An Eyring-Kramers law for the stochastic Allen-Cahn equation in dimension two

We study spectral Galerkin approximations of an Allen--Cahn equation over the two-dimensional torus perturbed by weak space-time white noise of strength $\sqrt{\varepsilon}$. We introduce a Wick renormalisation of the equation in order to have a system that is well-defined as the regularisation is removed. We show sharp upper and lower bounds on the transition times from a neighbourhood of the stable configuration $-1$ to the stable configuration $1$ in the asymptotic regime $\varepsilon \to 0$. These estimates are uniform in the discretisation parameter $N$, suggesting an Eyring-Kramers formula for the limiting renormalised stochastic PDE. The effect of the "infinite renormalisation" is to modify the prefactor and to replace the ratio of determinants in the finite-dimensional Eyring-Kramers law by a renormalised Carleman-Fredholm determinant.Comment: 28 pages, 1 Figure. Revised version with expanded discussio

Determinants of Public Sector Innovation: The Example of Capacity Development in Public Procurement

The Triple-Helix-Model stresses the idea that a successful national system of innovation ought to incorporate the complexity of three social subsystems: private sector economy, governmental system and science. Following the insight that the state and its agencies are important players in any system of innovation, we take a closer look at the innovative action in the public sphere. Therefore, we propose an analytical tool that allows a more detailed explanation of relevant determinants of innovative behaviour: (1) property rights, (2) capabilities, and (3) motivation. In order to show the relevance of these determinants, we tested the plausibility of our theoretical tool against the topic of public procurement of innovation. Five hypotheses were derived and then tested empirically by using a data set about German public procurement practice. Our linear regression model provides evidence for the hypotheses that framework conditions, special training, and motivation of procurement staff play a central role in demand-driven innovation of the public sector

Energy-filtered transmission electron microscopy of biological samples on highly transparent carbon nanomembranes

Ultrathin carbon nanomembranes (CNM) comprising crosslinked biphenyl precursors have been tested as support films for energy-filtered transmission electron microscopy (EFTEM) of biological specimens. Due to their high transparency CNM are ideal substrates for electron energy loss spectroscopy (EELS) and electron spectroscopic imaging (ESI) of stained and unstained biological samples. Virtually background-free elemental maps of tobacco mosaic virus (TMV) and ferritin have been obtained from samples supported by ~ 1 nm thin CNM. Furthermore, we have tested conductive carbon nanomembranes (cCNM) comprising nanocrystalline graphene, obtained by thermal treatment of CNM, as supports for cryoEM of ice-embedded biological samples. We imaged ice-embedded TMV on cCNM and compared the results with images of ice-embedded TMV on conventional carbon film (CC), thus analyzing the gain in contrast for TMV on cCNM in a quantitative manner. In addition we have developed a method for the preparation of vitrified specimens, suspended over the holes of a conventional holey carbon film, while backed by ultrathin cCNM

Präparation und Charakterisierung von Graphen basierend auf selbst-organisierten Monolagen

Weber N-E. Präparation und Charakterisierung von Graphen basierend auf selbst-organisierten Monolagen. Bielefeld: Universitätsbibliothek; 2014

Metal free graphene synthesis on insulating or semiconducting substrates

The present invention relates to a process for preparing graphene by chemical vapour deposition (CVD), wherein an insulating or semiconducting inorganic substrate is provided in a chemical vapour deposition (CVD) reactor and subjected to a thermal pre-treatment in a hydrogen-containing atmosphere,and graphene is deposited on the inorganic substrate by bringing a gaseous oxidant and a carbon-containing precursor into contact with the inorganic substrate

A Comprehensive Study of Module Layouts for Silicon Solar Cells Under Partial Shading

Integrated applications for solar energy production becomes increasingly important. The electrification of car bodies and building facades are only two prominent examples. In such applications shading becomes a challenging problem, since the classic serial interconnection of solar cells in terms of power output is highly vulnerable to partial shading. In this article, we investigate the three most common module layouts in the market (conventional, butterfly, and shingle string) and add a fourth layout (shingle matrix) to be introduced to the market in the future. We discuss an approach to cluster shadings occurring in urban surroundings into basic shapes like “rectangular” and “random”. Choosing a Monte Carlo technique in combination with latin hypercube sampling (LHS), we consider more than 3000 scenarios in total. For the evaluation of the scenarios, we conduct circuit simulations using LTspice. Furthermore, we define a normalization base, which considers only partial shading as a quantitative baseline for comparison. Our results show, that already for 200–400 scenarios the obtained output values stabilize. Among the investigated module layouts, the shingle matrix interconnection achieves the highest score, followed by a shingle string, half-cell butterfly and the conventional full-cell layout

Single-walled carbon nanotubes and nanocrystalline graphene reduce beam-induced movements in high-resolution electron cryo-microscopy of ice-embedded biological samples

For single particle electron cryo-microscopy (cryoEM), contrast loss due to beam-induced charging and specimen movement is a serious problem, as the thin films of vitreous ice spanning the holes of a holey carbon film are particularly susceptible to beam-induced movement. We demonstrate that the problem is at least partially solved by carbon nanotechnology. Doping ice-embedded samples with single-walled carbon nanotubes (SWNT) in aqueous suspension or adding nanocrystalline graphene supports, obtained by thermal conversion of cross-linked self-assembled biphenyl precursors, significantly reduces contrast loss in high-resolution cryoEM due to the excellent electrical and mechanical properties of SWNTs and graphene

A density-functional theory approach to the existence and stability of molybdenum and tungsten sesquioxide polymorphs

The sesquioxides of molybdenum and tungsten have been reported as thin films or on surfaces as early as 1971, but the preparation of bulk materials and their crystal structures are still unknown up to the present day. We present a systematic ab initio approach to their possible syntheses and crystal structures applying complementary methods and basis-set types. For both compounds, the corundum structure is the most stable and does not display any imaginary frequencies. Calculations targeted at a high-pressure synthesis starting from the stable oxides and metals predict a reaction pressure of 15 GPa for Mo2O3 and over 60 GPa for W2O3

Conditional human VEGF‐mediated vascularization in chicken embryos using a novel temperature‐inducible gene regulation (TIGR) system

Advanced heterologous transcription control systems for adjusting desired transgene expression are essential for gene function assignments, drug discovery, manufacturing of difficult to produce protein pharmaceuticals and precise dosing of gene‐based therapeutic interventions. Conversion of the Streptomyces albus heat shock response regulator (RheA) into an artificial eukaryotic transcription factor resulted in a vertebrate thermosensor (CTA; cold‐inducible transactivator), which is able to adjust transcription initiation from chimeric target promoters (PCTA) in a low‐temperature‐ inducible manner. Evaluation of the temperature‐dependent CTA-PCTA interaction using a tailored ELISA‐like cell‐free assay correlated increased affinity of CTA for PCTA with temperature downshift. The temperature‐inducible gene regulation (TIGR) system enabled tight repression in the chicken bursal B‐cell line DT40 at 41°C as well as precise titration of model product proteins up to maximum expression at or below 37°C. Implantation of microencapsulated DT40 cells engineered for TIGR‐controlled expression of the human vascular endothelial growth factor A (hVEGF121) provided low‐temperature‐induced VEGF‐mediated vascularization in chicken embryo