Surface micromachined membranes for tunnel transducers

We have developed low-temperature surface micromachining procedures for the fabrication of suspended SiO2/Si3N4 membranes. This fabrication method was integrated with electron beam lithography, anisotropic ion etching, and electroplating to construct electrostatically deflectable tunnel transducers. We show the structures and some preliminary measurements on the performance of these monolithic devices

Hybrid superprism with low insertion losses and suppressed cross-talk

We demonstrate with the two-dimensional finite-difference time-domain method that an adiabatic transition in a superprism with an interface along the [1 [overline 2]] direction enhances the transmission through the superprism to more than 90% (–0.5 dB) over the wavelength range 1.47–1.68 µm, including the telecommunication C and L bands. We also show that diffraction governed by a quasinegative index of refraction inside the superprism can be used to obtain nearly transform-limited beam widths at the output of the superprism. The reduction of the beam width at the output suppresses cross-talk and greatly enhances the achievable frequency resolution of the superprism

Discovering and quantifying nontrivial fixed points in multi-field models

We use the functional renormalization group and the $\epsilon$-expansion concertedly to explore multicritical universality classes for coupled $\bigoplus_i O(N_i)$ vector-field models in three Euclidean dimensions. Exploiting the complementary strengths of these two methods we show how to make progress in theories with large numbers of interactions, and a large number of possible symmetry-breaking patterns. For the three- and four-field models we find a new fixed point that arises from the mutual interaction between different field sectors, and we establish the absence of infrared-stable fixed point solutions for the regime of small $N_i$. Moreover, we explore these systems as toy models for theories that are both asymptotically safe and infrared complete. In particular, we show that these models exhibit complete renormalization group trajectories that begin and end at nontrivial fixed points.Comment: 10 pages, 6 figures; minor changes, as published in EPJ

Nonlinear Calculation Methods for Polymeric Materials in Structural Glass Construction - an Overview

Since time began there has been a strong fascination in foreseeing the behavior of buildings and constructions.  Now In order to predict this behavior, we use experimental, and increasingly more time- and cost-effective, computational simulations. Finite Element Analysis (FEA) is a method that has become increasingly prevalent and has become firmly established in aviation and vehicle construction for decades. In recent years, there has been a marked growth in the use of numerical simulations for the verification of adhesive bonds, particularly in façade development where polymeric materials such as sealants or thermoplastic spacers are becoming increasingly important. This is partly driven by their expansion stress behavior, which differs greatly from the classic linear behavior of established materials such as aluminum, steel or glass. The present work uses non-linear material laws for FEA and exhibits the behavior of the sealant joint in various load scenarios on several projects. The presented case studies show that the developed calculation methods can be used to describe polymeric materials very precisely and thus simulate a wide variety of load scenarios on glued components in time and money saving manner

Dimensioning of Elastic Adhesive Joints with Complex Geometries? – A Systematic Approach beyond ETAG 002

The current European standard for dimensioning silicone adhesive joints in structural glazing applications is defined in the ETAG 002. Although there are several decades of field experience with this standard it still has some major limitations and mainly uses an empirical concept based on an average force by area tension engineering approach. In addition there are a number of other restrictions for example the limitation of specific substrates and rectangular shaped joints with defined aspect ratios as well as the exclusion of joints with non-coplanar surfaces. The presented investigations are based on a combined numerical and experimental concept and demonstrate that appropriately designed elastic adhesive joints with complex geometries excluded by common standards can be evaluated and validated in a systematic and reliable way. The experimental test may easily be combined with well-established and proven aging test schemes, for which long-term reliable field experience is available. In addition any desired safety factor can be added

Can't read my broker face?—Tracing a motif and metaphor of expert knowledge through audiovisual images of the financial crisis

Based on the question of the representability of economy and economics in audiovisual media, developments on the financial markets have often been discussed as a depiction problem. The abstractness and complexity of economic interrelations seem to defy classical modes of storytelling and dramatization. Nevertheless, public opinion about economic changes and dependencies crucially relies on audiovisual media. But how can the public communicate in images, sounds, and words about forces that are out of sight and out of reach, and can supposedly only be adequately grasped by experts? In a case study on audiovisual images of the global financial crisis (2007–), this paper tracks and analyzes a recurring motif: the staging of expert knowledge as close-ups of expressive faces vis-à-vis computer screens in television news, documentaries, as well as feature films. It draws on the use of digital tools for corpus exploration (reverse image search) and the visualization of video annotations. By relating and comparing different staging strategies by which these “broker faces” become embodiments of turbulent market dynamics, the paper proposes to not regard them as repeated instantiations of the same metaphor, but as a developing web of cinematic metaphors. Different perspectives (news of market developments or historical accounts of crisis developments) and affective stances toward the global financial crisis are expressed in these variations of the face-screen constellation. The paper thus presents a selection of different appearances of “broker faces” as a medium for an audiovisual discourse of the global financial crisis. A concluding analysis of a scene from Margin Call focuses on its specific intertwining of expert and screen as an ambivalent movement figuration of staging insight. Between the feeling of discovery (of a potential future threat) and the sense of being haunted (by a menacing force), the film stages the emergence of a “broker face” in an atmospheric tension between suspense and melancholy. We argue that the film thereby reframes the motif and poses questions of agency, temporality, and expert knowledge

Interplay of the Chiral and Large N_c Limits in pi N Scattering

Light-quark hadronic physics admits two useful systematic expansions, the chiral and 1/N_c expansions. Their respective limits do not commute, making such cases where both expansions may be considered to be especially interesting. We first study pi N scattering lengths, showing that (as expected for such soft-pion quantities) the chiral expansion converges more rapidly than the 1/N_c expansion, although the latter nevertheless continues to hold. We also study the Adler-Weisberger and Goldberger-Miyazawa-Oehme sum rules of pi N scattering, finding that both fail if the large N_c limit is taken prior to the chiral limit.Comment: 10 pages, ReVTe

Waveguiding in planar photonic crystals

Photonic crystal planar circuits designed and fabricated in silicon on silicon dioxide are demonstrated. Our structures are based on two-dimensional confinement by photonic crystals in the plane of propagation, and total internal reflection to achieve confinement in the third dimension. These circuits are shown to guide light at 1550 nm around sharp corners where the radius of curvature is similar to the wavelength of light

Elemental surface analysis at ambient pressure by electron-induced x-ray fluorescence

The development of a portable surface elemental analysis tool, based on the excitation of characteristic x rays from samples at ambient pressure with a focused electron beam is described. This instrument relies on the use of a thin electron transmissive membrane to isolate the vacuum of the electron source from the ambient atmosphere. The major attributes of this instrument include rapid (several minutes) spectrum acquisition, nondestructive evaluation of elemental composition, no sample preparation, and high-to-medium (several hundreds µm) spatial resolution. The instrument proof-of-principle has been demonstrated in a laboratory setup by obtaining energy dispersive x-ray spectra from metal and mineral samples