On-line nuclear orientation study of184Au

The¹⁸⁴Au→¹⁸⁴Pt decay, studied on-line with the UNISOR facility at HHIRF, is discussed. Gamma-ray and conversion-electron spectroscopy of¹⁸⁴Pt as well as on-line nuclear orientation measurements of¹⁸⁴Au were done. A new low-lying level scheme of¹⁸⁴Pt is proposed. Two coexisting bands with different deformations and their respective γ-vibrational bands are established. Internal conversion coefficients for interband transitions between states with the same spin are extracted from the spectroscopy measurements. The relative E0 contents of the transitions are determined by combining internal conversion coefficients with E2/M1 mixing ratios deduced from gamma-ray anisotropies measured from oriented nuclei.     

Topological properties of the peptide bond in glycyl-L-threonine dihydrate based on a fast synchrotron/CCD-diffraction experiment at 100 K

The charge density of glycyl-L-threonine dihydrate is extracted from a synchrotron data set of 98405 reflections collected at 100 K with a Bruker CCD area detector up to a resolution of d=0.38 A (sintheta/lambda = 1.32 A 1). The data are interpreted in terms of the "rigid pseudoatom" model. The topology of the experimental density is analyzed and compared with the topology obtained experimentally for the constituting amino acids and to that derived from Hartree-Fock calculations for the isolated molecule. All critical points of the electron density at the covalent and hydrogen bonds, as well as those of the Laplacian, were located, thereby deriving quantitative topological data for the peptide and side chain bonds. Bond topological indices in the dipeptide compare well with those of the corresponding bonds in the building amino acids, thus suggesting transferability of electronic properties of atoms and functional groups when these are derived by Bader's partitioning. Discrepancies between theoretical and experimental results could be attributed to crystal field effects.     

Microphysiometric Measurement of PAF Receptor Responses to Ginkgolides

Microphysiometry was used to evaluate the effects of terpene trilactone and flavonoid constituents of Ginkgo biloba on human platelet‐activating‐factor receptor (PAFR). Inhibition of the platelet‐activating factor response by terpene trilactones was confirmed using this functional assay. Ginkgolide B (GB) and 10‐O‐benzyl‐GB showed the strongest inhibition (81 and 93%, resp.) of the PAFR response, while the flavonoids rutin, quercetin, and kaempferol showed negligible response inhibition. G. biloba extract mixtures were also tested, and results indicate possible synergistic effects among various components.     

Energy-dispersive x-ray laue measurements with anomalous dispersion effects

By using an energy dispersive solid state detector, harmonics were separated in a Lauetype diffraction experiment with a single crystal and white primary radiation (Bremsstrahlung) from a conventional x-ray tube. Intensity changes around the absorption edge of an atom species in the crystal could be verified according to theory.Dedicated to Prof. Dr. H.E. Müser on the occasion of his 60th birthday     

The charge delocalised beta,beta-carotene dication--preparation, structure elucidation by NMR and reactions with nucleophiles

The reaction between beta,beta-carotene and BF3-etherates has been investigated, leading to structural elucidation of the blue product, formed in appropriate organic solvents, as a symmetrical charge delocalised dication (lambda(max) 985 nm at room temperature in CHCl3) with considerable stability. The reaction, monitored by EPR studies at -25 degrees C, occurred via free radical intermediates. A C40H56BF3 intermediate was captured by EIMS. The detailed structure of the dication was established by COSY, HSQC, HMBC and 1D and 2D ROESY NMR techniques (600 MHz, CDCl3, -20 degrees C) leading to complete assignments of 1H and 13C chemical shifts and 3J(H,H) coupling constants. The effects of the two delocalised charges on chemical shift (charge distribution) and bond distance (3J(H,H)) were considered. The results are consistent with charge delocalisation mainly in the C-5-C-9 and C-5'-C-9' regions and with bond inversion to retro shifted double bonds in the central C-13-C-13' region. A convention for denoting the charge delocalisation and bond types is presented. The experimental results are discussed relative to previous theoretical calculations of the beta,beta-carotene dication structure. (All-E) and (15-Z)-beta,beta-carotene provided the same dication. The NIR spectra and stability of dications prepared in the same manner from the related carotenes 20,20'-dinor-beta,beta-carotene, heptapreno-beta,beta-carotene and nonapreno-beta,beta-carotene were examined for comparison. Reactions of the beta,beta-carotene dication with selected nucleophiles provided products including isocryptoxanthin, isocarotene and mutatochrome with H2O as nucleophile, and isocryptoxanthin methyl ether, 8-methoxy-7,8-dihydro-beta,beta-carotene and isocarotene with CH3ONa as nucleophile. The formation of these products is rationalised from the structure assigned to the dication.     

Spin squeezing and quantum correlations

We discuss the notion of spin squeezing considering two mutually exclusive classes of spin-s states, namely, oriented and non-oriented states. Our analysis shows that the oriented states are not squeezed while non-oriented states exhibit squeezing. We also present a new scheme for construction of spin-s states using 2s spinors oriented along different axes. Taking the case of s=1, we show that the ‘non-oriented’ nature and hence squeezing arise from the intrinsic quantum correlations that exist among the spinors in the coupled state.     

Effect of time-reversal noninvariance on nuclear γ-decay observables

Some criteria are proposed which should allow greatly increased sensitivity of nuclear γ-decay studies to possible time reversal violation. Hindrance can be a more significant criterion in choosing nuclei for investigation than that previously employed - namely multipole mixing ratios near unity.     

Nuclear orientation of 160Tb in Tb metal

The decay of ¹⁶⁰Tb oriented at low temperatures in Tb metal has been investigated, and angular distributions of 19 γ-rays have been determined. The reduction in anisotropy in polycrystalline metal samples is discussed. Multipole mixing ratios have been determined for many of the γ-rays. A critical discussion is given of the previously reported $\text{M2}\text{E1}$ mixing ratios, and previous nuclear orientation studies are re-analyzed in a consistent manner so that their results can be compared. It is shown that the nuclear orientation and angular correlation results for the 1178 keV transition are consistent only if E3/E1 mixing is present. The El branching ratios and $\text{M2}\text{E1}$ mixing ratios are analyzed on the basis of Coriolis-mixed K = 0, 1 and 2 character for the negative-parity levels of ¹⁶⁰Dy.     

gR and gK factors in deformed nuclei

The static and dynamic magnetic dipole moments of odd-mass and even-mass nuclei with 150R and intrinsic g-factors g_K.