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Nitrogen-doped perovskite type materials, Sr2Nb2O7−xNx (0, 1.5 < x < 2.8), have been studied as visible light-active photocatalysts for hydrogen production from methanol–water mixtures. Nitrogen doping in Sr2Nb2O7 red-shifted the light absorption edge into the visible light range and induced visible light photocatalytic activity. There existed an optimum amount of nitrogen doping that showed the maximum rate of hydrogen production. Among the potential variables that might cause this activity variation, the crystal structure appeared to be the most important. Thus, as the extent of N-doping increased, the original orthorhombic structure of the layered perovskite was transformed into an unlayered cubic oxynitride structure. The most active catalytic phase was an intermediate phase still maintaining the original layered perovskite structure, but with a part of its oxygen replaced by nitrogen and oxygen vacancy to adjust the charge difference between oxygen and doped nitrogen. These experimental observations were explained by density functional theory calculations. Thus, in Sr2Nb2O7−xNx, N 2p orbital was the main contributor to the top of the valence band, causing band gap narrowing while the bottom of conduction band due to Nb 4d orbital remained almost unchanged.

We investigated the influence of stand density [938 tree ha−1 for high stand density (HD), 600 tree ha−1 for medium stand density (MD), and 375 tree ha−1 for low stand density (LD)] on soil CO2 efflux (R S) in a 70-year-old natural Pinus densiflora S. et Z. forest in central Korea. Concurrent with R S measurements, we measured litterfall, total belowground carbon allocation (TBCA), leaf area index (LAI), soil temperature (ST), soil water content (SWC), and soil nitrogen (N) concentration over a 2-year period. The R S (t C ha−1 year−1) and leaf litterfall (t C ha−1 year−1) values varied with stand density: 6.21 and 2.03 for HD, 7.45 and 2.37 for MD, and 6.96 and 2.23 for LD, respectively. In addition, R S was correlated with ST (R 2 = 0.77–0.80, P

A recyclable gold catalyst is synthesized from readily available reagents by immobilizing gold nanoparticles in aluminum oxyhydroxide support through a simple sol–gel method. The catalyst showed the high activity even at room temperature in the aerobic oxidation of various alcohols and in the coupling reaction between primary alcohols and ketones.

We consider a variant of two-point Euclidean shortest path query problem: given a polygonal domain, build a data structure for two-point shortest path query, provided that query points always lie on the boundary of the domain. As a main result, we show that a logarithmic-time query for shortest paths between boundary points can be performed using O~ (n^5) preprocessing time and O(n^5) space where n is the number of corners of the polygonal domain and the O~ notation suppresses the polylogarithmic factor. This is realized by observing a connection between Davenport-Schinzel sequences and our problem in the parameterized space. We also provide a tradeoff between space and query time; a sublinear time query is possible using O(n^{3+epsilon}) space. Our approach also extends to the case where query points should lie on a given set of line segments., Comment: 12 pages, 3 figures, an extended abstract presented at ISAAC 2009

The aperture angle alpha(x, Q) of a point x not in Q in the plane with respect to a convex polygon Q is the angle of the smallest cone with apex x that contains Q. The aperture angle approximation error of a compact convex set C in the plane with respect to an inscribed convex polygon Q of C is the minimum aperture angle of any x in C Q with respect to Q. We show that for any compact convex set C in the plane and any k > 2, there is an inscribed convex k-gon Q of C with aperture angle approximation error (1 - 2/(k+1)) pi. This bound is optimal, and settles a conjecture by Fekete from the early 1990s. The same proof technique can be used to prove a conjecture by Brass: If a polygon P admits no approximation by a sub-k-gon (the convex hull of k vertices of P) with Hausdorff distance sigma, but all subpolygons of P (the convex hull of some vertices of P) admit such an approximation, then P is a (k+1)-gon. This implies the following result: For any k > 2 and any convex polygon P of perimeter at most 1 there is a sub-k-gon Q of P such that the Hausdorff-distance of P and Q is at most 1/(k+1) * sin(pi/(k+1))., Fixed incorrect affiliation

The nanofibrous ammonium titanate (NH4)2Ti3O7−xNx was hydrothermally synthesized by a new method proposed here from titanium oxysulfate precursor in a NH4OH solution under hydrothermal conditions a...

Nickel-loaded La2Ti2O7, one of the highly donor-doped (110) layered perovskite materials, has been found to be an efficient photocatalyst for simultaneous H2 production from water splitting and decomposition of tetramethylammonium hydroxide (TMAH) under UV irradiation.

Nanostructured cubic SrTiO3 particles were hydrothermally synthesized and studied experimentally/theoretically for photoreduction of water. The particles were doped with metal atoms (M=Ru,Rh,Ir,Pt,Pd), which acquired high cyrstallinity after thermal treatment. SrTiO3:Rh showed the highest rate of H2 evolution under λ>420nm photons. The density functional theory calculations of SrTixM1−xO3 (M=Ru,Rh,Ir,Pt) implied that the photocatalytic activity of SrTixRh1−xO3 was due to its suitable band energetics, and the induced hybridized Ti∕Rh orbitals in the bandgap of SrTiO3.

The accessory bones of the foot, such as the os tibiale externum, os trigonum and os peroneum are common, but the os intermetatarseum is less known. We operated on a soccer player who had symptomatic os intermetatarseum of both feet, and who achieved a good result through excision of the accessary bone. We report upon this case and review the literature.

For two points $p$ and $q$ in the plane, a straight line $h$, called a highway, and a real $v>1$, we define the \emph{travel time} (also known as the \emph{city distance}) from $p$ and $q$ to be the time needed to traverse a quickest path from $p$ to $q$, where the distance is measured with speed $v$ on $h$ and with speed 1 in the underlying metric elsewhere. Given a set $S$ of $n$ points in the plane and a highway speed $v$, we consider the problem of finding a \emph{highway} that minimizes the maximum travel time over all pairs of points in $S$. If the orientation of the highway is fixed, the optimal highway can be computed in linear time, both for the $L_1$- and the Euclidean metric as the underlying metric. If arbitrary orientations are allowed, then the optimal highway can be computed in $O(n^{2} \log n)$ time. We also consider the problem of computing an optimal pair of highways, one being horizontal, one vertical., 13 pages, 9 figures, preliminary version appeared at CATS'07

Graph product structure theory expresses certain graphs as subgraphs of the strong product of much simpler graphs. In particular, an elegant formulation for the corresponding structural theorems involves the strong product of a path and of a bounded treewidth graph, and allows to lift combinatorial results for bounded treewidth graphs to graph classes for which the product structure holds, such as to planar graphs [Dujmović et al., J. ACM, 67(4), 22:1-38, 2020]. In this paper, we join the search for extensions of this powerful tool beyond planarity by considering the h-framed graphs, a graph class that includes 1-planar, optimal 2-planar, and k-map graphs (for appropriate values of h). We establish a graph product structure theorem for h-framed graphs stating that the graphs in this class are subgraphs of the strong product of a path, of a planar graph of treewidth at most 3, and of a clique of size 3⌊ h/2 ⌋+⌊ h/3 ⌋-1. This allows us to improve over the previous structural theorems for 1-planar and k-map graphs. Our results constitute significant progress over the previous bounds on the queue number, non-repetitive chromatic number, and p-centered chromatic number of these graph classes, e.g., we lower the currently best upper bound on the queue number of 1-planar graphs and k-map graphs from 115 to 82 and from ⌊ 33/2(k+3 ⌊ k/2⌋ -3)⌋ to ⌊ 33/2 (3⌊ k/2 ⌋+⌊ k/3 ⌋-1) ⌋, respectively. We also employ the product structure machinery to improve the current upper bounds on the twin-width of 1-planar graphs from O(1) to 80. All our structural results are constructive and yield efficient algorithms to obtain the corresponding decompositions., LIPIcs, Vol. 248, 33rd International Symposium on Algorithms and Computation (ISAAC 2022), pages 23:1-23:15