Rapid determination of tannins in tanning baths by adaptation of BSA method

A rapid and reproducible method for the determination of tannins in vegetable tanning baths is proposed as a modification of the BSA method for grain tannins existing in literature. The protein BSA was used instead of leather powder employed in the Filter Method, which is adopted in Italy and various others countries of Central Europe. In this rapid method the tannin contents is determined by means a spectrophotometric reading and not by means a gravimetric analysis of the Filter Method. The BSA method, which belongs to mixed methods (which use both precipitation and complexation of tannins), consists of selective precipitation of tannin from a solution containing also non tannins by BSA, the dissolution of precipitate and the quantification of free tannin amount by its complexation with Fe(III) in hydrochloric solutions. The absorbance values, read at 522 nm, have been expressed in terms of tannic acid concentration by using a calibration curve made with standard solutions of tannic acid; these have been correlated with the results obtained by using the Filter Method.     

On the convergence of solutions of degenerate elliptic equations in divergence form

It is studied the convergence of solutions of Dirichlet problems for sequences of monotone operators of the type — div (a_h (x, D·)), where the functions a_h verify the following degenerate coerciveness assumption

Spherical molecularly imprinted polymers (SMIPs) via a novel precipitation polymerization in the controlled delivery of sulfasalazine

Spherical molecularly imprinted polymers (SMIPs) have been prepared via a novel precipitation polymerization using sulfasalazine (prodrug used in the diseases of the colon) as template. The sulfasalazine was incorporated into SMIPs and into a spherical non-imprinted polymer (control), and then the release rate of the bioactive agent at different pH values was evaluated. Considerable differences in the release characteristics between imprinted and non-imprinted polymers have been observed. This opens the possibility of the development of drug release systems capable of modulating the release of a specific molecule. Photomicrography of spherical molecularly imprinted polymers (SMIPs).     

The electro‐optical properties of ‘charged’ PDLCs

The application of high intensity electric fields to polymer dispersed liquid crystal (PDLC) films can induce changes in their electro‐optical properties and morphology. In particular, a quasilinear electro‐optical response to an external electric field can be achieved if an internal built‐in d.c. field is induced. In this work, we show how the liquid crystal/polymer weight ratio influences the electro‐optical response of ‘charged’ PDLCs, i.e. of PDLC films after the application of a high intensity electric field. We observed that a quasilinear electro‐optical response can be achieved in a well determined range of composition. Larger liquid crystal concentrations are unable to maintain the built‐in field, while PDLCs with lower liquid crystal loadings do not allow the onset of a built‐in d.c. field.     

CAESAR models for developmental toxicity

Background

The new REACH legislation requires assessment of a large number of chemicals in the European market for several endpoints. Developmental toxicity is one of the most difficult endpoints to assess, on account of the complexity, length and costs of experiments. Following the encouragement of QSAR (in silico) methods provided in the REACH itself, the CAESAR project has developed several models.

Results

Two QSAR models for developmental toxicity have been developed, using different statistical/mathematical methods. Both models performed well. The first makes a classification based on a random forest algorithm, while the second is based on an adaptive fuzzy partition algorithm. The first model has been implemented and inserted into the CAESAR on-line application, which is java-based software that allows everyone to freely use the models.

Conclusions

The CAESAR QSAR models have been developed with the aim to minimize false negatives in order to make them more usable for REACH. The CAESAR on-line application ensures that both industry and regulators can easily access and use the developmental toxicity model (as well as the models for the other four endpoints).

     

Preparation of Polymeric Membranes Entrapping β-Cyclodextrins and Their Molecular Recognition of Naringin

An amorphous polyetheretherketone known as PEEK-WC and a β-cyclodextrin derivative (O-octyloxycarbonyl-β-CD), insoluble in water, were used to prepare flat sheet membranes by the diffusion induced phase separation. It was found that the β-CD derivative entrapped in membranes is able to form a complex with naringin, a bitter component present in grapefruits. The recognition properties of the β-CD derivative immobilized in the PEEK-WC membranes towards naringin have been investigated as a function of the amount of β-CD derivative present in the casting solution. A significant improvement of the efficiency of theO-octyloxycarbonyl-β-CD was observed when an inclusion complex with naringin in the membrane was formed compared to when the β-CD derivative is dispersed in an aqueous solution of naringin. Washing with an alkaline solution allows an easy regeneration of the membranes and permits their reuse. No recognition properties were found for PEEK-WC membranes made without the β-CD derivative.     

A kinematical study of Kirchhoff-Rayleigh flow

Summary A method of calculating the separated flow of a viscous fluid is proposed, which allows to split up properly the boundary condition problem from the viscous phenomena. The theory is developed for the flow past a plate and yields wakes of finite extension having an underpressure which depends directly on the amount of vorticity diffusion and dissipation occurring in the fluid. Application of the method to real flows shows good agreement between the calculated and the measured velocity distributions in front of the plate and in the wake.

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Résumé Une méthode de calcul de l'écoulement décollé d'un fluide visqueux est proposée qui permet de séparer clairement le problème aux limites des phénomènes visqueux. La théorie est développée pour l'écoulement autour d'une plaque et donne des sillages de longueur finie ayant une dépression de culot directement dépendante de l'intensité de la diffusion et dissipation de la vorticité se produisant dans le fluide. L'application de la méthode à des écoulements réels montre une bonne concordance entre les répartitions de vitesse calculées et mesurées sur le devant de la plaque et dans le sillage.

     

Gas phase activation energy for unimolecular dissociation of biomolecular ions determined by focused RAdiation for gaseous multiphoton ENergy transfer (FRAGMENT)

We present a novel approach for the determination of activation energy for the unimolecular dissociation of a large (>50 atoms) ion, based on measurement of the unimolecular dissociation rate constant as a function of continuous-wave CO(2) laser intensity. Following a short ( approximately 1 s) induction period, CO(2) laser irradiation produces an essentially blackbody internal energy distribution, whose 'temperature' varies inversely with laser intensity. The only currently available method for measuring such activation energies is blackbody infrared radiative dissociation (BIRD). Compared with BIRD, FRAGMENT: (a) eliminates the need to heat the surrounding ion trap and vacuum chamber to each of several temperatures (each requiring hours for temperature equilibration); (b) offers a three-fold wider range of effective blackbody temperature; and (c) extends the range of applications to include initially cold ions (e.g., gas-phase H/D exchange). Our FRAGMENT-determined activation energy for dissociation of protonated bradykinin, 1.2 +/- 0.1 eV, agrees within experimental error to the value, 1.3 +/- 0.1 eV, previously reported by Williams et al. from BIRD experiments. Copyright 1999 John Wiley & Sons, Ltd.