Temperature dependence of the Casimir effect between metallic mirrors

We calculate the Casimir force and free energy for plane metallic mirrors at non-zero temperature. Numerical evaluations are given with temperature and conductivity effects treated simultaneously. The results are compared with the approximation where both effects are treated independently and the corrections simply multiplied. The deviation between the exact and approximated results takes the form of a temperature dependent function for which an analytical expression is given. The knowledge of this function allows simple and accurate estimations at the % level.Comment: 8 pages, 4 figures, uses RevTe

Conventional Chemotherapy Followed By Consolidation With Autologous Hematopoietic Transplantation vs Chemotherapy Alone In HIV+ Patients With Large B Cell Lymphoma (LBCL) In First Complete Remission (CR). A Retrospective Analysis On Behalf Of The EBMT Lymphoma Working Party And The GESIDA/PETHEMA Registry Of HIV+ Patients With Non-Hodgkin's Lymphoma (NHL)

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The Casimir force and the quantum theory of lossy optical cavities

We present a new derivation of the Casimir force between two parallel plane mirrors at zero temperature. The two mirrors and the cavity they enclose are treated as quantum optical networks. They are in general lossy and characterized by frequency dependent reflection amplitudes. The additional fluctuations accompanying losses are deduced from expressions of the optical theorem. A general proof is given for the theorem relating the spectral density inside the cavity to the reflection amplitudes seen by the inner fields. This density determines the vacuum radiation pressure and, therefore, the Casimir force. The force is obtained as an integral over the real frequencies, including the contribution of evanescent waves besides that of ordinary waves, and, then, as an integral over imaginary frequencies. The demonstration relies only on general properties obeyed by real mirrors which also enforce general constraints for the variation of the Casimir force.Comment: 18 pages, 6 figures, minor amendment

Geometry and material effects in Casimir physics - Scattering theory

We give a comprehensive presentation of methods for calculating the Casimir force to arbitrary accuracy, for any number of objects, arbitrary shapes, susceptibility functions, and separations. The technique is applicable to objects immersed in media other than vacuum, to nonzero temperatures, and to spatial arrangements in which one object is enclosed in another. Our method combines each object's classical electromagnetic scattering amplitude with universal translation matrices, which convert between the bases used to calculate scattering for each object, but are otherwise independent of the details of the individual objects. This approach, which combines methods of statistical physics and scattering theory, is well suited to analyze many diverse phenomena. We illustrate its power and versatility by a number of examples, which show how the interplay of geometry and material properties helps to understand and control Casimir forces. We also examine whether electrodynamic Casimir forces can lead to stable levitation. Neglecting permeabilities, we prove that any equilibrium position of objects subject to such forces is unstable if the permittivities of all objects are higher or lower than that of the enveloping medium; the former being the generic case for ordinary materials in vacuum.Comment: 44 pages, 11 figures, to appear in upcoming Lecture Notes in Physics volume in Casimir physic

Oxidation of laccase for improved cathode biofuel cell performances

Graphite rodswere modified by substituted aryldiazoniumsalts allowing subsequent laccase immobilisation and direct electron transfer at the cathode. Two covalent enzyme immobilisation methods were performed with carboxy and amino substituted grafted groups, either via the formation of an amide bond or a Schiff base between the glycosidic groups of the enzyme and the amino groups on the electrode surface, respectively. Laccase adsorption efficiency was consistently compared to the covalent attachment method on the same carbon surface, showing that the latter method led to a higher immobilisation yield when the electrode surface was functionalised with carboxylic groups, as shown fromboth laccase activitymeasurement towards an organic reducing substrate, ABTS, and quantitative XPS analysis. Both analytical methods led to similar laccase surface coverage estimations. From activity measurements, when laccase was covalently immobilised on the electrode functionalised with carboxylic groups, the surface coverage was found to be 43 ± 2% whereas it was only 10 ± 3% when laccase was adsorbed. Biocatalysed dioxygen reduction current was also higher in the case of covalent immobilisation. For the first time, oxidised laccase performances were compared to unmodified laccase, showing significant improved efficiencywhen using oxidised laccase: the current obtainedwith oxidised laccasewas 141±37 μAcm-2 compared to 28 ± 6 μA cm-2 for unmodified laccase after covalent immobilisation of the enzyme on a graphite electrode functionalised with carboxylic groups. © 2015 Elsevier B.V

Application of X-ray photoelectron spectroscopy to micro-organisms

The use of X-ray photoelectron spectroscopy (XPS) for the analysis of microbial cell surfaces is described and discussed. This technique is well established in materials science; however, its application to biological samples calls for special considerations owing to the complexity of their chemical composition and because living cells are delicate samples needing careful handling. The results presented for various microorganisms demonstrate how data on the elemental composition can be upgraded into information on the functional groups by peak decomposition and how this can in turn be indicative of the molecular constituents present at the cell surface. The reproducibility of the analysis of microbial surfaces is shown to be currently better than 10% for major elements and functions; it is mainly determined by the variability of the biological material. The reliability of the results is examined with respect to the possibility of systematic errors and the influence of experimental conditions. The effects of washing of the cells, freeze drying, storage and manipulation for introduction into the spectrometer are checked. Sample degradation under the X-ray beam is examined. The influence of surface contamination and of uncertainties concerning sensitivity factors is discussed on the basis of biochemical standard compound analysis. Different sets of data show the dependence of surface composition on the nutrient availability (nature of the culture medium, yeast extract concentration, phosphate concentration), culture age and physiological state (vegetative cells, spores) and its relation to surface morphology. Relationships are observed between the surface electrical properties and the phosphate or nitrogen surface concentrations, depending on the type of microorganism. The chemical composition parameter (nitrogen, oxygen, carbon bound only to carbon and hydrogen) related to surface hydrophobicity depends on the type of microorganism. The surface composition is also found to be relevant to the behaviour of microbial cells with respect to interfaces (flotation, aggregation, adhesion to a solid support)