the spectral features of the conformers expected to be trapped in the matrixes were observed experimentally. Annealing the xenon matrix from 20 to 60 K resulted in significant spectral changes, which were interpreted based on the barriers to intramolecular rotation. An estimation of the intramolecular hydrogen bond energy was carried out following three different methodologies.     

N,N-Di-iso-propylcarbamato complexes of boron

N,N-di- iso-propylcarbamato derivatives of boron(III) have been synthesized from di-iso-propylamine and boron trichloride in the presence of carbon dioxide. With a large excess of amine, a single boron product was obtained, [NH2i)Pr2][B(O2CNiPr2)4], 1, while with a lower excess a mixture of 1 and of the dinuclear derivative [B2(O2CNiPr2)6], 2, was produced. By heating in vacuo at 60 degrees C, solid 1 slowly converted to 2. The transformation was reversible, 2 giving 1 back with di- iso-propylamine under carbon dioxide at atmospheric pressure. The molecular structure of both compounds was established by X-ray diffraction methods. Compound 1 is constituted by ion-pairs where the ammonium cation is hydrogen-bonded to the mononuclear anion. Compound 2 is a dinuclear species with two bridging carbamato ligands. In both derivatives, boron shows tetrahedral coordination. As IR- and 1H NMR spectra of the two species are well differentiated, it is possible to monitor the interconversion of 1 and 2 by both spectroscopic methods.     

Density and bond-orientational relaxations in supercooled water

ABSTRACT

Recent computational studies have reported evidence of a metastable liquid–liquid phase transition (LLPT) in molecular models of water under deeply supercooled conditions. A competing hypothesis suggests, however, that non-equilibrium artefacts associated with coarsening of the stable crystal phase have been mistaken for an LLPT in these models. Such artefacts are posited to arise due to a separation of time scales in which density fluctuations in the supercooled liquid relax orders of magnitude faster than those associated with bond-orientational order. Here, we use molecular simulation to investigate the relaxation of density and bond-orientational fluctuations in three molecular models of water (ST2, TIP5P and TIP4P/2005) in the vicinity of their reported LLPT. For each model, we find that density is the slowly relaxing variable under such conditions. We also observe similar behaviour in the coarse-grained mW model of water. Our findings, therefore, challenge the key physical assumption underlying the competing hypothesis.     

Preclinical pharmacokinetics comparison between resveratrol 2-hydroxypropyl-β-cyclodextrin complex and resveratrol suspension after oral administration

Trans-Resveratrol (RV) is a natural polyphenol characterized by interesting pleiotropic potentials and health benefits, but its administration is hampered by a unsatisfactory pharmacokinetics. Various approaches have been identified to circumvent it: among them, 2-hydroxypropyl-β-cyclodextrins (HPβCD) are valuable strategy. Here, we compare the employment of HPβCD based formulation with a resveratrol nanosupension (obtained by diluting a RV ethanol solution with PBS, added of 0.05 % hydroxyethylcellulose) to improve RV bioavailability after oral administration to mice. The inclusion of RV in HPβCD was confirmed by differential scanning calorimetry, Fourier transformed infrared spectroscopy, and phase solubility study. The two formulations were orally administered to BALB-c mice. RV concentrations in plasma and tissues were detected at different time (0–120 min) by HPLC method. HPβCD complexation mediate a approximately fourfold increment in plasma RV C_max and  approximately twofold augment of RV AUC_0-120 in comparison with RV nanosuspension. Similar increased concentrations were observed in heart, liver, kidney and gut. In particular, HPβCD mediated a 5.5-folds increase of resveratrol concentration in the intestine, in comparison to the nanosuspension. In conclusion, based on our results, HPβCD complexation is a promising approach to increase the oral bioavailability of RV. Moreover, the achievement of high concentrations in gut suggested a potential employment of oral RV-HPβCD as anti-inflammatory/chemopreventive agent in this tissue.     

Dissociation of ground and nsigma* states of CF3Cl using multireference configuration interaction with singles and doubles and with multireference average quadratic coupled cluster extensivity corrections

Extended complete active space self-consistent field (CASSCF), multireference configuration interaction with singles and doubles (MR-CISD), and multireference average quadratic coupled cluster (MR-AQCC) calculations have been performed on the ground (S(0)) and first excited (nsigma(*),S(1)) states of the CF(3)Cl molecule. Full geometry optimizations have been carried out for S(0) as well as "relaxed" potential energy calculations for both states, along the C-Cl bond distance. Vertical excitation energies (DeltaE(vertical)), dissociation energies (DeltaE(diss)), dissociation enthalpies (DeltaH(diss)), and the oscillator strength (f) have also been computed. Basis set effects, basis set superposition error (BSSE), and spin-orbit and size-extensivity corrections have also been considered. The general agreement between theoretical and available experimental results is very good. The best results for the equilibrium geometrical parameters of S(0) (at MR-AQCCaug-cc-pVTZ+d level) are 1.762 and 1.323 A, for the C-Cl and C-F bond distances, respectively, while the corresponding experimental values are 1.751 and 1.328 A. The [angle](ClCF) and [angle](FCF) bond angles are in excellent agreement with the corresponding experimental values (110.3 degrees and 108.6 degrees ). The best calculated values for DeltaE(vertical), DeltaH(diss), and f are 7.63 eV [at the MR-AQCCaug-cc-pV(T+d)Z level], 3.59 eV[MR-AQCCaug-cc-pV(T+d)Z level+spin-orbit and BSSE corrections], and 2.74x10(-3) (MR-CISD/cc-pVTZ), in comparison with the corresponding experimental values of 7.7+/-0.1 eV, 3.68 eV, and 3.12 x 10(-3)+/-2.50 x 10(-4). The results concerning the potential energy curves for S(0) and S(1) show a tendency toward the nonoccurrence of crossing between these two states (in the intermediate region along the C-Cl coordinate), as the basis set size increases. Such tendency is accompanied by a decreasing well depth for the S(1) state. Dynamic electronic correlation (especially at the MR-AQCC level) is also an important factor toward an absence of crossing along the C-Cl coordinate. Further investigations of a possible crossing using gradient driven techniques (at CASSCF and MR-CISD levels) seem to confirm its absence.     

Diplophonia reappraised

The acoustic structure of diplophonia was investigated spectrographically and in terms of perturbation measures, while the perception of diplophonia among other voice qualities was confirmed auditorily by trained listeners. Recordings of pathological voices were presented to listeners for systematic evaluation, and narrowband spectrography was used to quantify the subharmonics within each sample. Subharmonics strongly correlated with the perception of diplophonia, but occurrence was mostly intermittent, and structure was highly variable between samples. Uniquely among voice qualities identified perceptually, diplophonia was found to correlate positively with the number of subharmonics (irrespective of percentage of occurrence) and with perturbation parameters measured separately. Exceptions to these group results indicated that diplophonia was perceived sometimes in the absence of subharmonic structure, and subharmonic structure was observed without a commensurate perception of diplophonia. In light of these data, a less deterministic relation between diplophonia and subharmonic structure is proposed.