628 research outputs found

    Structural investigation of cell wall polysaccharides extracted from wild Finnish mushroom Craterellus tubaeformis (Funnel Chanterelle)

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    Craterellus tubaeformis (Funnel Chanterelle) is among the most abundant wild mushrooms in Finland. Three polysaccharide fractions were sequentially extracted from the fruiting bodies of C. tubaeformis, using hot water, 2% and 25% KOH solutions, respectively, and purified. The monomer composition, molecular weight, and chemical structure were determined using chromatographic and spectroscopic methods. Thermogravimetric analysis was performed as well. The hot water extract consisted mainly of high-molecular weight -> 2,6)-alpha-Man-(1 -> and -> 6)-alpha-Gal-(1 -> chains, covalently bound to proteins. The alkali extracts consisted of acidic -> 6)-beta-Glc-(1 ->, with branches of short -> 3)-beta-Glc-(1 -> chains or single beta-Glc residues. The use of alkali influenced the glycosidic linkages, molecular mass and thermal stability of the polysaccharide fractions. The use of KOH 2% increased the amount of low molecular weight polysaccharides, resulting in bimodal molecular weight distributions, with little impact on the thermal stability. Conversely, extraction with KOH 25% provided low molecular weight polysaccharides with substantially reduced thermal stability

    Commissioning of the spede spectrometer with stable beams

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    The SPectrometer for Electron DEtection (SPEDE) has been constructed for in-beam nuclear structure studies using radioactive ion beams. SPEDE employs a silicon detector for detecting conversion electrons. It is designed to be used in conjunction with the MINIBALL spectrometer at HIE-ISOLDE, CERN.Peer reviewe

    Shape coexistence at the proton drip-line: First identification of excited states in 180Pb

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    Excited states in the extremely neutron-deficient nucleus, 180Pb, have been identified for the first time using the JUROGAM II array in conjunction with the RITU recoil separator at the Accelerator Laboratory of the University of Jyvaskyla. This study lies at the limit of what is presently achievable with in-beam spectroscopy, with an estimated cross-section of only 10 nb for the 92Mo(90Zr,2n)180Pb reaction. A continuation of the trend observed in 182Pb and 184Pb is seen, where the prolate minimum continues to rise beyond the N=104 mid-shell with respect to the spherical ground state. Beyond mean-field calculations are in reasonable correspondence with the trends deduced from experiment.Comment: 5 pages, 4 figures, submitted to Phys.Rev.

    First observation of excited states in 173Hg

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    The neutron-deficient nucleus 173Hg has been studied following fusion-evaporation reactions. The observation of gamma rays decaying from excited states are reported for the first time and a tentative level scheme is proposed. The proposed level scheme is discussed within the context of the systematics of neighbouring neutron-deficient Hg nuclei. In addition to the gamma-ray spectroscopy, the alpha decay of this nucleus has been measured yielding superior precision to earlier measurements.Comment: 5 pages, 4 figure

    Search for Fingerprints of Tetrahedral Symmetry in 156Gd^{156}Gd

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    Theoretical predictions suggest the presence of tetrahedral symmetry as an explanation for the vanishing intra-band E2-transitions at the bottom of the odd-spin negative parity band in 156Gd^{156}Gd. The present study reports on experiment performed to address this phenomenon. It allowed to determine the intra-band E2 transitions and branching ratios B(E2)/B(E1) of two of the negative-parity bands in 156Gd^{156}Gd.Comment: presented by Q.T. Doan at XLII Zakopane School of Physics: Breaking Frontiers: Submicron Structures in Physics and Biology, May 2008. 5 pages, minor corrections. To be published in the proceeding

    Flavour-coherent propagators and Feynman rules: Covariant cQPA formulation

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    We present a simplified and generalized derivation of the flavour-coherent propagators and Feynman rules for the fermionic kinetic theory based on coherent quasiparticle approximation (cQPA). The new formulation immediately reveals the composite nature of the cQPA Wightman function as a product of two spectral functions and an effective two-point interaction vertex, which contains all quantum statistical and coherence information. We extend our previous work to the case of nonzero dispersive self-energy, which leads to a broader range of applications. By this scheme, we derive flavoured kinetic equations for local 2-point functions Sk(t,t)S^{}_\mathbf{k}(t,t), which are reminiscent of the equations of motion for the density matrix. We emphasize that in our approach all the interaction terms are derived from first principles of nonequilibrium quantum field theory.Comment: 20 pages, 3 figures. Minor modifications, version published in JHE

    In-beam spectroscopic study of 244Cf

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    The ground-state rotational band of the neutron-deficient californium (Z = 98) isotope 244Cf was identified for the first time and measured up to a tentative spin and parity of I = 20+. The observation of the rotational band indicates that the nucleus is deformed. The kinematic and dynamic moments of inertia were deduced from the measured gamma-ray transition energies. The behavior of the dynamic moment of inertia revealed an up-bend due to a possible alignment of coupled nucleons in high-j orbitals starting at a rotational frequency of about hw = 0.20 MeV. The results were compared with the systematic behavior of the even-even N = 146 isotones as well as with available theoretical calculations that have been performed for nuclei in the region

    The SPEDE spectrometer

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    The electron spectrometer, SPEDE, has been developed and will be employed in conjunction with the Miniball spectrometer at the HIE-ISOLDE facility, CERN. SPEDE allows for direct measurement of internal conversion electrons emitted in-flight, without employing magnetic fields to transport or momentum filter the electrons. Together with the Miniball spectrometer, it enables simultaneous observation of {\gamma} rays and conversion electrons in Coulomb-excitation experiments using radioactive ion beams

    In-beam spectroscopic study of Cf-244

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    The ground-state rotational band of the neutron-deficient californium (Z = 98) isotope 244Cf was identified for the first time and measured up to a tentative spin and parity of I I-pi = 20(+). The observation of the rotational band indicates that the nucleus is deformed. The kinematic and dynamic moments of inertia were deduced from the measured gamma-ray transition energies. The behavior of the dynamic moment of inertia revealed an up-bend due to a possible alignment of coupled nucleons in high-j orbitals starting at a rotational frequency of about (h) over bar (omega) = 0.20 MeV. The results were compared with the systematic behavior of the even-even N = 146 isotones as well as with available theoretical calculations that have been performed for nuclei in the region.Peer reviewe

    Quasiparticle alignments and alpha-decay fine structure of Pt-175

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    Excited states and decay properties of 175 Pt have been investigated using the 92 Mo ( 86 Sr , 2 p n ) fusion-evaporation reaction. The JUROGAM I γ -ray spectrometer and the GREAT spectrometer were used in conjunction with the gas-filled recoil separator RITU for the measurement of the radiation at the target and focal plane positions, respectively. Two new band structures, assigned to be based on the I π = ( 7 / 2 − ) ground state in 175 Pt, have been established and the known yrast band has been extended up to I π = ( 49 / 2 + ) . Rotational properties of the excited states in 175 Pt have been investigated within the cranked shell-model formalism. The low-frequency changes in the alignments of the positive- and negative-parity bands are interpreted as a sign of proton-pair excitations in the rotating core. Furthermore, the α -decay measurements reveal a candidate for a fourth α -decay branch in 175 Pt, feeding a non-yrast state in 171 Os
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