Size effects in reactive circular site interactions

The complete series solution for the reactant diffusion and reaction at two diffusion-controlled chemically reactive surface sites of radii a(1) and a(2), located in an inert plane an arbitrary center-to-center distance d apart, is presented. Rigorous, analytical forms are developed to calculate the site reaction rates in terms of the dimensionless intersite distance σ[=d/(a(1) + a(2))] and the site radius ratio γ(=a(1)∕/a(2)). Numerical simulation and approximate theoretical results from the recent literature are compared to the exact site reaction rates. While general agreement was noted over the ranges of γ and σ, significant errors in the Wilemski-Fixman-Weiss site rates were found at small γ and σ < 3.     

Induced Nematic Phase of New Synthesized Laterally Fluorinated Azo/Ester Derivatives

A new series of laterally fluorinated mesomorphic compounds, namely 2-fluoro-4-((4-(alkyloxy)phenyl)diazenyl)phenyl 4-substitutedbenzoate (In_x) were prepared and evaluated for their mesophase behavior. The synthesized series constitutes five members that possess different terminally attached polar groups (X). Their molecular structures were confirmed by elemental analyses and both FT-IR and NMR spectroscopy. Examination of the prepared derivatives was conducted via experimental and theoretical tools. Mesomorphic investigations were carried by polarized optical microscopy (POM) and differential scanning calorimetry (DSC). DSC and POM measurements indicated that except for the un-substituted analogue, all other derivatives were purely nematogenic, possessing their nematic (N) mesophase enantiotropically. This is to say that insertions of terminal polar substituents on their mesogenic structures induced the N phase. In addition, the location of lateral and terminal polar moieties played a considerable role in achieving good thermal N stability. Computational calculations were investigated to determine the deduced optimized molecular structures. Theoretical data indicated that both size and polarity of the terminal substituent (X) have essential impact on the thermal parameters and optical properties of possible geometries.     

On the electronic structure of nitro-substituted bipyridines and their platinum complexes

We report the preparation and electrochemical studies of a systematic series of mono- and di-nitro-substituted 2,2'-bipyridine (bipy) compounds [x-NO(2)-bipy (x = 3,4) and x,x'-(NO(2))(2)-bipy (x,x' = 3, 4, 5)] and their complexes with platinum(II), [Pt(x-NO(2)-bipy)Cl(2)] and [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)]. The effect of the number and substitution pattern of the nitro groups on the low-lying acceptor molecular orbitals (involved in charge transfer transitions) is probed by in situ UV/Vis/NIR and EPR spectroelectrochemical methods, supported by DFT calculations. The LUMOs of x-NO(2)-bipy (x = 3-5) are largely localised on the NO(2)-pyridyl moiety; this is also true of their {PtCl(2)} complexes but with a small but significant shift of electron density from the nitro groups. The LUMOs of x,x'-(NO(2))(2)-bipy with x = 3 and 5 are delocalised over both NO(2)-pyridyl rings, but for 4,4'-(NO(2))(2)-bipy is localised on a single NO(2)-pyridyl ring. In all cases the LUMO of the [Pt(x,x'-(NO(2))(2)-bipy)Cl(2)] complexes is delocalised over both nitro-pyridyl rings. For all complexes, the 4(4') derivatives allows greatest overlap with metal valence orbitals in the LUMO.     

The composition and antimicrobial activities of Cyperus conglomeratus, Desmos chinensis var. lawii and Cyathocalyx zeylanicus essential oils

The essential oil compositions of the rhizomes of Cyperus conglomeratus (Cyperaceae) collected from Oman and the leaves of two Annonaceae plants, Desmos chinensis var. lawii and Cyathocalyx zeylanicus collected from India were studied by GC, GC-MS and 13C NMR spectroscopy. Twenty-six compounds, representing 84.4% of the oil were identified in C. conglomeratus, where eugenol (31.3%), alpha-cyperone (10.5%) and cyperotundone (8.4%) were the major compounds. Twelve compounds, constituting 100%, were identified in D. lawii oil, of which benzyl benzoate (58.7%), beta-caryophyllene (23.2%), limonene (4.9%) and alpha-humulene (4.0%) were the major constituents. Thirty-two compounds, comprising 98.0%, were identified in C. zeylanicus oil, of which beta-caryophyllene (21.6%), alpha-pinene (20.4%) and E-beta-ocimene (11.8%) were the major components. The antibacterial and antifungal activities of the oils were tested against a panel of five bacterial and two fungal strains. The oils showed moderate activity against all the tested microbial strains. The minimum inhibitory concentrations of the oils were also determined.     

A note on Schanuel’s conjectures for exponential logarithmic power series fields

In Ax (Ann. Math. 93(2):252–268, 1971), J. Ax proved a transcendency theorem for certain differential fields of characteristic zero : the differential counterpart of the still open Schanuel conjecture about the exponential function over ${\mathbb{C}}$ (Lang, Introduction to transcendental numbers, 1966). In this article, we derive from Ax’s theorem transcendency results in the context of differential valued exponential fields. In particular, we obtain results for exponential Hardy fields, Logarithmic-Exponential power series fields, and Exponential-Logarithmic power series fields.     

On a characterization of the essential spectra of some matrix operators and application to two-group transport operators

In this paper, we investigate the essential approximate point spectrum and the essential defect spectrum of a 2 × 2 block operator matrix on a Banach space. Furthermore, we apply the obtained results to two-group transport operators in the Banach space L _p ([−a, a] × [−1, 1]) × L _p ([−a, a] × [−1, 1]), a > 0, p ≥ 1.     

Determination of Y,Ba, Cu and O in superconductors by 14-MeV neutron activation

The possibility of using 14 MeV neutron activation for rapid, nondestructive elemental analysis of high T_c superconductors is considered. A method was elaborated and applied for investigating Y–Ba–Cu–O samples with different oxygen content. Derived from the measurements of a typical sample the uncertainty of the elemental concentrations, including oxygen, is not more than 1. 1%.     

Experimental investigation of statistical density function of decaying radioactive sources

The validity of the Poisson and theP(k) modified Poisson statistical density functions of observing k events in a short time interval t=T/n, proposed previously by others, is investigated experimentally in radioactive decay detection for various measuring times, T. The experiments to measure radioactive decay were performed with 89my (T_1/2=16.06 s), using a multichannel analyzer operating in the multiscaling mode. According to the results, Poisson statistics adequately describes the counting experiment for short measuring times (up to T<0.5 T_1/2) and its application is recommended. However, analysis of the data demonstrated, with confidence, that for long measurements (T>1 T_1/2) Poisson distribution is not valid and the modified Poisson function is preferable.