Intensity-Dependent Enhancement of Saturable Absorption in PbS-Au4 Nanohybrid Composites: Evidence for Resonant Energy Transfer by Auger Recombination

Intensity-dependent enhancement of saturable absorption in a film of PbS-Au4 nanohybrid composites has been observed by femtosecond time-resolved transient absorption measurement at 780 nm. The nonlinear absorption coefficient of saturable absorption in PbS-Au4 nanohybrid composites is found to be dependent on excitation irradiance and it is determined to be -2.9 cm/GW at 78 GW/cm2, an enhancement of nearly fourfold in comparison with that of pure PbS quantum dots (QDs). The enhancement is attributed to excitation of surface plasmon by resonant energy transfer between PbS QDs and Au nanoparticles through Auger recombination.Comment: 14 pages, 3 figures. Accepted in Appl. Phys. Lett. (2008

Converging an Overlay Network to a Gradient Topology

In this paper, we investigate the topology convergence problem for the gossip-based Gradient overlay network. In an overlay network where each node has a local utility value, a Gradient overlay network is characterized by the properties that each node has a set of neighbors with the same utility value (a similar view) and a set of neighbors containing higher utility values (gradient neighbor set), such that paths of increasing utilities emerge in the network topology. The Gradient overlay network is built using gossiping and a preference function that samples from nodes using a uniform random peer sampling service. We analyze it using tools from matrix analysis, and we prove both the necessary and sufficient conditions for convergence to a complete gradient structure, as well as estimating the convergence time and providing bounds on worst-case convergence time. Finally, we show in simulations the potential of the Gradient overlay, by building a more efficient live-streaming peer-to-peer (P2P) system than one built using uniform random peer sampling.Comment: Submitted to 50th IEEE Conference on Decision and Control (CDC 2011

Rapid changes of precipitation pH in Qinghai Province, the northeastern Tibetan Plateau

Rainfall monitoring programs were conducted in two industrial cities of China's Qinghai Province, Xining and Germu, in some periods of the 1980s and 1990s. The results show that the natural precipitation in this area is originally alkaline. Compared with the late 1980s records, pH values declined significantly from approximately 8 in the 1980s to below 7 in mid-1990s. Such rapid and drastic changes were attributed to fast industrial development that released a large amount of pollutants. Subsequent tough control on pollutant emission partly restored pH values back to above 7 in the late 1990s. The pH and rainfall chemical analyses indicate that alkaline rain in this continental arid region is caused by airborne dusts which originate from local alkaline soils. With decrease of pH value, the total ionic concentration of rainwater is increased because acids were added to the rainwater. © 2002 Elsevier Science B.V. All rights reserved.postprin

Exploring the biochemistry at the extracellular redox frontier of bacterial mineral Fe(III) respiration

Many species of the bacterial Shewanella genus are notable for their ability to respire in anoxic environments utilizing insoluble minerals of Fe(III) and Mn(IV) as extracellular electron acceptors. In Shewanella oneidensis, the process is dependent on the decahaem electron-transport proteins that lie at the extracellular face of the outer membrane where they can contact the insoluble mineral substrates. These extracellular proteins are charged with electrons provided by an inter-membrane electron-transfer pathway that links the extracellular face of the outer membrane with the inner cytoplasmic membrane and thereby intracellular electron sources. In the present paper, we consider the common structural features of two of these outer-membrane decahaem cytochromes, MtrC and MtrF, and bring this together with biochemical, spectroscopic and voltammetric data to identify common and distinct properties of these prototypical members of different clades of the outer-membrane decahaem cytochrome superfamily

Depth, balancing, and limits of the Elo model

-Much work has been devoted to the computational complexity of games. However, they are not necessarily relevant for estimating the complexity in human terms. Therefore, human-centered measures have been proposed, e.g. the depth. This paper discusses the depth of various games, extends it to a continuous measure. We provide new depth results and present tool (given-first-move, pie rule, size extension) for increasing it. We also use these measures for analyzing games and opening moves in Y, NoGo, Killall Go, and the effect of pie rules

Ethyl 5-hy­droxy-6-oxo-4-phenyl-5,6-dihydro-4H-cyclo­penta­[b]thio­phene-5-carboxyl­ate

In the title mol­ecule, C16H14O4S, the dihydro­cyclo­penta­thio­phenone ring system is almost planar, with an r.m.s. deviation of 0.060 Å from the best fit plane through all nine non-H atoms. The cyclo­penta­none ring adopts a severely flattened envelope conformation with the C atom carrying the OH and ethylcarboxylate substituents at the flap. This atom lies only 0.185 (3) Å from the plane through the other four C atoms. The phenyl substituent is inclined at 43.37 (5)° to the dihydro­cyclo­penta­thio­phenone mean plane. In the crystal, mol­ecules are linked by pairs of O—H⋯O hydrogen bonds, forming inversion dimers with R 2 2(10) ring motifs. Weak C—H⋯O hydrogen bonds also link mol­ecules into chains along c, while an approximately orthogonal set of C—H⋯O contacts form chains along b, resulting in layers lying parallel to (100). Inversion dimers also form through weaker R 2 2(12) C—H⋯S contacts, which combine with C—H⋯O contacts to form stacks along b