Aqueous solution and solid state interactions of lanthanide ions with a methacrylic ester polymer bearing pendant 15‐crown‐5 moieties

The interaction between trivalent lanthanide ions and poly(1,4,7,10,13‐pentaoxacyclopentadecan‐2‐yl‐methyl methacrylate), PCR5, in aqueous solution and in the solid state have been studied. In aqueous solution, evidence of a weak interaction between the lanthanides and PCR5 comes from the small red shift of the Ce(III) emission spectra and the slight broadening of the Gd(III) EPR spectra. From the Tb(III) lifetimes in the presence of H₂O and D₂O the loss of one or two water coordinated molecules is confirmed when Tb(III) is bound to PCR5. An association constant of the order of 200 M^?1 was obtained for a 1:1 (lanthanide:15‐crown‐5) complex from the shift of the polymer NMR signals induced by Tb(III). A similar association constant is obtained from the differences of the molar conductivity of Ce(III) solution at various concentrations in presence and absence of PCR5. When Tb(III) is adsorbed on PCR5 membranes, lifetime experiments in H₂O and D₂O confirm the loss of 5 or 6 water coordinated molecules indicating that in solid state the lanthanide(III)‐PCR5 interaction is stronger than in solution. The adsorption of Ce(III) in PCR5 membranes shows a Langmuir type isotherm, from which an equilibrium constant of 39 M^?1 has been calculated. SEM shows that the membrane morphology is not much affected by lanthanide adsorption. Support for lanthanide ion–crown interactions comes from ab initio calculations on 15‐crown‐5/La(III) complex. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1788–1799, 2007     

RZ-DPSK signal regeneration based on dual-pump phase-sensitive amplification in fibers

All-optical regeneration of differential phase-shift keying signals by means of a phase-sensitive amplification scheme solely based on highly efficient four-wave mixing in fibers is theoretically and numerically studied. The analytical and numerical investigation demonstrates almost ideal phase regeneration accompanied with enhanced amplitude noise suppression in the regime of pump depletion.     

Diblock copolymers based on allyl methacrylate: Synthesis,characterization, and chemical modification

Different diblock copolymers constituted by one segment of a monomer supporting a reactive functional group, like allyl methacrylate (AMA), were synthesized by atom transfer radical polymerization (ATRP). Bromo‐terminated polymers, like polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(butyl acrylate) (PBA) were employed as macroinitiators to form the other blocks. Copolymerizations were carried out using copper chloride with N,N,N′,N″,N″‐pentamethyldiethylenetriamine (PMDETA) as the catalyst system in benzonitrile solution at 70 °C. At the early stage, the ATRP copolymerizations yielded well‐defined linear block copolymers. However, with the polymerization progress a change in the macromolecular architecture takes place due to the secondary reactions caused by the allylic groups, passing to a branched and/or star‐shaped structure until finally yielding gel at monomer conversion around 40% or higher. The block copolymers were characterized by means of size exclusion chromatography (SEC), ¹H NMR spectroscopy, and differential scanning calorimetry (DSC). In addition, one of these copolymers, specifically P(BA‐b‐AMA), was satisfactorily modified through osmylation reaction to obtain the subsequent amphiphilic diblock copolymer of P(BA‐b‐DHPMA), where DHPMA is 2,3‐dihydroxypropyl methacrylate; demonstrating the feasibility of side‐chain modification of the functional obtained copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3538–3549, 2007     

Quantification of trace elements in human serum fractions by liquid chromatography and inductively coupled plasma mass spectrometry

On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO₃ buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd.     

Solution-Processed n-Type Organic Field-Effect Transistors With High on /off Current Ratios Based on Fullerene Derivatives

Solution-processed n-type organic field-effect transistors (OFETs) based on the fullerene derivative {6}-1-(3-(2- thienylethoxycarbonyl)-propyl)-{5}-l-phenyl-[5,6]-C61 (TEPP) and phenyl-C61-butyric acid methyl ester (PCBM) in a multiring source/drain structure are reported. Devices with TEPP show high electron mobility up to 7.8 x 10^-2 cm²/Vs in the saturation regime for bottom-contact OFETs with Au S/D electrodes with a solution-processed fullerene derivative. The ON/OFF ratios reported in this letter, which are in the range of 10⁵ -10⁶, are among the highest values reported for such devices. This mobility is always higher compared to PCBM devices prepared in identical conditions. The mobility of TEPP and PCBM increased with increasing temperatures in the range of 100-300 K with activation energy of 78 and 113 meV, respectively, which suggests that the thermally activated hopping of electrons is dominant in TEPP.     

On Critical Stability of Three Quantum Charges Interacting Through Delta Potentials

We consider three one-dimensional quantum, charged and spinless particles interacting through delta potentials. We derive sufficient conditions which guarantee the existence of at least one bound state.     

Butyltins in california river and lake marina waters

Butyltins were analyzed in waters from California river and lake marinas and were detected at the part per trillion (ppt) level in most locations. The tributyltin:dibutyltin (TBT/DBT) ratios in the fresh waters were similar to those in their saline counterparts indicating like rates of degradation in the two salinity regimes.     

A VLSI CMOS delay oriented waveform converter for polyphasefrequency synthesizer

In this paper, we present a waveform converter implemented on a 0.25-μm CMOS technology using a dedicated design methodology (Delay Oriented Design). The circuit converts a square wave signal in both in-phase and quadrature-phase sinusoidal differential outputs. It also multiplies the frequency by seven. The output frequency range of this converter extends from 1.05 GHz up to 2.17 GHz. This converter is dedicated for the design of a third-generation mobile phone synthesizer using a double-loop architecture. For an output frequency of 2 GHz, the measured phase noise at 10-kHz offset from the carrier is -97 dBc/Hz. The circuit consumes 50 mW from a 2.5-V supply