4,989 Works

Visualization of texture components using MTEX

Gennady Rafailov, El'ad N. Caspi, Ralf Hielscher, Eitan Tiferet, Roni Schneck & Sven C. Vogel
Knowledge of the appearance of texture components and fibres in pole figures, in inverse pole figures and in Euler space is fundamental for texture analysis. For cubic crystal systems, such as steels, an extensive literature exists and, for example, the book by Matthies, Vinel & Helming [Standard Distributions in Texture Analysis: Maps for the Case of Cubic Orthorhomic Symmetry, (1987), Akademie-Verlag Berlin] provides an atlas to identify texture components. For lower crystal symmetries, however, equivalent...

Coenzyme A-Conjugated Cinnamic Acids – Enzymatic Synthesis of a CoA-Ester Library and Application in Biocatalytic Cascades to Vanillin Derivatives

Martin Dippe, Anne-Katrin Bauer, Andrea Porzel, Evelyn Funke, Anna O. Müller, Jürgen Schmidt, Maria Beier & Ludger A. Wessjohann
Abstract We present a bioorthogonal method for the ligation of coenzyme A (CoA) with cinnamic acids. The reaction, which is the initial step in the biosynthesis of a multitude of bioactive secondary metabolites, is catalyzed by a promiscuous plant ligase and yields CoA conjugates with different functionalization in high purity and without formation of by-products. Its applicability in biosynthetic cascades is shown for the direct transformation of cinnamic acids into natural benzaldehydes (like vanillin) or...

Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin

D. Guinoiseau, S. J. G. Galer, W. Abouchami, M. Frank, E. P. Achterberg & G. H. Haug
Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient-like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient-like consumption-regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been...

Middle to Late Pleistocene Architecture and Stratigraphy of the Lower Bengal Fan—Integrating Multichannel Seismic Data and IODP Expedition 354 Results

Fenna Bergmann, Tilmann Schwenk, Volkhard Spiess & Christian France-Lanord
Utilizing a novel data set of integrated high-resolution multichannel seismic data with IODP Expedition 354 drilling results, a Middle to Late Pleistocene stratigraphy for the lower Bengal Fan is developed. The study reveals a high lateral and temporal variability of deposition expressed by lateral shifts (often exceeding 100 km) between successive channel-levee systems (CLSs), which occurred on average every ~15 kyr independent from sea-level changes. The CLSs are embedded in sheeted sediments deposited out of...

The Fingerprints of Flexure in Slab Seismicity

D. Sandiford, L. M. Moresi, M. Sandiford, R. Farrington & T. Yang
Earthquake moment tensors in eastern Pacific (ePac) slabs typically show downdip tensional (DT) axes, whereas in the western Pacific (wPac), they typically show downdip compressional (DC) axes or have mixed orientations indicative of unbending. Prevailing conceptual models emphasize uniform stress/deformation modes, that is, bulk slab stretching or shortening, as the dominant control on intermediate depth seismic expression. In contrast, we propose that a diversity of seismic expression, including DT- and DC-dominated regions, is consistent with...

The Secretome of Hypoxia Conditioned hMSC Loaded in a Central Depot Induces Chemotaxis and Angiogenesis in a Biomimetic Mineralized Collagen Bone Replacement Material

Mandy Quade, Pina Münch, Anja Lode, Sarah Duin, Corina Vater, Anastasia Gabrielyan, Angela Rösen-Wolff & Michael Gelinsky
Abstract The development of biomaterials with intrinsic potential to stimulate endogenous tissue regeneration at the site of injury is a main demand on future implants in regenerative medicine. For critical-sized bone defects, an in situ tissue engineering concept is devised based on biomimetic mineralized collagen scaffolds. These scaffolds are functionalized with a central depot loaded with a signaling factor cocktail, obtained from secretome of hypoxia-conditioned human mesenchymal stem cells (MSC). Therefore, hypoxia-conditioned medium (HCM)-production is...

On the exploration of a marine aquifer offshore Israel by long-offset transient electromagnetics

Klaus Lippert & Bülent Tezkan
The existence of aquifers extending from land beneath the sea floor up to a distance of several kilometres has been observed and examined all over the world. The coastal aquifer of Israel is a heavily used groundwater reservoir which has to be constantly monitored to ensure the drinking water supply. Former land-based electromagnetic measurements show that it is, in several places, blocked to seawater intrusion and is consequently a candidate for submarine extension. Multicomponent long-offset...

Comparing ground-based observations and a large-eddy simulation of shallow cumuli by isolating the main controlling factors of the mass flux distribution

Mirjana Sakradzija & Marcus Klingebiel
The distribution of mass flux at the cloud base has long been thought to be independent of large-scale forcing. However, recent idealized modelling studies have revealed its dependence on some large-scale conditions. Such dependence makes it possible to isolate the observed large-scale conditions, which are similar to those in large-eddy simulations (LES), in order to compare the observed and modelled mass flux distributions. In this study, we derive for the first time the distribution of...

Regioselective Functionalization of [2.2]Paracyclophanes: Recent Synthetic Progress and Perspectives

Zahid Hassan, Eduard Spuling, Daniel M. Knoll & Stefan Bräse
Abstract [2.2]Paracyclophane (PCP) is a prevalent scaffold that is widely utilized in asymmetric synthesis, π-stacked polymers, energy materials, and functional parylene coatings that finds broad applications in bio- and materials science. In the last few years, [2.2]paracyclophane chemistry has progressed tremendously, enabling the fine-tuning of its structural and functional properties. This Minireview highlights the most important recent synthetic developments in the selective functionalization of PCP that govern distinct features of planar chirality as well as...

A novel experimental approach for nanostructure analysis: simultaneous small-angle X-ray and neutron scattering

Ezzeldin Metwalli, Klaus Götz, Sebastian Lages, Christian Bär, Tobias Zech, Dennis M. Noll, Isabel Schuldes, Torben Schindler, Annemarie Prihoda, Herbert Lang, Jürgen Grasser, Mark Jacques, Luc Didier, Amrouni Cyril, Anne Martel, Lionel Porcar & Tobias Unruh
Exploiting small-angle X-ray and neutron scattering (SAXS/SANS) on the same sample volume at the same time provides complementary nanoscale structural information in two different contrast situations. Unlike an independent experimental approach, the truly combined SAXS/SANS experimental approach ensures the exactness of the probed samples, particularly for in situ studies. Here, an advanced portable SAXS system that is dimensionally suitable for installation in the D22 zone of ILL is introduced. The SAXS apparatus is based on...

Impact Experiment on Gneiss: The Effects of Foliation on Cratering Process

Amar Agarwal, Michael H. Poelchau, Thomas Kenkmann, Auriol Rae & Matthias Ebert
Two impact experiments were carried out on blocks of Maggia gneiss to assess the influence of mechanical target anisotropies on the cratering process. The experiments were done within the framework of Multidisciplinary Experimental and Modeling Impact Research Network. In one experiment the metamorphic foliation was vertical, that is, oriented perpendicular to the target surface, and in the other horizontal, that is, parallel to the target surface. This study reveals that due to preferred spallation along...

Lateral terrestrial water flow contribution to summer precipitation at continental scale – A comparison between Europe and West Africa with WRF‐Hydro‐tag ensembles

Joël Arnault, Benjamin Fersch, Thomas Rummler, Zhenyu Zhang, Gandome Mayeul Quenum, Jianhui Wei, Maximilian Graf, Patrick Laux & Harald Kunstmann
It is well accepted that summer precipitation can be altered by soil moisture condition. Coupled land surface – atmospheric models have been routinely used to quantify soil moisture – precipitation feedback processes. However, most of the land surface models (LSMs) assume a vertical soil water transport and neglect lateral terrestrial water flow at the surface and in the subsurface, which potentially reduces the realism of the simulated soil moisture – precipitation feedback. In this study,...

An endless summer: 2018 heat episodes in Europe in the context of secular temperature variability and change

Andreas Hoy, Stephanie Hänsel & Maurizio Maugeri
The year 2018 was affected by very long-lasting, stable summer conditions in vast parts of Europe, in many regions already starting in April and lasting until October. We investigate the thermal characteristics of this year in a secular time perspective, using a spatially well-distributed dataset of 67 European stations (west of ~30°E) with daily long-term air temperature observations. Our dataset comprises many of the longest and most reliable (homogenous) temperature measurements available in Europe, mainly...

Cellulose hydrogels physically crosslinked by glycine: Synthesis, characterization, thermal and mechanical properties

S. Palantöken, K. Bethke, V. Zivanovic, G. Kalinka, Janina Kneipp & Klaus Rademann
ABSTRACT Biopolymers are very efficient for significant applications ranging from tissue engineering, biological devices to water purification. There is a tremendous potential value of cellulose because of its being the most abundant biopolymer on earth, swellability, and functional groups to be modified. A novel, highly efficient route for the fabrication of mechanically stable and natural hydrogels is described in which cellulose and glycine are dissolved in an alkaline solution of NaOH and neutralized in an...

Homogeneous Catalyst Recycling and Separation of a Multicomponent Mixture Using Organic Solvent Nanofiltration

Johann-Kilian Schnoor, Martin Fuchs, Axel Böcking, Matthias Wessling & Marcel A. Liauw
Abstract In homogeneous catalysis, the application of organic solvent nanofiltration (OSN) has become a well-known alternative to common recycling methods. Even though some OSN membranes are commercially available, their classification and the scope of application have to be determined for the specific solvent mixture. The commercial membrane Evoniks DuraMem® 300 was tested in a mixture of ethanol, ethyl acetate, and cyclohexane with magnesium triflate as possible catalyst. The cross permeate fluxes were measured for two...

Photo-induced and Rapid Labeling of Tetrazine-Bearing Proteins via Cyclopropenone-Caged Bicyclononynes

Susanne V. Mayer, Anton Murnauer, Marie-Kristin Von Wrisberg, Marie-Lena Jokisch & Kathrin Lang
Abstract Inverse electron-demand Diels–Alder cycloadditions (iEDDAC) between tetrazines and strained alkenes/alkynes have emerged as essential tools for studying and manipulating biomolecules. A light-triggered version of iEDDAC (photo-iEDDAC) is presented that confers spatio-temporal control to bioorthogonal labeling in vitro and in cellulo. A cyclopropenone-caged dibenzoannulated bicyclo[6.1.0]nonyne probe (photo-DMBO) was designed that is unreactive towards tetrazines before light-activation, but engages in iEDDAC after irradiation at 365 nm. Aminoacyl tRNA synthetase/tRNA pairs were discovered for efficient site-specific incorporation...

Open-Cell Aluminum Foams by the Sponge Replication Technique: A Starting Powder Particle Study

Alina Sutygina, Ulf Betke & Michael Scheffler
Open-cell aluminum foams are manufactured by a sponge replication technique, and the effect of aluminum particles with different shapes and particle sizes on foam properties is studied. It is found that aluminum powder with spheroidal particles leads to aluminum foams with a lower strut porosity, a lower amount of alumina, and a higher compressive strength compared with foams manufactured from flaky, irregularly shaped aluminum powder. This effect is explained with the lower surface area of...

Catalytically Active Peptide–Gold Nanoparticle Conjugates: Prospecting for Artificial Enzymes

Dorian J. Mikolajczak, Allison A. Berger & Beate Koksch
Abstract The self-assembly of peptides onto the surface of gold nanoparticles has emerged as a promising strategy towards the creation of artificial enzymes. The resulting high local peptide density surrounding the nanoparticle leads to cooperative and synergistic effects, which result in rate accelerations and distinct catalytic properties compared to the unconjugated peptide. This Minireview summarizes contributions to and progress made in the field of catalytically active peptide–gold nanoparticle conjugates. The origin of distinct properties, as...

Monitoring of Cell Layer Integrity with a Current-Driven Organic Electrochemical Transistor

Leona V. Lingstedt, Matteo Ghittorelli, Maximilian Brückner, Jonas Reinholz, N. Irina Cr?Ciun, Fabrizio Torricelli, Volker Mailänder, Paschalis Gkoupidenis & Paul W. M. Blom
Abstract The integrity of CaCo-2 cell barriers is investigated by organic electrochemical transistors (OECTs) in a current-driven configuration. Ion transport through cellular barriers via the paracellular pathway is modulated by tight junctions between adjacent cells. Rupturing its integrity by H2O2 is monitored by the change of the output voltage in the transfer characteristics. It is demonstrated that by operating the OECT in a current-driven configuration, the sensitive and temporal resolution for monitoring the cell barrier...

Strategies for Analyzing Noncommon-Atom Heterovalent Interfaces: The Case of CdTe-on-InSb

Esperanza Luna, Achim Trampert, Jing Lu, Toshihiro Aoki, Yong-Hang Zhang, Martha R. McCartney & David J. Smith
Abstract Semiconductor heterostructures are intrinsic to a wide range of modern-day electronic devices, such as computers, light-emitting devices, and photodetectors. Knowledge of chemical interfacial profiles in these structures is critical to the task of optimizing the device performance. This work presents an analysis of the composition profile and strain across the noncommon-atom heterovalent CdTe/InSb interface, carried out using a combination of electron microscopy imaging techniques. Because of the close atomic numbers of the constituent elements,...

π-Conjugation Enables Ultra-High Rate Capabilities and Cycling Stabilities in Phenothiazine Copolymers as Cathode-Active Battery Materials

Pascal Acker, Luisa Rzesny, Cleber F. N. Marchiori, C. Moyses Araujo & Birgit Esser
Abstract In recent years, organic battery cathode materials have emerged as an attractive alternative to metal oxide–based cathodes. Organic redox polymers that can be reversibly oxidized are particularly promising. A drawback, however, often is their limited cycling stability and rate performance in a high voltage range of more than 3.4 V versus Li/Li+. Herein, a conjugated copolymer design with phenothiazine as a redox-active group and a bithiophene co-monomer is presented, enabling ultra-high rate capability and...

Monitoring freshwater–saltwater interfaces with SAMOS – installation effects on data and inversion

Mathias Ronczka, Thomas Günther, Michael Grinat & Helga Wiederhold
A major problem for the freshwater supply of coastal regions is the intrusion of saltwater into aquifers. Due to extensive extraction of freshwater to suffice increasing drinking water demands and/or in periods of reduced groundwater recharge, the equilibrium state may be disturbed. The result is an upconing or movement of the fresh–saline groundwater interface, which reduces the local drinking water resources at coastal regions or islands. The saltwater monitoring system (SAMOS) is a vertical electrode...

Magnetotelluric Apparent Resistivity Tensors for Improved Interpretations and 3-D Inversions

P. Hering, C. Brown & A. Junge
The complex magnetotelluric (MT) apparent resistivity tensor can be decomposed into two real tensors, the apparent resistivity and the resistivity phase tensors, which represent relationships between the observed electric field at a point on the Earth's surface and an associated apparent current density. We explain the differences between these tensors and conventional estimates of apparent resistivity and phase for simple resistivity environments and demonstrate, using canonical models in 1-D and 2-D environments, that both tensors...

A Bias-Free, Stand-Alone, and Scalable Photovoltaic–Electrochemical Device for Solar Hydrogen Production

Minoh Lee, Bugra Turan, Jan-Philipp Becker, Katharina Welter, Benjamin Klingebiel, Elmar Neumann, Yoo Jung Sohn, Tsvetelina Merdzhanova, Thomas Kirchartz, Friedhelm Finger, Uwe Rau & Stefan Haas
Abstract Although photovoltaic–electrochemical (PV–EC) water splitting is likely to be an important and powerful tool to provide environmentally friendly hydrogen, most developments in this field have been conducted on a laboratory scale so far. In order for the technology to make a sizeable impact on the energy transition, scaled up devices must be developed. Here a scalable (64 cm2 aperture area) artificial PV–EC device composed of triple-junction thin-film silicon solar cells in conjunction with an...

Nickela-electrocatalyzed C−H Alkoxylation with Secondary Alcohols: Oxidation-Induced Reductive Elimination at Nickel(III)

Shou-Kun Zhang, Julia Struwe, Lianrui Hu & Lutz Ackermann
Abstract Nickela-electrooxidative C−H alkoxylations with challenging secondary alcohols were accomplished in a fully dehydrogenative fashion, thereby avoiding stoichiometric chemical oxidants, with H2 as the only stoichiometric byproduct. The nickela-electrocatalyzed oxygenation proved viable with various (hetero)arenes, including naturally occurring secondary alcohols, without racemization. Detailed mechanistic investigation, including DFT calculations and cyclovoltammetric studies of a well-defined C−H activated nickel(III) intermediate, suggest an oxidation-induced reductive elimination at nickel(III).

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