Resonant enhancement of neutrinoless double-electron capture in 152Gd

In the search for the nuclide with the largest probability for neutrinoless double-electron capture, we have determined the Q(??) value between the ground states of (152)Gd and (152)Sm by Penning-trap mass-ratio measurements. The new Q(??) value of 55.70(18) keV results in a half-life of 10(26) yr for a 1 eV neutrino mass. With this smallest half-life among known 0ν?? transitions, (152)Gd is a promising candidate for the search for neutrinoless double-electron capture.     

A phase-imaging technique for cyclotron-frequency measurements

A novel approach to mass measurements at the 10^?9 level for short-lived nuclides with half-lives well below one second is presented. It is based on the projection of the radial ion motion in a Penning trap onto a position-sensitive detector. Compared with the presently employed time-of-flight ion-cyclotron-resonance technique, the novel approach is 25-times faster and provides a 40-fold gain in resolving power. Moreover, it offers a substantially higher sensitivity since just two ions are sufficient to determine the ion’s cyclotron frequency. Systematic effects specific to the technique that can change the measured cyclotron frequency are considered in detail. It is shown that the main factors that limit the maximal accuracy and resolving power of the technique are collisions of the stored ions with residual gas in the trap, the temporal instability of the trapping voltage, the anharmonicities of the trapping potential and the uncertainty introduced by the conversion of the cyclotron to magnetron motion.     

High average power Yb:CaF2 femtosecond amplifier with integrated simultaneous spatial and temporal focusing for laser material processing

A watt level, 10-kz repetition rate chirped pulse amplification system that has an integrated simultaneous spatial and temporal focusing (SSTF) processing system is demonstrated for the first time. SSTF significantly reduces nonlinear effects normally detrimental to beam control enabling the use of a low numerical aperture focus to quickly treat optically transparent materials over a large area. The integrated SSTF system has improved efficiency compared to previously reported SSTF designs, which combined with the high-repetition rate of the laser, further optimizes its capability to provide rapid, large volume processing.     

The adhesion and spreading of thrombocyte vesicles on electrode surfaces

The interaction of thrombocyte vesicles with the surface of metal electrodes, i.e., mercury, gold and gold electrodes modified with self assembled monolayers (SAM), was studied with the help of chronoamperometry, atomic force microscopy, and quartz crystal microbalance measurements. The experimental results show that the interaction of the thrombocyte vesicles with the surface of the electrodes depends on the hydrophobicity of the latter: whereas on very hydrophobic surfaces (mercury and gold functionalized with SAM) the thrombocyte vesicles disintegrate and form a monolayer of lipids, on the less hydrophobic gold surface a bilayer is formed. The chronoamperometric measurements indicate the possibility of future applications to probe membrane properties of thrombocytes.     

Electrostatics of nucleic acid folding under conformational constraint

RNA folding is enabled by interactions between the nucleic acid and its ion atmosphere, the mobile sheath of aqueous ions that surrounds and stabilizes it. Understanding the ion atmosphere requires the interplay of experiment and theory. However, even an apparently simple experiment to probe the ion atmosphere, measuring the dependence of DNA duplex stability upon ion concentration and identity, suffers from substantial complexity, because the unfolded ensemble contains many conformational states that are difficult to treat accurately with theory. To minimize this limitation, we measured the unfolding equilibrium of a DNA hairpin using a single-molecule optical trapping assay, in which the unfolded state is constrained to a limited set of elongated conformations. The unfolding free energy increased linearly with the logarithm of monovalent cation concentration for several cations, such that smaller cations tended to favor the folded state. Mg(2+) stabilized the hairpin much more effectively at low concentrations than did any of the monovalent cations. Poisson-Boltzmann theory captured trends in hairpin stability measured for the monovalent cation titrations with reasonable accuracy, but failed to do so for the Mg(2+) titrations. This finding is consistent with previous work, suggesting that Poisson-Boltzmann and other mean-field theories fail for higher valency cations where ion-ion correlation effects may become significant. The high-resolution data herein, because of the straightforward nature of both the folded and the unfolded states, should serve as benchmarks for the development of more accurate electrostatic theories that will be needed for a more quantitative and predictive understanding of nucleic acid folding.     

The Elusive p-air cross section

For the \(\bar pp\) and pp systems, we have used all of the extensive data of the Particle Data Group [K. Hagiwara et al. (Particle Data Group), Phys. Rev. D 66, 010001 (2002)]. We then subject these data to a screening process, the “Sieve” algorithm [M. M. Block, physics/0506010], in order to eliminate “ outliers” that can skew a χ² fit. With the “Sieve” algorithm, a robust fit using a Lorentzian distribution is first made to all of the data to sieve out abnormally high Δχ _i ² , the individual i^th point’s contribution to the total χ². The χ² fits are then made to the sieved data. We demonstrate that we cleanly discriminate between asymptotic ln s and ln² s behavior of total hadronic cross sections when we require that these amplitudes also describe, on average, low energy data dominated by resonances. We simultaneously fit real analytic amplitudes to the “sieved” high energy measurements of \(\bar pp\) and pp total cross sections and ρ-values for \(\sqrt s \) ≥ GeV, while requiring that their asymptotic fits smoothly join the the σ _pp and σ_pp total cross sections at \(\sqrt s \) = 4.0 GeV—again both in magnitude and slope. Our results strongly favor a high energy ln² s fit, basically excluding a ln s fit. Finally, we make a screened Glauber fit for the p-air cross section, using as input our precisely-determined pp cross sections at cosmic ray energies.     

Scattering of 64 eV to 3 keV neutrons from polyethylene and graphite and the coherence length problem

We measured the neutron scattering intensity ratios from polyethylene (CH2) relative to graphite (C) at several discrete final energies, of narrow widths (approximately 3 eV) between 64 eV and 3 keV. The final energies were selected using a 238U filter. This experiment was carried out to search for any anomaly in the n-p scattered intensities from CH2 caused by the neutron coherence length. The scattered intensity ratios were found to conform to conventional expectations and no anomaly was observed.     

RheoDSC: design and validation of a new hybrid measurement technique

A newly developed hyphenated technique is presented that combines an existing rheometer and differential scanning calorimeter (DSC) into a single experimental setup. Through the development of a fixation accessory inside the cell of the calorimeter and the introduction of an add-on unit for the rheometer, the simultaneous calorimetric and rheological measurement inside the well-controlled thermal environment of a Tzero™ DSC cell opens new experimental possibilities. The evolution of thermal and flow properties of a material can be simultaneously monitored during steady or oscillatory shear flow and regular or modulated temperature DSC measurements. The technique offers interesting opportunities for the investigation of flow-induced transitions, such as crystallization or phase separation, and provides a possibility for high-throughput screening of materials. The signal quality of the novel technique in comparison to the stand-alone techniques is demonstrated by the evaluation of the calibration factors and by measurements on standard materials. Finally, combined rheological and calorimetric melting and crystallization experiments on polycaprolacton are performed.     

ChemInform Abstract: RE10TCd3 (RE: Y,Tb - Tm,Lu; T: Fe,Co, Ni,Ru, Rh,Pd) - Rare Earth-Rich Phases with Ordered anti-Co2Al5 Structure.

The title compounds are synthesized from the elements (flowing Ar, 1500 K for 2 min, 1300 K for 45 min, and 900 K for 2 h) and characterized by powder XRD.