4,988 Works

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...

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...

Transferrin-Coated Nanodiamond–Drug Conjugates for Milliwatt Photothermal Applications

Sean Harvey, Marco Raabe, Anna Ermakova, Yingke Wu, Todd Zapata, Chaojian Chen, Hao Lu, Fedor Jelezko, David Y. W. Ng & Tanja Weil
Abstract Fluorescent nanodiamonds (fNDs) are unique carbon-based nanomaterials due to their outstanding optical and magnetic properties. However, realization of the full potential of fNDs is often limited by their processability because fNDs aggregate strongly in both organic and aqueous solutions. Therefore, robust and potentially universal coating strategies are urgently needed to address these limitations. Derived from mussel foot proteins, the polymerization of l-3,4-dihydroxyphenylalanine (l-DOPA) provides important surface functional groups including amines, carboxylic acid, alcohols, and...

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,...

Distinct Mechanisms Underlying Interannual to Decadal Variability of Observed Salinity and Nutrient Concentration in the Northern North Sea

Johannes Pätsch, Viktor Gouretski, Iris Hinrichs & Vimal Koul
The influence of large-scale oceanic circulation on salinity in the northern North Sea has lead to the hypothesis that nutrient concentrations in this region are also driven by remote oceanic anomalies. Here, using a newly established biogeochemical data set of the North Sea, we show that interannual to decadal variability in winter nutrient concentrations exhibits distinct phase deviations from salinity. The variability in salinity is explained by zonal shifts in the position of the subpolar...

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...

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...

Synthetic Photoelectrochemistry

Joshua P. Barham & Burkhard König
Abstract Photoredox catalysis (PRC) and synthetic organic electrochemistry (SOE) are often considered competing technologies in organic synthesis. Their fusion has been largely overlooked. We review state-of-the-art synthetic organic photoelectrochemistry, grouping examples into three categories: 1) electrochemically mediated photoredox catalysis (e-PRC), 2) decoupled photoelectrochemistry (dPEC), and 3) interfacial photoelectrochemistry (iPEC). Such synergies prove beneficial not only for synthetic “greenness” and chemical selectivity, but also in the accumulation of energy for accessing super-oxidizing or -reducing single electron...

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).

Lateglacial and Holocene environmental history of the central Kola region, northwestern Russia revealed by a sediment succession from Lake Imandra

Matthias Lenz, Larisa Savelieva, Larisa Frolova, Anna Cherezova, Matthias Moros, Marlene Baumer, Raphael Gromig, Natalia Kostromina, Niyaz Nigmatullin, Vasili Kolka, Benrd Wagner, Grigory Fedorov & Martin Melles
Bolshaya Imandra, the northern sub-basin of Lake Imandra, was investigated by a hydro-acoustic survey followed by sediment coring down to the acoustic basement. The sediment record was analysed by a combined physical, biogeochemical, sedimentological, granulometrical and micropalaeontological approach to reconstruct the regional climatic and environmental history. Chronological control was obtained by 14C dating, 137Cs, and Hg markers as well as pollen stratigraphy and revealed that the sediment succession offers the first continuous record spanning the...

Effects of Conventional Uric Acid–Lowering Therapy on Monosodium Urate Crystal Deposits

Hanna Ellmann, Sara Bayat, Elizabeth Araujo, Bernhard Manger, Arnd Kleyer, Alexander Cavallaro, Michael Lell, Hannah Schenker, David Simon, Koray Tascilar, Herbert S. B. Baraf, Georg Schett & Jürgen Rech
Objective Few studies have systematically and quantitatively addressed the impact of urate-lowering therapy on monosodium urate (MSU) deposits. This study was undertaken to analyze the effect of lifestyle measures and conventional urate-lowering therapy on MSU deposits in patients with gout. Methods In this prospective study, subjects with gout according to the American College of Rheumatology/European League Against Rheumatism classification criteria and presence of MSU deposits seen on dual-energy computed tomography (DECT) scans received either lifestyle...

The Slab Puzzle of the Alpine-Mediterranean Region: Insights From a New, High-Resolution, Shear Wave Velocity Model of the Upper Mantle

Amr El-Sharkawy, Thomas Meier, Sergei Lebedev, Jan H. Behrmann, Mona Hamada, Luigia Cristiano, Christian Weidle & Daniel Köhn
Mediterranean tectonics since the Lower Cretaceous has been characterized by a multiphase subduction and collision history with temporally and spatially variable, small-scale plate configurations. A new shear wave velocity model of the Mediterranean upper mantle (MeRE2020), constrained by a very large set of over 200,000 broadband (8–350 s), interstation, Rayleigh wave, phase velocity curves, illuminates the complex structure and fragmentation of the subducting slabs. Phase velocity maps computed using these measurements were inverted for depth-dependent,...

Sodium Sulfide Cathodes Superseding Hard Carbon Pre-sodiation for the Production and Operation of Sodium–Sulfur Batteries at Room Temperature

Luise Maria Bloi, Jonas Pampel, Susanne Dörfler, Holger Althues & Stefan Kaskel
Abstract This study demonstrates for the first time a room temperature sodium–sulfur (RT Na–S) full cell assembled based on a pristine hard carbon (HC) anode combined with a nanostructured Na2S/C cathode. The development of cells without the demanding, time-consuming and costly pre-sodiation of the HC anode is essential for the realization of practically relevant RT Na–S prototype batteries. New approaches for Na2S/C cathode fabrication employing carbothermal reduction of Na2SO4 at varying temperatures (660 to 1060...

Conversion of γ-Valerolactone to Ethyl Valerate over Metal Promoted Ni/ZSM-5 Catalysts: Influence of Ni0/Ni2+ Heterojunctions on Activity and Product Selectivity

Vijay Kumar Velisoju, Deshetti Jampaiah, Naresh Gutta, Ursula Bentrup, Angelika Brückner, Suresh K. Bhargava & Venugopal Akula
Abstract Promoter (Cr, Mo and W) modified Ni/ZSM-5 catalysts were explored in the vapor phase conversion of γ-valerolactone (GVL) to ethyl valerate (EV; gasoline blender) at atmospheric pressure. Among the three different promoters (Cr, Mo and W) tested the Mo-modified catalyst was found to be the best candidate. In addition, this catalyst was found to be stable up to 50 h reaction time with an insignificant decrease in activity. The good catalytic performance is related...

Linear Relationship Between Aftershock Productivity and Seismic Coupling in the Northern Chile Subduction Zone

S. Hainzl, C. Sippl & B. Schurr
The aftershock productivity is known to strongly vary for different mainshocks of the same magnitude, which cannot be simply explained by random fluctuations. In addition to variable source mechanisms, different rheological properties might be responsible for the observed variations. Here we show, for the subduction zone of northern Chile, that the aftershock productivity is linearly related to the degree of mechanical coupling along the subduction interface. Using the earthquake catalog of Sippl et al. (2018,...

Controlling Through-Space and Through-Bond Exchange Pathways in Bis-Cobaltocenes for Molecular Spintronics†

Sarah Puhl, Torben Steenbock, Carmen Herrmann & Jürgen Heck
Abstract Pinching molecules via chemical strain suggests intuitive consequences, such as compression at the pinched site and clothespin-like opening of other parts of the structure. If this opening affects two spin centers, it should result in reduced communication between them. We show that for naphthalene-bridged biscobaltocenes with competing through-space and through-bond pathways, the consequences of pinching are far less intuitive: despite the known dominance of through-space interactions, the bridge plays a much larger role for...

Tunable Thermoelastic Anisotropy in Hybrid Bragg Stacks with Extreme Polymer Confinement

Zuyuan Wang, Konrad Rolle, Theresa Schilling, Patrick Hummel, Alexandra Philipp, Bernd A. F. Kopera, Anna M. Lechner, Markus Retsch, Josef Breu & George Fytas
Abstract Controlling thermomechanical anisotropy is important for emerging heat management applications such as thermal interface and electronic packaging materials. Whereas many studies report on thermal transport in anisotropic nanocomposite materials, a fundamental understanding of the interplay between mechanical and thermal properties is missing, due to the lack of measurements of direction-dependent mechanical properties. In this work, exceptionally coherent and transparent hybrid Bragg stacks made of strictly alternating mica-type nanosheets (synthetic hectorite) and polymer layers (polyvinylpyrrolidone)...

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...

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...

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...

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