Parallel Fabrication of Plasmonic Nanocone Sensing Arrays

A fully parallel approach for the fabrication of arrays of metallic nanocones and triangular nanopyramids is presented. Different processes utilizing nanosphere lithography for the creation of etch masks are developed. Monolayers of spheres are reduced in size and directly used as masks, or mono‐ and double layers are employed as templates for the deposition of aluminum oxide masks. The masks are transferred into an underlying gold or silver layer by argon ion milling, which leads to nanocones or nanopyramids with very sharp tips. Near the tips the enhancement of an external electromagnetic field is particularly strong. This fact is confirmed by numerical simulations and by luminescence imaging in a confocal microscope. Such localized strong fields can amongst others be utilized for high‐resolution, high‐sensitivity spectroscopy and sensing of molecules near the tip. Arrays of such plasmonic nanostructures thus constitute controllable platforms for surface‐enhanced Raman spectroscopy. A thin film of pentacene molecules is evaporated onto both nanocone and nanopyramid substrates, and the observed Raman enhancement is evaluated.     

Sonoluminescence: How bubbles glow

Abstract

We review recent attempts to elucidate the phenomenon of sonoluminescence in terms of fundamental principles. We focus mainly on the processes which generate the light, but other relevant facts, such as the bubble dynamics, must also be considered for the understanding of the physics involved. Our emphasis is on single bubble sonoluminescence which in recent years has received much attention, but we also look at some of the excellent work on multiple bubble sonoluminescence and its spectral characteristics for clues. The weakly ionized gas models were recently studied most thoroughly and are remarkably successful when combined with a hydrodynamic bubble model, in terms of reproducing observed spectral shapes, intensities, optical pulse widths and the dependencies of these observables on the experimental parameters. Other radiation models, such as proton tunnelling radiation and the confined electron model, were not combined with hydrodynamic models and/or have freely adjustable parameters so that their relevance to sonoluminescence studies is at present less critically tested.     

Deterministic global optimization of steam cycles using the IAPWS-IF97 model

Optimization and Engineering - The IAPWS-IF97 (Wagner et al. (2000) J Eng Gas Turbines Power 122:150) is the state-of-the-art model for the thermodynamic properties of water and steam for...     

Lagrange extraction and projection for NURBS basis functions: A direct link between isogeometric and standard nodal finite element formulations

We introduce Lagrange extraction and projection that link a C⁰ nodal basis with a smooth B‐spline basis. Our technology is equivalent to Bézier extraction and projection but offers an alternative implementation based on the interpolatory property of nodal basis functions. The Lagrange extraction operator can be constructed by simply evaluating B‐spline basis functions at nodal points and eliminates the need for introducing Bernstein polynomials as new shape functions. The Lagrange projection operator is defined as the inverse of the Lagrange extraction operator and directly relates function values at nodal points to element‐level B‐spline coefficients of a local interpolant. For geometries based on polynomial B‐splines, our technology allows the implementation of isogeometric analysis in standard nodal finite element codes with simple algorithms and minimal intrusion. Copyright © 2016 John Wiley & Sons, Ltd.     

Application and Future Challenges of Functional Nanocarbon Hybrids

Hybridizing nanocarbons, such as carbon nanotubes (CNTs) or graphene, with an active material is a powerful strategy towards designing next‐generation functional materials for environmental and sustainable energy applications. While research on nanocomposites, created by dispersing the nanocarbon into polymer or ceramic matrices, began almost immediately after the popularization of CNTs and graphene in 1991 and 2004, respectively, nanocarbon hybrids are a relatively recent addition to the family of composite materials. In contrast to nanocomposites, which typically combine the intrinsic properties of both compounds, nanocarbon hybrids additionally provide access to both a large surface area required for gas/liquid‐solid interactions and an extended interface, through which charge and energy transfer processes create synergistic effects that result in unique properties and superior performance. This progress report looks at the history of research on nanocarbons (fullerenes, CNTs and graphene) and their composites and hybrids, presents the origin of synergistic effects, reviews the most intriguing results on nanocarbon hybrid performance in heterogeneous catalysis, electrocatalysis, photocatalysis, batteries, supercapacitors, photovoltaics and sensors, and discusses remaining challenges and future research directions.     

Shadowing vs. distality for actions of ℝ n

This article introduces the notion of weakly parametrized (wp) shadowing for actions of groups ? ^m ?×?? ⁿ , where m,?n?≥?0 and m?+?n?>?0. The possibility of coexistence of distality and shadowing for actions of ? ⁿ is discussed. It is proven that an equicontinuous action of ? ⁿ on a compact connected space possessing wp-shadowing is actually minimal. Moreover, distal real flows (?-actions) on one-dimensional compact metric spaces are characterized as constant-one suspensions over adding machines.     

Highly compact imaging using Bessel beams generated by ultraminiaturized multi-micro-axicon systems

Employing Bessel beams in imaging takes advantage of their self-reconstructing properties to achieve small focal points while maintaining a large depth of focus. Bessel beams are efficiently generated using axicons, and their utility in scanning imaging systems, such as optical coherence tomography (OCT), has been demonstrated. As these systems are miniaturized to allow, for example, endoscopic implementations, micro-axicons are required to assure the maintenance of a large depth of focus. We demonstrate here the design, fabrication, and application of molded micro-axicons for use in silicon-based micro-optical benches. It is shown that arrangements of multiple convex and concave axicons may be implemented to optimize the depth of focus in a miniaturized OCT system, using a telescopic optical arrangement of considerably shorter optical system length than that achievable with classical micro-optics.     

Dating multiple change points in the correlation matrix

A nonparametric procedure for detecting and dating multiple change points in the correlation matrix of sequences of random variables is proposed. The procedure is based on a recently proposed test for changes in correlation matrices at an unknown point in time. Although the procedure requires constant expectations and variances, only mild assumptions on the serial dependence structure are assumed. The convergence rate of the change point estimators is derived and the asymptotic validity of the procedure is proved. Moreover, the performance of the proposed algorithm in finite samples is illustrated by means of a simulation study and the analysis of a real data example with financial returns. These examples show that the algorithm has large power in finite samples.     

Polar Side Chains Enhance Processability,Electrical Conductivity,and Thermal Stability of a Molecularly p‐Doped Polythiophene

Molecular doping of organic semiconductors is critical for optimizing a range of optoelectronic devices such as field‐effect transistors, solar cells, and thermoelectric generators. However, many dopant:polymer pairs suffer from poor solubility in common organic solvents, which leads to a suboptimal solid‐state nanostructure and hence low electrical conductivity. A further drawback is the poor thermal stability through sublimation of the dopant. The use of oligo ethylene glycol side chains is demonstrated to significantly improve the processability of the conjugated polymer p(g₄2T‐T)—a polythiophene—in polar aprotic solvents, which facilitates coprocessing of dopant:polymer pairs from the same solution at room temperature. The use of common molecular dopants such as 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) is explored. Doping of p(g₄2T‐T) with F4TCNQ results in an electrical conductivity of up to 100 S cm^?1. Moreover, the increased compatibility of the polar dopant F4TCNQ with the oligo ethylene glycol functionalized polythiophene results in a high degree of thermal stability at up to 150 °C.