Diffusion and jump-length distribution in liquid and amorphous Cu33_{33}Zr67_{67}

Using molecular dynamics simulation, we calculate the distribution of atomic jum ps in Cu$_{33}$Zr$_{67}$ in the liquid and glassy states. In both states the distribution of jump lengths can be described by a temperature independent exponential of the length and an effective activation energy plus a contribution of elastic displacements at short distances. Upon cooling the contribution of shorter jumps dominates. No indication of an enhanced probability to jump over a nearest neighbor distance was found. We find a smooth transition from flow in the liquid to jumps in the g lass. The correlation factor of the diffusion constant decreases with decreasing temperature, causing a drop of diffusion below the Arrhenius value, despite an apparent Arrhenius law for the jump probability

Separated Oscillatory Fields for High-Precision Penning Trap Mass Spectrometry

Ramsey's method of separated oscillatory fields is applied to the excitation of the cyclotron motion of short-lived ions in a Penning trap to improve the precision of their measured mass. The theoretical description of the extracted ion-cyclotron-resonance line shape is derived out and its correctness demonstrated experimentally by measuring the mass of the short-lived $^{38}$Ca nuclide with an uncertainty of $1.6\cdot 10^{-8}$ using the ISOLTRAP Penning trap mass spectrometer at CERN. The mass value of the superallowed beta-emitter $^{38}$Ca is an important contribution for testing the conserved-vector-current hypothesis of the electroweak interaction. It is shown that the Ramsey method applied to mass measurements yields a statistical uncertainty similar to that obtained by the conventional technique ten times faster.Comment: 5 pages, 4 figures, 0 table

Advances in metabolism and genetic control of astringency in persimmon (Diospyros kaki Thunb.) fruit: A review.

Persimmon fruits accumulate proanthocyanidins during development. Proanthocyanidins form insoluble complexes with saliva proteins, which promote a sensation of dryness in the mouth called astringency. Persimmon cultivars are classified according to pollination and the presence of astringency at harvest. The different characteristics between persimmon cultivars lead to different metabolic pathways for the loss of astringency. The aim of this review is to gather information about the advances in the literature on the metabolism of astringency in persimmon fruit. Persimmon proanthocyanidins are mostly catechins or epicatechins, biosynthesized from substrates of the shikimic acid pathway, via biosynthetic pathways of phenylpropanoids and flavonoids, from gallic acid units, or from precursors of the anthocyanin pathway. Two enzymes have been identified as key enzymes to this pathway: leucoanthocyanidin reductase and anthocyanidin reductase. Non-astringent cultivars accumulate proanthocyanidins during fruit development, however, the expression of genes that encode essential enzymes of the biosynthetic pathway is reduced in the early stages, interrupting the accumulation of proanthocyanidins. Acetaldehyde is the responsible compound for the polymerization of proanthocyanidins and the consequent reduction of astringency. In certain non-astringent cultivars, proanthocyanidins are polymerized by acetaldehyde in the final stages of fruit development and transported to the vacuole, blocking the biosynthetic pathway. Two transport proteins, GST and MATE, are supposed to be essential in this process. In other nonastringent cultivars, the loss of astringency can happen due to the dilution of proanthocyanidins as a result of the increase in fruit volume. The removal of astringency in astringent cultivars occurs through the application of postharvest treatments that induce the synthesis of acetaldehyde by the fruit. Exposure to ethylene, high CO2 concentration or ethanol are the most used technologies for this purpose. Despite the advances made in the last decade, the astringency metabolism is complex and involves several metabolic pathways that still need to be elucidated for a better understanding of the effects of astringency removal in persimmon fruit

Laser spectroscopy of hyperfine structure in highly-charged ions: a test of QED at high fields

An overview is presented of laser spectroscopy experiments with cold, trapped, highly-charged ions, which will be performed at the HITRAP facility at GSI in Darmstadt (Germany). These high-resolution measurements of ground state hyperfine splittings will be three orders of magnitude more precise than previous measurements. Moreover, from a comparison of measurements of the hyperfine splittings in hydrogen- and lithium-like ions of the same isotope, QED effects at high electromagnetic fields can be determined within a few percent. Several candidate ions suited for these laser spectroscopy studies are presented.Comment: 5 pages, 1 figure, 1 table. accepted for Canadian Journal of Physics (2006

Evidence for a breakdown of the Isobaric Multiplet Mass Equation: A study of the A=35, T=3/2 isospin quartet

Mass measurements on radionuclides along the potassium isotope chain have been performed with the ISOLTRAP Penning trap mass spectrometer. For 35K T1/2=178ms) to 46K (T1/2=105s) relative mass uncertainties of 2x10-8 and better have been achieved. The accurate mass determination of 35K (dm=0.54keV) has been exploited to test the Isobaric Multiplet Mass Equation (IMME) for the A=35, T=3/2 isospinquartet. The experimental results indicate a deviation from the generally adopted quadratic form.Comment: 8 pages, 4 figure

Unusual T_c variation with hole concentration in Bi_2Sr_{2-x}La_xCuO_{6+\delta}

We have investigated the $T_c$ variation with the hole concentration $p$ in the La-doped Bi 2201 system, Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6+\delta}$. It is found that the Bi 2201 system does not follow the systematics in $T_c$ and $p$ observed in other high-$T_c$ cuprate superconductors (HTSC's). The $T_c$ vs $p$ characteristics are quite similar to what observed in Zn-doped HTSC's. An exceptionally large residual resistivity component in the inplane resistivity indicates that strong potential scatterers of charge carriers reside in CuO$_2$ planes and are responsible for the unusual $T_c$ variation with $p$, as in the Zn-doped systems. However, contrary to the Zn-doped HTSC's, the strong scatter in the Bi 2201 system is possibly a vacancy in the Cu site.Comment: RevTeX, 3 figures, to be published in the Physical Review

HITRAP: A facility at GSI for highly charged ions

An overview and status report of the new trapping facility for highly charged ions at the Gesellschaft fuer Schwerionenforschung is presented. The construction of this facility started in 2005 and is expected to be completed in 2008. Once operational, highly charged ions will be loaded from the experimental storage ring ESR into the HITRAP facility, where they are decelerated and cooled. The kinetic energy of the initially fast ions is reduced by more than fourteen orders of magnitude and their thermal energy is cooled to cryogenic temperatures. The cold ions are then delivered to a broad range of atomic physics experiments.Comment: 8 pages, 11 figure

Penning trap mass measurements on (99-109)$Cd with ISOLTRAP and implications on the rp process

Penning trap mass measurements on neutron-deficient Cd isotopes (99-109)Cd have been performed with the ISOLTRAP mass spectrometer at ISOLDE/CERN, all with relative mass uncertainties below 3*10^8. A new mass evaluation has been performed. The mass of 99Cd has been determined for the first time which extends the region of accurately known mass values towards the doubly magic nucleus 100Sn. The implication of the results on the reaction path of the rp process in stellar X-ray bursts is discussed. In particular, the uncertainty of the abundance and the overproduction created by the rp-process for the mass A = 99 is demonstrated by reducing the uncertainty of the proton-separation energy of 100In Sp(100In) by a factor of 2.5.Comment: 14 pages, 9 figure