Measurement of Tau branching ratios

Using the data accumulated at LEP in 1989 and 1990 with the ALEPH detector, the inclusive and exclusive branching ratios of the lepton have been measured assuming lepton universality inZ ⁰ decays. The inclusive branching fractions for the decay into one, three, and five charged particles have been determined to be (85.45±0.97)%, (14.35±0.48)%, and (0.10±0.05)%, respectively, in agreement with the world averages. New undetected decay modes are determined to have a branching fraction of less than 2.1% at 95% CL. The measured branching ratios for quasi-exclusive channels are slightly larger than, but consistent with the world averages, except for the modes 3 hadrons+v andhadron+2⁰ v , which are significantly larger. These latter branching ratios have been found to be (9.5±0.7)% and (10.2±1.1)%, respectively. The sum of all the measured quasi-exclusive branching ratios is (100.4±1.8)%. A fully exclusive analysis of modes with neutral pions shows no evidence for new photonic decay modes with a branching fraction limit of 3.4% at 95% CL.Supported by CAICYT, Spain     

From the dynamics of gaseous stars to the incompressible Euler equations

A model for the dynamics of gaseous stars is introduced and formulated by the Navier-Stokes-Poisson system for compressible, reacting gases. The combined quasineutral and inviscid limit of the Navier-Stokes-Poisson system in the torus Tn is investigated. The convergence of the Navier-Stokes-Poisson system to the incompressible Euler equations is proven for the global weak solution and for the case of general initial data.     

Uncatalyzed solventless Diels-Alder reaction of 2-amino-3-nitroacrylate: synthesis of new epimeric 2-amino-3-nitro-norbornene- and norbornane-2-carboxylic acids

A highly diastereoselective Diels-Alder reaction between cyclopentadiene and ethyl (Z)-2-N-Boc-amino-3-nitroacrylate in neat conditions affords the ethyl 2-t-butoxycarbonylamino-3-endo-nitro-bicyclo[2.2.1]hept-5-ene-2-exo-carboxylate: a new constrained carbocyclic amino acid. Catalytic hydrogenation of this cycloadduct gave the corresponding reduced norbornane derivative. A preliminary investigation into the chemistry of these two amino acids was performed. In particular, the epimerization to their corresponding 3-exo-nitro compounds by treatment both with acid and base was studied. From this study, valuable information on the endo/exo process at the C-3 carbon atom, as well as on the stability of the different stereomers, was obtained. The stability is closely related to the presence or the absence of the double bond in the ring and to the substitution pattern. Finally, deprotection of the amino acid function has been performed.     

Synthesis and spectroscopic characterization of new triorganotin(IV) complexes with the bis(1‐methyl‐1H‐imidazol‐2‐ylthio)acetate ligand: effects on trout erythrocyte components

Triorganotin(IV) derivatives containing the anionic ligand bis(1‐methyl‐1H‐imidazol‐2‐ylthio)acetate [(S‐tim)₂CHCO₂]⁻ were synthesized from the reaction between R₃SnCl acceptors (R = Me and Ph) and the sodium salt of the ligand. Mono‐nuclear complexes of the type [(S‐tim)₂CHCO₂]SnR₃ were obtained, which were fully characterized by elemental analyses and FT‐IR in the solid state, and by NMR (¹H, ¹³C and ¹¹⁹Sn) spectroscopy and electrospray ionization mass in solution. The toxic effects shown by these compounds on trout erythrocyte components showed that the toxicity of the organotin(IV) complexes depends on the nature and on the lipophilicity of the substituents on the metal centre. Copyright © 2007 John Wiley & Sons, Ltd.     

Neurophysiological and functional MRI evidence of reorganization of cortical motor areas in cerebral arteriovenous malformation

Functional magnetic resonance imaging (fMRI) research has shown that brain arteriovenous malformations (AVMs) lead to reorganization of cortical motor areas. Since it is known that blood oxygenation level-dependent signal in fMRI may be influenced by the hemodynamic perturbation associated with the presence of the AVM, in the present study, a combined exploration with fMRI and transcranial magnetic stimulation was performed in a patient with a right rolandic AVM in order to explore the relationship between neuronal and hemodynamic activity. The combined protocol of investigation adopted in this study was able to provide significant information regarding neuronal activity of the different cortical areas that partake to post-lesional reorganization.     

Mg–Ce Alloys. Experimental investigation by Smith thermal analysis

The magnesium-cerium system has been partially revised in the Ce-rich and Mg-rich regions by using results obtained with the Smith thermal analysis (STA) technique. Nine alloys were examined and, after the thermal measurements,were subjected to phase analysis by means of X-ray powder diffraction (XRD), optical(LOM) and scanning electron microscopy (SEM), and electron probe microanalysis (EPMA).The coordinates of the invariant reactions, many of them very close to each other, were established and compared with literature data where a call for a deeper investigation was proposed as the thermal values were open to different interpretations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Direct Visualization of Pyrrole Reactivity upon Confinement within a Cyclodextrin Metal–Organic Framework

Metal–organic frameworks can be used as porous templates to exert control over polymerization reactions. Shown here are the possibilities offered by these crystalline, porous nanoreactors to capture highly‐reactive intermediates for a better understanding of the mechanism of polymerization reactions. By using a cyclodextrin framework the polymerization of pyrrole is restricted, capturing the formation of terpyrrole cationic intermediates. Single‐crystal X‐ray diffraction is used to provide definite information on the supramolecular interactions that induce the formation and stabilization of a conductive array of cationic complexes.     

Isothermal Crystallization of Isotactic Poly(propylene) Studied by Superfast Calorimetry

The isothermal crystallization behavior and the structure and morphology of isotactic poly(propylene) (iPP) and iPP/hydrogenated hydrocarbon resin (HR) 90/10 blend were analyzed. To cover the entire temperature range, isothermal crystallizations were studied using superfast calorimetry at a high cooling rate in the range 0 to 110 °C, and by conventional DSC at a low cooling rate in the range 120 to 140 °C. Structural and morphological changes due to the different thermal treatments were also analyzed. The complete crystallization curve ranging from T_g to T_m showed bimodal crystallization behaviors for both iPP and iPP/HR 90/10 blend. This result is explained by taking into consideration the polymorph properties of iPP. It is in fact assumed that the curve from T_g to 60 °C referred mainly to the crystallization kinetics of the iPP mesomorphic form by homogeneous nucleation, whereas the curve from 60 °C to T_m mainly represented the crystallization kinetic curve for the monoclinic α form by heterogeneous nucleation. This hypothesis is confirmed by the analysis of the structures obtained using wide angle X‐ray experiments. Moreover, the addition of HR to iPP causes a drastic reduction in the crystallization rate of iPP in both regions due to the diluent effect of the miscible resin.

     

Synthesis and conformational analysis of small peptides containing 6-endo-BT(t)L scaffolds as reverse turn mimetics

Two new dipeptide isosteres derived from L-leucine and meso-tartaric acid derivatives, named 6-endo-BTL and 6-endo-BtL, were inserted in a small peptide by means of SPPS, and the conformational features of the resulting peptides 3 and 4 were studied by NMR, IR, and molecular modeling techniques. The presence of a reverse turn conformation was observed in all the structures, suggesting the key role of the scaffolds as reverse turn promoters. Peptides 3 and 4 did not adopt a preferred conformation as indicated by the presence of equilibria between open turn and intramolecular hydrogen-bonded structures. 6-endo-BTL-peptide 3 showed a 3:1 mixture of conformers. The major conformer adopted mainly an open turn structure in equilibrium with hydrogen-bonded structures. The minor conformer displayed a better organized structure with a 14-membered ring hydrogen-bond typical of a beta-hairpin-like structure, in equilibrium with a gamma-turn, too. 6-endo-BtL-peptide 4 showed a unique conformer, and did not adopt as good a conformation as 3, due to the bulky equatorial substituent at C-2. Thus, marked structural differences between peptides containing 6-endo-BTL and 6-endo-BtL scaffolds as reverse turn inducers exist.