Worldsheet Instantons and Torsion Curves

We study aspects of worldsheet instantons relevant to a heterotic standard model. The non-simply connected Calabi-Yau threefold used admits Z_3 x Z_3 Wilson lines, and a more detailed investigation shows that the homology classes of curves are H_2(X,Z)=Z^3+Z_3+Z_3. We compute the genus-0 prepotential, this is the first explicit calculation of the Gromov-Witten invariants of homology classes with torsion (finite subgroups). In particular, some curve classes contain only a single instanton. This ensures that the Beasley-Witten cancellation of instanton contributions cannot happen on this (non-toric) Calabi-Yau threefold.Comment: 9 pages. To appear in the proceedings of the first Sowers Theoretical Physics workshop, Virginia Tech, May 200

Causes of brain dysfunction in acute coma: a cohort study of 1027 patients in the emergency department

BACKGROUND: Coma of unknown etiology (CUE) is a major challenge in emergency medicine. CUE is caused by a wide variety of pathologies that require immediate and targeted treatment. However, there is little empirical data guiding rational and efficient management of CUE. We present a detailed investigation on the causes of CUE in patients presenting to the ED of a university hospital. METHODS: One thousand twenty-seven consecutive ED patients with CUE were enrolled. Applying a retrospective observational study design, we analyzed all clinical, laboratory and imaging findings resulting from a standardized emergency work-up of each patient. Following a predefined protocol, we identified main and accessory coma-explaining pathologies and related these with (i.a.) GCS and in-hospital mortality. RESULTS: On admission, 854 of the 1027 patients presented with persistent CUE. Their main diagnoses were classified into acute primary brain lesions (39%), primary brain pathologies without acute lesions (25%) and pathologies that affected the brain secondarily (36%). In-hospital mortality associated with persistent CUE amounted to 25%. 33% of patients with persistent CUE presented with more than one coma-explaining pathology. In 173 of the 1027 patients, CUE had already resolved on admission. However, these patients showed a spectrum of main diagnoses similar to persistent CUE and a significant in-hospital mortality of 5%. CONCLUSION: The data from our cohort show that the spectrum of conditions underlying CUE is broad and may include a surprisingly high number of coincidences of multiple coma-explaining pathologies. This finding has not been reported so far. Thus, significant pathologies may be masked by initial findings and only appear at the end of the diagnostic work-up. Furthermore, even transient CUE showed a significant mortality, thus rendering GCS cutoffs for selection of high- and low-risk patients questionable. Taken together, our data advocate for a standardized diagnostic work-up that should be triggered by the emergency symptom CUE and not by any suspected diagnosis. This standardized routine should always be completed - even when initial coma-explaining diagnoses may seem evident

Quantifying the costs of transport networks’ components

In dieser Arbeit werden die Kosten von Straßentransportnetzwerken mit Hilfe von verschiedenen Datenquellen und Methodiken quantifiziert

Time Resolved Measurements of pH in Aqueous Magnesium‐Air Batteries during Discharge and Its Impact for Future Applications

In aqueous magnesium air batteries, the influence of the electrochemical behavior on pH of the electrolyte has not been investigated yet, which has a critical effect on the cell performance. We have monitored the evolution of the pH at various discharge current densities in situ in the Mg-air primary cells, which produce sparingly soluble magnesium hydroxide (Mg(OH)$_{2}$). These experiments show the temporal evolution of the pH of the electrolyte in the cell discharge, depending on the current density. The pH first increases rapidly to a maximum of pH 11 and then drops down slowly to the equilibrium at pH 10.7. At the peak pH oversaturation of Mg(OH)$_{2}$ is paramount, leading to the precipitation which balances the Mg(OH)$_{2}$ concentration in the electrolyte. This precipitation process coats both cathode and anode which leads to a decrease in cell efficiency and voltage. The results show that the cell design of Mg-air batteries is important for their lifetime and cell performance. The performance of the aqueous magnesium cell is increased several folds when the design is changed to a simple electrolyte flow cell

Immuno-Thrombotic Effects of Platelet Serotonin

Platelets transport and store serotonin at a high concentration in dense granules and release it upon activation. Abnormal serotonin concentrations in the blood plasma or increased platelet serotonin release promote the development of thrombosis, sepsis, allergic asthma, myocardial infarction, and stroke. Consequently, experimental data suggest possible benefits of serotonin receptor blockade or inhibition of platelet serotonin uptake in the indicated human diseases. Here, we highlight the current state of basic biological research regarding the role of platelet serotonin in normal and pathophysiological conditions focusing on thrombotic and inflammatory diseases. We also describe the possible clinical applicability of targeting thrombo-immune-modulatory effects of platelet serotonin to treat common health problems

White and green rust chimneys accumulate RNA in a ferruginous chemical garden

Mechanisms of nucleic acid accumulation were likely critical to life's emergence in the ferruginous oceans of the early Earth. How exactly prebiotic geological settings accumulated nucleic acids from dilute aqueous solutions, is poorly understood. As a possible solution to this concentration problem, we simulated the conditions of prebiotic low-temperature alkaline hydrothermal vents in co-precipitation experiments to investigate the potential of ferruginous chemical gardens to accumulate nucleic acids via sorption. The injection of an alkaline solution into an artificial ferruginous solution under anoxic conditions (O2 < 0.01% of present atmospheric levels) and at ambient temperatures, caused the precipitation of amakinite (“white rust”), which quickly converted to chloride-containing fougerite (“green rust”). RNA was only extractable from the ferruginous solution in the presence of a phosphate buffer, suggesting RNA in solution was bound to Fe2+ ions. During chimney formation, this iron-bound RNA rapidly accumulated in the white and green rust chimney structure from the surrounding ferruginous solution at the fastest rates in the initial white rust phase and correspondingly slower rates in the following green rust phase. This represents a new mechanism for nucleic acid accumulation in the ferruginous oceans of the early Earth, in addition to wet-dry cycles and may have helped to concentrate RNA in a dilute prebiotic ocean