Study of the order–disorder transition and martensitic transformation in a Cu–Al–Be alloy by EELS

Changes in 3d states occupancy associated with order–disorder transition and martensitic transformation in a Cu–Al–Be alloy was investigated by electron energy loss spectroscopy (EELS) in both high energy and low energy loss regions. From the high energy loss region, the Cu L_2,3 white-line intensities, which reflect the unoccupied density of states in 3d bands, was measured for three states of the alloy: disordered austenite, ordered austenite and martensite. It was found that the white-line intensity remains the same during order–disorder transition but appears slightly smaller in martensite, indicating that some electrons left Cu 3d bands or some hybridization took place during phase transformation. From the low energy loss region, the optical joint density of states (OJDS) was obtained by Kramers–Kronig analysis. As maxima observed in the OJDS spectra are assigned to interband transitions, these spectra can be used to probe changes in the electronic band structure. The analysis shows that during the martensitic transformation, the peaks positions and relative intensities in the OJDS spectra undergoes noticeable changes, which are associated with interband transitions.     

Effect of excess halide on the palladium‐catalyzed insertion‐triggered radical copolymerization of methyl acrylate and 1‐hexene

[Pd₂(μ‐Cl)₂(C₆F₅)₂(tht)₂] ( 1 ) is a very efficient initiator of the radical polymerization of methyl acrylate, but it is not active in the polymerization of methyl methacrylate or in the copolymerization with 1‐hexene. The addition of an excess of NBu₄Cl to solutions of [Pd₂(μ‐Cl)₂(C₆F₅)₂(tht)₂] ( 1 ) provides an initiator system that copolymerizes methyl acrylate and 1‐hexene by an insertion‐triggered radical mechanism. Random copolymers are obtained with 11% incorporation of 1‐hexene in moderate yields (about 35%). Studies of the decomposition products obtained after the first insertion of methyl acrylate in the Pd? C₆F₅ bond of 1 show that the addition of excess halide in the presence of monomer favors the homolytic cleavage of the Pd? C bond, and the generation of the radicals that are active species in the polymerization, versus alternative evolution pathways. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5682–5691, 2006     

Magneto-volume effects in Fe–Cu solid solutions

The magnetic properties of Fe–Cu metastable solid solutions have been investigated by means of neutron diffraction and magnetisation measurements. These compounds exhibit ferromagnetic order with Curie temperatures above room temperature for concentrations beyond 40 at% in Fe. The magnetic moment at 5 K can reach values over 2 μ_B, while the high field susceptibility is similar to that found in FCC–FeNi Invar alloys. These features together with the low values for the linear coefficient for thermal expansion in the ferromagnetic region suggest that magneto-volume anomalies, including Invar behaviour, play a major role in the magnetic properties of this system when the crystal structure is face centred cubic. Such behaviour could be explained using theoretical total-band energy calculations.     

Study of the Capabilities of the ALICE inner tracking system stand-alone for HBT analysis

Results are shown from a Monte Carlo simulation study of the capabilities of the Inner Tracking System of the ALICE experiment, used in standalone mode, for HBT analysis of Pb?Pb collisions at LHC energies (5.5 ATeV). Different values of the coherence factor and the Gaussian source radius have been studied. For this purpose, a specific ITS stand-alone tracking algorithm, based on the Denby-Peterson neural algorithm, has been developed.     

Synthesis and biological evaluation of 6-oxa-nor-tropane glycomimetics as glycosidase inhibitors

The preparation of polyhydroxylated 6-oxa-nor-tropane glycomimetics structurally related to the glycosidase inhibitor family of the calystegines is reported. The synthetic strategy involves the furanose→piperidine rearrangement of 5-deoxy-5-ureido-l-idose precursors, followed by intramolecular glycosylation involving the primary hydroxyl group. Inversion of the configuration at C-3 in the resulting 6-oxa-(+)-calystegine B₂ analogue allows accessing the elusive 3-epi-6-oxa-(+)-calystegine B₂ skeleton. Acid-catalyzed opening of the nor-tropane bicycle was observed, however, which could be avoided by careful neutralization of the reaction mixture. The inhibition results suggest that (+)-calystegine B₂ derivatives and the corresponding C-3 epimers can be seen as glucomimetics and galactomimetics, respectively, pointing to a 1-azasugar mode of action for this family of alkaloids.     

Application of extraction disks in dissolution tests of clenbuterol and levothyroxine tablets by capillary electrophoresis

Sample preparation procedures using octadecyl (C₁₈) extraction disks were developed to obtain accurate and reproducible results for determinations of clenbuterol (20 μg per dose) and levothyroxine (100 μg per dose) in dissolution media of solid oral dosage forms. Preconcentration of samples allowed final concentrations of 1.1 μg/ml of clenbuterol and 4.0 μg/ml of levothyroxine to be reached prior to CE analysis. The results obtained by CE were in good agreement with those of HPLC. The precision of the migration time, peak area, peak height and accuracy were determined in both intea-day (n = 6) and inter-day (n =18) assays. Linearity was demonstrated over the ranges 0.5–80.0 μg/ml of clenbuterol and 1.0–30.0 μg/ml of levothyroxine. The mean recoveries were higher than 94.0%, ranging from 50 to 125% levels with respect to dose potencies. The proposed methodology may be generally applied to determine drugs at ng/ml concentrations.