Copper(II) bromide as efficient catalyst for silyl- to bisarylmethyl ethers interconversion (transprotection)

Primary and secondary silylated alcohols are easily converted to bis(methoxyphenyl)methyl (BMPM) ethers in good yields using CuBr₂ as catalyst in acetonitrile at room temperature. Various other protecting groups are compatible with this mild and convenient process.     

A Bis-Acridinium Macrocycle as Multi-Responsive Receptor and Selective Phase-Transfer Agent of Perylene

A bis-acridinium cyclophane incorporating switchable acridinium moieties linked by a 3,5-dipyridylanisole spacer was studied as a multi-responsive host for polycyclic aromatic hydrocarbon guests. Complexation of perylene was shown to be the most effective and was characterized in particular by a charge-transfer band as signal output. Effective catch and release of the guest was triggered by both chemical (proton/hydroxide) and redox stimuli. Moreover, the dicationic host was also easily switched between organic and perfluorocarbon phases for applications related to the enrichment of perylene from a mixture of polycyclic aromatic hydrocarbons.     

Transient and statistical measurement techniques for two-phase flows: A critical review

Much work has been expended in the study of two-phase, gas-liquid flows. While it has been recognized superficially that such flows are not homogeneous in general, little attention has been paid to the inherent discreteness of the two-phase systems. It has been a relatively recent development that fluctuating characteristics of two-phase flows have been studied in detail. As a result, new experimental devices and techniques have been developed for use in obtaining measurements of quantities previously ignored. This paper reviews and summarizes these methods in an effort to emphasize the importance of the fluctuating nature of these flows and as a guide to further research in this field.     

Conductometric tyrosinase biosensor for the detection of diuron, atrazine and its main metabolites

The determination of diuron, atrazine, desisopropylatrazine (DIA) and desethylatrazine (DEA) were investigated using conductometric tyrosinase biosensor. Tyrosinase was immobilised on the biosensor sensitive part by allowing it to mix with bovine serum albumin (BSA) and then cross-linking in saturated glutaraldehyde (GA) vapour for 30 min. The determination of pollutants in a solution was performed by comparison of the output signal (i.e percentage of the enzymatic activity) of the biosensor before and after contact with pollutants. The measurement of the enzymatic activity was performed using 4-chlorophenol, phenol and catechol substrates and response times ranging from 1 to 5 min were observed. A 4-chlorophenol substrate was used to detect pesticides. A 30 min contact time of the biosensor in the pollutant solution was used. Under the experimental conditions employed, detection limits for diuron and atrazine were about 1 ppb and dynamic range of 2.3-2330 and 2.15-2150 ppb were obtained for diuron and atrazine, respectively. A relative standard deviation (n=3) of the output signal was estimated to be 5% and a slight drift of 1.5 μS h⁻¹ was observed. The 90% of the enzyme activity was still maintained after 23 days of storage in a buffer solution at 4 °C.     

Elasto-visco-plastic modeling of mild steels for sheet forming applications over a large range of strain rates

A physically based elasto-visco-plastic constitutive model is presented and compared to experimental results for three different mild steels. The experiments consist of tensile tests ranging from quasi-static conditions up to strain rates of 10³ s^?1 as well as quasi-static simple and reverse shear tests at different amounts of pre-strain. Additional two-step sequential mechanical tests (Bauschinger and orthogonal effects) have been performed to further evaluate the ability of the model to describe strain-path changes at moderate/large strains. The model requires significantly fewer material parameters compared to other visco-plasticity models from the literature, while being able to describe some of the main features of the strain-rate sensitivity of mild steels. Accordingly, the parameter identification is simple and intuitive, requiring a relatively small set of experiments. The strain-rate sensitivity modeling is not restricted to a particular hardening law and thus provides a general framework in which advanced hardening equations can be adopted.     

Preparation of Chiral Building Blocks for Starburst Dendrimer Synthesis

Double aldols, formally derived from acetic acid and two different aldehydes, as obtained by addition of the enolate of (R,R)-2-(tert-butyl)-6-methyl-1,3-dioxan-4-one ( A ) to various aldehydes, are reduced to triols which are actually substituted chiral ‘tris(hydroxymethyl)methanes’ (see B and 3–8 ). Etherifications of the three OH groups of these triols with functionalized halides (allyl, 4-(silyloxy)but-2-en-l-yl, 4-substituted benzyl) and esterifications with pent-4-enoic and 3,5-dinitrobenzyl chlorides, followed by functional group manipulations, lead to the potential center pieces 14–30 for the construction of chiral dendrimers: the building blocks prepared contain the required ‘spacers’ between the core unit, as well as three vinyl groups, three aryl bromide groups, three alcoholic or phenolic OH groups, three mesylate groups, three ester groups, or six arylamino groups at the terminus of their branches. The new compounds are all obtained on a preparative scale and are fully characterized (including elemental analysis).     

The two-phase water/silicon oil bioreactor prospects in off-gas treatment

Research was carried out to develop a biphasic biologic reactor able to clean the gas effluents polluted by volatile organic compounds. Initially, Rhodococcus erythropolis T 902.1 was selected on the basis of its capacity to degrade isopropylbenzene (IPB). The effect of gas flow and IPB concentration on the biodegadation of IPB was evaluated. The results show that the use of silicon oil allows large quantities of IPB to be absorbed within the medium of biologic abatement. On the other hand, the biodegradation rate was directly correlated to the inlet flow of IPB. Thus, the reactor presents interesting opportunities for the biologic treatment of gas effluents.     

The β-lactone route to α,β-unsaturated δ-lactones. Total syntheses of (±)-goniothalamin and (−)-massoialactone

The HF-induced translactonization of 2′-silyloxy-3-trimethylsilyl-2-oxetanones, obtained through Lewis acid-promoted [2+2] cycloaddition between β-silyloxyaldehydes and trimethylsilylsilylketene, into α,β-unsaturated δ-lactones is applied to the syntheses of (±)-goniothalamin and (−)-massoialactone.