Test of charge conjugation invariance

We report on the first determination of upper limits on the branching ratio (BR) of eta decay to pi0pi0gamma and to pi0pi0pi0gamma. Both decay modes are strictly forbidden by charge conjugation (C) invariance. Using the Crystal Ball multiphoton detector, we obtained BR(eta-->pi0pi0gamma)<5 x 10(-4) at the 90% confidence level, in support of C invariance of isoscalar electromagnetic interactions of the light quarks. We have also measured BR(eta-->pi0pi0pi0gamma)<6 x 10(-5) at the 90% confidence level, in support of C invariance of isovector electromagnetic interactions.     

Nuclear spectroscopy of neutron-richA=145 nuclei

A study of theβ-decay of neutron-richA=145 fission products was undertaken by the use of the two recoil separators LOHENGRIN and JOSEF and the ISOL-type separator OSTIS. Theβ-decaying isotopes¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce were extensively studied. Level schemes for¹⁴⁵La,¹⁴⁵Ce and¹⁴⁵Pr were deduced fromγ and conversion electron spectra,γγ, X γ delayed andβγ coincidences. TheQ _β -values have been measured for the¹⁴⁵Ba,¹⁴⁵La and¹⁴⁵Ce decays.     

GPC analysis of degraded annealed single crystals

Annealed polyethylene single crystals have been degraded with fuming nitric acid, and the molecular weight distribution of the fragments determined by using a gel-permeation chromatograph. Peaks due to chain folding were observed in these distributions as for unannealed single crystals. The peaks moved to lower molecular weight with increasing degradation time. Comparison of the lowest molecular weight peak length after a given degradation time with the low-angle x-ray periodicity before degradation gave information about a disordered surface layer. The thickness of this layer at early states of degradation was dependent solely on annealing temperature, though changes in the layer must have occurred with annealing time, since there was an increase in reaction rate with annealing time. At higher degradation states, the thickness of the layer was dependent solely on the original low-angle periodicity. This has been related to the depth at which some folds are buried beneath the lamellar surfaces. The relevance of these observations to the structure of annealed single crystals is discussed.     

Observation of polarization in bottomonium production at square root of s = 38.8 GeV

We present a measurement of the polarization observed for bottomonium states produced in p-Cu collisions at square root of s = 38.8 GeV. The angular distribution of the decay dimuons of the Upsilon(1S) state shows no polarization at small values of the fractional longitudinal momentum x(F) and transverse momentum p(T) but significant positive transverse production polarization for either p(T)>1.8 GeV/c or for x(F)>0.35. The Upsilon(2S+3S) (unresolved) states show a large transverse production polarization at all values of x(F) and p(T) measured. These observations challenge NRQCD calculations of the polarization expected in the hadronic production of bottomonium states.     

Anti-viral cyclam macrocycles : rapid zinc uptake at physiological pH

NMR and UV-vis spectroscopic studies show that Zn(II) binds to cyclam rapidly at micromolar concentrations, an observation relevant to the anti-viral activity and co-receptor binding of anti-HIV cyclams.     

Metallocyclodextrins as building blocks in noncovalent assemblies of photoactive units for the study of photoinduced intercomponent processes

Cyclodextrin cups have been employed to build supramolecular systems consisting of metal and organic photoactive/redox-active components; the photoinduced communication between redox-active units assembled in water via noncovalent interactions is established. The functionalization of a beta-cyclodextrin with a terpyridine unit, ttp-beta-CD, is achieved by protection of all but one of the hydroxyl groups by methylation and attachment of the ttp unit on the free primary hydroxyl group. The metalloreceptors [(beta-CD-ttp)Ru(ttp)][PF(6)](2), [(beta-CD-ttp)Ru(tpy)][PF(6)](2), and [Ru(beta-CD-ttp)(2)][PF(6)](2) are synthesized and fully characterized. The [(beta-CD-ttp)Ru(ttp)][PF(6)](2) metalloreceptor exhibits luminescence in water, centered at 640 nm, from the (3)MLCT state with a lifetime of 1.9 ns and a quantum yield of Phi = 4.1 x 10(-)(5). Addition of redox-active quinone guests AQS, AQC, and BQ to an aqueous solution of [(beta-CD-ttp)Ru(ttp)](2+) results in quenching of the luminescence up to 40%, 20%, and 25%, respectively. Measurement of the binding strength indicates that, in saturation conditions, 85% for AQS and 77% for AQC are bound. The luminescence quenching is attributed to an intercomponent electron transfer from the appended ruthenium center to the quinone guest inside the cavity. Control experiments demonstrate no bimolecular quenching at these conditions. A photoactive osmium metalloguest, [Os(biptpy)(tpy)][PF(6)], is designed with a biphenyl hydrophobic tail for insertion in the cyclodextrin cavity. The complex is luminescent at room temperature with an emission band maximum at 730 nm and a lifetime of 116 ns. The osmium(III) species are formed for the study of photoinduced electron transfer upon their assembly with the ruthenium cyclodextrin, [(beta-CD-ttp)Ru(ttp)](2+). Time-resolved spectroscopy studies show a short component of 10 ps, attributed to electron transfer from Ru(II) to Os(III) giving an electron transfer rate 9.5 x 10(9) s(-)(1).