Twin-Wire Networks for Zero Interconnect, High-Density 4-Wire Electrical Characterizations of Materials

Four-wire measurements have been introduced by Lord Kelvin in 1861 and have since become the standard technique for characterizing small resistances and impedances. However, high-density 4-wire measurements are generally complex, time-consuming, and inefficient because of constraints on interconnects, pads, external wires, and mechanical contacts, thus reducing reproducibility, statistical significance, and throughput. Here, we introduce, systematically design, analyze, and experimentally validate zero interconnect networks interfaced to external instrumentation by couples of twin wire. 3D-printed holders with magnets, interconnects, nonadhesive layers, and spacers can effortlessly establish excellent electrical connections with tunable or minimum contact forces and enable accurate measurements even for delicate devices, such as thin metals on soft polymers. As an example, we measured all the resistances of a twin-wire 29-resistor network made of silver-nanoparticle ink printed on polyimide, paper, or photo paper, including during sintering or temperature calibration, resulting in an unprecedentedly easy and accurate characterization of both resistivity and its temperature coefficient. The theoretical framework and experimental strategies reported here represent a breakthrough toward zero interconnect, simple, and efficient high-density 4-wire characterizations, can be generalized to other 4-wire measurements (impedances, sensors) and can open the way to more statistically meaningful and reproducible analyses of materials, high-throughput measurements, and minimally invasive characterizations of biomaterials.

Mechanically axially chiral catenanes and noncanonical mechanically axially chiral rotaxanes

The term chiral was introduced by Lord Kelvin over a century ago to describe objects that are distinct from their own mirror image. Chirality is relevant in many scientific areas, but particularly chemistry because different mirror image forms of a molecule famously have different biological properties. Chirality typically arises in molecules due to a rigidly chiral arrangement of covalently bonded atoms. Less generally appreciated is that molecular chirality can arise when molecules are threaded through one another to create a mechanical bond. For example, when two molecular rings with chemically distinct faces are joined like links in a chain the resulting structure is chiral even when the rings themselves are not. We re-examined the symmetry properties of such mechanically axially chiral catenanes and in doing so identified a straightforward route to these molecules from simple building blocks. This also led to the discovery of a previously overlooked mechanical stereogenic unit that can arise when such a ring encircles a dumbbell-shaped axle to generate a rotaxane. These insights allowed us to produce the first highly enantioenriched axially chiral catenane and the same approach gave access to a molecule containing the newly identified noncanonical axially chiral rotaxane motif. With methods to access these structures in hand, the process of exploring their properties and applications can now begin.

Métricas de resiliência: uma reflexão conceptual no contexto da gestão do risco

A aplicação do conceito de resiliência no domínio da gestão de crises e do risco é relativamente recente mas tem tido um desenvolvimento muito relevante. O termo resiliência tem sido aplicado ao longo do tempo a diferentes áreas e a palavra resiliência pode ser considerada como parcialmente polissémica. Desde a mecânica dos materiais, a psicologia e a ecologia, a resiliência veio no século XXI acompanhar o termo sustentabilidade e caracterizar uma característica de gestão e da capacidade de reabilitação de instalações e sistemas naturais. A gestão da resiliência constitui um processo complementar e interligado ao da gestão do risco e que envolve diversas dimensões sociais e técnicas.Com a evolução da técnica e em particular com a aplicação de novas tecnologias de análise e de apoio à decisão, as frases atribuídas a Lord Kelvin (1824-1907) “o que não se pode medir não é possível melhorar” ou “o que é real pode sempre ser mensurável” poderão ser uma justificação filosófica, entre outras razões práticas, do interesse na caracterização e nas análises quantitativas. Com efeito, os conceitos de risco e de resiliência podem ser abordados por diferentes metodologias mas verifica-se um grande interesse prático na quantificação desses conceitos. Surge assim o tema da conceptualização e da métrica da resiliência. Na bibliografia podem-se encontrar diferentes modos para definir e quantificar a resiliência em engenharia, envolvendo as suas múltiplas dimensõesO texto é baseado numa análise bibliográfica da matéria e numa subsequente reflexão pessoal com a finalidade de apresentar métodos simplificados de métrica da resiliência bem como numa análise crítica das vantagens na quantificação da resiliência e também das suas limitações.

Centrifugal Waves in Tornado-like Vortices: Kelvin’s solutions and their Applications to Multiple-Vortex Development and Vortex Breakdown

About 140 years ago, Lord Kelvin derived the equations describing waves that travel along the axis of concentrated vortices such as tornadoes. Although Kelvin’s vortex waves, also known as centrifugal waves, feature prominently in the engineering and uid dynamics literature, they have not attracted as much attention in the field of atmospheric science. To remedy this circumstance, Kelvin’s elegant derivation is retraced, and slightly generalized, to obtain solutions for a hierarchy of vortex ows that model basic features of tornado-like vortices. This treatment seeks to draw attention to the important work that Lord Kelvin did in this field, and reveal the remarkably rich structure and dynamics of these waves. Kelvin’s solutions help explain the vortex breakdown phenomenon routinely observed in modeled tornado-like vortices, and it is shown that his work is compatible with the widely used criticality condition put forth by Benjamin in 1962. Moreover, it is demonstrated that Kelvin’s treatment, with the slight generalization, includes unstable wave solutions that have been invoked to explain some aspects of the formation of multiple-vortex tornadoes. The analysis of the unstable solutions also forms the basis for determining whether e.g., an axisymmetric or a spiral vortex breakdown occurs. Kelvin’s work thus helps understand some of the visible features of tornado-like vortices.

Lord Kelvin was wrong: About the effectiveness of innovation indexes

Innovation is a fashionable concept, as many economic (and elec-tion),1 international 2 and state 3 programmes show. Fashion might not be the essential part of the scientific discourse, however, even judging by the politicians’ declarations, innovation is certainly a popular topic and a point of interest for many scholars. One would even dare to claim that innovation policy attracts more positive attention than defence policy. In the times of economic crisis and austerity that are both affecting the Eurozone, it seems that authorizing expenses on innovation is easier than defending even limited military budgets. The economists themselves are also more inclined to claim it is innovation not war that stimulates the economy.4 Since the states are usually considered as the most active in that field, the term innovation policy was quickly coined. It encompasses all state actions directed at innovation. Some of these actions form so-called innovation indices (also known as innovation indicators), whose main aim is to measure innovation performance of the country. Other entities, private companies or individuals being the example, often engage in innovation process as well and are, to some extent, included in innovation measures. By large though these indices show the role of the state. Since they attempt to measure innovative performance, when we ask about their effectiveness, we ask about the effectiveness of innovation policies, and ultimately, the impact innovation (and innovation policies) has on economy. We will argue that the effectiveness of these innovation indicators in achieving the goal that is set before them can be questioned. Nonetheless they are still taken into account when innovation policies are shaped. In order to prove our thesis we decided to divide the paper into smaller sections. First, we will describe innovation as a theoretical concept and show its place in economic models. Then we will try answer the question why innovation is measured. Since the main goal of this paper is critique of current innovation measures, we will present two traditional (and most popular at the same time) innovation indicators and most important arguments against them. We will also include indices that are considered alternative to the traditional measures. The most important and conclusive part of this paper will be devoted to the critique of both old and new indices, and any innovation indicators in general.

The Gordian Knot

Chapter 22 includes a brief survey of knots and their uses. The nineteenth-century physicist Lord Kelvin suggested that atoms might be knots in the aether. This idea led to the development of knot theory as a branch of mathematics. Knots are classified by their crossing number. As the crossing number increases, the number of prime knots rises rapidly. This chapter explains an important class of knots known as torus knots that can be produced by winding a string around a torus. Knots that are formed of more than one component are known as links.

The Gibbs-Thomson Equation

The external surface of a material has an atomic or molecular structure that is different from the bulk material. So does any internal interface within a material. Because of this, the energy of a material or any grain or particle within it increases with the curvature of its bounding surface, as described by the Gibbs-Thomson equation. This chapter explains how surfaces control the nucleation of new phases during reactions such as solidification and precipitation, the coarsening and growth of particles during heat treatment, the equilibrium shape of crystals, and the surface adsorption and segregation of solutes and impurities. The Gibbs-Thomson was predated by a number of related equations; it is not clear whether it is named after J. J. Thomson or William Thomson (Lord Kelvin); and it was not put into its current usual form until after Gibbs’, Thomson’s and Kelvin’s time. J. J. Thomson was the third Cavendish Professor of Physics at Cambridge University. He discovered the electron, which had a profound impact on the world, notably via Thomas Edison’s invention of the light bulb, and subsequent building of the world’s first electricity distribution network. William Thomson was Professor of Natural Philosophy at Glasgow University. He made major scientific developments, notably in thermodynamics, and he helped build the first trans-Atlantic undersea telegraph. Because of his scientific pre-eminence, the absolute unit of temperature, the degree Kelvin, is named after him.

Sir George Gabriel Stokes, Bart (1819–1903): his impact on science and scientists

Lucasian Professor Sir George Gabriel Stokes was appointed joint-Secretary of the Royal Society in 1854, a post he held for the unprecedented period of 31 years, relinquishing the role when he succeeded T.H. Huxley as President in 1885. An eminent scientist of the Victorian era, Stokes explained fluorescence (he also coined the word) and his hydrodynamical formulae (the ‘Navier–Stokes equations’) remain ubiquitous today in the physics of any phenomenon involving fluid flows, from pipelines to glaciers to large-scale atmospheric perturbations. He also made seminal advances in optics and mathematics, and formulae that bear his name remain widely used today. The historiography however appears to understate Stokes's significant impact on science as unacknowledged collaborator on a wide range of scientific developments. His scientific peers regarded him as a mentor, advisor, designer of crucial experiments and, as editor of the Royal Society's scientific journals, arbiter of the standards of excellence in scientific communication to be attained before publication would be considered. Three brief case studies on Stokes's correspondence with Lord Kelvin, Sir William Crookes and the chemist Arthur Smithells exemplify how his impact was conveyed through the work of other scientists. This paper also begins consideration of why the character and worldview of Stokes led him to eschew personal reputation and profit for the sake of science and the Royal Society, and of how the development of the discipline of history of science has impacted on historiography relating to Stokes and others. This article is part of the theme issue ‘Stokes at 200 (Part 1)’.

James Joule

Joule’s journey to his energy conservation law began with his unsuccessful evaluation of the electric motor as a means to achieve perpetual motion. A series of subsequent experiments eventually led him to a definitive experiment in which he demonstrated the transformation of work (a falling weight) into heat (a spinning paddle that heated water) occurs at a precise ratio called the mechanical equivalent of heat (MEH). This and other of his experiments proved that heat is not a conserved quantity and that heat and work are simply two forms of a conserved quantity later to be called energy. He shared his findings with William Thomson (Lord Kelvin) who then went on to establish the field of thermodynamics.