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Geometry and Electronic Structure of the P-Cluster in Nitrogenase Studied by Combined Quantum Mechanical and Molecular Mechanical Calculations and Quantum Refinement

We have studied the geometry and electronic structure of the P-cluster in nitrogenase in four oxidation states: PN, P1+, P2+, and P3+. We have employed combined quantum mechanical and molecular mechanical (QM/MM) calculations, using two different density-functional theory methods, TPSS and B3LYP. The calculations confirm that the side chain of Ser-188 is most likely deprotonated in the partly oxid

Reducing ambipolar off-state leakage currents in III-V vertical nanowire tunnel FETs using gate-drain underlap

Tunnel Field-Effect Transistors (TFETs) are an emerging alternative to CMOS for ultralow power and neuromorphic applications. The off current (Ioff) and, hence, the subthreshold swing (S) in these devices are limited by ambipolarity, which degrades its capabilities in complementary circuits. Here, we investigate experimentally vertical InAs/InGaAsSb/GaSb nanowire TFETs with gate-drain underlap as

You don't really want to be that mixed : Insiders' voices from a multicultural classroom

What can a music teacher do in a school where half of the students belong to minority cultures? In music education research there are many reports on the important role music has in preventing social exclusion. These reports refer to music’s power to serve both as aim and means to build efficient learning environments in multicultural schools (see for example Bamford, 2006; Bauer, 2005; Beck, 1993

A Review of SD-logic Resources in Information Systems

The evolution from a Goods-dominant logic (GD-logic) into a Service-dominant logic (SD-logic) is marked by fundamental changes in how we leverage resources for innovation. The current paper offers a review of SD-logic resources within the field of Information Systems (IS). It uses a scoping review method of papers from the senior scholars’ basket of journals and the two flagship IS conferences: EC

Refractive hard x-ray vortex phase plates

In this Letter, we report on the creation of hard x-ray beams carrying orbital angular momentum of topological charge −ℏ and −3ℏ at a photon energy of 8.2 keV via spiral phase plates made out of fused silica by ultrashort-pulsed laser ablation. The phase plates feature a smooth phase ramp with a 0.5 μm nominal step height and a surface roughness of 0.5 μm. The measured vortex beams show submicrome

A versatile nanoreactor for complementary in situ X-ray and electron microscopy studies in catalysis and materials science

Two in situ 'nanoreactors' for high-resolution imaging of catalysts have been designed and applied at the hard X-ray nanoprobe endstation at beamline P06 of the PETRA III synchrotron radiation source. The reactors house samples supported on commercial MEMS chips, and were applied for complementary hard X-ray ptychography (23 nm spatial resolution) and transmission electron microscopy, with additio

Ptychographic characterization of polymer compound refractive lenses manufactured by additive technology

The recent success in the development of high-precision printing techniques allows one to manufacture free-standing polymer structures of high quality. Two-photon polymerization lithography is a mask-less technique with down to 100 nm resolution that provides full geometric freedom. It has recently been applied to the nanofabrication of X-ray compound refractive lenses (CRLs). In this article we r

Nanofocusing with aberration-corrected rotationally parabolic refractive X-ray lenses

Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) have been recovered for various lens sets and X-ray beam configurations. Due to manufacturing via an embossing process, aberrations of individual lenses within the investigated ensemble are very similar. By deriving a mean single-lens deformation for the ensemble, aberrations of any arbitrary lens stack

PtyNAMi : Ptychographic nano-analytical microscope at PETRA III - Interferometrically tracking positions for 3D x-ray scanning microscopy using a ball-lens retroreflector

In recent years, ptychography has revolutionized x-ray microscopy in that it is able to overcome the diffraction limit of x-ray optics, pushing the spatial resolution limit down to a few nanometers. However, due to the weak interaction of x rays with matter, the detection of small features inside a sample requires a high coherent fluence on the sample, a high degree of mechanical stability, and a

Structure and Composition of Isolated Core-Shell (In,Ga) N/GaN Rods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In,Ga)N/GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we

Quantitative characterization of aberrations in x-ray optics

Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale, stringent requirements are put on X-ray optics manufacturing and metrology. As a result, these optics often suffer from aberrations. Until now, X-ray optics were mainly characterized by their focal spot size and efficiency. How- ever, both measures provide only insufficient information about optics qu

Hard x-ray nanoprobe of beamline P06 at PETRA III

The hard x-ray scanning microscope at beamline P06 of PETRA III at DESY in Hamburg serves a large user community, from physics, chemistry, and nanotechnology to the bio-medical, materials, environmental, and geosciences. It has been in user operation since 2012, and is mainly based on nanofocusing refractive x-ray lenses. Using refractive optics, nearly Gaussian-limited nanobeams in the range from

Direct membrane filtration of municipal wastewater in Norway

Real raw municipal wastewater is treated abiotic in combination of chemical and mechanical treatment with microfiltration as the final treatment step. This rather new treatment concept is described as direct membrane filtration and has been tested in a smaller scale in Sweden. The presented concept in this study is significantly larger (386 times) and is built in Norway to compare both studies per

HAMLET, a protein complex from human milk has bactericidal activity and enhances the activity of antibiotics against pathogenic Streptococci

HAMLET is a protein-lipid complex derived from human milk that was first described for its tumoricidal activity. Later studies showed that HAMLET also has direct bactericidal activity against select species of bacteria, with highest activity against Streptococcus pneumoniae Additionally, HAMLET in combination with various antimicrobial agents can make a broader range of antibiotic-resistant bacter