Intrinsic Surface Dipoles Control the Energy Levels of Conjugated Polymers

Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3‐hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of π‐conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first‐principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the π‐electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design.     

Die Virtuelle Poststelle des Bundes

Zusammenfassung  Die Virtuelle Poststelle (VPS) des Bundes wurde jetzt nach Common Criteria evaluiert und zertifiziert. Dieses nach Signaturgesetz best?tigte E-Government-Kommunikations-Gateway erm?glicht rechtsverbindliche elektronische Signaturen. Die Autoren stellen die VPS vor und erl?utern das durchgeführte Evaluierungsverfahren. Dr. S?nke Maseberg Berater für Datenschutz und Datensicherheit, Common-Criteria-Evaluator datenschutz nord GmbH Dipl. Inf. Matthias Intemann Produktmanagement, Projektleitung Evaluierung Dipl. Inf. Ingo Schumann Produktmanagement, Projektleitung Evaluierung     

Manufacture and application of ultra-small micro end mills

The use of micro parts and micro structured elements has constantly grown over the past decade. Milling with micro end-mills belongs to the manufacturing technologies which offer a high potential for competitive micro machining. However, the design criteria for the micro end-mills and their manufacture pose many challenges. In this paper, first the design and manufacture of single-edge micro end-mills with diameters between 10 and 50 μm and a variable helix angle is described. Second, the use of these end-mills in titanium and polymethyl methacrylate (PMMA) is described to demonstrate their potential.     

Sicherheitsmechanismen für kontaktlose Chips im deutschen elektronischen Personalausweis

Zusammenfassung  Dieser Artikel gibt einen überblick über die Ziele und die Funktion der Sicherheitsmechanismen, wie sie voraussichtlich im deutschen elektronischen Personalausweis zur Anwendung kommen. Dr. Jens Bender Referent im Bundesamt für Sicherheit in der Informationstechnik (BSI) Dr. Dennis Kügler Referent im Bundesamt für Sicherheit in der Informationstechnik (BSI) Dr. Marian Margraf Referent im Bundesministerium des Innern (BMI) Dr. Ingo Naumann Referent im Bundesamt für Sicherheit in der Informationstechnik (BSI), derzeit nationaler Experte bei der European Network and Information Security Agency (ENISA)     

Configurable Resistive Response in BaTiO3 Ferroelectric Memristors via Electron Beam Radiation

Ferroelectric oxide memristors are currently in the highlights of a thriving area of research aiming at the development of nonvolatile, adaptive memories for applications in neuromorphic computing. However, to date a precise control of synapse-like functionalities by adjusting the interplay between ferroelectric polarization and resistive switching processes is still an ongoing challenge. Here, it is shown that by means of controlled electron beam radiation, a prototypical ferroelectric film of BaTiO₃ can be turned into a memristor with multiple configurable resistance states. Ex situ and in situ analyses of current/voltage characteristics upon electron beam exposure confirm the quasi-continuous variation of BaTiO₃ resistance up to two orders of magnitude under the typical experimental conditions employed in electron beam patterning and characterization techniques. These results demonstrate an unprecedented effective route to locally and scalably engineering multilevel ferroelectric memristors via application of moderate electron beam radiation.     

Direct Evidence for Membrane Transport of Host-Plant-Derived Pyrrolizidine Alkaloid N-Oxides in Two Leaf Beetle Genera

The chrysomelid leaf beetles Longitarsus jacobaeae, Oreina cacaliae, and O. speciosissima sequester pyrrolizidine alkaloids from their asteracean host plants and store them as nontoxic N-oxides. Previous analyses showed that Longitarsus is able to N-oxidize protoxic tertiary PAs, but did not resolve in which form N-oxides are taken up. For Oreina, beetles seem able to directly transmit the polar PA N-oxides from the gut into the hemolymph and prevent any reduction of them in the gut yielding protoxic free bases. Here, we confirm the predicted direct uptake of PAs as N-oxides by Oreina, and elucidate the situation for Longitarsus by applying double-labeled [14C]senecionine [18O]N-oxide as tracer. The beetles were fed with the tracer and subsequently senecionine N-oxide was recovered from the defensive secretions (Oreina) and beetle extracts (Longitarsus), purified by HPLC, and submitted to ESI-MS, GC-MS, and analysis of the specific radioactivity. The 18O-label is retained without any loss in the labeled senecionine N-oxide recovered from the two Oreina species. Analysis of the Longitarsus experiment was complicated by a contamination of the HPLC-purified senecionine N-oxide with a second compound, identified as a dihydrosenecionine N-oxide by high-resolution CID analysis. The dihydrosenecionine N-oxide, probably the 15,20-dihydro derivative, constitutes a major idiosyncratic senecionine metabolite present in the beetle. The recovered senecionine N-oxide retained 74% 18O-label. The remaining 25% is mostly due to loss of 18O by reduction and subsequent re-N-oxidation. The experiments confirm for both beetle genera a direct uptake of the polar nontoxic PA N-oxides, which requires specific membrane carriers. Accumulation of detrimental free base PA is prevented by glucosylation (Oreina) or N-oxidation (Longitarsus).     

The myosin coiled-coil is a truly elastic protein structure

Coiled-coils occur in a variety of proteins involved in mechanical and structural tasks in the cell. Their mechanical properties are important in various contexts ranging from hair elasticity to synaptic fusion. Beyond their importance in biology, coiled-coils have also attracted interest as programmable protein sequences for the design of novel hydrogels and materials. We have studied the elastic properties of the myosin coiled-coil at the single molecule level. The coiled-coil undergoes a massive structural transition at forces between 20 and 25 pN where the coil extends to about 2.5 times its original length. Unlike all other proteins investigated mechanically so far, this transition is reversible on a timescale of less than a second, making the coiled-coil a truly elastic protein.     

Multidimensional Integrated Chalcogenides Nanoarchitecture Achieves Highly Stable and Ultrafast Potassium‐Ion Storage

Potassium‐ion batteries (KIBs) have come into the spotlight in large‐scale energy storage systems because of cost‐effective and abundant potassium resources. However, the poor rate performance and problematic cycle life of existing electrode materials are the main bottlenecks to future potential applications. Here, the first example of preparing 3D hierarchical nanoboxes multidimensionally assembled from interlayer‐expanded nano‐2D MoS₂@dot‐like Co₉S₈ embedded into a nitrogen and sulfur codoped porous carbon matrix (Co₉S₈/NSC@MoS₂@NSC) for greatly boosting the electrochemical properties of KIBs in terms of reversible capacity, rate capability, and cycling lifespan, is reported. Benefiting from the synergistic effects, Co₉S₈/NSC@MoS₂@NSC manifest a very high reversible capacity of 403 mAh g^?1 at 100 mA g^?1 after 100 cycles, an unprecedented rate capability of 141 mAh g^?1 at 3000 mA g^?1 over 800 cycles, and a negligible capacity decay of 0.02% cycle^?1, boosting promising applications in high‐performance KIBs. Density functional theory calculations demonstrate that Co₉S₈/NSC@MoS₂@NSC nanoboxes have large adsorption energy and low diffusion barriers during K‐ion storage reactions, implying fast K‐ion diffusion capability. This work may enlighten the design and construction of advanced electrode materials combined with strong chemical bonding and integrated functional advantages for future large‐scale stationary energy storage.     

Coherent multiresolution isosurface ray tracing

We implement and evaluate a fast ray tracing method for rendering large structured volumes. Input data is losslessly compressed into an octree, enabling residency in CPU main memory. We cast packets of coherent rays through a min/max acceleration structure within the octree, employing a slice-based technique to amortize the higher cost of compressed data access. By employing a multiresolution level of detail (LOD) scheme in conjunction with packets, coherent ray tracing can efficiently render inherently incoherent scenes of complex data. We achieve higher performance with lesser footprint than previous isosurface ray tracers, and deliver large frame buffers, smooth gradient normals and shadows at relatively lesser cost. In this context, we weigh the strengths of coherent ray tracing against those of the conventional single-ray approach, and present a system that visualizes large volumes at full data resolution on commodity computers.