Electroluminescence from a polythiophene molecular wire suspended in a plasmonic scanning tunneling microscope junction

The electroluminescence of a polythiophene wire suspended between two metallic electrodes is probed using a scanning tunneling microscope. Under positive sample voltage, the spectral and voltage dependencies of the emitted light are consistent with the fluorescence of the wire junction mediated by localized plasmons. This emission is strongly attenuated for the opposite polarity. Both emission mechanism and polarity dependence are similar to what occurs in organic light emitting diodes (OLED) but at the level of a single molecular wire.Comment: to be published in Physical Review Letter

Imaging isodensity contours of molecular states with STM

We present an improved way for imaging the local density of states with a scanning tunneling microscope, which consists in mapping the surface topography while keeping the differential conductance (d$I$/d$V$) constant. When archetypical C$_{60}$ molecules on Cu(111) are imaged with this method, these so-called iso-d$I$/d$V$ maps are in excellent agreement with theoretical simulations of the isodensity contours of the molecular orbitals. A direct visualization and unambiguous identification of superatomic C$_{60}$ orbitals and their hybridization is then possible

Pulling and Stretching a Molecular Wire to Tune its Conductance

A scanning tunnelling microscope is used to pull a polythiophene wire from a Au(111) surface while measuring the current traversing the junction. Abrupt current increases measured during the lifting procedure are associated to the detachment of molecular sub-units, in apparent contradiction with the expected exponential decrease of the conductance with wire length. \textit{Ab initio} simulations reproduce the experimental data and demonstrate that this unexpected behavior is due to release of mechanical stress in the wire, paving the way to mechanically gated single-molecule electronic devices

Topologically localized excitons in single graphene nanoribbons

Excitonic emission from atomically precise graphene nanoribbons (GNRs) synthesised on a metal surface is probed with atomic-scale spatial resolution using a scanning tunneling microscopy (STM) approach. A STM-based strategy to transfer the GNRs to a partially insulating surface is used to prevent light emission quenching of the ribbons by the metal substrate. Sub-nanometer resolved STM-induced fluorescence spectra reveal emission from localized dark excitons build upon the topological end states of the GNRs. A low frequency vibronic emission comb whose characteristics change with the GNR length is attributed to longitudinal acoustic modes confined to a finite box. Overall, our study provides a novel path to investigate the interplay between excitons, vibrons and topology in atomically precise graphene nanostructures

Chest CT Findings and SARS-CoV-2 Infection in Trauma Patients-Is There a Prediction towards Higher Complication Rates?

BACKGROUND Polytrauma patients with SARS-CoV-2 infections may be associated with an increased complication rate. The main goal of this study was to analyze the clinical course of trauma patients with COVID infection and a positive CT finding. METHODS This was a retrospective in-hospital study. Polytrauma patients diagnosed with SARS-CoV-2 infections were included in our analysis. The outcome parameters were pulmonary complication during admission, pulmonary embolism, pleural effusion, pneumonia, mortality, length of stay and readmission < 30 days. RESULTS 48 patients were included in the study. Trauma patients in the age-adjusted matched-pair analysis with typical changes in SARS-CoV-2 infection in CT findings showed significantly more pulmonary complications in general and significantly more cases of pneumonia (complications: 56% vs. 11%, p = 0.046; pneumonia 44% vs. 0%, p = 0.023). In addition, the clinical course of polytrauma patients with SARS-CoV-2 infection showed a high rate of pulmonary complications in the inpatient course (53%). CONCLUSION The results of our study show that the changes in the CT findings of trauma patients with SARS-CoV-2 infection are a good indicator of further inpatient outcomes. Similarly, polytrauma patients with a SARS-CoV-2 infection and positive CT findings are shown to have increased risk for pulmonary complications

Demokratie auf dem Rückzug? Zur Konfrontation zwischen amerikanischem Präsidenten und Kongress über einen Truppenabzug aus dem Irak

Im US-Präsidentschaftswahlkampf 2008 ist der Irakkrieg eines der wichtigsten Themen. Die Amerikaner sind allmählich kriegsmüde und die Mehrheit befürwortet einen Truppenrückzug aus dem Irak. Das brachten bereits der Ausgang der Kongresswahlen im Jahr 2006 sowie regelmäßige Meinungsumfragen zum Ausdruck. Es ist nun anzunehmen, dass in der ältesten Demokratie der Welt Volkes Wille direkten Einfluss auf die Politik haben müsste. Doch dies ist nur bedingt der Fall. Besonders Präsident George W. Bush hat wiederholt klargestellt, dass die Stimmung in der Bevölkerung für ihn in der Irakfrage nicht maßgebend sei. Für ihn zähle vielmehr, wie die Generäle vor Ort die aktuelle Sicherheitslage und die Fortschritte einschätzen. Dagegen versucht der seit Ende 2006 von Demokraten dominierte Kongress immer wieder, Rückzugspläne mit festen Fristen zu etablieren. Bislang ist sein Erfolg jedoch bescheiden. Vor allem die fehlende Unterstützung der Republikaner im Kongress und die Blockadepolitik des Präsidenten waren dafür verantwortlich. Hinter der Konfrontation steht eine tiefergehende Auseinandersetzung über die Kompetenzverteilung zwischen Präsident und Kongress bei Kriegsentscheidungen, die in der US-Verfassung in einer Grauzone bleibt. Stephanie Sohnius verknüpft vor diesem verfassungsrechtlichen Hintergrund die Aufarbeitung der aktuell wichtigsten USaußenpolitischen Debatte mit der Frage, ob sich die Demokratie in den USA in der Ära des „Krieges gegen den Terrorismus“ (weiterhin) auf dem Rückzug befindet

Many-body description of STM-induced fluorescence of charged molecules

A scanning tunneling microscope is used to study the fluorescence of a model charged molecule (quinacridone) adsorbed on a sodium chloride (NaCl)-covered metallic sample. Fluorescence from the neutral and positively charged species is reported and imaged using hyper-resolved fluorescence microscopy. A many-body excitation model is established based on a detailed analysis of voltage, current and spatial dependencies of the fluorescence and electron transport features. This model reveals that quinacridone adopts a large palette of charge states, transient or not, depending on the voltage used and the nature of the underlying substrate. This model has a universal character and explains the electronic and fluorescence properties of many other molecules adsorbed on thin insulators

Ten-Year Minimum Follow-up Study of First Metatarsophalangeal Joint Fusion in Young vs Old Patients

BACKGROUND Painful degenerative joint disease (DJD) of the first metatarsophalangeal joint (MTP I), or hallux rigidus, mainly occurs in later stages of life. For end-stage hallux rigidus, MTP I arthrodesis is considered the gold standard. As young and active patients are affected considerably less frequently, it currently remains unclear, whether they benefit to the same extent. We hypothesized that MTP I arthrodesis in younger patients would lead to an inferior outcome with decreased rates of overall with lower rates of patient postoperative pain and function compared to an older cohort. METHODS All patients aged 60 years. Minimum follow-up was 10 years. Outcome measures were Tegner activity score (TAS), a "Virtual Tegner activity score" (VTAS), the visual analog scale (VAS), and the Foot Function index (FFI). RESULTS Sixty-one MTP I fusions (n = 28 young, n = 33 old) in 46 patients were included in our study at an average of 14 years after surgery. Younger patients experienced significantly more pain relief as reflected by changes in VAS and FFI Pain subscale scores. No difference in functional outcomes was found with change in the FFI function subscale or in the ability to have desired functional outcomes using the ratio of TAS to VTAS. Revision rate did not differ between the two groups apart from hardware removal, which was significantly more likely in the younger group. CONCLUSION In patients below the age of 50 years with end-stage DJD of the first metatarsal joint, MTP I arthrodesis not only yielded highly satisfactory postoperative results at least equal outcome compared to an older cohort of patients aged >60 years at an average 14 years' follow-up. Based on these findings, we consider first metatarsal joint fusion even for young patients is a valid option to treat end-stage hallux rigidus. LEVEL OF EVIDENCE Level III, a case-control study