Voltage Dependence of the Amplitude of Aharonov-Bohm Oscillations in Mesoscopic Metal Rings

We investigated the influence of a DC-bias voltage V_DCon the Aharonov–Bohm oscillations in mesoscopic metal rings.The amplitude of the oscillations fluctuates as a function ofV_DC with a typical voltage scale corresponding to theThouless energy. We also observed a square-root like increaseof the amplitude with increasing V_DC. This behavior is inagreement with the theoretical prediction of the fluctuationsof the nonlinear conductance in singly connectednanostuctures.     

Hochwasserschutz im Land Bremen – Anpassung an prognostizierte Klimaänderungen

Im Beitrag wird auf Besonderheiten bei der Umsetzung des Generalplans Küstenschutz Niedersachsen/Bremen im Land Bremen eingegangen. Im ersten Teil werden die Grundlagen und Ergebnisse des Generalplans sowie die administrative Aufstellung des Landes Bremen zur Anpassung des Hochwasserschutzes beschrieben. Das Instrument der Kostenvergleichsrechnung wird vorgestellt, welches in Bremen bereits im frühen Projektstadium zur Bewertung der Vorzugslösungen eingesetzt wird. Ein wichtiger Aspekt bei der Umsetzung des Generalplans sind die technischen Anforderungen, die sich aus den bestehenden Hochwasserschutzanlagen ergeben. Weiterhin müssen im Land Bremen die Maßnahmen zum Hochwasserschutz im Wesentlichen unter Berücksichtigung der bestehenden konstruktiv geprägten Ufer (Spundwände und Kaianlagen) umgesetzt werden. Dabei sind spezielle Anforderungen hinsichtlich der aktuellen und zukünftigen Nutzung insbesondere in den Hafenrevieren zu berücksichtigen. Beispielhaft werden begleitende Projekte der INROS LACKNER AG vorgestellt. Flood protection in the Federal State and the city of Bremen by adjustment of climate changes. The present article describes how the Federal State and the Free Hanseatic City of Bremen adapts its flood protection with respect to climate changes and global sea level rise. Design basics are compiled in the “Generalplan Küstenschutz Niedersachsen/Bremen” (General Plan for Coastal Protection – Lower Saxony/Bremen). Main results of the general plan will be described and administrative aspects of the adaptation of the flood protection elements in Bremen will be lined out. Special technical requirements as the consideration of existing walls and dikes will be described. Also requirements from harbour operation, recreational use and urban architecture have to be considered as the Bremen port partly undergoes a rapid change in this regard. The instrument of cost analysis will be introduced which is utilised in Bremen at an early stage of planning in order to develop cost effective measures of public founded projects. Mentioned topics will be described based on projects carried out by INROS LACKNER AG.     

Quantification of four major metabolites of embryotoxic N-methyl- and N-ethyl-2-pyrrolidone in human urine by cooled-injection gas chromatography and isotope dilution mass spectrometry

N-Methyl- and N-ethyl-2-pyrollidone (NMP and NEP) are frequently used industrial solvents and were shown to be embryotoxic in animal experiments. We developed a sensitive, specific, and robust analytical method based on cooled-injection (CIS) gas chromatography and isotope dilution mass spectrometry to analyze 5-hydroxy-N-ethyl-2-pyrrolidone (5-HNEP) and 2-hydroxy-N-ethylsuccinimide (2-HESI), two newly identified presumed metabolites of NEP, and their corresponding methyl counterparts (5-HNMP, 2-HMSI) in human urine. The urine was spiked with deuterium-labeled analogues of these metabolites. The analytes were separated from urinary matrix by solid-phase extraction and silylated prior to quantification. Validation of this method was carried out by using both, spiked pooled urine samples and urine samples from 56 individuals of the general population with no known occupational exposure to NMP and NEP. Interday and intraday imprecision was better than 8% for all metabolites, while the limits of detection were between 5 and 20 μg/L depending on the analyte. The high sensitivity of the method enables us to quantify NMP and NEP metabolites at current environmental exposures by human biomonitoring.     

Ion release from magnesium materials in physiological solutions under different oxygen tensions

Although magnesium as degradable biomaterial already showed clinical proof of concepts, the design of new alloys requires predictive in vitro methods, which are still lacking. Incubation under cell culture conditions to obtain “physiological” corrosion may be a solution. The aim of this study was to analyse the influence of different solutions, addition of proteins and of oxygen availability on the corrosion of different magnesium materials (pure Mg, WE43, and E11) with different surface finishing. Oxygen content in solution, pH, osmolality and ion release were determined. Corrosion led to a reduction of oxygen in solution. The influence of oxygen on pH was enhanced by proteins, while osmolality was not influenced. Magnesium ion release was solution-dependent and enhanced in the initial phase by proteins with delayed release of alloying elements. The main corrosion product formed was magnesium carbonate. Therefore, cell culture conditions are proposed as first step toward physiological corrosion.     

Cover Picture: Screening for Cytochrome P450 Reactivity by Harnessing Catalase as Reporter Enzyme (ChemBioChem 4/2009)

The cover picture shows a bacterial cytochrome P450 enzyme (CYP152A1, blue protein) screening for new substrates, such as nifidepine (highlighted green). The identification of novel reactivities of P450 enzymes is of major importance for applications in biocatalysis, biosensing and metabolic engineering. In their contribution on p. 751 ff, Niemeyer et al. report a novel assay for the rapid and facile screening of substrate libraries for organic hydroperoxide‐mediated P450 reactivity. Peroxide depletion is monitored in a fluorescence microplate assay, by harnessing a previously undescribed reactivity of the enzyme catalase (orange protein structure). The assay thus connects the occurrence of P450 reactivity with a universal read‐out, thereby circumventing the need for substrate‐specific detection schemes.

     

Scalable Functionalization of Optical Fibers Using Atomically Thin Semiconductors

Atomically thin transition metal dichalcogenides are highly promising for integrated optoelectronic and photonic systems due to their exciton-driven linear and nonlinear interactions with light. Integrating them into optical fibers yields novel opportunities in optical communication, remote sensing, and all-fiber optoelectronics. However, the scalable and reproducible deposition of high-quality monolayers on optical fibers is a challenge. Here, the chemical vapor deposition of monolayer MoS₂ and WS₂ crystals on the core of microstructured exposed-core optical fibers and their interaction with the fibers’ guided modes are reported. Two distinct application possibilities of 2D-functionalized waveguides to exemplify their potential are demonstrated. First, the excitonic 2D material photoluminescence is simultaneously excited and collected with the fiber modes, opening a novel route to remote sensing. Then it is shown that third-harmonic generation is modified by the highly localized nonlinear polarization of the monolayers, yielding a new avenue to tailor nonlinear optical processes in fibers. It is anticipated that the results may lead to significant advances in optical-fiber-based technologies.     

A Computational Framework for Magnetic Polyoxometalates and Molecular Spin Structures: CONDON 2.0

The emergence of increasingly complex molecular magnets, driven in particular by polyoxometalate chemistry, requires theoretical tools to accurately model and understand their magnetic phenomena. At the same time the unambiguous verification of model Hamiltonians remains a challenge, tied to factors ranging from available independent experimental data sets to available computation resources. Focusing on several recent examples for magnetically functionalized polyoxometalates and polynuclear coordination complexes, we demonstrate the recent developments of CONDON 2.0 that aim to address these issues, and suggest measurement protocols that will aid our multi-parameter computational approach.