Hybrid materials utilizing polyelectrolyte-derivatized carbon nanotubes and vanadium-mixed addenda heteropolytungstate for efficient electrochemical charging and electrocatalysis

Preparation and electrochemical behavior of new hybrid materials composed of multi-walled carbon nanotubes (CNTs) that were derivatized with poly(diallyldimethylammonium) chloride and modified with vanadium-mixed addenda Dawson-type heteropolytungstate, [P₂W₁₇VO₆₂]^8?, is described here. These nanostructured composite systems exhibited fast dynamics of charge propagation. They were characterized by the transport (effectively diffusional) kinetic parameter of approximately 8?×?10^?8 cm^?2 s^?1/2 and the specific capacitance parameter of 82 F g^?1 (at the charging/discharging current of 200 mA g^?1). The latter parameter for bare CNTs was found to be only 50 F g^?1 under analogous conditions. These observations were based on the results of galvanostatic charging–discharging, cyclic voltammetric, and AC impedance spectroscopic measurements. The improved capacitance properties were attributed to the systems’ pseudocapacitive features originating from the fast redox transitions of the [P₂W₁₇VO₆₂]^8? polyanions. In addition to the fast redox conduction, the proposed organic–inorganic hybrid materials exhibited interesting electrocatalytic activity toward reduction of bromate in the broad concentration range (sensitivity, 0.24 mA cm^?2 mmol^?1 dm³).     

Expeditious synthesis of ‘P’-protected macrocycles en route to lanthanide chelate metal complexes

Phosphonic acid appended tetraazacyclododecane (cyclen)-based macrocycles are attractive metal-ion chelators for diagnostic imaging and therapeutic delivery. Here, we report a novel P-protected methodology that facilitates the rapid synthesis and purification of targeted phosphonic acid bearing macrocycles. Purification of these intermediates is facile, and deprotection using neat TFA is rapid, yet mild enough to preserve the integrity of delicate peptides and/or targeting moieties.     

Regularity of the Optimal Feedback and the Value Function in Convex Problems of Optimal Control

An optimal feedback mapping, leading to necessary and sufficient conditions for optimality in terms of a closed-loop differential inclusion, is derived in the setting of fully convex generalized problems of Bolza. Results are translated to the format of control problems with linear dynamics and convex costs. Properties of the feedback mapping, with focus on single-valuedness and continuity, are analyzed through those of the value function and of the Hamiltonian. Conditions guaranteeing differentiability of the value function are obtained through the analysis of its subdifferential as a maximal monotone operator and of the generalized Hamiltonian dynamics.     

Identification of In Vitro Metabolites of Amoxicillin in Human Liver Microsomes by LC–ESI/MS

Amoxicillin (AMOX) metabolism in human liver microsomes was studied in vitro using liquid chromatography–mass spectrometry (LC/MS). Amoxicillin was incubated with human liver microsomes along with NADPH, and the reaction mixture was analyzed by LC/MS to obtain the specific metabolic profile of the studied antibiotic drug. Positive electrospray ionization was employed as the ionization source. An ACE C18-column (4.6 mm × 150 mm, 3 μm) was implemented with acetonitrile and water (+0.1 % formic acid) in isocratic mode as the mobile phase at the flow 0.4 mL min^?1. The chemical structures of metabolites were proposed on the basis of the accurate mass measurement of the protonated molecule as well as their main product. Six phase I and one phase II metabolites were detected and structurally described. The metabolism of AMOX occurred via oxidation, hydroxylation and oxidative deamination, as well as through combination of these reactions. Compound M7, with glucuronic acid was also observed as phase II metabolite. Neither sulfate nor glutathione conjugates were detected. This study presents novel information about the chemical structure of the potential AMOX metabolites and provides vital data for further pharmacokinetic and in vivo metabolism studies.     

Photonic crystal fibers with material anisotropy

In this paper we are modeling the interplay of material and form birefringence in photonic crystal fibers. We introduce an efficient numerical method for the calculation of the modal structure. Our approach relies solving the fully vectorial wave equation for the transverse magnetic field and the respective propagation constants using a plane wave expansion. The method accounts for a simple form of material anisotropy. Our analysis is relevant to certain application areas, and in particular to fiber sensing, where material birefringence arises for instance due to transversally applied mechanical stress. We analyze the influence of material birefringence on the modal birefringence and the state of polarization of the fundamental mode.     

Retroperitoneal germ cell neoplasm: MR and CT.

A case of germ cell neoplasm in an undescended retroperitoneal testicle is reported. CT revealed a large mass most consistent with a chronic hematoma. MRI demonstrated findings typical for neoplasm, and this was confirmed on biopsy.     

Pharmacokinetic study of amoxicillin in human plasma by solid‐phase microextraction followed by high‐performance liquid chromatography–triple quadrupole mass spectrometry

Sensitive and selective analytical procedures based on high‐performance liquid chromatography with mass spectrometric detection were developed for the determination of amoxicillin in human plasma samples. Samples were prepared by applying in‐house manufactured molecularly imprinted solid‐phase microextraction probes. The detection of target compounds was performed in multiple reaction monitoring mode. The multiple reaction monitoring detection was operated in the positive electrospray ionization mode using the transitions of m/z 366 ([M + H]⁺) → 349 for amoxicillin and m/z 390 ([M + H]⁺) → 372 for gemifloxacin. The method was validated with precision within 15% relative standard deviation and accuracy within 15% relative error. The method was successfully applied to study of the pharmacokinetics of amoxicillin in human plasma after oral administration of amoxicillin. Copyright © 2013 John Wiley & Sons, Ltd.     

Periodic inclusion of room-temperature-ferromagnetic metal phosphide nanoparticles in carbon nanotubes

We demonstrate the use of sequential catalytic growth to encapsulate iron, nickel-iron, and iron-cobalt phosphide catalyst nanoparticles periodically along the entire lengths of carbon nanotubes. Investigations by local electron spectroscopies and electron diffraction reveal the compositions and crystal structures of the encapsulated particles. Significantly, high spatial resolution magnetic characterization using magnetic force microscopy and off-axis electron holography demonstrates that encapsulated iron-cobalt phosphide nanoparticles are ferromagnetic at room temperature, in accordance with the properties of bulk metal phosphides of the same structure and composition.     

Precursor and Solvent Effects in the Nonhydrolytic Synthesis of Complex Oxide Nanoparticles for Bioimaging Applications by the Ether Elimination (Bradley) Reaction

Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol–gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu³⁺. They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu‐doped BaTiO₃ particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes.     

A Bistable Poly[2]catenane Forms Nanosuperstructures

Side‐chain poly[2]catenanes at the click of a switch! A bistable side‐chain poly[2]catenane has been synthesized and found to form hierarchical self‐assembled hollow superstructures of nanoscale dimensions in solution. Molecular electromechanical switching (see picture) of the material is demonstrated, and the ground‐state equilibrium thermodynamics and switching kinetics are examined as the initial steps towards processible molecular‐based electronic devices and nanoelectromechanical systems.