Fingerprints for spin-selection rules in the interaction dynamics of O2 at Al(111)

We performed mixed quantum-classical molecular dynamics simulations based on first-principles potential-energy surfaces to demonstrate that the scattering of a beam of singlet O2 molecules at Al(111) will enable an unambiguous assessment of the role of spin-selection rules for the adsorption dynamics. At thermal energies we predict a sticking probability that is substantially less than unity, with the repelled molecules exhibiting characteristic kinetic, vibrational and rotational signatures arising from the non-adiabatic spin transition.Comment: 4 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Ab initio quality neural-network potential for sodium

An interatomic potential for high-pressure high-temperature (HPHT) crystalline and liquid phases of sodium is created using a neural-network (NN) representation of the ab initio potential energy surface. It is demonstrated that the NN potential provides an ab initio quality description of multiple properties of liquid sodium and bcc, fcc, cI16 crystal phases in the P-T region up to 120 GPa and 1200 K. The unique combination of computational efficiency of the NN potential and its ability to reproduce quantitatively experimental properties of sodium in the wide P-T range enables molecular dynamics simulations of physicochemical processes in HPHT sodium of unprecedented quality.Comment: 8 pages, 11 figures, 2 table

Dissociation of O2 at Al(111): The Role of Spin Selection Rules

A most basic and puzzling enigma in surface science is the description of the dissociative adsorption of O2 at the (111) surface of Al. Already for the sticking curve alone, the disagreement between experiment and results of state-of-the-art first-principles calculations can hardly be more dramatic. In this paper we show that this is caused by hitherto unaccounted spin selection rules, which give rise to a highly non-adiabatic behavior in the O2/Al(111) interaction. We also discuss problems caused by the insufficient accuracy of present-day exchange-correlation functionals.Comment: 4 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Rituximab therapy for pure red cell aplasia due to anti-epoetin antibodies in a woman treated with epoetin-alfa: a case report

<p>Abstract</p> <p>Introduction</p> <p>Pure red cell aplasia due to anti-epoetin antibodies is a known complication of epoetin therapy for anemia due to chronic kidney disease. This disease has not previously been well described in the setting of therapy for chronic hepatitis C virus infection. While treatment for pure red cell aplasia due to anti-epoetin antibodies is usually with immunosuppressive therapy such as calcineurin inhibition, the safety of this treatment in chronic hepatitis C virus infection is unknown. To date, little has been published on the efficacy of rituximab on pure red cell aplasia due to anti-epoetin antibodies.</p> <p>Case presentation</p> <p>This report describes a 65-year-old Asian-American woman who developed pure red cell aplasia from high titer neutralizing anti-epoetin antibodies after epoetin-alfa therapy during ribavirin and peg-interferon treatment for chronic hepatitis C virus infection. We describe the outcome of her treatment with rituximab. The reticulocyte count increased, and anti-epoetin antibody titer decreased with a loss of neutralizing activity <it>in vitro</it>, leading to a reduction in blood transfusions, and eventual resolution of anemia, without reactivation of hepatitis C virus.</p> <p>Conclusion</p> <p>The diagnosis of pure red cell aplasia from anti-epoetin antibodies should be considered in patients undergoing therapy for chronic hepatitis C virus infection who develop severe anemia after administration of erythropoietin or darbepoetin. Though it is currently an off-label indication, rituximab is a therapeutic option for patients with pure red cell aplasia due to anti-epoetin antibodies.</p

Non-adiabatic Effects in the Dissociation of Oxygen Molecules at the Al(111) Surface

The measured low initial sticking probability of oxygen molecules at the Al(111) surface that had puzzled the field for many years was recently explained in a non-adiabatic picture invoking spin-selection rules [J. Behler et al., Phys. Rev. Lett. 94, 036104 (2005)]. These selection rules tend to conserve the initial spin-triplet character of the free O2 molecule during the molecule's approach to the surface. A new locally-constrained density-functional theory approach gave access to the corresponding potential-energy surface (PES) seen by such an impinging spin-triplet molecule and indicated barriers to dissociation which reduce the sticking probability. Here, we further substantiate this non-adiabatic picture by providing a detailed account of the employed approach. Building on the previous work, we focus in particular on inaccuracies in present-day exchange-correlation functionals. Our analysis shows that small quantitative differences in the spin-triplet constrained PES obtained with different gradient-corrected functionals have a noticeable effect on the lowest kinetic energy part of the resulting sticking curve.Comment: 17 pages including 11 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

A New Type of distributed Enamel based Clearing Electrode

Clearing electrodes can be used for electron cloud (EC) suppression in high intensity particle accelerators. In this paper the use of low and highly resistive layers on a dielectric substrate are examined. The beam coupling impedance of such a structure is evaluated. Furthermore the clearing efficiency as well as technological issues are discussed