Propagation of mesons in asymmetric nuclear matter in a density-dependent coupling model

We study the propagation of the light mesons σ,ω,ρ, and a₀(980) in dense hadronic matter in an extended derivative scalar coupling model. Within the scheme proposed it is possible to unambiguously define effective density-dependent couplings at the Lagrangian level. We first apply the model to study asymmetric nuclear matter with fixed isospin asymmetry, and then we pay particular attention to hypermatter in β-equilibrium. The equation of state and the potential contribution to the symmetry coefficient arising from the mean-field approximation are investigated. Received: 16 October 2001 / Accepted: 10 January 2002     

Room-temperature synthesis and conductivity of the pyrochlore type Dy2(Ti1−yZry)2O7 (0?y?1) solid solution

Different compositions in a solid solution of general formula Dy₂(Ti_1−yZr_y)₂O₇, showing high oxygen ion conductivity, have been successfully prepared at room temperature via mechanochemical synthesis. Stoichiometric mixtures of the constituent oxides were dry milled together in a planetary ball mill by using zirconia vials and balls. Chemical changes in the powder mixtures as a function of composition and milling time were followed by X-ray diffraction and revealed that, in all cases and after milling for 19 h, the powder mixtures consisted of a single phase. Electrical properties were measured on sintered pellets as a function of frequency, temperature and zirconium content, revealing an increase in conductivity of more than one order of magnitude for y?0.4, which, as observed in the similar Y₂(Ti_1−yZr_y)₂O₇, has been related with the onset of disordering of the anion sublattice. Despite increasing structural disorder with increasing Zr content, conductivity remains almost constant for y>0.6, reaching a maximum value of ∼5×10⁻³ for Dy₂Zr₂O₇ at 900 °C.     

Influence of the preparation procedure on the properties of polyaniline based magnetic composites

A versatile process for the preparation of composite films consisting of magnetite (Fe₃O₄) nanoparticles embedded in a polyaniline (PANI) matrix is reported. Spectroscopic properties of polyaniline matrix (PANI-EB), polyaniline protonated with camphor sulfonic acid (PANI-CSA_0.5) PANI-ES and PANI/Fe₃O₄-CSA_0.5 composites were studied, both in the state of the solutions of m-cresol and in thin films processed from the same solvents. The results of these studies indicate that m-cresol can be used for PANI/Fe₃O₄ composite preparation. Such films show both reasonably high electrical conductivity and magnetic permeability. A controlled application of a magnetic field during the casting process resulted in the formation of the materials with an unusual combination of magnetic and transport properties. The obtained films show the behavior that can be explained by the presence of both ferromagnetic and paramagnetic phases. The superparamagnetic contribution, if any, is very small. Application of the external magnetic field during fabrication of the composites stimulates creation of the aggregates of magnetic particles which, although keeps conductivity at a relatively high level, leads to a small decrease of the conductivity value.     

Photoionization and photodissociation dynamics of the B 1sigmau + and C 1Piu states of H2 and D2

The photoionization and photodissociation dynamics of H(2) and D(2) in selected rovibrational levels of the B (1)Sigma(u) (+) and C (1)Pi(u) states have been investigated by velocity map ion imaging. The selected rotational levels of the B (1)Sigma(u) (+) and C (1)Pi(u) states are prepared by three-photon excitation from the ground state. The absorption of fourth photon results in photoionization to produce H(2)(+) X (2)Sigma(g)(+) or photodissociation to produce a ground-state H(1s) atom and an excited H atom with n >or= 2. The H(2) (+) ion can be photodissociated by absorption of a fifth photon. The resulting H(+) or D(+) ion images provide information on the vibrational state dependence of the photodissociation angular distribution of the molecular ion. The excited H(n >or= 2) atoms produced by the neutral dissociation process can also be ionized by the absorption of a fifth photon. The resulting ion images provide insight into the excited state branching ratios and angular distributions of the neutral photodissociation process. While the experimental ion images contain information on both the ionic and neutral processes, these can be separated based on constraints imposed on the fragment translational energies. The angular distribution of the rings in the ion images indicates that the neutral dissociation of molecular hydrogen and its isotopes is quite complex, and involves coupling to both doubly excited electronic states and the dissociation continua of singly excited Rydberg states.     

Mimicking primary processes in photosynthesis—covalently linked porphyrin quinones

Porphyrin quinones (P-Qs), covalently linked via different aliphatic bridges, have been synthesized and studies in their (porphyrin) cationic and (semiquinone) anionic radical states by EPR, ENDOR and TRIPLE resonance techniques. Electron transfer (ET) from the porphyrin donor to the quinone acceptor could be observed by time-resolved picosecond fluorescence spectroscopy (singlet ET) and by time-resolved EPR spectroscopy (triplet ET) in isotropic fluid solution and in anisotropic media (liquid crystals and reversed micelles). Steady-state in situ photoexcitation of P-Qs in CTAB cationic reversed micelles yielded the corresponding semiquinone radical anions. In TRITON X-100 reversed micelles both the radical cation of the porphyrin and the radical anion of the semiquinone could be detected, which occured in complete emission. In covalently linked porphyrin flavins ET from the photoexcited porphyrin fragment to the flavin and, in addition, energy transfer from the photoexcited flavin to the porphyrin could be observed.     

On some multiplicative product of kth derivative of Dirac's delta in x0+|x| and x0−|x|

In this paper we give a sense to the products $${{\left| x \right|^{(n - 2)/2} }} \cdot \frac{{\delta ^{(k - 1)} (x_0 + \left| x \right|)}} {{\left| x \right|^{(n - 2)/2} }}$$ and $\delta ^{(k - 1)} (x_0 - \left| x \right|) \cdot \delta ^{(k - 1)} (x_0 + \left| x \right|)$ . The first of them is a generalization of the product $${{\left| x \right|^{(n - 2)/2} }} \cdot \frac{{\delta (x_0 + \left| x \right|)}} {{\left| x \right|^{(n - 2)/2} }}{\text{ }}$$ given in [1, p. 158].     

Effect of methoxyl groups on the NMR spectra: configuration and conformation of natural and synthetic indanic and tetralinic structures

Here, we studied the influence of the methoxyl groups attached at C‐7 and C‐2′ of natural and synthetic 1‐arylindanes on the chemical shift of the signal of bibenzylic hydrogen and carbon atoms and J_1,2 coupling constants. This influence was also analysed in natural 1‐aryltetralins and related compounds that possess methoxyl and/or hydroxyl groups bound at C‐8 and C‐2′. The methoxyl groups attached at C‐7 in indanes or at C‐8 in tetralins produce a deshielding signal at H‐1 and shield at C‐1 and a strong decrease in the value of J_1,2 due to the pseudoequatorial location adopted by the aryl group bound at C‐1, avoiding an ‘A^1,3 strain’. Furthermore, compounds with hydroxyl or methoxyl groups in C‐2′, in the absence of substituents of C‐7 or C‐8, present a strong deshielding signal at H‐1, strong shield of the C‐1 signal and a decrease in the value of J_1,2. This is attributed to the stereoelectronic effects of the methoxyl or hydroxyl groups, which we have called ‘Asarone effect’. NOESY experiments were conducted to confirm the configuration and conformation of some of the compounds included in this work. This study shows that both effects, A^1,3 strain and Asarone effect, must be taken into account when the structure of natural indanes and tetralins is analysed by using ¹H‐NMR and ¹³C‐NMR spectra. Copyright © 2016 John Wiley & Sons, Ltd.     

Four Oxidation States in a Single Photoredox Nickel‐Based Catalytic Cycle: A Computational Study

The computational characterization of the full catalytic cycle for the synthesis of indoline from the reaction between iodoacetanilide and a terminal alkene catalyzed by a nickel complex and a photoactive ruthenium species is presented. A variety of oxidation states of nickel, Ni⁰, Ni^I, Ni^II, and Ni^III, is shown to participate in the mechanism. Ni⁰ is necessary for the oxidative addition of the C?I bond, which goes through a Ni^I intermediate and results in a Ni^II species. The Ni^II species inserts into the alkene, but does not undergo the reductive elimination necessary for C?N bond formation. This oxidatively induced reductive elimination can be accomplished only after oxidation to Ni^III by the photoactive ruthenium species. All the reaction steps are computationally characterized, and the barriers for the single‐electron transfer steps calculated using a modified version of the Marcus Theory.     

Synchronizing Substrate Activation Rates in Multicomponent Reactions with Metal–Organic Framework Catalysts

A study on the influence of the cation coordination number, number of Lewis acid centers, concurrent existence of Lewis base sites, and structure topology on the catalytic activity of six new indium MOFs, has been carried out for multicomponent reactions (MCRs). The new indium polymeric frameworks, namely [In₈(OH)₆(popha)₆(H₂O)₄]?3 H₂O ( InPF‐16 ), [In(popha)(2,2′‐bipy)]?3 H₂O ( InPF‐17 ), [In₃(OH)₃(popha)₂(4,4′‐bipy)]?4 H₂O ( InPF‐18 ), [In₂(popha)₂(4,4′‐bipy)₂]?3 H₂O ( InPF‐19 ), [In(OH)(Hpopha)]?0.5 (1,7‐phen) ( InPF‐20 ), and [In(popha)(1,10‐phen)]?4 H₂O ( InPF‐21 ) (InPF=indium polymeric framework, H₃popha=5‐(4‐carboxy‐2‐nitrophenoxy)isophthalic acid, phen=phenanthroline, bipy=bipyridine), have been hydrothermally obtained by using both conventional heating (CH) and microwave (MW) procedures. These indium frameworks show efficient Lewis acid behavior for the solvent‐free cyanosilylation of carbonyl compounds, the one pot Passerini 3‐component (P‐3CR) and the Ugi 4‐component (U‐4CR) reactions. In addition, InPF‐17 was found to be a highly reactive, recyclable, and environmentally benign catalyst, which allows the efficient synthesis of α‐aminoacyl amides. The relationship between the Lewis base/acid active site and the catalytic performance is explained by the 2D seven‐coordinated indium framework of the catalyst InPF‐17 . This study is an attempt to highlight the main structural and synthetic factors that have to be taken into account when planning a new, effective MOF‐based heterogeneous catalyst for multicomponent reactions.