Artículos con la etiqueta ‘química’

New Form of Carbon is Stronger Than Graphene and Diamond

Por • 17 ago, 2013 • Category: Leyes

The sixth element, carbon, has given us an amazing abundance of extraordinary materials. Once there was simply carbon, graphite and diamond. But in recent years chemists have added buckyballs, nanotubes and any number of exotic shapes created out of graphene, the molecular equivalent of chickenwire. The new material is called carbyne. It is a chain of carbon atoms that are linked either by alternate triple and single bonds or by consecutive double bonds. All this should whet the appetite of nanotechnologists hoping to design ever more exotic nanomachines, such as nanoelectronic and spintronic devices. Given the advances being made in manufacturing this stuff, we may not have long to wait before somebody begins exploiting the extraordinary mechanical properties of carbyne chains for real.

The Kinetics of Wealth and the Origin of the Pareto Law

Por • 7 ene, 2013 • Category: Economía

An important class of economic models involve agents whose wealth changes due to transactions with other agents. Several authors have pointed out an analogy with kinetic theory, which describes molecules whose momentum and energy changes due to interactions with other molecules. We pursue this analogy and derive a Boltzmann equation for the time evolution of the wealth distribution of a population of agents for the so-called Yard-Sale Model of wealth exchange. We examine the solutions to this equation by a combination of analytical and numerical methods, and investigate its long-time limit. We study an important limit of this equation for small transaction sizes, and derive a partial integrodifferential equation governing the evolution of the wealth distribution in a closed economy. We then describe how this model may be extended to include features such as production, inflation, and taxation.

An information-processing approach to the origin of life

Por • 20 dic, 2012 • Category: Ambiente

“To a physicist or chemist life seems like ‘magic matter,’” Davies explained. “It behaves in extraordinary ways that are unmatched in any other complex physical or chemical system. Such lifelike properties include autonomy, adaptability and goal-oriented behavior — the ability to harness chemical reactions to enact a pre-programmed agenda, rather than being a slave to those reactions. “We believe the transition in the informational architecture of chemical networks is akin to a phase transition in physics, and we place special emphasis on the top-down information flow in which the system as a whole gains causal purchase over its components, This approach will reveal how the logical organization of biological replicators differs crucially from trivial replication associated with crystals (non-life). By addressing the causal role of information directly, many of the baffling qualities of life are explained.”

Sequential Voronoi diagram calculations using simple chemical reactions

Por • 19 nov, 2012 • Category: Educacion

In our recent paper [de Lacy Costello et al. 2010] we described the formation of complex tessellations of the plane arising from the various reactions of metal salts with potassium ferricyanide and ferrocyanide loaded gels. In addition to producing colourful tessellations these reactions are naturally computing generalised Voronoi diagrams of the plane. The reactions reported previously were capable of the calculation of three distinct Voronoi diagrams of the plane. As diffusion coupled with a chemical reaction is responsible for the calculation then this is achieved in parallel. Thus an increase in the complexity of the data input does not utilise additional computational resource. Additional benefits of these chemical reactions is that a permanent record of the Voronoi diagram calculation (in the form of precipitate free bisectors) is achieved, so there is no requirement for further processing to extract the calculation results. Previously it was assumed that the permanence of the results was also a potential drawback which limited reusability. This paper presents new data which shows that sequential Voronoi diagram calculations can be performed on the same chemical substrate.

A Note on the Prehistory of Superheavy Elements

Por • 26 jul, 2012 • Category: Educacion

Artificially produced chemical elements heavier than uranium have been known for more than seventy years and the number of superheavy elements continues to grow. Presently 26 transuranic elements are known. This paper examines the earliest scientific interest in the very heavy elements and the related question of an upper limit of the periodic system. In the period from the 1880s to the early 1930s, three kinds of questions appealed to a minority of physicists and chemists: (1) Why is uranium the heaviest known element? (2) Do there exist transuranic or superheavy elements elsewhere in the universe? (3) Is there a maximum number of elements, corresponding to a theoretical limit for the periodic system? The early attempts to answer or clarify these questions lacked a foundation in nuclear physics, not to mention the total lack of experimental evidence, which explains why most of them were of a speculative nature. Although the speculations led no nothing, they are interesting in their own right and deserve a place in the history of the physical sciences.

multiple of 12 for Avogadro

Por • 19 feb, 2012 • Category: Ambiente

The new International System of Units may let us select an integer value for Avogadro’s number. Some might prefer an integer that’s divisible by 12, so that an integer number of $^{12}C$ atoms may be associated (at least to first order) with a gram’s mass. For educational as well as practical reasons it may also help to choose a {\em physically-meaningful} definition, within measurement error of the current numeric value. Cubes of diamond face-centered-cubic Si and (much rarer) face-centered-cubic C have been proposed, but these structures don’t have naturally occurring facets (or numbers of atoms generally divisible by 12). We show here that graphite prisms formed by stacking $m$ hexagonal graphene sheets, with $m$ Carbon-12 atoms on each side, are a natural solution to this challenge.

Hegel’s philosophy of the chemical process: a rehabilitation

Por • 24 sep, 2011 • Category: Crítica

In the Science of Logic, philosophy analyses and develops concepts. If a concept proves to be inconsistent, thought is compelled to move to a more comprehensive concept that resolves the contradiction revealed in the former one. Thus, thought uses its own resources and refers to concrete material only as an illustration or example. On the other hand, in the Philosophy of Nature, philosophy takes a thoroughgoing empirical approach. One gathers everything experience tells us about nature, looks at all determinations discovered and, by recognizing their relations and considering them as a whole, «constructs the concept» (Hegel). The categories analyzed in the Science of Logic are conditions of the approach of the Philosophy of Nature that proceeds in a radically empirical way (p. 208). The latter turns out to be systematic, because the speculative concept arises if the empirical data are grasped in their synthesis. Ultimately, the Hegelian ‘spirit’ is the subject that combines logic and nature. ‘Spirit’ means the achievements of finite subjective spirits, as members of the universal intellectual community reflecting the ‘real process’ in which logical thought and empirical chemistry are united (p. 211). In these efforts, Hegel’s philosophy has its place.

Matemáticos crean una «tabla periódica» de las formas

Por • 18 feb, 2011 • Category: Leyes

Un equipo de matemáticos del Imperial College London pretende identificar las formas indivisibles, en tres, cuatro y cinco dimensiones, que son los “ladrillos” básicos de formas más complejas. La intención es crear una “tabla” de formas, similar a la tabla periódica de los elementos, en la que se reflejen las formas básicas y sus propiedades, expresadas en ecuaciones relativamente simples. Esta herramienta resultará muy útil en múltiples áreas, desde la visión artificial hasta la física teórica, afirman los investigadores.

Tree-like giant is largest molecule ever made

Por • 11 ene, 2011 • Category: Ciencia y tecnología

To create their molecular giant, Schlüter and his colleagues started with standard polymerisation, in which smaller molecules join up to form a long chain. To this carbon and hydrogen backbone, they added branches made of benzene rings and nitrogen, as well as carbon and hydrogen.

Químicos de Gran Bretaña y China inventan el “agua seca”

Por • 30 ago, 2010 • Category: Ciencia y tecnología

Químicos británicos junto con sus colegas chinos lograron crear una sustancia que se llama «agua seca» compuesta de gotas microscópicas de agua recubiertas de silicio.