Modeling the Influence of Public’s Memory on the Corruption–Popularity Dilemma in Politics

We consider the problem of a rational politician who gains benefit from both being popular and corrupt. In 1994, Feichtinger and Wirl studied this trade-off by means of an infinite-horizon optimal control approach. We reconsider the problem over a finite time horizon, to model the dilemma of a politician who stays in office for a limited period of time and wishes to be reelected. We also include explicitly the possibility that awareness of politician’s conduct to the general population is delayed and the effect of such delay on the politician’s optimal behavior is analyzed. We show the outcomes under several different scenarios, with particular reference to the role of the politician’s communication skills. One general conclusion is that the synergy of a good public’s memory and immediate knowledge of corruption may often help the people to protect themselves from political corruption. Moreover, this synergy may greatly enhance the popularity of a politician with poor communication skills, provided that he/she aims at maximizing benefit from popularity during his/her mandate.     

Quantum nondemolition measurements on two-level atomic systems and temporal Bell inequalities

The evolution of a two-level system subjected to stimulated transitions which is undergoing a sequence of measurements of the level occupation probability is evaluated. Its time correlation function is compared to the one obtained through the pure Schr?dinger evolution. Systems of this kind have been recently proposed for testing the quantum mechanical predictions against those of macrorealistic theories, by means of temporal Bell inequalities. The classical requirement of noninvasivity, needed to define correlation functions in the realistic case, finds a quantum counterpart in the quantum nondemolition condition. The consequences on the observability of quantum mechanically predicted violations to temporal Bell inequalities are drawn and compared to the already dealt case of the rf-SQUID dynamics. Received: 28 March 1996 / Revised version: 13 August 1996     

Asymptotics of Two-boundary First-exit-time Densities for Gauss-Markov Processes

Methodology and Computing in Applied Probability - The problem of escape times from a region confined by two time-dependent boundaries is considered for a class of Gauss-Markov processes....     

Dynamic behaviour of a discrete-time SIR model with information dependent vaccine uptake

This paper proposes and analyzes a discrete-time deterministic SIR model with information dependent immunization behaviour, where vaccination coverage at birth during any period of time is a general phenomenological function of the risk of infection that is perceived at the beginning of the period. Results on existence of equilibria, their local stability, and system persistence are proved. Then, by considering the noteworthy subcase of a piecewise linear ‘prevalence-dependent’ coverage function, the local stability of the endemic state is proved and conditions for its global asymptotic stability are given. Some insight on both Neimarck-Sacher and period-doubling bifurcations are provided. Overall we show that prevalence-dependent coverage is an essentially stabilising force. However period-doubling bifurcations are possible though under stressed parameter constellations.     

Protein diffusion coefficients determined by macroscopic-gradient Rayleigh interferometry and dynamic light scattering

Dynamic light scattering (DLS) is extensively used for measuring macromolecule diffusion coefficients. Contrary to classical techniques based on macroscopic concentration gradients, DLS probes microscopic fluctuations in concentration. DLS accuracy and its concordance with macroscopic-gradient techniques remains an outstanding important issue. We measured lysozyme diffusion coefficients in aqueous salt using both DLS and Rayleigh interferometry, a highly accurate macroscopic-gradient technique. The precision of our results is unprecedented. We find that our DLS values were systematically 2% higher than interferometry values. We believe that our interferometric measurements have produced the most accurate diffusion data ever reported for a protein, providing a new standard for quality control of DLS measurements. Furthermore, by interferometry, we have determined the whole diffusion coefficient matrix required for rigorously describing lysozyme-salt coupled diffusion. For the first time, we experimentally demonstrate that DLS does not provide the protein diffusion coefficient but one eigenvalue of the diffusion coefficient matrix.     

Synthesis of a bridgehead nitrogen system. Imidazo[1,5-b]pyridazine derivatives

3,4-Dibenzoyl-2-oxobutyrate 4-semicarbazone ( 6a ), ethyl 2,4-dioxo-3-phenacylvalerate 3-semicarbazone ( 6b ) and diethyl phenacyloxalectate 3-semicarbazone ( 6c ) via acid catalysed intramolecular cyclization afforded 2-phenyl-4-R-3H-imidazo[1,5-d]pyridazine-5,7-(6H)diones ( 8d,e,f ). Elemental analyses and spectroscopic data (ir, nmr, ms) were in good agreement with the assigned structures.     

Modulation of drug transport properties by multicomponent diffusion in surfactant aqueous solutions

Diffusion coefficients of drug compounds are crucial parameters used for modeling transport processes. Interestingly, diffusion of a solute can be generated not only by its own concentration gradient but also by concentration gradients of other solutes. This phenomenon is known as multicomponent diffusion. A multicomponent diffusion study on drug-surfactant-water ternary mixtures is reported here. Specifically, high-precision Rayleigh interferometry was used to determine multicomponent diffusion coefficients for the hydrocortisone-tyloxapol-water system at 25 degrees C. For comparison, diffusion measurements by dynamic light scattering were also performed. In addition, drug solubility was measured as a function of tyloxapol concentration, and drug-surfactant thermodynamic interactions using the two-phase partitioning model were characterized. The diffusion results are in agreement with a proposed coupled multicomponent diffusion model for ternary mixtures relevant to nonionic drug and surfactant molecules. Theoretical examination of diffusion-based drug transport in the presence of concentration gradients of micelles shows that drug fluxes and drug concentration profiles are significantly affected by coupled multicomponent diffusion. This work provides guidance for the development of accurate models of diffusion-based controlled release in multicomponent systems and for the applications of micelle concentration gradients to the modulation of diffusion-based drug transport.     

A note on the global behaviour of the network-based SIS epidemic model

In this note we introduce the study of the global behaviour of the network-based SIS epidemic model recently proposed by Pastor-Satorras and Vespignani [Epidemic spreading in scale-free networks, Phys. Rev. Lett. 86 (2001) 3200], characterized in case of homogeneous scale-free networks by a very small epidemic threshold, and extended by Olinky and Stone [Unexpected epidemic threshold in heterogeneous networks: the role of disease transmission, Phys. Rev. E 70 (2004) 03902(r)]. We show that the above model may be read as a particular case of the classical multi-group SIS model proposed by Lajmainovitch and Yorke [A deterministic model for gonorrhea in a nonhomogeneous population, Math. Biosci. 28 (1976) 221] and extended by Aronsson and Mellander [A deterministic model in biomathematics. Asymptotic behaviour and threshold conditions, Math. Biosci. 49 (1980) 207]. Thus, by applying the methods used for SIS multi-group models, we straightforwardly show, for the first time, that the local conditions identified in the physics literature also determine the global behaviour of a disease spreading on a network. Finally, we briefly study the case in which the force of infection is non-linear, by showing that multiple coexisting equilibria are possible, and by giving a global threshold condition for the extinction.     

Surfactant assisted polymerization of tetrafluoroethylene in supercritical carbon dioxide with a pilot scale batch reactor

Chain‐free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO₂), at 50 °C and 121–133 bar, with tertiary‐amyl‐per‐pivalate as a free radical initiator, using a 5‐L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant‐free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200–500 μm. Quite interestingly, when the free acid surfactant was used, a clear acceleration of the polymerization rate was observed and smaller polymer particles with more regular quasi‐spherical morphology were obtained. Melt fusion crystallinity of as‐polymerized poly(TFE) seemed not substantially affected by the presence of the stabilizers and was rather high (80–86%) suggesting that polymerization mainly occurs at polymer particle surface. All these elements suggest that FLUOROLINK® 7004H PFPE carboxylic acid decreases coagulation of primary polymer particles leading to an increase in polymer surface area. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 257–266, 2008     

Experimental and computational evidence for an inversion in guest capacity in high-generation triazine dendrimer hosts

The synthesis, characterization, and host-guest chemistry of high-generation triazine dendrimers are described. With pyrene and camptothecin as guests, experiments revealed that the guest capacity of odd-generation triazine dendrimers increased until generation 7 but decreased at generation 9. Molecular dynamics simulations conducted in explicit solvent showed a useful fingerprint for this behavior in radial distribution functions of water molecules penetrating the interior of the dendrimers. A linear relationship between the guest capacity of dendrimers measured experimentally and the number of water molecules within the interior determined computationally was observed.