A new and high yielding synthesis of unstable pyrroles via a modified Clauson-Kaas reaction

An investigation of the reaction requirements to effect the Clauson-Kaas pyrrole synthesis led to the formulation of a new procedure that avoids the contact of pyrroles to heat or strongly acidic conditions that cause decomposition of the desired products. The procedure involves mild hydrolysis of 2,5-dimethoxytetrahydrofuran in water to the activated species 2,5-dihydroxytetrahydrofuran that reacts with primary amines in an acetate buffer at room temperature to give N-substituted pyrroles in high yield. In the case of chiral amines, pyrrole formation proceeds with no detectable epimerisation. Acid- or heat-sensitive pyrroles are also obtained in high yield and purity.     

Coherent state transfer between an electron and nuclear spin in (15)N@C(60)

Electron spin qubits in molecular systems offer high reproducibility and the ability to self-assemble into larger architectures. However, interactions between neighboring qubits are "always on," and although the electron spin coherence times can be several hundred microseconds, these are still much shorter than typical times for nuclear spins. Here we implement an electron-nuclear hybrid scheme which uses coherent transfer between electron and nuclear spin degrees of freedom in order to both effectively turn on or off interqubit coupling mediated by dipolar interactions and benefit from the long nuclear spin decoherence times (T(2n)). We transfer qubit states between the electron and (15)N nuclear spin in (15)N@C(60) with a two-way process fidelity of 88%, using a series of tuned microwave and radio frequency pulses and measure a nuclear spin coherence lifetime of over 100 ms.     

Combinatorial study of a gold nanoparticle infusion process in a polymer film

A novel two-step process is described for infusion of gold nanoparticles (5–20 nm typical diameter) into a polymer film. The technique is demonstrated for the first time in a thermoplastic polyurethane elastomer (TPU). An amine-functional monomer, 2-(diethylamino)ethyl methacrylate, and a free-radical photoinitiator are infused into the surface of the TPU, followed by photopolymerization. An amine-functional semi-interpenetrating network (SIPN) is created within a shallow (~100 μm) surface layer. In the second step, a gold salt, HAuCl₄·3H₂O, is infused into the SIPN from a ternary solvent mixture, and redox reaction with the immobilized amine functional groups produces Au⁰ nanoparticles. Combinatorial processing is conducted to visualize the interdependent effects of two variables, monomer soak time (t ₁) and gold salt solution soak time (t ₂). Combinatorial infusion is accomplished by creating orthogonal gradients in t ₁ and t ₂ in a square TPU plate, allowing examination of sample color, particle size, and polydispersity over a wide range of parameter space. Small angle X-ray scattering (SAXS) is employed as non-invasive means to characterize the Au⁰ particles at three locations in the plate. SAXS measurements are validated by TEM analysis of Au⁰ particle size in a reference sample. A rationale is developed for changing particle size and polydispersity through variation of simple process parameters.     

Common fixed point results for noncommuting mappings without continuity in generalized metric spaces

Using the setting of a generalized metric space, a fixed point theorem is proved for one map, and several fixed point theorems are proved for two maps. These results generalize several well known comparable results in the literature.     

A new one-step iterative scheme for approximating common fixed points of two multivalued nonexpansive mappings

In this paper, we introduce a new one-step iterative process to approximate the common fixed points of two multivalued nonexpansive mappings. We will also prove a strong convergence theorem in a uniformly convex Banach space under the multivalued version of so-called Condition (A′).     

Molecular dynamics of reactions between (4,0) zigzag carbon nanotube and hydrogen peroxide under extreme conditions

ABSTRACT

Single-wall carbon nanotubes (CNTs) have been suggested as potential materials for use in next-generation gas sensors. The sidewall functionalisation of CNTs facilitates gas molecule adsorption. In this study, density functional theory (DFT)-based ab initio molecular dynamics simulations are performed for a periodic zigzag single-wall (4,0) CNT surrounded by a monolayer of hydrogen peroxide molecules in an attempt to find conditions that favour sidewall functionalisation. The dependency of dynamics on charge states of the system is examined. It is found negative charges favour reactions that result in the functionalisation of the CNT. First principles molecular dynamics of defect formation yields chemically reasonable structure of stable defects, which can be reproduced in CNTs of any diameter and chirality. The explored hydroxyl and hydroperoxyl defects increase conductivity in a large diameter (10,0) CNT, while decrease conductivities in a small diameter (4,0) CNT.     

The convergence of matrix transforms for certain Markov chains

In this paper it is shown that, for certain classes of matrices, the matrix transform of a periodic strongly ergodic stochastic matrix P converges.     

Structural characterization of phosphatidyl-<Emphasis Type="Italic">myo</Emphasis>-inositol mannosides from <Emphasis Type="Italic">Mycobacterium bovis</Emphasis> bacillus calmette guérin by multiple-stage quadrupole ion-trap mass spectrometry with electrospray ionization. I. PIMs and lyso-PIMs

We described a multiple-stage ion-trap mass spectrometric approach to characterize the structures of phosphatidylinositol and phosphatidyl-myoinositol mannosides (PIMs) in a complex mixture isolated from Mycobacterium bovis Bacillus Calmette Guérin. The positions of the fatty acyl substituents of PIMs at the glycerol backbone can be easily assigned, based on the findings that the ions arising from losses of the fatty acid substituent at sn-2 as molecules of acid and of ketene, respectively (that is, the [M - H - R(2)CO(2)H](-) and [M - H - R(2)CHCO](-) ions), are respectively more abundant than the ions arising from the analogous losses at sn-1 (that is, the [M - H - R(1)CO(2)H](-) and [M - H - R(1)CHCO](-) ions) in the MS(2) product-ion spectra of the [M - H](-) ions desorbed by electrospray ionization (ESI). Further dissociation of the [M - H - R(2)CO(2)H](-) and [M - H - R(1)CO(2)H](-) ions gives rise to a pair of unique ions corresponding to losses of 74 and 56 Da (that is, [M - H - R(x)CO(2)H - 56](-) and [M - H - R(x)CO(2)H - 74](-) ions, x = 1, 2), respectively, probably arising from various losses of the glycerol. The profile of the ion-pair in the MS(3) spectrum of the [M - H - R(2)CO(2)H](-) ion is readily distinguishable from that in the MS(3) spectrum of the [M - H - R(1)CO(2)H](-) ion and thus the assignment of the fatty acid substituents at the glycerol backbone can be confirmed. The product-ion spectra of the [M - H](-) ions from 2-lyso-PIM and from 1-lyso-PIM are discernible and both spectra contain a unique ion that arises from primary loss of the fatty acid substituent at the glycerol backbone, followed by loss of a bicyclic glycerophosphate ester moiety of 136 Da. The combined structural information from the MS(2) and MS(3) product-ion spectra permit the complex structures of PIMs that consist of various isomers to be unveiled in detail.