Empirical likelihood for balanced ranked-set sampled data

Ranked-set sampling (RSS) often provides more efficient inference than simple random sampling (SRS). In this article, we propose a systematic nonparametric technique, RSS-EL, for hypothesis testing and interval estimation with balanced RSS data using empirical likelihood (EL). We detail the approach for interval estimation and hypothesis testing in one-sample and two-sample problems and general estimating equations. In all three cases, RSS is shown to provide more efficient inference than SRS of the same size. Moreover, the RSS-EL method does not require any easily violated assumptions needed by existing rank-based nonparametric methods for RSS data, such as perfect ranking, identical ranking scheme in two groups, and location shift between two population distributions. The merit of the RSS-EL method is also demonstrated through simulation studies. This work was supported by National Natural Science Foundation of China (Grant No. 10871037)     

Search for lowest-energy fullerenes: C98 to C110

By combining the semiempirical density-functional based tight-binding optimization with density-functional theory single-point energy calculation at the PBE1PBE/6-311G level, we propose an efficient computational approach to determine lowest-energy structures of large-sized carbon fullerenes. Our studies show that C(92) (D(3): 28) and C(94) (C(2): 43) are the new leading candidates for the lowest-energy structures of C(92) and C(94). Moreover, for the first time, the lowest-energy structures of C(98)-C(110) are identified on the basis of the density-functional theory calculation. The lowest-energy isomers C(102) (C(1): 603) and C(108) (D(2): 1771) are readily isolated experimentally because they are much lower in energy than their other low-lying IPR isomers.     

The first structurally characterized nitrosyl heme thiolate model complex

The NO ligand in the formally {FeNO}6 compound [Fe(oep)(NO)(thiolate)] is bent, and does not impart a significant structural trans effect to the Fe-S bond.     

Application of a multi-dentate amphiphilic compound to transfer silver nanoparticles into an organic solvent

A multi-dentate amphiphilic compound, 3,3'-(dodecylazanediyl)-bis-[N-(2-aminoethyl)propanamide] (12C-2NH2) has been synthesized. The molecular structure was characterized by Fourier transform infrared (FT-IR) spectroscopy, ultraviolet-visible (UV-vis) spectra, nuclear magnetic resonance (NMR) spectra, and fast atom bombardment mass (FAB-MS) spectra. 12C-2NH2 was employed to stabilize silver nanoparticles. Surface properties and stability of silver nanoparticles were controlled by adjusting the 12C-2NH2 to silver (0) molar ratio. 12C-2NH2 was also applied to transfer silver nanoparticles from an aqueous to an organic phase. The transfer efficiency depends on 12C-2NH2 concentration. When 12C-2NH2 to silver (0) molar ratio was 2:1, the highest efficiency of phase transfer to toluene was obtained. These 12C-2NH2 stabilized silver nanoparticles are very stable over a period of four days in toluene.     

Interfacial tension in phase-separated aqueous cationic/anionic surfactant mixtures

Interfacial tensions in two aqueous phase-separated cationic/anionic surfactant mixtures, CTAB/AS and 12-3-12/AS, without and with NaBr added were determined by the spinning drop method at 318.15 K. CTAB, 12-3-12 and AS are the abbreviations for cetyltrimethylammonium bromide, 1,3-propanediyl-bis(dodecyldimethylammonium bromide) and sodium dodecyl sulfonate, respectively. The interfacial tension sigma was found to be in the range of 0.06-21 microNm(-1). Toward a better understanding of the influence of the concentration difference between the separated phases in aqueous two-phase systems (ATPS) to interfacial tension, compositions of equilibrium phases were determined by elemental analysis coupled with material balance and electroneutrality. The investigation indicates that the concentration differences of surfactant ions between the separated phases and the adsorption of surfactant ions at the interface are the decisive factors determining the magnitude of interfacial tension.     

Enantioselective synthesis of N1999A2

An enantioselective synthetic route to the enediyne antibiotic N1999A2 (1) is described, proceeding in 21 steps (0.4% yield, 77% average yield per step) from (R)-(+)-glycidol. The route involves the convergent assembly of three components: a (1-iodovinyl) stannane (2), a 1,5-hexadiyne-3,4-diol derivative (3), and a substituted naphthoic acid (4). Important transformations in the synthetic sequence include the palladium-catalyzed coupling of 2 and 3, an intramolecular oxidative cyclization of a terminal bisacetylene, and a transannular anionic (bi)cyclization of a cyclic bromoenetriyne. The careful selection and manipulation of protective groups throughout the sequence proved to be critical to the development of the synthetic route, where all late-stage intermediates were unstable and could not be concentrated. In the final step of the sequence, three protective groups were removed in a single operation, providing synthetic N1999A2 (1) in 76% yield. Conditions were found that, for the first time, led to the precipitation of 1 as a solid.     

Novel potentiometric and optical silver ion-selective sensors with subnanomolar detection limits

Ten Ag⁺-selective ionophores have been characterized in terms of their potentiometric selectivities and complex formation constants in solvent polymeric membranes. The compounds with π-coordination show much weaker interactions than those with thioether or thiocarbamate groups as the coordinating sites. Long-term studies with the best ionophores show that the lower detection limit of the best Ag⁺ sensors can be maintained in the subnanomolar range for at least 1 month. The best ionophores have also been characterized in fluorescent microspheres. The so far best lower detection limits of 3 × 10⁻¹¹ M (potentiometrically) and 2 × 10⁻¹¹ M Ag⁺ (optically) are found with bridged thiacalixarenes.     

Electrostatic field-adapted molecular fractionation with conjugated caps for energy calculations of charged biomolecules

An electrostatic field-adapted molecular fractionation with conjugated caps (EFA-MFCC) approach is implemented for treating macromolecules with several charge centers. The molecular fragmentation is performed in an "electrostatic field," which is described by putting point charges on charge centers, directly affecting the Hamiltonians of both fragments and conjugated caps. So the present method does not need truncation during the calculation of electrostatic interactions. Our test calculations on a series of charged model systems and biological macromolecules using the HF and B3LYP methods have demonstrated that this approach is capable of describing the electronic structure with accuracy comparable to other fragment-based methods. The EFA-MFCC approach is an alternative way for predicting the total energies of charged macromolecules with acyclic, loop, and intersectional loop structures and interaction energies between two molecules.     

Stability for parametric implicit vector equilibrium problems

In this paper, we consider a class of parametric implicit vector equilibrium problems in Hausdorff topological vector spaces where a mapping f and a set K are perturbed by parameters and λ, respectively. We establish sufficient conditions for the upper semicontinuity and lower semicontinuity of the solution set mapping S:Λ₁×Λ₂→2^X for such parametric implicit vector equilibrium problems.     

Existence of Solutions to Generalized Vector Quasi-Equilibrium Problems with Discontinuous Mappings

Let X, Y be two finite-dimensional topological vector spaces, Z a Hausdorff topological vector space, K C X and D C Z be two nonempty sets, C be a pointed, closed, and convex cone in Y with int C ≠θ Let S ： K → 2^K and T ： K → 2^D be two multivalued mappings, and φ ： K × D × K → Y be a trifunction. In this paper, we consider the generalized vector quasi-equilibrium problem, which is formulated by finding X∈ K and y∈ T（x） such that x∈ E S（x） and φ（x,y, u） （∈/） -int C for all u ∈ S（x）. We establish an existence result in which T is not supposed to have any continuity property. Our results extend and improve the corresponding results of Cubiotti, Yao and Guo.