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Edge Length (edge + length)
Selected AbstractsControlling the Edge Length of Gold Nanoprisms via a Seed-Mediated Approach,ADVANCED FUNCTIONAL MATERIALS, Issue 9 2006E. Millstone Abstract A straightforward method is investigated for controlling and reinitiating the growth of single-crystalline Au nanoprisms. This work is based on seeding methodology, and depends on the slow reduction of metal ions onto the surface of a growing nanoprism. In this manner, we can tailor the edge length of Au nanoprisms between 100 and 300,nm without changing their thickness or crystallinity. Each nanoprism size has been characterized by UV-vis-NIR (NIR: near-IR) spectroscopy, transmission electron microscopy (TEM) techniques, and statistical analysis. Based on this work and existing silver halide crystal-growth theories, a preliminary mechanism is proposed which comments on the interplay between crystal growth and surface chemistry that ultimately dictates the morphology of the resulting nanostructure. [source] Cobalt Nanoskeletons: One-Pot Solution Synthesis of Cubic Cobalt Nanoskeletons (Adv. Mater.ADVANCED MATERIALS, Issue 16 200916/2009) Cubic Co nanoskeletons with an edge length of 100 nm can be prepared by a facile one-step solution method. In work reported on p. 1636 by Ying Ma, Fangli Yuan, Jiannian Yao, and co-workers, CoO nanoparticles of ,10 nm are subjected to self-aggregating, in situ reduction, Ostwald ripening, and facet-selective coordination-assisted etching to form these novel structures, which exhibit excellent magnetic properties. Simple control of the shape can be achieved by altering the reaction time. [source] One-Pot Solution Synthesis of Cubic Cobalt NanoskeletonsADVANCED MATERIALS, Issue 16 2009Xi Wang Cubic Co nanoskeletons with an edge length of 100,nm are prepared by a facile one-pot solution method. The cubic Co nanoskeletons synthesized exhibit excellent magnetic properties and mesopore structures. This work may provide an easy way to control the synthesis of hollow metal nanopolyhedra by introducing an appropriate etching agent into the synthetic process. [source] Near-shortest and K-shortest simple pathsNETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2005W. Matthew Carlyle Abstract We present a new algorithm for enumerating all near-shortest simple (loopless) s - t paths in a graph G = (V, E) with nonnegative edge lengths. Letting n = |V| and m = |E|, the time per path enumerated is O(nS(n, m)) given a user-selected shortest-path subroutine with complexity O(S(n, m)). When coupled with binary search, this algorithm solves the corresponding K -shortest paths problem (KSPR) in O(KnS(n, m)(log n+ log cmax)) time, where cmax is the largest edge length. This time complexity is inferior to some other algorithms, but the space complexity is the best available at O(m). Both algorithms are easy to describe, to implement and to extend to more general classes of graphs. In computational tests on grid and road networks, our best polynomial-time algorithm for KSPR appears to be at least an order of magnitude faster than the best algorithm from the literature. However, we devise a simpler algorithm, with exponential worst-case complexity, that is several orders of magnitude faster yet on those test problems. A minor variant on this algorithm also solves "KSPU," which is analogous to KSPR but with loops allowed. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 46(2), 98,109 2005 [source] Trigonal sodium calcium germanate, Na2.54Ca1.73Ge3O9ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2001Fumito Nishi Single crystals of a new germanate, Na2.54Ca1.73Ge3O9, have been synthesized. The structure has a six-membered ring of GeO4 tetrahedra, which is similar to the rings of the silicate analogue Na2Ca2Si3O9, and both structures contain pseudo-cubic subcells with an edge length of 3.8,Å. The details of the two compounds are slightly different, however. For example, two O atoms are statistically distributed about twofold axes in the title compound, while the silicate analogue has no such O-atom distributions. In addition, the title germanate has an extra partially populated metal site containing 54,(4)% Na, with no equivalent site in the silicate analogue. [source] Facile Synthesis of Gold Octahedra by Direct Reduction of HAuCl4 in an Aqueous SolutionCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2010Weiyang Li Abstract This paper describes a water-based protocol that provides a simple, convenient, and environmentally benign route to the synthesis of Au octahedra. Specifically, we obtained single-crystal Au octahedra (ca.,85,% of the product) with an edge length of 32.4±2.3,nm and singly twinned, truncated bipyramids (ca.,15,%) by reducing HAuCl4 with N -vinyl pyrrolidone in an aqueous solution in the presence of a proper amount of cetyltrimethylammonium chloride (CTAC). Our mechanistic study indicates that the formation of Au octahedra could be explained by oxidative etching, a pathway that has already been validated for the synthesis of nanocrystals for a number of different noble metals. [source] Improved intermolecular force field for molecules containing H, C, N, and O atoms, with application to nucleoside and peptide crystalsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2001Donald E. Williams Abstract A new intermolecular force field for nitrogen atoms in organic molecules was derived from a training dataset of 76 observed azahydrocarbon crystal structures and 11 observed heats of sublimation. The previously published W99 force field for hydrogen, carbon, and oxygen was thus extended to include nitrogen atoms. Nitrogen atoms were divided into four classes: N(1) for triply bonded nitrogen, N(2) for nitrogen with no bonded hydrogen (except the triple bonded case), N(3) for nitrogen with one bonded hydrogen, and N(4) for nitrogen with two or more bonded hydrogens. H(4) designated hydrogen bonded to nitrogen. Wavefunctions of 6-31g** quality were calculated for each molecule and the molecular electric potential (MEP) was modeled with net atomic and supplementary site charges. Lone pair electron charge sites were included for nitrogen atoms where appropriate, and methylene bisector charges were used for CH2 and CH3 groups when fitting the MEP. XH bond distances were set to standard values for the wave function calculation and then foreshortened by 0.1 Å for the MEP and force field fitting. Using the force field optimized to the training dataset, each azahydrocarbon crystal structure was relaxed by intermolecular energy minimization. Predicted maximum changes in unit cell edge lengths for each crystal were 3% or less. The complete force field for H, C, N, and O atoms was tested by intermolecular energy relaxation of nucleoside and peptide molecular crystals. Even though these molecules were not included in any of the training datasets for the force field, agreement with their observed crystal structures was very good, with predicted unit cell edge shifts usually less than 2%. These tests included crystal structures of representatives of all eight common nucleosides found in DNA and RNA, 15 dipeptides, four tripeptides, two tetrapeptides, and a pentapeptide with two molecules in the asymmetric unit. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1154,1166, 2001 [source] Near-shortest and K-shortest simple pathsNETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2005W. Matthew Carlyle Abstract We present a new algorithm for enumerating all near-shortest simple (loopless) s - t paths in a graph G = (V, E) with nonnegative edge lengths. Letting n = |V| and m = |E|, the time per path enumerated is O(nS(n, m)) given a user-selected shortest-path subroutine with complexity O(S(n, m)). When coupled with binary search, this algorithm solves the corresponding K -shortest paths problem (KSPR) in O(KnS(n, m)(log n+ log cmax)) time, where cmax is the largest edge length. This time complexity is inferior to some other algorithms, but the space complexity is the best available at O(m). Both algorithms are easy to describe, to implement and to extend to more general classes of graphs. In computational tests on grid and road networks, our best polynomial-time algorithm for KSPR appears to be at least an order of magnitude faster than the best algorithm from the literature. However, we devise a simpler algorithm, with exponential worst-case complexity, that is several orders of magnitude faster yet on those test problems. A minor variant on this algorithm also solves "KSPU," which is analogous to KSPR but with loops allowed. © 2005 Wiley Periodicals, Inc. NETWORKS, Vol. 46(2), 98,109 2005 [source] Robust location problems with pos/neg weights on a treeNETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2001Rainer E. Burkard Abstract In this paper, we consider different aspects of robust 1-median problems on a tree network with uncertain or dynamically changing edge lengths and vertex weights which can also take negative values. The dynamic nature of a parameter is modeled by a linear function of time. A linear algorithm is designed for the absolute dynamic robust 1-median problem on a tree. The dynamic robust deviation 1-median problem on a tree with n vertices is solved in O(n2 ,(n) log n) time, where ,(n) is the inverse Ackermann function. Examples show that both problems do not possess the vertex optimality property. The uncertainty is modeled by given intervals, in which each parameter can take a value randomly. The absolute robust 1-median problem with interval data, where vertex weights might also be negative, can be solved in linear time. The corresponding deviation problem can be solved in O(n2) time. © 2001 John Wiley & Sons, Inc. [source] | |||||||||||||