First Measurement of a Long-Lived π

The adapted DIRAC experiment at the CERN PS accelerator observed for the first time long-lived hydrogenlike π^{+}π^{-} atoms, produced by protons hitting a beryllium target. A part of these atoms crossed the gap of 96 mm between the target and a 2.1 µm thick platinum foil, in which most of them dissociated. Analyzing the observed number of atomic pairs, n_{A}^{L}=436_{-61}^{+157}|_{tot}, the lifetime of the 2p state is found to be τ_{2p}=(0.45_{-0.30}^{+1.08}|_{tot})×10^{-11} s, not contradicting the corresponding QED 2p state lifetime τ_{2p}^{QED}=1.17×10^{-11} s. This lifetime value is three orders of magnitude larger than our previously measured value of the π^{+}π^{-} atom ground state lifetime τ=(3.15_{-0.26}^{+0.28}|_{tot})×10^{-15} s. Further studies of long-lived π^{+}π^{-} atoms will allow us to measure energy differences between p and s atomic states and so to discriminate between the isoscalar and isotensor ππ scattering lengths with the aim to check QCD predictions.

Observation of π

The observation of hydrogenlike πK atoms, consisting of π^{-}K^{+} or π^{+}K^{-} mesons, is presented. The atoms are produced by 24 GeV/c protons from the CERN PS accelerator, interacting with platinum or nickel foil targets. The breakup (ionization) of πK atoms in the same targets yields characteristic πK pairs, called "atomic pairs," with small relative momenta Q in the pair center-of-mass system. The upgraded DIRAC experiment observed 349±62 such atomic πK pairs, corresponding to a signal of 5.6 standard deviations. This is the first statistically significant observation of the strange dimesonic πK atom.

Hyaluronic Acid inhibits polycation induced cellular responses.

Positively charged macromolecules cause a variety of pathological events through their electrostatic interaction with anionic sites present on the membrane of target cells. In the present study we have investigated the effect of hyaluronic acid, a negatively charged molecule, on rat paw oedema induced by poly-L-lysine as well as on histamine release from rat mast cells and nitric oxide formation from rabbit aorta, both induced by this polycation. The results indicate that hyaluronic acid is able to suppress these poly-L-lysine induced effects with a mechanism which possibly depends on its negative charges which may balance the effects of positively charged polycations.

Evaluation of soft-tissue calcifications in dermatomyositis with 99mTc-phosphate compounds: case report.

A whole-body scan with 99mTc-pyrophosphate and 85Sr-nitrate demonstrates extension of calcinosis in one case of dermatomyositis with cutaneous, subcutaneous, and muscular calcinosis. The authors suggest the potential use of 99mTc-phosphate compounds as an auxiliary instrument in the evaluation of dermatomyositis-polymyositis syndrome.

[Sensitivity of the thyroideal cell to external irradiation]. / Sensibilidad de la célula tiroidea a irradiación externa

Evaluation of the variation in thyroid function utilizing 131I uptake in patients exposed to external radiation to the thyroid gland for reasons not related to this gland. The study was initiated with 54 patients who were examined prior to irradiation. They received an average dose of 5.650 r to the gland in a period of 5-6 weeks. Upon completion of the radiation therapy an abrupt drop in the uptake values occurred reaching the hypofunction range and one month later there is a recovery to 80% of the initial level and the value remains stable up to one year. Followed, year after year, a progressive reduction occurs in the uptake value up to a period of 6 years when the 2 surviving patients have returned to the hypothyroid level. The number of patients during the latter years of the study is too low to be statistically significant. The usefulness of this observation is discussed and a comparison is made of the external irradiation effects and the effects of 131I therapy.