Perfect equilibrium and lexicographic beliefs

We extend the results of Blume, Brandenberger, and Dekel (1991b) to obtain a finite characterization of perfect equilibria in terms of lexicographic probability systems (LPSs). The LPSs we consider are defined over individual strategy sets and thus capture the property of independence among players' actions. Our definition of a product LPS over joint actions of the players is shown to be canonical, in the sense that any independent LPS on joint actions is essentially equivalent to a product LPS according to our definition. Received February 2002/Final version June 2002 We would like to thank Adam Brandenburger, Eddie Dekel, Arthur Robson, Peter Streufert, and Robert Wilson for their helpful comments. Govindan acknowledges research support from the Social Sciences and Humanities Research Council of Canada.     

A Cournot–Nash–Bertrand game theory model of a service-oriented Internet with price and quality competition among network transport providers

This paper develops a game theory model of a service-oriented Internet in which profit-maximizing service providers provide substitutable (but not identical) services and compete with the quantities of services in a Cournot–Nash manner, whereas the network transport providers, which transport the services to the users at the demand markets, and are also profit-maximizers, compete with prices in Bertrand fashion and on quality. The consumers respond to the composition of service and network provision through the demand price functions, which are both quantity and quality dependent. We derive the governing equilibrium conditions of the integrated game and show that it satisfies a variational inequality problem. We then describe the underlying dynamics, and provide some qualitative properties, including stability analysis. The proposed algorithmic scheme tracks, in discrete-time, the dynamic evolution of the service volumes, quality levels, and the prices until an approximation of a stationary point (within the desired convergence tolerance) is achieved. Numerical examples demonstrate the modeling and computational framework.     

Infrared spectrum and absorption coefficient of the cofactor flavin in water

Flavins play a key role as redox cofactors of enzymes involved in important metabolic processes. Moreover, they undergo photochemical reactions as chromophores in sensors of blue light or magnetic field in many organisms. The reaction mechanisms of flavoproteins have been investigated by infrared spectroscopy and theoretical studies. However, basic information on flavins in the infrared spectral range has been missing, such as absorption spectra in water and absorption coefficients. Here, the cofactors flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) were investigated in aqueous medium by Fourier transform infrared spectroscopy. Transmission and attenuated total reflection (ATR) configuration were employed in direct comparison. Absorption spectra in the range of 920–1800 cm⁻¹ were determined after accurate subtraction of the contributions from the water vibrations. The important carbonyl vibrations were resolved at 1661 and 1712 cm⁻¹. The absorption spectra may serve as a reference for theoretical and experimental studies on the effect of the microenvironment on the flavin cofactor. Furthermore, the molar absorption coefficient of FAD at 1547 cm⁻¹ was determined to 2200 L mol⁻¹ cm⁻¹ with an integral absorption coefficient of ∼50,000 L mol⁻¹ cm⁻². These values are prerequisite for the determination of reaction yields in flavoproteins from reaction-induced difference spectra.     

Imaging Non-Local Magnetization Dynamics

Many fundamental processes in magnetism take place on a nanometer length and sub-picosecond time scale. An important example of such phenomena in magnetism is ultrafast, spin-polarized transport of laser-excited hot electrons, which is now being recognized as playing a crucial role for novel spintronic devices and for optically induced magnetic switching. Recent experimental examples include the demonstration of all-optical helicity dependent control of spin-polarized currents at interfaces [1 T.J. Huisman, Nature Nanotechn., doi:10.1038/nnano.2015.331 (2016).[Crossref] , [Google Scholar]], the design of novel and efficient terahertz emitters [2 T. Seifert, arXiv:1510.03729 (2015). [Google Scholar]], and nanoscale spin reversal in chemically heterogeneous GdFeCo driven by non-local transfer of angular momentum [3 C.E. Graves, Nat. Mater. 12, 293–298 (2013).[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]. In particular, for advanced information technologies with bit densities already exceeding 1 terabit per square inch with bit cell dimensions of (15 × 38 nm²) [4 R. Wood, IEEE Transaction on Magnetics 38, 1711 (2000).[Crossref], [Web of Science ®] , [Google Scholar]], it is of fundamental importance to understand and eventually control the mechanisms responsible for optically induced spin dynamics on the nanoscale.     

Probing FtsZ and tubulin with C8-substituted GTP analogs reveals differences in their nucleotide binding sites

The cytoskeletal proteins, FtsZ and tubulin, play a pivotal role in prokaryotic cell division and eukaryotic chromosome segregation, respectively. Selective inhibitors of the GTP-dependent polymerization of FtsZ could constitute a new class of antibiotics, while several inhibitors of tubulin are widely used in antiproliferative therapy. In this work, we set out to identify selective inhibitors of FtsZ based on the structure of its natural ligand, GTP. We found that GTP analogs with small hydrophobic substituents at C8 of the nucleobase efficiently inhibit FtsZ polymerization, whereas they have an opposite effect on the polymerization of tubulin. The inhibitory activity of the GTP analogs on FtsZ polymerization allowed us to crystallize FtsZ in complex with C8-morpholino-GTP, revealing the binding mode of a GTP derivative containing a nonmodified triphosphate chain.     

Nucleophilic catalysis of hydrazone formation and transimination: implications for dynamic covalent chemistry

Aniline accelerates hydrazone formation and transimination through nucleophilic catalysis. To demonstrate the method, unprotected peptides are reacted and then scrambled using a hydrazone reaction under conditions relevant for biological applications. The strong enhancement in the rate of hydrazone equilibration broadens the scope of this stable imine in the field of dynamic covalent chemistry.