Potential variability of decisional skills in uncertain dichotomous choice situations

The main concern of this paper is the selection of optimal decision rules for groups of individuals with identical preferences but diverse and potentially variable independent decisional skills. Employing the uncertain dichotomous choice model the main results illustrate how optimality and sensitivity analysis can be pursued while explicitly recognizing decision-making costs associated with potential variability of decisional skills. For panels of experts consisting of three members our analysis focuses on three special cases of potential variability in individual skills. The extended optimality problem is analyzed resolving the dilemma which of the two common rules, the simple majority rule or the expert rule, is the better selection for the group. The sensitivity of the two rules to variability of decisional skills is also investigated.     

Gödel's universe in a Supertube shroud

We demonstrate that certain supersymmetric G?del-like universe solutions of supergravity are not solutions of string theory. This is achieved by realizing that supertubes are Bogomol'nyi-Prasad-Sommerfeld states in these spaces, and under certain conditions, when wrapping closed timelike curves, some world-volume modes develop negative kinetic terms. Since these universes are homogeneous, this instability takes place everywhere in space-time. We also construct a family of supergravity solutions which locally look like the G?del universe inside a domain wall made out of supertubes, but have very different asymptotic structure. One can adjust the volume inside the domain wall so there will be no closed timelike curves, and then those spaces seem like perfectly good string backgrounds.     

On solution of higher approximations to boundary layer flows

Résumé Pour trouver des approximations d'un ordre élevé dans les problèmes de couche limite, l'auteur propose une méthode qui unifie le approches de Meksyn et Görtler. Les valeurs initiales, pour les approximations successives de Görtler, sont evaluées à l'aide de la methode de Meksyn. Toutes les valeurs initiales sont obtaneues par différentiation d'une seule équation. Les résultats obtenus sont au moins équivalent à ceux obtenus par la méthode de Hsu, avec considérablement moins de calculs.     

Superradiance and energy transfer within a system of atoms

We investigate cooperative effects in energy relaxation and energy transfer for N atoms in a thermal radiation field with superradiance master equations as well as a closed set of coupled moment equations. Both spatially large and spatially small systems are considered. For small systems nonlinear rate equations for the energy are related to the moment equations. Symmetry of the small system to interchanging atoms is used to incorporate off-diagonal solutions of the superradiance master equation in expressions for the probability of the transfer of energy from one group of atoms to another. The long time excitation probability for initially unexcited atoms is large and strongly correlated. Cooperative processes in a large system which fall off with the distance between a cooperating pair of atoms include energy loss and transfer terms in the master equation. The energy transfer is oscillatory in time. Energy relaxation is shown by numerical solution to become cooperative in a very sudden manner as the scale of the atomic system is decreased through the resonant wavelength.     

Path-integral computations of tunneling processes

The application of the path-integral methodology of Chandler and Wolynes [D. Chandler and P. G. Wolynes, J. Chem. Phys. 74, 4078 (1981)] to the calculation of one-electron-tunneling probabilities is revisited. We show that the evaluation of the kink free energy that is related to the tunneling splitting is associated with "polymer bead" distributions over a continuous distribution of scaled barriers, which makes both the calculation and its physical interpretation relatively difficult. In particular, we find that relative to other available techniques the method converges slowly and suffers from inaccuracies associated with the finite-temperature aspect of the calculation, and that past tentative identification of the bead distribution over the barrier with a physical picture of a "tunneling path" should be reassessed.     

Photoinactivation of Deinococcus radiodurans: An Unusual Gram-Positive Microorganism

Abstract— Deinococcus radiodurans is an extremely resistant bacteria to both the mutagenic and lethal effects of ionizing radiation. In the present study, we examined photoinactivation of D. radiodurans by two photosensitizers, the hydrophilic cationic 5, 10, 15, 20-tetra(4- N -methylpyridyl)porphine (TMPyP) and deuteroporphyrin (Dp), which is more hydrophobic. The effects of illumination with various lights at different wavelengths were also examined. Efficient photoinactivation was obtained when D. radiodurans cells were irradiated by blue light (400–450 nm) and treated with TMPyP at a concentration of 0.73 μ M . Under these conditions the viability of the culture was found to be decreased by almost seven orders of magnitude after 2 min of treatment at an intensity of only 2 J/cm². Treatment of the bacterial cells by TMPyP or Dp resulted in an efflux of potassium and magnesium from the cells as well as phosphate loss as a function of light dose. These results can be regarded as a consequence of membrane damage, because transmission electron microscopy revealed cell membrane damage shortly after exposure of the treated bacteria to light. In addition, asymmetric septation and filamentous chromosomal DNA were seen. It seems that the cytoplasmic membrane damage in this bacterial species plays a more important role than in other gram-positive or even gram-negative bacteria, rendering this radiation-resistant bacterium susceptible to photosensitization.     

Intracellular antimicrobial photodynamic therapy: a novel technique for efficient eradication of pathogenic bacteria

The increasing resistance of bacteria to antibiotics is a serious problem, caused in part by excessive and improper use of these drugs. One alternative to traditional antibiotic therapy is photodynamic antimicrobial chemotherapy (PACT) which is based on the use of a photosensitizer (PS), activated by illumination with visible light. The poor penetration of visible light through the skin limits the application of PACT to the treatment of skin infections or the use of invasive procedures. To overcome this problem we report the exploitation of light emitted as a result of the chemiluminescent reaction of luminol to excite the PS and we call this process chemiluminescent photodynamic antimicrobial therapy (CPAT). We studied the effect of free and liposome-encapsulated PS (methylene blue or toluidine blue) on bacteria under excitation by either white external light or chemiluminescence emitted by free or liposome-enclosed luminol. PACT showed slightly better performance that CPAT for free and encapsulated PS for both types of bacteria. CPAT resulted in a three log suppression of Staphylococcus aureus and two log suppression of Escherichia coli growth. The use of CPAT may prove to be a novel and more effective form of antimicrobial therapy, particularly for internal infections not easily accessible to traditional PACT.     

Increased superconducting transition temperature of a niobium thin film proximity coupled to gold nanoparticles using linking organic molecules

The superconducting critical temperature, T(C), of thin Nb films is significantly modified when gold nanoparticles (NPs) are chemically linked to the Nb film, with a consistent enhancement when using 3 nm long disilane linker molecules. The T(C) increases by up to 10% for certain linker length and NP size. No change is observed when the nanoparticles are physisorbed with nonlinking molecules. Electron tunneling spectra acquired on the linked NPs below T(C) typically exhibit zero-bias peaks. We attribute these results to a pairing mechanism coupling electrons in the Nb and the NPs, mediated by the organic linkers.