Alternating copolymerisation of styrene and carbon monoxide in ionic liquids

Room temperature ionic liquids have been used as solvents for the palladium-catalysed copolymerisation of styrene and carbon monoxide. The behaviour of various ionic liquids, the nature and concentration of palladium catalyst, and the reusability of the catalyst-ionic liquid system are discussed. The effects of cation, anion and alkyl chain length of the ionic liquids on the reaction are also addressed. The yield of the polyketone in the ionic liquid systems is enhanced over conventional solvents studied under similar conditions.

Polar, non-coordinating ionic liquids as solvents for the alternating copolymerization of styrene and CO catalyzed by cationic palladium catalysts

The palladium-catalyzed copolymerization of styrene and CO in an ionic liquid solvent, 1-hexylpyridinium bis(trifluoromethanesulfonyl) imide, gave improved yields and increased molecular weights compared to polymerizations run in methanol.

Alternating ring-opening metathesis copolymerization of bicyclo[2.2.1]hept-2-ene and cyclopentene

Almost alternating copolymers of bicyclo[2.2.1]hept-2-ene and cyclopentene have been formed by ring-opening metathesis polymerization using a RuCl3-phenol catalyst system; this highly novel result is attributed to differential steric influences exerted by a hydrogen-bonded solvent cage which encloses the catalyst site.

Timing and trajectory in rhythm production

The Wing-Kristofferson movement timing model (A. M. Wing & A. B. Kristofferson, 1973a, 1973b) distinguishes central timer and motor implementation processes. Previous studies have shown that increases in interresponse interval (IRI) variability with mean IRI are due to central timer processes, not motor implementation. The authors examine whether this is true with IRI duration changes in binary rhythm production. Ten participants provided IRI and movement data in bimanual synchronous tapping under equal (isochronous) and alternating (rhythm) interval conditions. Movement trajectory changes were observed with IRI duration (300, 500, or 833 ms) and for 500-ms IRIs produced in rhythm contexts (300/500 ms, 500/833 ms). However, application of the Wing-Kristofferson model showed that duration and context effects on IRI variability were attributable largely to timer processes with relatively little effect on motor processes.

Paired associative transcranial alternating current stimulation increases the excitability of corticospinal projections in humans

Many types of non-invasive brain stimulation alter corticospinal excitability (CSE). Paired associative stimulation (PAS) has attracted particular attention as its effects ostensibly adhere to Hebbian principles of neural plasticity. In prototypical form, a single electrical stimulus is directed to a peripheral nerve in close temporal contiguity with transcranial magnetic stimulation delivered to the contralateral primary motor cortex (M1). Repeated pairing of the two discrete stimulus events (i.e. association) over an extended period either increases or decreases the excitability of corticospinal projections from M1, contingent on the interstimulus interval. We studied a novel form of associative stimulation, consisting of brief trains of peripheral afferent stimulation paired with short bursts of high frequency (≥80 Hz) transcranial alternating current stimulation (tACS) over contralateral M1. Elevations in the excitability of corticospinal projections to the forearm were observed for a range of tACS frequency (80, 140 and 250 Hz), current (1, 2 and 3 mA) and duration (500 and 1000 ms) parameters. The effects were at least as reliable as those brought about by PAS or transcranial direct current stimulation. When paired with tACS, muscle tendon vibration also induced elevations of CSE. No such changes were brought about by the tACS or peripheral afferent stimulation alone. In demonstrating that associative effects are expressed when the timing of the peripheral and cortical events is not precisely circumscribed, these findings suggest that multiple cellular pathways may contribute to a long term potentiation-type response. Their relative contributions will differ depending on the nature of the induction protocol that is used.

The alternating least-squares algorithm for CDPCA

Clustering and Disjoint Principal Component Analysis (CDP CA) is a constrained principal component analysis recently proposed for clustering of objects and partitioning of variables, simultaneously, which we have implemented in R language. In this paper, we deal in detail with the alternating least-squares algorithm for CDPCA and highlight its algebraic features for constructing both interpretable principal components and clusters of objects. Two applications are given to illustrate the capabilities of this new methodology.

A Playful Glance at Hierarchical Questions for Two-Way Alternating Automata

Two-way alternating automata were introduced by Vardi in order to study the satisfiability problem for the modal μ-calculus extended with backwards modalities. In this paper, we present a very simple proof by way of Wadge games of the strictness of the hierarchy of Motowski indices of two-way alternating automata over trees.

The impact of drug-induced dyskinesias on rapid alternating movements in patients with Parkinson's disease

We investigated the likelihood that hypokinesia/bradykinesia coexist with druginduced dyskinesias (DID) in patients with Parkinson's disease (PD). The influence of dyskinesias on rapid alternating movements (RAM) was investigated in ten dyskinetic patients (DPD). Their motor performance was compared to that of ten age/gendermatched non-dyskinetic patients (NDPD) and ten healthy control subjects. Whole-body magnitude (WBM) and fast pronation-supination at the wrist were recorded using 6- degrees of freedom magnetic motion tracker and forearm rotational sensors, respectively. Subjects were asked to pronate-supinate their dominant hand for 10s. Pre- and postmeasures were taken in a neutral position for 20s. RANGE (measure of hypokinesia), DURATION (measure of bradykinesia). VELOCITY (measure of bradykinesia) and IRREGULARITY (measure of fluctuations in movement amplitude) were used to assess RAM performance. Results showed that DPD patients had greater WBM than NDPD and control groups during rest and RAM performance. There were no differences in performance between NDPD and DPD groups for RANGE, DURATION and VELOCITY, despite significant longer disease duration for the DPD group (DPD = 15.5 ± 6.2 years versus NDPD = 6.6 ± 2.6 years). However, both the NDPD and DPD groups showed lower RANGE, longer DURATION, and reduced VELOCITY compared to controls,, suggesting the presence of bradykinesia and hypokinesia. In the case of IRREGULARITY, DPD patients showed clear fluctuations in movement amplitude compared to the NDPD and control groups. However, the lack of correlation between WBM and IRREGULARITY within the DPD group (Spearman's rank order, Rho - 0.31, p > 0.05), suggests that DID was not the primary cause of the fluctuating movementamplitude observed in that group. In conclusion, these findings suggest that DID may coexists with bradykinesia and hypokinesia, but that they are not inevitably accompanied with worsening motor performance.

On Alternating Non-Context-Free Grammars

We study several extensions of the notion of alternation from context-free grammars to context-sensitive and arbitrary phrase-structure grammars. Thereby new grammatical characterizations are obtained for the class of languages that are accepted by alternating pushdown automata.

Anion-directed synthesis of metal-organic frameworks based on 2-picolinate Cu(II) complexes: a ferromagnetic alternating chain and two unprecedented ferromagnetic fish backbone chains

Three new polynuclear copper(II) complexes of 2-picolinic acid (Hpic), {[Cu-2(pic)(3)(H2O)]ClO4}(n) (1), {[Cu-2(pic)(3)(H2O)]BF4}(n) (2), and [Cu-2(pic)3(H2O)(2)(NO3)](n) (3), have been synthesized by reaction of the "metalloligand" [Cu-(pic)(2)] with the corresponding copper(II) salts. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. Compounds 1 and 2 are isomorphous and crystallize in the triclinic system with space group P (1) over bar, while 3 crystallizes in the monoclinic system with space group P2(1)/n. The structural analyses reveal that complexes 1 and 2 are constructed by "fish backbone" chains through syn-anti (equatorial-equatorial) carboxylate bridges, which are linked to one another by syn-anti (equatorial-axial) carboxylate bridges, giving rise to a rectangular grid-like two-dimensional net. Complex 3 is formed by alternating chains of syn-anti carboxylate-bridged copper(II) atoms, which are linked together by strong H bonds involving coordinated nitrate ions and water molecules and uncoordinated oxygen atoms from carboxylate groups. The different coordination ability of the anions along with their involvement in the H-bonding network seems to be responsible for the difference in the final polymeric structures. Variable-temperature (2-300 K) magnetic susceptibility measurement shows the presence of weak ferromagnetic coupling for all three complexes that have been fitted with a fish backbone model developed for 1 and 2 (J = 1.74 and 0.99 cm(-1); J' = 0.19 and 0.25 cm(-1), respectively) and an alternating chain model for 3 (J = 1.19 cm(-1) and J' = 1.19 cm(-1)).

Pyrene-functionalised, alternating copolyimide for sensing nitroaromatic compounds

A novel, pyrene-functionalised copolymer has been synthesised in a single step via imidisation of poly(maleic anhydride-alt-1-octadecene) with 1-pyrenemethylamine, and its potential for the detection of volatile nitro aromatic compounds (NACs) evaluated. The new copolymer forms complexes in solution with NACs such as 2,5-dinitrobenzonitrile, as shown by H-1 NMR, UV-vis and fluorescence spectroscopy. Moreover, thin films of this copolymer, cast from THF solution, undergo almost instantaneous fluorescence quenching when exposed to the vapour of 2,5-dinitrobenzonitrile (a model for TNT) at ambient temperatures and pressures.