52 research outputs found
Localization Game on Geometric and Planar Graphs
The main topic of this paper is motivated by a localization problem in cellular networks. Given a graph G we want to localize a walking agent by checking his distance to as few vertices as possible. The model we introduce is based on a pursuit graph game that resembles the famous Cops and Robbers game. It can be considered as a game theoretic variant of the metric dimension of a graph. We provide upper bounds on the related graph invariant ζ(G), defined as the least number of cops needed to localize the robber on a graph G, for several classes of graphs (trees, bipartite graphs, etc). Our main result is that, surprisingly, there exists planar graphs of treewidth 2 and unbounded ζ(G). On a positive side, we prove that ζ(G) is bounded by the pathwidth of G. We then show that the algorithmic problem of determining ζ(G) is NP-hard in graphs with diameter at most 2. Finally, we show that at most one cop can approximate (arbitrary close) the location of the robber in the Euclidean plane
Double bubbles: a new structural motif for enhanced electron-hole separation in solids
Electron–hole separation for novel composite systems comprised of secondary building units formed
from different compounds is investigated with the aim of finding suitable materials for photocatalysis.
Pure and mixed SOD and LTA superlattices of (ZnO)12 and (GaN)12, single-shell bubbles are constructed
as well as core@shell single component frameworks composed of larger (ZnO)48 and (GaN)48 bubbles
with each containing one smaller bubble. Enthalpies of formation for all systems are comparable with
fullerenes. Hole and electron separation is achieved most efficiently by the edge sharing framework
composed of (GaN)12@(ZnO)48 double bubbles, with the hole localised on the nitrogen within the smaller
bubbles and the excited electron on zinc within the larger cages
The James Webb Space Telescope Mission
Twenty-six years ago a small committee report, building on earlier studies,
expounded a compelling and poetic vision for the future of astronomy, calling
for an infrared-optimized space telescope with an aperture of at least .
With the support of their governments in the US, Europe, and Canada, 20,000
people realized that vision as the James Webb Space Telescope. A
generation of astronomers will celebrate their accomplishments for the life of
the mission, potentially as long as 20 years, and beyond. This report and the
scientific discoveries that follow are extended thank-you notes to the 20,000
team members. The telescope is working perfectly, with much better image
quality than expected. In this and accompanying papers, we give a brief
history, describe the observatory, outline its objectives and current observing
program, and discuss the inventions and people who made it possible. We cite
detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space
Telescope Overview, 29 pages, 4 figure
Studies on the Kinetics of Doxazosin Degradation in Simulated Environmental Conditions and Selected Advanced Oxidation Processes
The photochemical behavior of doxazosin (DOX) in simulated environmental conditions using natural waters taken from local rivers as a solvent was studied. The chemical characteristics of applied waters was done and a correlation analysis was used to explain the impact of individual parameters of matrix on the rate of the DOX degradation. It was stated that DOX is a photoliable compound in an aqueous environment. Its degradation is promoted by basic medium, presence of environmentally important ions such as Cl−, NO3−, SO42− and organic matter. The kinetics of DOX reactions with OH− and SO4− radicals were examined individually. The UV/H2O2, classical Fenton and photo-Fenton processes, were applied for the generation of hydroxyl radicals while the UV/VIS:Fe2(SO4)3:Na2SO2 system was employed for production of SO4− radicals. The obtained results pointed that photo-Fenton, as well as UV/VIS:Fe2(SO4)3:Na2SO2, are very reactive in ratio to DOX, leading to its complete degradation in a short time. A quantitative density functional theory (DFT) mechanistic study was carried out in order to explain the molecular mechanism of DOX degradation using the GAUSSIAN 09 program
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