A note on atomic density

In atomic systems, electron density has a simple finite expansion in spherical harmonics times radial factors. The difficulties in the calculation of some radial factors are illustrated in the low‐lying states of the carbon atom. Single‐particle methods such as Hartree–Fock and approximate density functional theory cannot ensure the correct expansion of the density in spherical harmonics. Wave‐function methods are appropriate but, as some expansion terms are entirely due to correlation, these methods only will give correct results for high‐quality variational functions. Using full‐configuration integration (CI), all the terms predicted by the theory appear and are not negligible but the convergence of the term due to correlation toward its correct value is uncertain even for very large CI spaces. © 2012 Wiley Periodicals, Inc.     

A continuous-mode model of the mode locking in a pump-modulated laser

The active mode-locking process of the multimode laser with an external pump modulation is theoretically investigated in the frequency domain within the framework of the continuous-mode approximation. Intermode interaction and mode-coupling effects, including both AM and FM modulations, are naturally considered in a hierarchical equation of the mode components derived from the multimode Maxwell-Bloch equations. It is reduced to a continuous-mode equation that can be solved analytically in a stationary case, and used to discuss the spectral line shape and the phase dynamics of mode-components as a function of modulation amplitude and detuning of the modulation frequency. We predict a novel oscillation existing below the threshold of the ordinary complete mode-locking: The intensity of the total electric field yields a stable pulse train but its phase varies irregularly in time. This semi-locked state is characterized by a nonlinear chirping, an asymmetric spectrum, and drifting phases of the field mode-components.     

UV Protective,Antioxidant, Antibacterial and Compostable Polylactic Acid Composites Containing Pristine and Chemically Modified Lignin Nanoparticles

Polylactic acid (PLA) films containing 1 wt % and 3 wt % of lignin nanoparticles (pristine (LNP), chemically modified with citric acid (caLNP) and acetylated (aLNP)) were prepared by extrusion and characterized in terms of their overall performance as food packaging materials. Morphological, mechanical, thermal, UV–Vis barrier, antioxidant and antibacterial properties were assayed; appropriate migration values in food simulants and disintegration in simulated composting conditions were also verified. The results obtained indicated that all lignin nanoparticles succeeded in conferring UV-blocking, antioxidant and antibacterial properties to the PLA films, especially at the higher filler loadings assayed. Chemical modification of the fillers partially reduced the UV protection and the antioxidant properties of the resulting composites, but it induced better nanoparticles dispersion, reduced aggregates size, enhanced ductility and improved aesthetic quality of the films through reduction of the characteristic dark color of lignin. Migration tests and disintegration assays of the nanocomposites in simulated composting conditions indicated that, irrespectively of their formulation, the multifunctional nanocomposite films prepared behaved similarly to neat PLA.     

Arens Regularity of Semigroup Algebras with Certain Locally Convex Topologies

The authors have recently introduced and studied a locally convex topology β¹(S) on the semigroup algebra M_a(S) of a locally compact semigroup S; as the main result, they showed that the strong dual of (M_a(S),β¹(S)) can be identified with the Banach space L^∞₀(S,M_a(S)) for a large class of locally compact semigroups S. Here, an application of this result is made to define and investigate an Arens multiplication on the second dual of (M_a(S),β¹(S)).     

Azahelicene-Fused BODIPY Analogues Showing Circularly Polarized Luminescence

Helical carbazole-based BODIPY analogues were readily synthesized via aza[7]helicenes. The structures of azahelicene-incorporated BF₂ dyes were elucidated by x-ray diffraction analysis. DFT calculations revealed that the π-conjugated system expanded from the helicene moiety to the BODIPY framework. The azahelicene-fused boron complexes showed the Cotton effects and the circularly polarized luminescence (CPL) in the visible region. Furthermore, an axially chiral binaphthyl group was attached to the helically chiral dyes, which enhanced the chiroptical properties.     

Natural radioactivity and radiation hazards assessment of soil samples from the area of Tuzla and Lukavac,Bosnia and Herzegovina

The results of activity concentration measurements of natural occurring radioactive nuclides ²³⁸U, ²³⁵U, ²³²Th, ²²⁶Ra, and ⁴⁰K in surface soil samples collected in the area of cities Tuzla and Lukavac, northeast region of Bosnia and Herzegovina were presented. Soil sampling was conducted at the localities that are situated in the vicinity of industrial zones of these cities. The measured activity was in the range from (8?±?4) to (95?±?28) Bq kg^–1 for ²³⁸U, from (0.41?±?0.06) to (4.6?±?0.7) Bq kg^–1 for ²³⁵U, from (7?±?1) to (66?±?7) Bq kg^–1 for ²³²Th, from (6?±?1) to (55?±?6) Bq kg^–1 for ²²⁶Ra, and from (83?±?12) to (546?±?55) Bq kg^–1 for ⁴⁰K. In order to evaluate the radiological hazard of the natural radioactivity for people living near industrial zones, the absorbed dose rate, the annual effective dose and the radium equivalent activity have been calculated and compared with the internationally approved values.     

Redesign of enzyme for improving catalytic activity and enantioselectivity toward poor substrates: manipulation of the transition state

Secondary alcohols having bulky substituents on both sides of the hydroxy group are inherently poor substrates for most lipases. In view of this weakness, we redesigned a Burkholderia cepacia lipase to create a variant with improved enzymatic characteristics. The I287F/I290A double mutant showed a high conversion and a high E value (>200) for a poor substrate for which the wild-type enzyme showed a low conversion and a low E value (5). This enhancement of catalytic activity and enantioselectivity of the variant resulted from the cooperative action of two mutations: Phe287 contributed to both enhancement of the (R)-enantiomer reactivity and suppression of the (S)-enantiomer reactivity, while Ala290 created a space to facilitate the acylation of the (R)-enantiomer. The kinetic constants indicated that the mutations effectively altered the transition state. Substrate mapping analysis strongly suggested that the CH/π interaction partly enhanced the (R)-enantiomer reactivity, the estimated energy of the CH/π interaction being -0.4 kcal mol(-1). The substrate scope of the I287F/I290A double mutant was broad. This biocatalyst was useful for the dynamic kinetic resolution of a variety of bulky secondary alcohols for which the wild-type enzyme shows little or no activity.     

Biogenous iron oxide-immobilized palladium catalyst for the solvent-free Suzuki–Miyaura coupling reaction

Iron oxide produced by iron-oxidizing bacteria, Leptothrix ochracea, (biogenous iron oxide: BIO) was used as a support for immobilized palladium catalysts with organic cross-linkers. Palladium immobilized on BIO bearing imidazolium chloride delivered the desired biaryl products in sufficient yields in the Suzuki–Miyaura coupling reactions under solvent-free conditions and could be reused several times without significant loss of catalytic activity. It is shown that BIO can be exploited as a useful support for immobilization of palladium and the BIO-immobilized palladium catalyst effectively promotes the solvent-free Suzuki–Miyaura coupling reactions.     

Effect of purification on dielectric properties near the commensurate‐incommensurate transition point of Rb2ZnCl4

Purification of Rb₂ZnCl₄ by recrystallization and zone melting is described in detail and the results of chemical analysis are given. Single crystals were grown from an aqueous solution which had been purified by repeated recrystallization. The thermal hysteresis of the dielectric constant in the purified crystal was reduced to 0.2 K from 2.8 K in the unpurified crystal. The switching time of the field-induced commensurate-incommensurate transition was shortened significantly in the vicinity of T_c . These indicate the weakening of pinning in the purified crystal. The low relaxation frequency of domain wall motion in the commensurate phase starts to rise abruptly when the transition to the incommensurate phase begins. This is understood to reflect a process in which the isolated domain walls are incorporated into the discommensuration lattice of the incommensurate phase. The mathematical analysis of the ordinary recrystallization process and the reverse process is given in Appendix.     

First Examples Exhibiting both Double Melting Behavior and Mesomorphism in a Series of Long Chain Substituted Compounds: 1,3-Di(p-n-alkoxyphenyl)propane-1,3-dione

A new series of β-diketones substituted by the same kind of chains, (alkoxy groups) having different lengths (C_nO-Diketone, n = 1-12), has been synthesized. It was found that C_nO-Diketone shows triple melting behavior for n = 1, double melting behavior for n = 2-7, and smectic mesomorphism for n = 8-12. It is the first example exhibiting both double (triple) melting behavior and mesomorphism in a series of long chain substituted compounds, so far as we know. Furthermore, it is noteworthy that the critical change from double melting behavior to mesomorphism occurs between n = 7 and n = 8, which is also the first example in the long chain substituted compounds, so far as we know.