Direct measurement of the lifetime of the neutral pion

The lifetime of the neutral pion (π⁰) has been directly measured. The lifetime has been found to be τ_π⁰ = (0.897±0.022±0.017) × 10^?16 s. The systematic error results from uncertainties in the momentum spectrum of the π⁰ used for the measurement. This measurement yields a decay width of the π⁰ of (7.34±0.18±0.11) eV. An axial anomaly calculation, which neglects the finite mass of the π⁰, predicts a value of 7.87 eV.     

The four-pion final state in pp annihilations at 5.7 GeV/c

577 events from $\text{p}\text{p}\text{→2π}{}^{\mathrm{+}}\text{2π}{}^{\mathrm{?}}$ annihilations at 5.7 GeV/c are analyzed. Single-particle spectra are studied and an effective matrix element in the form Π_i=1⁴ exp(?Bp_Ti²) is determined. The rates for production of ?° and f⁰ mesons are estimated and the influence of resonances on the angular distributions of pions and dipions is investigated. Transverse momenta correlations can be explained using peripheral phase space.     

Controlled transport and focusing of laser-accelerated protons with miniature magnetic devices

This Letter demonstrates the transporting and focusing of laser-accelerated 14 MeV protons by permanent magnet miniature quadrupole lenses providing field gradients of up to 500 T/m. The approach is highly reproducible and predictable, leading to a focal spot of (286 x 173) microm full width at half maximum 50 cm behind the source. It decouples the relativistic laser-proton acceleration from the beam transport, paving the way to optimize both separately. The collimation and the subsequent energy selection obtained are perfectly applicable for upcoming high-energy, high-repetition rate laser systems.     

Epr and endor of free radicals formed during the aerobic oxidation of chlorogenic acid and of caffeic acid in strongly alkaline solution

The proton hyperline coupling constants in three free radicals which are formed during the aerobic oxidation of either chlorogenic acid or of caffeic acid in strongly alkaline solution have been measured using EPR and ENDOR spectroscopy and the three radicals thus characterised. Possible identities for the free radicals are discussed.     

Radical cyclization of sugar-derived beta-(alkynyloxy)acrylates: synthesis of novel fused ethers

[formula: see text] Tributyltin radical mediated cyclization of carbohydrate-derived beta-(alkynyloxy)acrylates leading to highly functionalized cis- and trans-fused bicyclic ethers of various ring sizes is described. The efficacy of the radical cyclization is nicely illustrated in the iterative construction of a trans-fused tricyclic tetrahydropyran.     

Di­methyl 9,10‐anthracenedi­carboxyl­ate: a centrosymmetric transoid molecule

In the crystal structure of the title compound, C₁₈H₁₄O₄, there are two independent mol­ecules, both of which are exactly centrosymmetric and therefore have a transoid arrangement of the ester substituents. The planes of these are inclined at 63.90 (4) and 61.02 (5)° to the anthracene central ring in the two mol­ecules because of steric interactions, preventing electronic delocalization. The observed conformation is in agreement with molecular‐modelling calculations for the isolated mol­ecule, indicating no major influence from crystal‐packing forces.     

Über die Löslichkeit organischer Säuren und ihrer Salze

Analytical and Bioanalytical Chemistry -     

Fluorescence studies of lens epithelial cells and their constituents

Steady-state and time-resolved fluorescence measurements have been made of human and rabbit lens epithelial cells and their total soluble protein. Excitation at 350 nm results in broad fluorescence spectra peaking at 450 nm and stretching into the visible past 650 nm. The fluorescence excitation spectra peak around 350 nm. We assign the species responsible for this absorption and fluorescence as NADPH. Because the absorption of near-UV light (300-400 nm) is responsible for cell damage and death, we postulate that excited states of NADPH are implicated in the mechanisms of cell damage. Preirradiation with 355 nm light leads to a loss of NADPH fluorescence but with no change in decay kinetics. Possible mechanisms for cell damage are explored.