Casimir-Polder Potential in Thermal Non-Equilibrium

Different non-equilibrium situations have recently been considered when studying the thermal Casimir--Polder interaction with a body. We show that the Keldysh Green function method provides a very general common framework for such studies where non-equilibrium of either the atom or the body with the environment can be accounted for. We apply the results to the case of ground state polar molecules out of equilibrium with their environment, observing several striking effects. We consider thermal Casimir--Polder potentials in planar configurations, and new results for a molecule in a cylindrical cavity are reported, showing similar characteristic behaviour as found in planar geometry.Comment: Contribution to Proceedings of QFEXT09, Norman Oklahoma, September 2009. 10 pages, 2 figures. Section 2 revised; final, accepted version

Second order coupling between excited atoms and surface polaritons

Casimir-Polder interactions between an atom and a macroscopic body are typically regarded as due to the exchange of virtual photons. This is strictly true only at zero temperature. At finite temperature, real-photon exchange can provide a significant contribution to the overall dispersion interaction. Here we describe a new resonant two-photon process between an atom and a planar interface. We derive a second order effective Hamiltonian to explain how atoms can couple resonantly to the surface polariton modes of the dielectric medium. This leads to second-order energy exchanges which we compare with the standard nonresonant Casimir-Polder energy.Comment: 7 pages, 2 figure

Flammability behaviour of wood and a review of the methods for its reduction

Wood is one of the most sustainable, aesthetically pleasing and environmentally benign materials. Not only is wood often an integral part of structures, it is also the main source of furnishings found in homes, schools, and offices around the world. The often inevitable hazards of fire make wood a very desirable material for further investigation. As well as ignition resistance and a low heat release rate, timber products have long been required to resist burn-through and maintain structural integrity whilst continuing to provide protection when exposed to fire or heat. Various industry standard tests are thus required to ensure adequate protection from fire is provided. When heated, wood undergoes thermal degradation and combustion to produce gases, vapours, tars and char. In order to understand and alter the fire behaviour of wood, it is necessary to know in as much detail as possible about its processes of decomposition. Various thermal analysis and flammability assessment techniques are utilised for this purpose, including thermogravimetric analysis, cone calorimetry and the single burning item test. The results of such tests are often highly dependent on various parameters including changes to the gas composition, temperature, heating rate, and sample shape size. Potential approaches for fire retarding timber are reviewed, identifying two main approaches: char formation and isolating layers. Other potential approaches are recognised, including the use of inorganic minerals, such as sericrite, and metal foils in combination with intumescent products. Formulations containing silicon, nitrogen and phosphorus have been reported, and efforts to retain silicon in the wood have been successful using micro-layers of silicon dioxide. Nano-scale fire retardants, such as nanocomposite coatings, are considered to provide a new generation of fire retardants, and may have potential for wood. Expandable graphite is identified for use in polymers and has potential for wood provided coating applications are preferred

Resonant vibrations, peak broadening and noise in single molecule contacts: beyond the resonant tunnelling picture

We carry out experiments on single-molecule junctions at low temperatures, using the mechanically controlled break junction technique. Analyzing the results received with more than ten different molecules the nature of the first peak in the differential conductance spectra is elucidated. We observe an electronic transition with a vibronic fine structure, which is most frequently smeared out and forms a broad peak. In the usual parameter range we find strong indications that additionally fluctuations become active even at low temperatures. We conclude that the electrical field feeds instabilities, which are triggered by the onset of current. This is underscored by noise measurements that show strong anomalies at the onset of charge transport

The Challenge of Co-Religionist Commerce

This Article addresses the rise of co-religionist commerce in the United States—that is, the explosion of commercial dealings that take place between co-religionists who intend their transactions to achieve both commercial and religious objectives. To remain viable, coreligionist commerce requires all the legal support necessary to sustain all other commercial relationships. Contracts must be enforced, parties must be protected against torts, and disputes must be reliably adjudicated. Under current constitutional doctrine, co-religionist commercial agreements must be translated into secular terminology if they are to be judicially enforced. But many religious goods and services cannot be accurately translated without religious terms and structures. To address this translation problem, courts could make use of contextual tools of contract interpretation, thereby providing the necessary evidence to give meaning to co-religionist commercial agreements. However, contextual approaches to co-religionist commerce have been undermined by two current legal trends—one in constitutional law, the other in commercial law. The first is New Formalism, which discourages courts from looking to customary norms and relational principles to interpret commercial instruments. The second is what we call Establishment Clause Creep, which describes a growing judicial reticence to adjudicate disputes situated within a religious context. Together, these two legal developments prevent courts from using context to interpret and enforce co-religionist commercial agreements. This Article proposes that courts preserve co-religionist commerce with a limited embrace of contextualism. A thorough inquiry into context, which is discouraged by both New Formalist and many Establishment Clause doctrines, would allow courts to surmise parties\u27 intents and distinguish commercial from religious substance. Empowering the intent of co-religionist parties and limiting the doctrinal developments that threaten to undermine co-religionist commerce can secure marketplace dealings without intruding upon personal faith

Surface-induced heating of cold polar molecules

We study the rotational and vibrational heating of diatomic molecules placed near a surface at finite temperature on the basis of macroscopic quantum electrodynamics. The internal molecular evolution is governed by transition rates that depend on both temperature and position. Analytical and numerical methods are used to investigate the heating of several relevant molecules near various surfaces. We determine the critical distances at which the surface itself becomes the dominant source of heating and we investigate the transition between the long-range and short-range behaviour of the heating rates. A simple formula is presented that can be used to estimate the surface-induced heating rates of other molecules of interest. We also consider how the heating depends on the thickness and composition of the surface.Comment: 17 pages, 7 figure