Lack of cooperation (free riding) is one of the key problems that confronts today's P2P systems. What makes this problem particularly difficult is the unique set of challenges that P2P systems pose: large populations, high turnover, a symmetry of interest, collusion, zero-cost identities, and traitors. To tackle these challenges we model the P2P system using the Generalized Prisoner's Dilemma (GPD),and propose the Reciprocative decision function as the basis of a family of incentives techniques. These techniques are fullydistributed and include: discriminating server selection, maxflow-based subjective reputation, and adaptive stranger policies. Through simulation, we show that these techniques can drive a system of strategic users to nearly optimal levels of cooperation.
We report the first measurements of the spectrally resolved absolute internal luminescence quantum efficiency and surface recombination velocity of an InGaN-GaN multiquantum well (MQW) structures. The absolute external quantum efficiency is measured by referencing the measured photoluminescence (PL) from the sample with the reading measured from the laser off of the perfect 100% white lambertian reflector.
No abstract is provided for this article.
Abstract Aus der Reaktion von Tetraäthylammonium hydroxid mit HF und anschließendem raschen Trocknen wird das Tetraäthylammoniuni fluorid‐Pentahydrat gewonnen.
Abstract : Several results in the area of complex dynamics of arrays of nonlinear dynamical systems have been obtained, including sufficient conditions for synchronization, estimates of dimensional characteristics of 2D patterns, effects of sidewall forcing on Turning patterns and bifurcation scenarios of nonautonomous chaotic circuits. A CNN universal machine cell was designed in VLSI technology. Several image enhancement, filtering and compression CNN algorithms were developed. Several mathematical problems and models were implemented on the CNN architecture, including the Navier-Stokes equations, mathematical morphological operators, cellular automata, models of population dynamics, models of pattern formation and models of optical illusions.
Aminierung nur an einer Stelle: Die palladiumkatalysierte Umsetzung von Hydrazin- und Hydroxylaminderivaten mit Dienen und Allylestern verläuft mit einer Vielzahl an Palladiumliganden unter C-N-Bindungsbildung an der höher substituierten Position der Allylzwischenstufe (siehe Schema; X=NCPh2 oder OR; Ac=Acetyl). Diese Reaktionen eröffnen einen Zugang zu hoch substituierten primären Aminen durch einfache N-O- und N-N-Bindungsspaltung. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2007/z701899_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.
Zinc is an essential metal ion for human growth and development, the disruption of cellular Zn 2+ homeostasis being implicated in several major disorders including Alzheimer's disease, diabetes, and cancer. The molecular mechanisms of Zn 2+ physiology and pathology are insufficiently understood, however, owing in part to the lack of tools for measuring changes in intracellular Zn 2+ concentrations with high spatial and temporal fidelity. To address this critical need, we have synthesized, characterized, and applied an intracellular fluorescent probe for the ratiometric imaging of Zn 2+ based on a tautomeric seminaphthofluorescein platform. Zin-naphthopyr 1 (ZNP1) affords single-excitation, dual-emission ratiometric detection of intracellular Zn 2+ through Zn 2+ -controlled switching between fluorescein and naphthofluorescein tautomeric forms. The probe features visible excitation and emission profiles, excellent selectivity responses for Zn 2+ over competing Ca 2+ and Mg 2+ ions at intracellular concentrations, a dissociation constant ( K d ) for Zn 2+ of <1 nM, and an 18-fold increase in fluorescence emission intensity ratio (λ 624 /λ 528 ) upon zinc binding. We demonstrate the value of the ZNP1 platform for biological applications by imaging changes in intracellular [Zn 2+ ] in living mammalian cells. Included is the ratiometric detection of endogenous pools of intracellular Zn 2+ after NO-induced release of Zn 2+ from cellular metalloproteins. We anticipate that ZNP1 and related probes should find utility for interrogating the biology of Zn 2+ .
The relative rates of the migratory insertions of alkenes into the M-X bonds of (PMe(3))(2)Rh(eta(2)-CH(2) horizontal lineCHR)(X) (R = H, Me; X = CH(3), NH(2), OH) have been analyzed by DFT calculations. These insertions are computed to form metallacycles containing a metal-carbon bond and either an agostic interaction, a dative metal-nitrogen bond, or a dative metal-oxygen bond. The computed barriers for migratory insertion into the metal-hydroxo and metal-amido bonds are lower than those for insertion into the metal-methyl bond. Application of Bader's atoms-in-molecules analysis and natural localized molecular orbital analysis implies that the barriers for alkene insertion into M-X bonds are controlled by the degree of M-X bonding in the transition state, which correlates with the degree of M-X bonding in the initial product. The Rh-X bond orders in the transition states for migratory insertion of ethylene into the Rh-NH(2) and Rh-OH bonds in (PH(3))(2)Rh(eta(2)-C(2)H(4))(NH(2)) and (PH(3))(2)Rh(eta(2)-C(2)H(4))(OH) are much larger than that in the transition state for insertion into the Rh-C bond of (PH(3))(2)Rh(eta(2)-C(2)H(4))(CH(3)). The free energy barriers for 1,2- and 2,1-insertions of propene into the rhodium complexes were also calculated, and the barrier for 1,2-insertion was found to be lower than that for 2,1-insertion. Most striking, the DeltaDeltaG(double dagger) values for 1,2- versus 2,1-insertion of propene into these rhodium complexes were calculated to increase in the order X = CH(3) < NH(2) < OH. The increasing stability of the 1,2-insertion product with increasing polarity of the C-X bonds parallels the relative stabilities of linear versus branched alkanes, amines, and alcohols.
Differentially pumped X-ray photoelectron spectroscopy has been used to study the surface composition of sulfuric acid (H2SO4) and sulfuric acid/water mixtures in equilibrium with various atmospheric species. Nitric acid uptake in sulfuric acid solutions was observed below ≈ 220K. Compared to the theoretically predicted bulk composition, a significant enrichment of nitrogen was observed at the interface. The uptake of background water in sulfuric acid below 200 K was responsible for the reversible uptake of CO2, moderated through the formation of carbonic acid (H2CO3). For CH2O, Cl2, NO, and NO2, no observable surface species were observed over the temperature range studied (≈180−298 K).
