ALBERT

Description: Author(s): Bruno Schuler, Mats Persson, Sami Paavilainen, Niko Pavliček, Leo Gross, Gerhard Meyer, and Jascha Repp The formation of extended electron states in one-dimensional nanostructures is of key importance for the function of molecular electronics devices. In this paper, using a combination of atomic force microscopy, scanning tunneling spectroscopy, and tight-binding calculations the authors investigate the confinement of electronic states to controlled Cl vacancy pairs in a NaCl bilayer on Cu(111). They reveal that electron-phonon coupling has great influence on these quantities. [Phys. Rev. B 91, 235443] Published Wed Jun 24, 2015

Description: Culture medium from an isolate of the fungus Aspergillus candidus was extracted, fractionated and examined to discover compounds antagonistic to plant-parasitic nematodes that are important pathogens of agricultural crops. Column, thin layer and preparative chromatographies and spectral and elemental analyses, were used to isolate and identify two major constituents of an active fraction (Fraction F) obtained from the medium. Compound 1 was identified as 2-hydroxypropane-1, 2, 3-tricarboxylic acid (citric acid). Compound 2 was identified as 3-hydroxy-5-methoxy-3-(methoxycarbonyl)-5-oxopentanoic acid, an isomer of 1, 2-dimethyl citrate. Compound 1 and a citric acid standard, each tested at 50 mg mL –1 in water, decreased hatch from eggs of the plant-parasitic nematode Meloidogyne incognita by more than 94%, and completely immobilized second-stage juveniles after 4–6 days exposure. Fraction F and Compounds 1 and 2 decreased the mobility of adults of the plant-parasitic nematode Ditylenchus destructor in vitro . Fraction F (25 mg mL –1 ) inhibited mobility 〉99% at 72 hrs. Compounds 1 and 2 (50 mg mL –1 ) each inhibited mobility more than 25% at 24 hr and more than 50% at 72 hr. This is the first assignment of nematode-antagonistic properties to specifically identified A. candidus metabolites.

Description: Author(s): Tatiana Krishtop, Manuel Houzet, and Julia S. Meyer We investigate theoretically the nonlocal conductance through a superconducting wire in tunnel contact with normal and ferromagnetic leads. In the presence of an in-plane magnetic field, the superconducting density of states is spin split, and the current injected from the normal lead is spin polari... [Phys. Rev. B 91, 121407] Published Thu Mar 12, 2015

Description: RNA–RNA interactions are fast emerging as a major functional component in many newly discovered non-coding RNAs. Basepairing is believed to be a major contributor to the stability of these intermolecular interactions, much like intramolecular basepairs formed in RNA secondary structure. As such, using algorithms similar to those for predicting RNA secondary structure, computational methods have been recently developed for the prediction of RNA–RNA interactions. We provide the first comprehensive comparison comprising 14 methods that predict general intermolecular basepairs. To evaluate these, we compile an extensive data set of 54 experimentally confirmed fungal snoRNA–rRNA interactions and 102 bacterial sRNA–mRNA interactions. We test the performance accuracy of all methods, evaluating the effects of tool settings, sequence length, and multiple sequence alignment usage and quality. Our results show that—unlike for RNA secondary structure prediction—the overall best performing tools are non-comparative energy-based tools utilizing accessibility information that predict short interactions on this data set. Furthermore, we find that maintaining high accuracy across biologically different data sets and increasing input lengths remains a huge challenge, causing implications for de novo transcriptome-wide searches. Finally, we make our interaction data set publicly available for future development and benchmarking efforts.

Description: Author(s): Ch. Zaum, K. M. Meyer-auf-der-Heide, and K. Morgenstern We follow the diffusion of CO molecules on Cu(111) by time-lapsed low-temperature scanning tunneling microscopy. The diffusivity of individual CO molecules oscillates with the distance to its nearest neighbor due to the long-range interaction mediated by the surface state electrons. The markedly dif... [Phys. Rev. B 97, 155437] Published Mon Apr 30, 2018

Description: Author(s): René Meyer, Alexander F. Zurhelle, Roger A. De Souza, Rainer Waser, and Felix Gunkel The electrical properties of donor-doped SrTi O 3 ( n -STO) are profoundly affected by an oxidation-induced metal-insulator transition (MIT). Here we employ dynamical numerical simulations to examine the high-temperature MIT of n -STO over a large range of time and length scales. The simulations are base… [Phys. Rev. B 94, 115408] Published Tue Sep 06, 2016

Description: Author(s): Fabrizio Dolcini, Manuel Houzet, and Julia S. Meyer We study the effect of a magnetic field on the current-phase relation of a topological Josephson junction formed by connecting two superconductors through the helical edge states of a quantum spin-Hall insulator. We predict that the Zeeman effect along the spin quantization axis of the helical edges… [Phys. Rev. B 92, 035428] Published Fri Jul 24, 2015

Description: Author(s): Erik Eriksson, Roman-Pascal Riwar, Manuel Houzet, Julia S. Meyer, and Yuli V. Nazarov The investigation of topological transitions in quantum systems is a thriving area of modern research. The authors recently predicted that multiterminal Josephson junctions realize a novel type of topological matter. Weyl singularities may appear in the Andreev bound-state spectrum of junctions with four superconducting terminals, giving rise to topological transitions as the superconducting phases are tuned. These transitions manifest themselves in a quantization of the transconductance between two voltage-biased terminals in fundamental units of 4 e 2 2/ h , where e is the electric charge and h is the Planck constant. The present work addresses the observability of this effect. The quantized transconductance is associated with adiabatic transport at fixed occupations of the Andreev states. On the other hand, a bias voltage leads to multiple Andreev reflections, where a quasiparticle is dissipatively transferred from the occupied states below the superconducting gap to the empty states above the superconducting gap. By computing the currents in the presence of weak inelastic relaxation, the authors establish the voltage threshold below which the equilibrium occupations of the Andreev states are restored, and the transconductances reach their quantized values. The results are an important step towards experimental verification of the topological properties of multiterminal Josephson junctions. [Phys. Rev. B 95, 075417] Published Tue Feb 14, 2017

Description: Biologically-based water recovery systems are a regenerative, low energy alternative to physiochemical processes to reclaim water from wastewater. This report summarizes the results of the Alternative Water Processor (AWP) Integrated Test, conducted from June 2013 until April 2014. The system was comprised of four (4) membrane aerated bioreactors (MABRs) to remove carbon and nitrogen from an exploration mission wastewater and a coupled forward and reverse osmosis system to remove large organic and inorganic salts from the biological system effluent. The system exceeded the overall objectives of the test by recovering 90% of the influent wastewater processed into a near potable state and a 64% reduction of consumables from the current state of the art water recovery system on the International Space Station (ISS). However, the biological system fell short of its test goals, failing to remove 75% and 90% of the influent ammonium and organic carbon, respectively. Despite not meeting its test goals, the BWP demonstrated the feasibility of an attached-growth biological system for simultaneous nitrification and denitrification, an innovative, volume- and consumable-saving design that does not require toxic pretreatment.

Description: In membrane-aerated biofilm reactors (MABRs), hollow fibers are used to supply oxygen to the biofilms and bulk fluid. A pressure and concentration gradient between the inner volume of the fibers and the reactor reservoir drives oxygen mass transport across the fibers toward the bulk solution, providing the fiber-adhered biofilm with oxygen. Conversely, bacterial metabolic gases from the bulk liquid, as well as from the biofilm, move opposite to the flow of oxygen, entering the hollow fiber and out of the reactor. Metabolic gases are excellent indicators of biofilm vitality, and can aid in microbial identification. Certain gases can be indicative of system perturbations and control anomalies, or potentially unwanted biological processes occurring within the reactor. In confined environments, such as those found during spaceflight, it is important to understand what compounds are being stripped from the reactor and potentially released into the crew cabin to determine the appropriateness or the requirement for additional mitigation factors. Reactor effluent gas analysis focused on samples provided from Kennedy Space Center's sub-scale MABRs, as well as Johnson Space Center's full-scale MABRs, using infrared spectroscopy and gas chromatography techniques. Process gases, such as carbon dioxide, oxygen, nitrogen, nitrogen dioxide, and nitrous oxide, were quantified to monitor reactor operations. Solid Phase Microextraction (SPME) GC-MS analysis was used to identify trace volatile compounds. Compounds of interest were subsequently quantified. Reactor supply air was examined to establish target compound baseline concentrations. Concentration levels were compared to average ISS concentration values and/or Spacecraft Maximum Allowable Concentration (SMAC) levels where appropriate. Based on a review of to-date results, current trace contaminant control systems (TCCS) currently on board the ISS should be able to handle the added load from bioreactor systems without the need for secondary mitigation.