[3+2] Fragmentation of a Pentaphosphido Ligand by Cyanide

The activation of white phosphorus (P4) by transition‐metal complexes has been studied for several decades, but the functionalization and release of the resulting (organo)phosphorus ligands has rarely been achieved. Herein we describe the formation of rare diphosphan‐1‐ide anions from a P5 ligand by treatment with cyanide. Cobalt diorganopentaphosphido complexes have been synthesized by a stepwise reaction sequence involving a low‐valent diimine cobalt complex, white phosphorus, and diorganochlorophosphanes. The reactions of the complexes with tetraalkylammonium or potassium cyanide afford a cyclotriphosphido cobaltate anion 5 and 1‐cyanodiphosphan‐1‐ide anions [R2PPCN]− (6‐R). The molecular structure of a related product 7 suggests a novel reaction mechanism, where coordination of the cyanide anion to the cobalt center induces a ligand rearrangement. This is followed by nucleophilic attack of a second cyanide anion at a phosphorus atom and release of the P2 fragment

Die Welt jenseits der Oszillografen : ein Streitgespräch zwischen dem Hirnforscher Wolf Singer und dem Philosophen Marcus Willaschek

Neurowissenschaftler fordern einen illusionslosen Umgang mit Begriffen wie Willensfreiheit und Bewusstsein. Philosophen kritisieren offen die Thesen von Hirnforschern. Stehen sich diese Positionen unversöhnlich gegenüber? Wo gibt es Möglichkeiten einer Annäherung, gar einer Kooperation? Der Religionsphilosoph Prof. Dr. Thomas M. Schmidt und der Biologe Stefan Kieß loten die Situation in Frankfurt aus; ihre Gesprächspartner sind der Hirnforscher Prof. Dr. Wolf Singer (links), Direktor am Max-Planck-Institut für Hirnforschung, und Prof. Dr. Marcus Willaschek (rechts), Philosoph an der Universität Frankfurt

Evaluation of interface quality in organ-cultured lamellar corneal transplants

Background: With increasing numbers of lamellar keratoplasties, eye banks are challenged to deliver precut lamellar donor tissue. In Europe, the most common technique of corneal storage is organ culture which requires a deswelling process before surgical processing. The aim of this study was to investigate the influence of different deswelling times on the cutting plane quality after microkeratome-assisted lamellar dissection. Methods: Eight paired donor corneas (16 specimens) not suitable for transplantation were organ cultured under standard conditions at the Eye Bank of the Ludwig-Maximilians Universität, Munich, Germany. Pairs of corneal buttons were analyzed during the deswelling process in dextrane-containing medium. While one cornea was cut at an early time point during the deswelling process and put back into deswelling medium thereafter, the partner cornea was completely deswollen and dissected after 72 hours. Specimens were then further processed for scanning electron microscopy. Surface quality was assessed both digitally using Scanning Probe Imaging Processing software, and manually by three blinded graders. Results: The corneal buttons processed at the beginning of the deswelling process had a smoother surface when compared to the partner cornea that was cut at the end of the deswelling process. In our setting, no relevant difference was detectable between manual and automated microkeratome dissection. Conclusion: For lamellar keratoplasty, organ-cultured corneas should be processed at an early stage during the deswelling process. We interpret the smoother dissection plane during early deswelling as a result of mechanical properties in a highly hydrated cornea

Non-perturbative effects in semi-leptonic B_c decays

We discuss the impact of the soft degrees of freedom inside the B_c meson on its rate in the semi-leptonic decay B_c -> X l nu_l where X denotes light hadrons below the D^0 threshold. In particular we identify contributions involving soft hadrons which are non-vanishing in the limit of massless leptons. These contributions become relevant for a measurement of the purely leptonic B_c decay rate, which due to helicity suppression involves a factor m_l^2 and thus is much smaller than the contributions involving soft hadrons.Comment: LaTeX, 22 pages, 1 figur

ZNF804A genotype modulates neural activity during working memory for faces

Copyright © 2013 S. Karger AG, Basel.Peer reviewedPublisher PD

Spin interference in silicon one-dimensional rings

We present the first findings of the spin transistor effect caused by the Rashba gate-controlled ring embedded in the p-type self-assembled silicon quantum well that is prepared on the Si (100) surface. The coherence and phase sensitivity of the spin-dependent transport of holes are studied by varying the value of the external magnetic field and the gate voltage that are perpendicular to the plane of the double-slit ring. Firstly, the quantum scatterers connected to two one-dimensional leads and the quantum point contact inserted in the one of the arms of the double-slit ring are shown to define the amplitude and the phase of the Aharonov-Bohm and the Aharonov-Casher conductance oscillations. Secondly, the amplitude and phase sensitivity of the 0.7 feature of the hole quantum conductance staircase revealed by the quantum point contact inserted are found to result from the interplay of the spontaneous spin polarization and the Rashba spin-orbit interaction.Comment: 2 pages, 2 figures, presented at the 5th International Conference on Strongly Correlated Electron Systems, SCES'05, Vienna, Austria, 26-30 July, 200