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101.
102.
A repairman makes a round-trip along a set of customers. He starts in his home location, visits each customer exactly once, and returns home. The cost of his trip has to be shared by the customers. A cooperative cost game, calledrouting game, is associated with this allocation problem, and anO(n 2) algorithm is given which computes a core element of a routing game if the core is non-empty. The non-emptiness of the core depends on the tour which is traversed by the repairman. Several procedures are given to construct tours which guarantee the non-emptiness of the core. 相似文献
103.
Lee James W. Mets Laurens Greenbaum Elias 《Applied biochemistry and biotechnology》2002,98(1-9):37-48
At elevated light intensities (greater than ∼200 μE/[m2·s]), the kinetic imbalance between the rate of photon excitation and thermally activated electron transport results in saturation
of the rate of photosynthesis. Since maximum terrestrial solar radiation can reach 200 μE/(m2·s), a significant opportunity exists to improve photosynthetic efficiency at elevated light intensities by achieving a kinetic
balance between photon excitation and electron transport, especially in designed large-scale photosynthetic reactors in which
a low-cost and efficient biomass production system is desired. One such strategy is a reduction in chlorophyll (chl) antenna
size in relation to the reaction center that it serves. In this article, we report recent progress in this area of research.
Light-saturation studies for CO2 fixation were performed on an antenna-deficient mutant of Chlamydomonas (DS521) and the wild type (DES15) with 700 ppm of CO2 in air. The light-saturated rate for CO2 assimilation in the mutant DS521 was about two times higher (187 μmol/[h·mg of chl]) than that of the wild type, DES15 (95
μmol/[h·mg of chl]). Significantly, a partial linearization of the light-saturation curve was also observed. These results
confirmed that DS521 has a smaller relative chl antenna size and demonstrated that reduction of relative antenna size can
improve the overall efficiency of photon utilization at higher light intensities. The antenna-deficient mutant DS521 can provide
significant resistance to photoinhibition, in addition to improvement in the overall efficiency of CO2 fixation at high light. The experimental data reported herein support the idea that reduction in chl antenna size could have
significant implications for both fundamental understanding of photosynthesis and potential application to improve photosynthetic
CO2 fixation efficiency.
The article was authored by a contractor of the U.S. government under contract no. DE-AC05-00OR22725. Accordingly, the U.S.
government retains a nonexclusive, royaltyfree license to publish or reproduce the published form of this contribution, or
allow others to do so, for U.S. government purposes. 相似文献
104.
Vallée RA Tomczak N Vancso GJ Kuipers L van Hulst NF 《The Journal of chemical physics》2005,122(11):114704
We investigated the nanometer scale mobility of polymers in the glassy state by monitoring the dynamics of embedded single fluorophores. Recently we reported on fluorescence lifetime fluctuations which reflect the segmental rearrangement dynamics of the polymer in the surroundings of the single molecule probe. Here we focus on the nature of these fluorescence lifetime fluctuations. First the potential role of quenching and molecular conformational changes is discussed. Next we concentrate on the influence of the radiative density of states on the spontaneous emission of individual dye molecules embedded in a polymer. To this end we present a theory connecting the effective-medium theory to a cell-hole model, originating from the Simha-Somcynsky free-volume theory. The relation between the derived distributions of free volume and fluorescence lifetime allows one to determine the number of segments involved in the local rearrangement directly from experimental data. Results for two different polymers as a function of temperature are presented. 相似文献
105.
Bert Vreman Bernard J. Geurts N. G. Deen J. A. M. Kuipers J. G. M. Kuerten 《Flow, Turbulence and Combustion》2009,82(1):47-71
Large-eddy simulations (LES) of a vertical turbulent channel flow laden with a very large number of solid particles are performed.
The motivation for this research is to get insight into fundamental aspects of co-current turbulent gas-particle flows, as
encountered in riser reactors. The particle volume fraction equals about 1.3%, which is relatively high in the context of
modern LES of two-phase flows. The channel flow simulations are based on large-eddy approximations of the compressible Navier–Stokes
equations in a porous medium. The Euler–Lagrangian method is adopted, which means that for each individual particle an equation
of motion is solved. The method incorporates four-way coupling, i.e., both the particle-fluid and particle–particle interactions
are taken into account. The results are compared to single-phase channel flow in order to investigate the effect of the particles
on turbulent statistics. The present results show that due to particle–fluid interactions the mean fluid profile is flattened
and the boundary layer is thinner. Compared to single-phase turbulent flow, the streamwise turbulence intensity of the gas
phase is increased, while the normal and spanwise turbulence intensities are reduced. This finding is generally consistent
with existing experimental data. The four-way coupled simulations are also compared with two-way coupled simulations, in which
the inelastic collisions between particles are neglected. The latter comparison clearly demonstrates that the collisions have
a large influence on the main statistics of both phases. In addition, the four-way coupled simulations contain stronger coherent
particle structures. It is thus essential to include the particle–particle interactions in numerical simulations of two-phase
flow with volume fractions around one percent. 相似文献
106.
Anderson C Antonello M Baller B Bolton T Bromberg C Cavanna F Church E Edmunds D Ereditato A Farooq S Fleming B Greenlee H Guenette R Haug S Horton-Smith G James C Klein E Lang K Laurens P Linden S McKee D Mehdiyev R Page B Palamara O Partyka K Patch A Rameika G Rebel B Rossi B Soderberg M Spitz J Szelc AM Weber M Yang T Zeller G;ArgoNeuT Collaboration 《Physical review letters》2012,108(16):161802
The ArgoNeuT Collaboration presents the first measurements of inclusive muon neutrino charged current differential cross sections on argon. Obtained in the NuMI neutrino beam line at Fermilab, the flux-integrated results are reported in terms of outgoing muon angle and momentum. The data are consistent with the Monte Carlo expectation across the full range of kinematics sampled, 0°<θ(μ)<36° and 0
相似文献
107.
Quist PA Beek WJ Wienk MM Janssen RA Savenije TJ Siebbeles LD 《The journal of physical chemistry. B》2006,110(21):10315-10321
The photogeneration and decay of charge carriers in blend films of ZnO nanoparticles (diameter 5 nm) and poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) or poly(3-hexylthiophene) (P3HT) were studied by means of microwave-photoconductance measurements. Excitation of the polymer in the visible spectrum was found to lead to a transient photoconductance due to dissociation of excitons at the interface between ZnO and the conjugated polymer. From the similar decay kinetics of the photoconductance and the effects of UV illumination, it is concluded that the measured photoconductance is due to electrons in ZnO. Increasing the weight fraction of ZnO in the blend films leads to a higher photoconductance. This is attributed to enhanced formation of mobile electrons by interfacial dissociation of excitons at clusters of ZnO nanoparticles rather than at individual nanoparticles. The dependence of the photoconductance on the weight fraction of ZnO is found to be different for ZnO:MDMO-PPV and ZnO:P3HT blends. This is most likely due to the presence of a smaller number of relatively large ZnO clusters in ZnO:P3HT blends and a shorter exciton diffusion length, as compared with ZnO:MDMO-PPV blends. After exposure of the blend films to UV light, a significant increase in the magnitude and the lifetime of the photoconductance is observed. This is explained in terms of the filling of electron traps in ZnO by UV exposure. 相似文献
108.
Rönnburg KE Mohler E Roskos HG Ortner K Becker CR Molenkamp LW 《Physical review letters》2006,96(11):117203
Time-resolved optical spin-quantum-beat measurements performed on magnetically doped II-VI bulk semiconductors reveal an increase of the electron spin dephasing time with rising temperature typical for motional narrowing. With the dephasing being notably faster than in undoped II-VI semiconductors, the magnetic dopants must play a key role, modifying the known dephasing mechanisms and introducing new ones. Focusing on the latter, we theoretically explore the spin dephasing channel arising from magnetization fluctuations sampled by the itinerant excitons. This mechanism suffices to explain quantitatively the results of our time-resolved Faraday-rotation experiments on optically excited Cd(1-x)Mn(x)Te which we present here as a function of magnetic field, temperature and manganese dopant density. In addition to electron spin-quantum beats, some of our experiments reveal hole spin beats as well. 相似文献
109.
We identify a route towards achieving a negative index of refraction at optical frequencies based on coupling between plasmonic waveguides that support backwards waves. We show how modal symmetry can be exploited in metal-dielectric waveguide pairs to achieve negative refraction of both phase and energy. Control of waveguide coupling yields a metamaterial consisting of a one-dimensional multilayer stack that exhibits an isotropic index of -1 at a free-space wavelength of 400?nm. The concepts developed here may inspire new low-loss metamaterial designs operating close to the metal plasma frequency. 相似文献
110.
Laurens D. B. Mandemaker Miguel Rivera-Torrente Dr. Robert Geitner Carolien M. Vis Prof. Dr. Bert M. Weckhuysen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(44):19713-19720
Surface-mounted metal–organic frameworks (SURMOFs) show promising behavior for a manifold of applications. As MOF thin films are often unsuitable for conventional characterization techniques, understanding their advantageous properties over their bulk counterparts presents a great analytical challenge. In this work, we demonstrate that MOFs can be grown on calcium fluoride (CaF2) windows after proper functionalization. As CaF2 is optically (in the IR and UV/Vis range of the spectrum) transparent, this makes it possible to study SURMOFs using conventional spectroscopic tools typically used during catalysis or gas sorption. Hence, we have measured HKUST-1 during the adsorption of CO and NO. We show that no copper oxide impurities are observed and also confirm that SURMOFs grown by a layer-by-layer (LbL) approach possess Cu+ species in paddlewheel confirmation, but 1.9 times less than in bulk HKUST-1. The developed methodology paves the way for studying the interaction of any adsorbed gases with thin films, not limited to MOFs, low temperatures, or these specific probe molecules, pushing the boundaries of our current understanding of functional porous materials. 相似文献