Spin-resolved electron-impact ionization of lithium

Electron-impact ionization of lithium is studied using the convergent close-coupling (CCC) method at 25.4 and 54.4 eV. Particular attention is paid to the spin-dependence of the ionization cross sections. Convergence is found to be more rapid for the spin asymmetries, which are in good agreement with experiment, than for the underlying cross sections. Comparison with the recent measured and DS3C-calculated data of Streun et al (1999) is most intriguing. Excellent agreement is found with the measured and calculated spin asymmetries, yet the discrepancy between the CCC and DS3C cross sections is very large

Calculation of the free-free transitions in the electron-hydrogen scattering S-wave model

The S-wave model of electron-hydrogen scattering is evaluated using the convergent close-coupling method with an emphasis on scattering from excited states including an initial state from the target continuum. Convergence is found for discrete excitations and the elastic free-free transition. The latter is particularly interesting given the corresponding potential matrix elements are divergent

Verwendungsraten von Prothesen der unteren Extremität in Deutschland und der Schweiz: Ein Vergleich der Jahre 2005-2008

Zusammenfassung: Hintergrund: In den USA hat die Verwendung der totalen Hüftprothese innerhalb der letzten Dekade stark zugenommen. Es ist jedoch nicht bekannt, ob sich dieser Trend auf andere Länder übertragen lässt. Ziel dieser Untersuchung war daher der detaillierte Vergleich der Verwendungsraten von Hüft-, Knie- und OSG-Prothesen in der BRD und der Schweiz im Zeitraum 2005-2008 und ein Sekundärvergleich mit den USA. Patienten und Methoden: Aus Daten der beiden statistischen Bundesämter wurden die Einwohnerzahl, Geschlechts- und Altersverteilung sowie die Anzahl von Primär- und Revisionseingriffen ermittelt. Aus diesen Kennzahlen konnte die Anzahl von Primär-, Revisions- und Gesamteingriffen, der Revisionslast, von Primär- und Revisionsraten pro 100.000 Einwohner und Jahr sowie geschlechts- und altersspezifische Primär- und Revisionsraten berechnet werden. Ein im Vergleich dazu reduzierter Datensatz aus den USA stammt direkt vom Autor der entsprechenden Auswertungen. Ergebnisse: In Deutschland, der Schweiz und den USA stieg die Anzahl der Voll- und Teilhüftprothesenimplantationen pro 100.000 Personen von 235,8, 238,2 und 116,8 im Jahr 2005 auf 254,7, 262,7 und 127,3 an. Für Voll- und Teilknieprothesen lagen die Raten bei 156,3, 140,1 und 178,2 Implantationen in 2005 und 188,3, 176,8 und 213,6 in 2008. Die Revisionslast für Hüftprothesen lag in der BRD in 2005 mit 13,6% um 3,6% höher als in der Schweiz und betrug 11,2% in den USA. In 2008 lag sie mit 15,1% um 4,6% höher als in der Schweiz und betrug wiederum 11,2% in den USA. Für Knieprothesen lag die Last in der BRD in 2005 bei 11,1% und damit 3,5% höher als in der Schweiz; in den USA betrug sie 7,4%. In 2008 lag sie bei 12,8% und somit 4,2% höher als in der Schweiz und betrug 8,9% in den USA. In allen 3 Ländern lag die Revisionslast für Knieprothesen stets unter derjenigen für Hüftprothesen. Schlussfolgerung: In allen 3 Ländern stiegen die Primärraten für Hüft- und Knieprothesen an, diejenigen für Knieprothesen stärker. Die Revisionslasten lagen in 2008 für beide Prothesentypen in der BRD am höchsten. In der Schweiz gab es eine vorübergehende Senkung der Revisionslasten und erst ab 2007 wieder einen Anstieg. Die Verwendungsrate von Hüftprothesen pro 100.000 Einwohner lag in den USA stark unter den Raten der BRD und der Schweiz, für Knieprothesen lag sie leicht darübe

Hyperspherical partial wave theory applied to electron hydrogen-atom ionization calculation for equal energy sharing kinematics

Hyperspherical partial wave theory has been applied here in a new way in the calculation of the triple differential cross sections for the ionization of hydrogen atoms by electron impact at low energies for various equal-energy-sharing kinematic conditions. The agreement of the cross section results with the recent absolute measurements of R\"oder \textit {et al} [51] and with the latest theoretical results of the ECS and CCC calculations [29] for different kinematic conditions at 17.6 eV is very encouraging. The other calculated results, for relatively higher energies, are also generally satisfactory, particularly for large $\Theta_{ab}$ geometries. In view of the present results, together with the fact that it is capable of describing unequal-energy-sharing kinematics [35], it may be said that the hyperspherical partial wave theory is quite appropriate for the description of ionization events of electron-hydrogen type systems. It is also clear that the present approach in the implementation of the hyperspherical partial wave theory is very appropriate.Comment: 16 pages, 9 figures, LaTeX file and EPS figures. To appear in Phys. Rev.

Photocontrolled Chignolin-Derived ß-Hairpin Peptidomimetics

Supramolecular templating techniques have been widely used to direct the formation of porous materials with the goal of introducing permanent mesoporosity. While surfactant-directed self-assembly has been exploited for inorganic materials such as titania, silica, organosilica, and zeolites, it has rarely been applied to metal-organic frameworks (MOFs) and coordination polymers. Here we introduce a new family of gemini surfactant-directed zinc imidazolates, referred to as mesostructured imidazolate frameworks (MIFs), and present a detailed study on the influence of different gemini-type surfactants on the formation mechanism and structures of the resulting zinc imidazolates. The proposed formation mechanism for MIF-type materials involves co-assembly and crystallization processes that yield lamellar mesostructured imidazolate frameworks. Understanding and controlling such processes also has implications for the syntheses of microporous zinc imidazolate framework (ZIF) materials, whose formation can be suppressed in surfactant-rich solutions, whereas formation of MIF materials is favored in the presence of surfactants and triggered by the addition of halogenides. Solid-state 2D 13C1H HETCOR NMR measurements on prototypic CTAB-directed MIF-1 establish that the head group moieties of the surfactant molecules interact strongly with the zinc-imidazolate-bromide sheets. Additionally, the NMR analyses suggest that MIF-1 has a significant fraction of surfactant molecules that are interdigitated between the zinc-imidazolate-bromide sheets with an antiparallel stacking arrangement, consistent with the high thermal and chemical stability of the MIF hybrid materials

Competing Ground States of the New Class of Halogen-Bridged Metal Complexes

Based on a symmetry argument, we study the ground-state properties of halogen-bridged binuclear metal chain complexes. We systematically derive commensurate density-wave solutions from a relevant two-band Peierls-Hubbard model and numerically draw the the ground-state phase diagram as a function of electron-electron correlations, electron-phonon interactions, and doping concentration within the Hartree-Fock approximation. The competition between two types of charge-density-wave states, which has recently been reported experimentally, is indeed demonstrated.Comment: 4 pages, 5 figures embedded, to appear in J. Phys. Soc. Jp

Heisenberg exchange parameters of molecular magnets from the high-temperature susceptibility expansion

We provide exact analytical expressions for the magnetic susceptibility function in the high temperature expansion for finite Heisenberg spin systems with an arbitrary coupling matrix, arbitrary single-spin quantum number, and arbitrary number of spins. The results can be used to determine unknown exchange parameters from zero-field magnetic susceptibility measurements without diagonalizing the system Hamiltonian. We demonstrate the possibility of reconstructing the exchange parameters from simulated data for two specific model systems. We examine the accuracy and stability of the proposed method.Comment: 13 pages, 7 figures, submitted to Phys. Rev.

Polarons and bipolarons in strongly interacting electron-phonon systems

The Holstein Hubbard and Holstein t--J models are studied for a wide range of phonon frequencies, electron--electron and electron--phonon interaction strengths on finite lattices with up to ten sites by means of direct Lanczos diagonalization. Previously the necessary truncation of the phononic Hilbert space caused serious limitations to either very small systems (four or even two sites) or to weak electron--phonon coupling, in particular in the adiabatic regime. Using parallel computers we were able to investigate the transition from `large' to `small' polarons in detail. By resolving the low--lying eigenstates of the Hamiltonian and by calculating the spectral function we can identify a polaron band in the strong--coupling case, whose dispersion deviates from the free--particle dispersion at low and intermediate phonon frequencies. For two electrons (holes) we establish the existence of bipolaronic states and discuss the formation of a bipolaron band. For the 2D Holstein t--J model we demonstrate that the formation of hole--polarons is favoured by strong Coulomb correlations. Analyzing the hole--hole correlation functions we find that hole binding is enhanced as a dynamical effect of the electron--phonon interaction.Comment: 23 pages (Revtex) with 13 figures (ps, uuencoded