Synthesis of olefins via a Wittig reaction mediated by triphenylarsine

An arsine-mediated Wittig reaction for the synthesis of olefins is described. After heating triphenylarsine in the presence of an activated alkyl bromide for 30 min, the resulting arsonium salt condensed with aldehydes in as little as 5 min at room temperature, yielding the olefins in high yields. Aromatic, heteroaromatic, and alkyl aldehydes were all suitable substrates for this process.     

Piezoelectric Immunosensors for Environmental Monitoring

This article is a tutorial review of piezoelectric immunosensors and their application to environmental monitoring.

The basic theory and historical developments of piezoelectricity are introduced. The development of piezoelectric sensors and eventually immunosensors for the specific detection of analytes of environmental importance are mentioned. The various assay formats and their advantages as well as examples of the different approaches taken by different analysers are also mentioned. Current developments within this laboratory on the development of piezoelectric immunosensors for the detection of okadaic acid and microcystin-LR are briefly introduced. The major drawbacks of piezoelectric immunosensors and their potential future are also discussed.     

Design and application of low-cost infrared data systems

The adaptation of a standard minicomputer to the processing of infrared spectroscopic data is described. The computer is interfaced to one of three high-performance infrared spectrophotometers and is supported by a flexible software package designed for the spectroscopist. The development of these computerized dispersive spectroscopy systems is discussed in terms of hardware and software. An indication of performance is included by reference to specific analytical applications.     

The metal complexes of some azo and azomethine dyestuffs : Part I. Spectra in water,and in dioxan/water in the wavelength range 320-600 mμ

The visible, spectra of the highly sensitive colorimetric reagent 4-(2-pyridylazo)-resorcinol (I), and of the coloured cpmplexes formed with copper(II), nickel(II), cobalt(II), lead(II), and uranium(VI) were obtained in water and in aqueous dioxan. The structures of these complexes were determined by spectrophotometric methods, and chelation by (I) established as essentially terdentate. Comparison is made with the visible spectra of salicylidene-2-aminopyridine (II), 2-(o-hydroxy-phenyl-imino-methyl)-pyridine (III), and benzeneazoresorcinol (IV), and of the metal complexes of (II) (III) and (IV). The red coloration obtained with 4-(2-pyridylazo)-resorcinol is explained by the presence of a pseudo-phenanthroline system and an o-o'-disubstituted azo system, the active groups in chelation being the pyridine nitrogen atom, the azo nitrogen farthest from the heterocycle, and the o-hydroxyl group.     

Synthesis, structure, and properties of [Pt(II)(diimine)(dithiolate)] dyes with 3,3'-, 4,4'-, and 5,5'-disubstituted bipyridyl: applications in dye-sensitized solar cells

A family of [Pt(II)(diimine)(dithiolate)] complexes of general formula [Pt{X,X'(CO(2)R)(2)-2,2'-bipyridyl}(maleonitriledithiolate)] (where X = 3, 4, or 5 and R = H or Et) have been synthesized, spectroscopically and electrochemically characterized, and attached to a TiO(2) substrate to be tested as solar cell sensitizers. A single-crystal X-ray structure showing a large torsion angle between the bipyridyl rings was determined for [Pt{3,3'(CO(2)Et)(2)-2,2'-bipyridyl}(maleonitriledithiolate)].MeCN. The effect of changing the position of the bipyridyl substituents from 3,3' to 4,4' and 5,5' is discussed with reference to structural and electronic changes seen within the different members of the family of molecules. The first UV/vis/NIR spectroelectrochemical study of complexes of this general formula is discussed. All three complexes (where R = H) were tested as solar cell sensitizers, with the 3,3'-disubstituted bipyridyl complex giving an intermediate dye loading value but superior photovoltaic performance to those of the other two. The performance of this sensitizer is then compared with that of a well-known Ru polypyridyl sensitizer, the ditetrabutylammonium salt of [RuL(2)(NCS)(2)] (L = 2,2'-bipyridyl-4,4'-dicarboxylato), commonly called N719.     

Functional neural network analysis in frontotemporal dementia and Alzheimer's disease using EEG and graph theory

Background  

Although a large body of knowledge about both brain structure and function has been gathered over the last decades, we still have a poor understanding of their exact relationship. Graph theory provides a method to study the relation between network structure and function, and its application to neuroscientific data is an emerging research field. We investigated topological changes in large-scale functional brain networks in patients with Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD) by means of graph theoretical analysis of resting-state EEG recordings. EEGs of 20 patients with mild to moderate AD, 15 FTLD patients, and 23 non-demented individuals were recorded in an eyes-closed resting-state. The synchronization likelihood (SL), a measure of functional connectivity, was calculated for each sensor pair in 0.5–4 Hz, 4–8 Hz, 8–10 Hz, 10–13 Hz, 13–30 Hz and 30–45 Hz frequency bands. The resulting connectivity matrices were converted to unweighted graphs, whose structure was characterized with several measures: mean clustering coefficient (local connectivity), characteristic path length (global connectivity) and degree correlation (network 'assortativity'). All results were normalized for network size and compared with random control networks.