359 research outputs found
Classical trajectory Monte Carlo model calculations for the antiproton-induced ionization of atomic hydrogen at low impact energy
The three-body dynamics of the ionization of the atomic hydrogen by 30 keV
antiproton impact has been investigated by calculation of fully differential
cross sections (FDCS) using the classical trajectory Monte Carlo (CTMC) method.
The results of the calculations are compared with the predictions of quantum
mechanical descriptions: The semi-classical time-dependent close-coupling
theory, the fully quantal, time-independent close-coupling theory, and the
continuum-distorted-wave-eikonal-initial-state model. In the analysis
particular emphasis was put on the role of the nucleus-nucleus (NN) interaction
played in the ionization process. For low-energy electron ejection CTMC
predicts a large NN interaction effect on FDCS, in agreement with the quantum
mechanical descriptions. By examining individual particle trajectories it was
found that the relative motion between the electron and the nuclei is coupled
very weakly with that between the nuclei, consequently the two motions can be
treated independently. A simple procedure is presented by which the NN
interaction effect can be included into the calculations carried out without
it.Comment: 8 pages, 6 figure
Role of two-electron processes in the excitation-ionization of lithium atoms by fast ion impact
We study excitation and ionization in the 1.5 MeV/amu O-Li collision
system, which was the subject of a recent reaction-microscope-type experiment
[Fischer \textit{et al.}, Phys. Rev. Lett. \textbf{109}, 113202 (2012)].
Starting from an independent-electron model based on determinantal wave
functions and using single-electron basis generator method and continuum
distorted-wave with eikonal initial-state calculations we show that pure single
ionization of a lithium -shell electron is too weak a process to explain the
measured single differential cross section. Rather, our analysis suggests that
two-electron excitation-ionization processes occur and have to be taken into
account when comparing with the data. Good agreement is obtained only if we
replace the independent-electron calculation by an independent-event model for
one of the excitation-ionization processes and also take a shake-off process
into account
Differential cross sections for single ionization of Li in collisions with fast protons and O ions
We study the process of single ionization of Li in collisions with H and
O projectile ions at 6 MeV and 1.5-MeV/amu impact energies,
respectively. Using the frameworks of the independent-electron model and the
impact parameter picture, fully (FDCS) and doubly (DDCS) differential cross
sections are evaluated in the continuum distorted-wave with eikonal
initial-state approximation. Comparisons are made with the recent measurements
of LaForge \textit{et al} [J. Phys. B \textbf{46} 031001 (2013)] for the DDCS
and Hubele \textit{et al} [Phys. Rev. Lett. \textbf{110} 133201 (2013)] for the
FDCS, respectively. For O impact inclusion of the heavy particle (NN)
interaction in the calculations is crucial and effects of polarization due to
the presence of the projectile ion have also to be taken into account for
getting very good agreement with the measured data. Our calculation reproduces
the satellite peak structure seen in the FDCS for the Li(2s) measurement, which
we explain as being formed by a combination of the binary and NN interactions
Doubly-differential cross section calculations for -shell vacancy production in lithium by fast O ion impact
Inner-shell vacancy production for the O-Li collision system at 1.5
MeV/amu is studied theoretically. The theory combines single-electron
amplitudes for each electron in the system to extract multielectron information
about the collision process. Doubly-differential cross sections obtained in
this way are then compared with the recent experimental data by LaForge et al.
[J. Phys. B 46, 031001 (2013)] yielding good resemblance, especially for low
outgoing electron energy. A careful analysis of the processes that contribute
to inner-shell vacancy production shows that the improvement of the results as
compared to single-active-electron calculations can be attributed to the
leading role of two-electron excitation-ionization processes
Personalized home pages - a working environment on the World Wide Web
The World Wide Web is one of the most common interfaces to the Internet and thus to the global office as it provides an easy-to-use and self-explaining user interface for teleworkers. However WWW based interfaces are relatively rigid and are lacking ways of user customization or setting preferences. The new service oriented approach presented here builds upon the strength of the WWW interface to Internet services but enhances it by the power of individual customization. The Personalized Home Page (PHP) system is built on a framework capable to describe all Internet services in a uniform way using the terminology of weak agency. This paper gives an overview of the PHP system with a short description of the agent based framework behind. Examples introduce the actual use of the system
Agent based Internet (WWW) services
The evolution of the World Wide Web heads towards the use of more and more intelligent services. A possible solution to implement this service oriented view of World Wide Web is to use agents. A framework is proposed to provide agent-based Internet services via WWW. A case study introduces the actual use of this framework and its relation to the agent technology. As an implementation effort the Personalized Home Page (PHP) system is presented here. investigates the application of this voting tool for rating purposes
Electrophysiological, biochemical, and bioinformatic methods for studying CFTR channel gating and its regulation.
CFTR is the only member of the ABC (ATP-binding cassette) protein superfamily known to function as an ion channel. Most other ABC proteins are ATP-driven transporters, in which a cycle of ATP binding and hydrolysis, at intracellular nucleotide binding domains (NBDs), powers uphill substrate translocation across the membrane. In CFTR, this same ATP-driven cycle opens and closes a transmembrane pore through which chloride ions flow rapidly down their electrochemical gradient. Detailed analysis of the pattern of gating of CFTR channels thus offers the opportunity to learn about mechanisms of function not only of CFTR channels but also of their ABC transporter ancestors. In addition, CFTR channel gating is subject to complex regulation by kinase-mediated phosphorylation at multiple consensus sites in a cytoplasmic regulatory domain that is unique to CFTR. Here we offer a practical guide to extract useful information about the mechanisms that control opening and closing of CFTR channels: on how to plan (including information obtained from analysis of multiple sequence alignments), carry out, and analyze electrophysiological and biochemical experiments, as well as on how to circumvent potential pitfalls
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