Positronium scattering by lithium

We report cross sections for Ps(1s)-Li(2s) scattering in the energy range up to 30 eV. The calculations have been carried out in a coupled state approximation. The Ps states consist of both eigenstates and pseudostates. the latter to allow for ionization of the Ps. The atom is treated as a frozen core represented by it model potential which supports the valence orbitals. The coupled state expansion includes only the 2s and 2p states of the atom as well as in unphysical Is state which exists in the model potential. The inclusion of this Is state is necessary in order to avoid pronounced false pseudostructure. Results are presented for excitation and ionization of the Ps as well as collisions in which the Ps(1s) remains unchanged. These results also differentiate between the case where the Li(2s) remains unexcited and where it is excited to the 2p level. (c) 2005 Published by Elsevier B.V.

Emission lines of Na-like ions in spectra obtained with the Solar EUV Research Telescope and Spectrograph (SERTS)

Theoretical emission-line ratios involving transitions in the 236-412 Angstrom wavelength range are presented for the Na-like ions Ar viii, Cr xiv, Mn xv, Fe xvi, Co xvii, Ni xviii and Zn xx. A comparison of these with an extensive data set of the solar active region, quiet-Sun, subflare and off-limb observations, obtained during rocket flights by the Solar EUV Research Telescope and Spectrograph (SERTS), reveals generally very good agreement between theory and experiment. This indicates that most of the Na-like ion lines are reliably detected in the SERTS observations, and hence may be employed with confidence in solar spectral analyses. However, the features in the SERTS spectra at 236.34 and 300.25 Angstrom, originally identified as the Ni xviii 3p (2) P-3/2 -3d (2) D- 3/2 and Cr xiv 3p (2) P-3/2 -3d (2) D-5/2 transitions, respectively, are found to be due to emission lines of Ar xiii (236.34 Angstrom) and possibly S v or Ni vi (300.25 Angstrom). The Co xvii 3s (2) S-3p (2) P-3/2 line at 312.55 Angstrom is always badly blended with an Fe xv feature at the same wavelength, but Mn xv 3s (2) S-3p (2) P-1/2 at 384.75 Angstrom may not always be as affected by second-order emission from Fe xii 192.37 Angstrom as previously thought. On the other hand, we find that the Zn xx 3s (2) S-3p (2) P-3/2 transition can sometimes make a significant contribution to the Zn xx/Fe xiii 256.43- Angstrom blend, and hence care must be taken when using this feature as an Fe xiii electron density diagnostic. A line in the SERTS-89 active region spectrum at 265.00 Angstrom has been re-assessed, and we confirm its identification as the Fe xvi 3p (2) P-3/2 -3d (2) D-3/2 transition.

Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons

We present a technique for simultaneous focusing and energy selection of high-current, mega-electron volt proton beams With the use of radial, transient electric fields (107 to 1010 volts per meter) triggered on the inner walls of a hollow microcylinder by an intense subpicosecond laser pulse. Because of the transient nature of the focusing fields, the proposed method allows selection of a desired range out of the spectrum of the polyenergetic proton beam. This technique addresses current drawbacks of laser-accelerated proton beams, such as their broad spectrum and divergence at the source.

Inelastic current-voltage spectroscopy of atomic wires

A tight-binding model is developed to describe the electron-phonon coupling in atomic wires under an applied voltage and to model, their inelastic current-voltage spectroscopy. Particular longitudinal phonons are found to have greatly enhanced coupling to the electronic states of the system. This leads to a large drop in differential conductance at threshold energies associated with these phonons. It is found that with increasing tension these energies decrease, while the size of the conductance drops increases, in agreement with experiment.

Power dissipation in nanoscale conductors

A previous tight-binding model of power dissipation in a nanoscale conductor under an applied bias is extended to take account of the local atomic topology and the local electronic structure. The method is used to calculate the power dissipated at every atom in model nanoconductor geometries: a nanoscale constriction, a one-dimensional atomic chain between two electrodes with a resonant double barrier, and an irregular nanowire with sharp corners. The local power is compared with the local current density and the local density of states. A simple relation is found between the local power and the current density in quasiballistic geometries. A large enhancement in the power at special atoms is found in cases of resonant and anti-resonant transmission. Such systems may be expected to be particularly unstable against current-induced modifications.

Postoperative residuial block after intermediate-acting neuromuscular blocking drugs

Summary The frequency and duration of postoperative residual neuromuscular block on arrival of 150 patients in the recovery ward following the use of vecuronium (n = 50), atracurium (n = 50) and rocuronium (n = 50) were recorded. Residual block was defined as a train-of-four ratio of 0.8 after arrival in the recovery ward were 9.2 [1-61], 6.9 [1-24] and 14.7 [1.5-83] min for the vecuronium, atracurium and rocuronium, respectively. None of the 10 patients who did not receive neuromuscular blocking drugs had train-of-four ratios