Study of the production of a strange (S = −1) dibaryon in the interactions of K− and π+ on deuterium below 1.5GeV/c

The production of a strange dibaryonic system called H⁺₁ (M = 2.13 GeV/c², S = ?1), has been studied with a missing mass spectrometer, at the CERN Proton Synchrotron, in the reaction K^?d → π^?H⁺₁ and in the line-reversed reaction π⁺d → K⁺H⁺₁ between 0.9 and 1.4 GeV/c.The reactions

$\text{K}{}^{\mathrm{?}}\text{d}\text{→ π}{}^{\mathrm{?}}\text{X}{}^{\mathrm{+}}$

,

$\text{π}{}^{\mathrm{<mtext>d</mtext>}}\text{→}\text{K}{}^{\mathrm{+}}\text{X}{}^{\mathrm{+}}$

,have been studied in a missing mass spectrometer at CERN. The experiment (PS159) is well adapted to search for a signal in the missing mass X⁺ (B = 2, S = ?1) produced in the backward c.m.s. direction, between 2.0 and 2.3 GeV/c². The two reactions have been analysed at three different beam settings: 1.4, 1.06 and 0.92 GeV/c for reaction (1) and 1.4, 1.2 and 1.06 GeV/c for reaction (2).     

Electrophilic Azido Selenenylation of Alkenes. A Simple Synthetic Route to Racemic Taxol Side Chain

Simple alkenes react with PhSeOTf and NaN₃ in MeCN to afford β-phenylseleno azides as the result of a stereospecific trans addition. The regioselectivity of the process is determined by the structure of the alkene.     

Quantification of drug amorphous fraction by DSC

The processes of production of drugs and dosage forms in the solid state often cause unwanted transformation of portions of the substances into amorphous state, with significant changes of properties such as stability and bio-availability. When this amorphous fraction is of the order of a few percent, it usually goes unnoticed, but it should be accurately determined within a quality control system. In this work, we consider a model drug, perphenazine, where partial amorphisation may be induced by standard mechanical treatments. We show that Differential Scanning Calorimetry (DSC) leads to consistent estimations of the amorphous fractions induced by the treatment. Furthermore, DSC also yields the expected amounts of amorphous perphenazine when analysing known mixtures of perfectly crystalline samples (untreated) and partially amorphous samples (treated). We show that even amorphous fractions of the order of 1% are accurately estimated by our method.     

Stemodane Diterpenes and Diterpenoids: Isolation,Structure Elucidation,Biogenesis, Biosynthesis,Biological Activity,Biotransformations, Metabolites and Derivatives Biological Activity,Rearrangements

The scientific activity carried out over forty-five years on stemodane diterpenes and diterpenoids structure elucidation, biogenesis, biosynthesis, biological activity and biotransformations was reviewed.     

“Modified” phase equilibria

Summary The Authors examine first and second order phase equilibria for classical bodies in the sense of Toupin and Truesdell[9], by assuming a partial equality between the intensive thermal substates of the two phases.In the case of first order equilibria, a system of partial differential equations for the equilibrium manifold is proposed. This system, which reduces to the generalized Clapeyron equations on the assumption of complete equality of the intensive variables[13], is shown to be always integrable.In the case of second order equilibria, a similar modification of the generalized Ehrenfest equations[14] is proved. A straight-forward derivation of the integrability conditions for the system of partial differential equations is given.

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Sommario Gli Autori esaminano gli equilibri di fase del primo e del secondo ordine per corpi classici nel senso di Toupin and Truesdell[9], nella ipotesi di eguaglianza parziale dei sottostati termici intensivi delle due fasi.Nel caso di equilibri del primo ordine gli Autori deducono un sistema di equazioni alle derivate parziali per la varietà di equilibrio, estendendo le equazioni di Clapeyron generalizzate relative agli equilibri di fase con completa eguaglianza delle variabili intensive[13]. Vengono ricavate e discusse le condizioni di integrabilità del sistema.Per gli equilibri del secondo ordine, gli Autori pervengono ad un sistema di equazioni che estende le equazioni di Ehrenfest generalizzate, perchè rimuovono l'ipotesi di totale eguaglianza delle variabili intensive[14]. Anche di questo sistema vengono ricavate le condizioni di integrabilità.

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Work supported by the Gruppo Nazionale per la Fisica Matematica, C.N.R.     

Effect of matrix viscosity on the extent of exfoliation in EVA/organoclay nanocomposites

The influence of matrix viscosity and polarity on ethylene‐vinyl acetate copolymer (EVA) nanocomposites was studied. Five different EVA grades, with different melt flow indexes (MFIs) and/or vinyl acetate (VA) contents, were mixed with two montmorillonite (MMT) nanoclays: pristine and modified with a polar surfactant, producing 75/25 w/w% masterbatches which were subsequently diluted in the EVA matrix to obtain 5 wt% MMT nanocomposites. Although the same VA content, WAXS results, rheological measurements and TEM analysis showed that the lower the EVA viscosity, the greater the tendency to obtain exfoliated and well dispersed nanocomposites with the organically modified clay. On the other hand, the high viscosity EVA nanocomposites showed that the (001) organoclay diffraction peak was shifted to higher values of 2θ, suggesting lamellae collapsing. TGA and FTIR measurements were used to probe the thermal degradation of organoclay; furthermore, it was not possible to identify, by the techniques used, any reaction between the VA groups and hydroxyl surfactant groups. Thus, it was inferred that the organic surfactant was removed (or ejected) from the clay galleries as a consequence of huge shear tensions developed during processing of the masterbatches/nanocomposites with high viscosity EVA matrices. Copyright © 2009 John Wiley & Sons, Ltd.