Quantification and dating of floodplain sedimentation in a medium-sized catchment of the German uplands: a case study from the Aar Valley in the southern Rhenish Massif, Germany

The distribution, thickness and composition of the floodplain sediments in the valleys of the Aar and its tributaries (Taunus Mountains) were investigated by way of extensive fieldwork at 25 locations. In the entire catchment area, 48.8 million tons of loamy floodplain fines could be assessed. Most of these were deposited since late medieval times due to extensive historical land use and forest clearing, especially in the mining region along the middle course of the Aar. In its lower course, the enhanced sedimentation ofloamy f loodplain sediments started during the Bronze Age

Moment analysis for localization in random Schrödinger operators

We study localization effects of disorder on the spectral and dynamical properties of Schrödinger operators with random potentials. The new results include exponentially decaying bounds on the transition amplitude and related projection kernels, including in the mean. These are derived through the analysis of fractional moments of the resolvent, which are finite due to the resonance-diffusing effects of the disorder. The main difficulty which has up to now prevented an extension of this method to the continuum can be traced to the lack of a uniform bound on the Lifshitz-Krein spectral shift associated with the local potential terms. The difficulty is avoided here through the use of a weak-L1 estimate concerning the boundary-value distribution of resolvents of maximally dissipative operators, combined with standard tools of relative compactness theor

Single-photon emission at a rate of 143 MHz from a deterministic quantum-dot microlens triggered by a mode-locked vertical-external-cavity surface-emitting laser

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 107, 041105 (2015) and may be found at https://doi.org/10.1063/1.4927429.We report on the realization of a quantum dot (QD) based single-photon source with a record-high single-photon emission rate. The quantum light source consists of an InGaAs QD which is deterministically integrated within a monolithic microlens with a distributed Bragg reflector as back-side mirror, which is triggered using the frequency-doubled emission of a mode-locked vertical-external-cavity surface-emitting laser (ML-VECSEL). The utilized compact and stable laser system allows us to excite the single-QD microlens at a wavelength of 508 nm with a pulse repetition rate close to 500 MHz at a pulse width of 4.2 ps. Probing the photon statistics of the emission from a single QD state at saturation, we demonstrate single-photon emission of the QD-microlens chip with g(2)(0) < 0.03 at a record-high single-photon flux of (143 ± 16) MHz collected by the first lens of the detection system. Our approach is fully compatible with resonant excitation schemes using wavelength tunable ML-VECSELs, which will optimize the quantum optical properties of the single-photon emission in terms of photon indistinguishability.BMBF, 03V0630, Entwicklung einer Halbleiterbasierten Einzelphotonenquelle für die Quanteninformationstechnologie (QSOURCE)DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeDFG, 192635911, GRK 1782: Funktionalisierung von HalbleiternDFG, 223848855, SFB 1083: Struktur und Dynamik innerer Grenzfläche

Ganzheitlichkeit in der Lebensmittelmittelforschung

Ein Grund für die bislang schwierige bis unmögliche anbauspezifische Zuordnung frischer oder verarbeiteter landwirtschaftlicher Erzeugnisse besteht nach Ansicht von Wissenschaftlerinnen und Wissenschaftlern aus privaten und staatlichen Forschungseinrichtungen des Öko-landbaus in der Art der angewendeten analytischen Methoden zur Qualitätsbewertung. Wäh-rend fast alle gängigen chemisch-analytischen Methoden für eine Differenzierung offensicht-lich nicht genügen, scheinen verschiedene, gegenwärtig jedoch naturwissenschaftlich nicht anerkannte, komplementäre Analysenmethoden eine Unterscheidung treffen zu können. Diese schreiben der Lebensmittelstruktur, äußerer Form, Formerhalt und innerer Formation als Qua-litätskriterium eine besondere Bedeutung zu und können so zwischen verschiedenen Produk-tionsverfahren, Sorten, Verarbeitungsgraden u.a. unterscheiden. Die komplementären Methoden sind jedoch im Hinblick auf ihre Spezifität zur Unterschei-dung der Produktionsverfahren, Vergleichbarkeit, Präzision, Robustheit noch umfassend zu validieren. Obwohl die komplementären Methoden auch nach dieser Validierung nicht notwendigerweise Aussagen über die Qualität der Lebensmittel aus unterschiedlichen Produktionsverfahren zulassen, ist die Möglichkeit der Unterscheidung von konventionell erzeugten Lebensmitteln und Bio-Lebensmitteln gleichwohl von hohem Interesse. Die SAG empfiehlt daher ausdrücklich die Validierung der beschriebenen ganzheitlichen Methoden auf naturwissenschaftlich-statistischer Grundlage zu komplementären Methoden der Qualitätserfassung

Chemoenzymatic enantioselective synthesis of phenylglycine and phenylglycine amide by direct coupling of the Strecker synthesis with a nitrilase reaction

The conversion of rac-phenylglycinonitrile by different variants of the nitrilase from Pseudomonas fluorescens EBC191 (EC 3.5.5.1) was studied and the amounts and chiral composition of the formed phenylglycine and phenylglycine amide compared. Muteins that converted rac-phenylglycinonitrile to extraordinarily high amounts of phenylglycine or phenylglycine amide were tested for the chemoenzymatic enantioselective one-pot synthesis of (R)- and (S)-phenylglycine and (R)- and (S)-phenylglycine amide. The chemoenzymatic synthesis combined the initial step in the traditional chemical Strecker synthesis which results in the formation of rac-phenylglycinonitrile from benzaldehyde, cyanide, and ammonia with the enzymatic conversion of the formed nitrile by the nitrilase variants. The aminonitrile synthesis was optimized in order to obtain conditions which allowed under mildly alkaline conditions (pH 9.5) maximal yields of phenylglycinonitrile and the in-situ racemization of the compound. The racemic phenylglycinonitrile was directly converted under the alkaline conditions without any interposed purification step by cells of Escherichia coli overexpressing recombinant nitrilase variants. The application of a mutant of E. coli defect in a (S)-phenylglycine amide hydrolysing peptidase (E. coli JM109ΔpepA) expressing a highly reaction- and (R)-specific nitrilase variant allowed the synthesis of (R)-phenylglycine with ee-values ≥ 95% in yields up to 81% in relation to the initially added benzaldehyde. These yields indicated a dynamic kinetic resolution which involved the racemization of (S)- to (R)-phenylglycinonitrile under the used alkaline conditions with the concurrent hydrolysis of (R)-phenylglycinonitrile to (R)-phenylglycine. The addition of resting cells of E. coli JM109ΔpepA synthesizing an amide forming nitrilase variant to the final product of the Strecker synthesis and/or using E. coli strains with an intact aminopeptidase gene resulted in the preferred formation of (S)-phenylglycine amide, (R)-phenylglycine amide or (S)-phenylglycine

Associations between dietary patterns and post-bronchodilation lung function in the SAPALDIA cohort

Background: Chronic obstructive pulmonary disease (COPD) is not restricted to smokers. Dietary habits may contribute to the disease occurrence. Epidemiological studies point to a protective effect of fruit and vegetable intake against COPD. Objective: To investigate the associations between dietary patterns and parameters of lung function related to COPD in the Swiss Cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA). Methods: Data were included from the second follow-up assessment of the SAPALDIA cohort in 2010-2011 using a food frequency questionnaire. Principal component factor analysis was used to derive dietary patterns, whose association with FEV1, FEV1/FVC, FEF2575, and COPD was investigated by applying multivariate regression analyses. Results: After adjustment for potential confounders, the “prudent dietary pattern” characterised by the predominant food groups vegetables, fruits, water, tea and coffee, fish, and nuts was positively associated with FEV1 (increase of 40 mL per SD, p < 0.001). Also for factor 3 (“high-carbohydrate diet”), we found a significant positive association with FEV1 (with an increase per SD of 36 mL, p = 0.006). Conclusions: The main results are consistent with a protective effect of a diet rich in fruits, vegetables, fish, and nuts against age-related chronic respiratory disease. If confirmed in prospective cohorts, our results may guide nutritional counselling towards respiratory health promotion

Synthesis of (R)-mandelic acid and (R)-mandelic acid amide by recombinant E. coli strains expressing a (R)-specific oxynitrilase and an arylacetonitrilase

Chiral 2-hydroxycarboxylic acids and 2-hydroxycarboxamides are valuable synthons for the chemical industry. The biocatalytic syntheses of (R)-mandelic acid and (R)-mandelic acid amide by recombinant Escherichia coli clones were studied. Strains were constructed which simultaneously expressed a (R)-specific oxynitrilase (hydroxynitrile lyase) from the plant Arabidopsis thaliana together with the arylacetonitrilase from the bacterium Pseudomonas fluorescens EBC191. In addition, recombinant strains were constructed which expressed a previously described acid tolerant variant of the oxynitrilase and an amide forming variant of the nitrilase. The whole cell catalysts which simultaneously expressed the (R)-specific oxynitrilase and the wild-type nitrilase transformed in slightly acidic buffer systems benzaldehyde plus cyanide preferentially to (R)-mandelic acid with ee-values > 95%. The combination of the (R)-specific oxynitrilase with the amide forming nitrilase variant gave whole cell catalysts which converted at pH-values ≤ pH 5 benzaldehyde plus cyanide with a high degree of enantioselectivity (ee > 90%) to (R)-mandelic acid amide. The acid and the amide forming catalysts also converted chlorinated benzaldehydes with cyanide to chlorinated mandelic acid or chlorinated mandelic acid amides. Efficient systems for the biocatalytic production of (R)-2-hydroxycarboxylic acids and (R)-2-hydroxycarboxamides were generated.Projekt DEA