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排序方式: 共有79条查询结果,搜索用时 265 毫秒
61.
Colm óDúnlaing Chee K Yap 《Journal of Algorithms in Cognition, Informatics and Logic》1985,6(1):104-111
A new approach to certain motion-planning problems in robotics is introduced. This approach is based on the use of a generalized Voronoi diagram, and reduces the search for a collision-free continuous motion to a search for a connected path along the edges of such a diagram. This approach yields an O(n log n) algorithm for planning an obstacle-avoiding motion of a single circular disc amid polygonal obstacles. Later papers will show that extensions of the approach can solve other motion-planning problems, including those of moving a straight line segment or several coordinated discs in the plane amid polygonal obstacles. 相似文献
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We present an analysis of the mean-field kinetics of Brownian coagulation of droplets and polymers driven by input of monomers which aims to characterize the long time behavior of the cluster size distribution as a function of the inverse fractal dimension, a, of the aggregates. We find that two types of long time behavior are possible. For 0≤a<1/2 the size distribution reaches a stationary state with a power law distribution of cluster sizes having exponent 3/2. The amplitude of this stationary state is determined exactly as a function of a. For 1/2相似文献
64.
Lahav M Durkan C Gabai R Katz E Willner I Welland ME 《Angewandte Chemie (International ed. in English)》2001,40(21):4095-4097
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Colm P. McMahon Sarah J. Killoran Robert D. ONeill 《Journal of Electroanalytical Chemistry》2005,580(2):193-202
The glucose sensitivity and oxygen dependence of a variety of implantable biosensors based on glucose oxidase (GOx), incorporating an electrosynthesized poly-o-phenylenediamine (PPD) permselective barrier on 125-μm diameter Pt disks (PtD) and cylinders (PtC, 1-mm length), were measured and compared. Full glucose calibrations and experimental monitoring of solution oxygen concentration allowed us to determine apparent Michaelis–Menten parameters for glucose and oxygen. In the linear region of glucose response, the most sensitive biosensor design studied was PtD/PPD/GOx (enzyme deposited over polymer) that was 20 times more sensitive than the more widely used PtC/GOx/PPD (enzyme immobilized before polymer deposition) configuration. The oxygen dependence, quantified as KM(O2), of both active and less active designs was surprisingly similar, a finding that could be rationalized in terms of an increase in KM(G) with increased enzyme loading. The PtD/PPD/GOx design will now enable us to explore glucose concentration dynamics in smaller and layered brain regions with good sensitivity and minimal interference from fluctuations in tissue pO2. 相似文献
66.
L. Avaldi R. Camilloni P. Letardi G. Stefani I. E. McCarthy X. Zhang H. R. J. Walters Colm T. Whelan 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1992,23(4):341-345
Absolute triple differential cross sections for the ionisation of He by electrons with energies near 300 eV have been measured in asymmetric conditions. The kinematics of the experiment select ionising events which belong to the intermediate regime of energy and momentum transfer. The experiments are compared with the distorted wave Born approximation. 相似文献
67.
Mallon CT McNally A Keyes TE Forster RJ 《Journal of the American Chemical Society》2008,130(30):10002-10007
Molecular junctions incorporating monolayers of surface-active cyclodextrins have been formed by bringing macroscopic platinum and mercury electrodes together. Monolayers of the host di-6A,6B-deoxy-6-(4-pyridylmethyl)amino-gamma-cyclodextrin (CD) have been formed on platinum electrodes and backfilled with 1-nonanethiol. Significantly, the tunneling current for bilayer junctions in which the mercury surface is modified with a C16 alkane thiol depends markedly on the nature of the CD guest. Junctions where nonconjugated guests, such as adamantane, are included in the CD show an order of magnitude lower current than junctions incorporating the conjugated guest C60. Moreover, monolayer junctions of CD backfilled with 1-nonanethiol exhibit potential-dependent currents in the presence of CD guest molecule [Co(biptpy)2](2+) but not for [Co(tpy)2](2+), which is structurally analogous but cannot associate with CD. Significantly, unlike bilayer systems, when only one electrode is modified, mechanical pressure is required to form a stable tunneling junction and these junctions cannot be formed and separated reversibly. 相似文献
68.
Fiona O'Sullivan Tara Raftery Michiel van Weele Jos van Geffen Deirdre McNamara Colm O'Morain Nasir Mahmud Dervla Kelly Martin Healy Maria O'Sullivan Lina Zgaga 《Photochemistry and photobiology》2019,95(4):1060-1067
Sunshine is considered to be the most important source of vitamin D. Due to an increased risk of skin cancer, sun avoidance is advised, but this directly contributes to the high prevalence of vitamin D deficiency. The simple solution is to advise vitamin D supplementation. The aim of this study was to examine the absolute and relative contribution of sunshine and supplementation to vitamin status. This study was a secondary analysis of an RCT of 92 Crohn's disease patients in remission (49% female, median age = 44). Participants were randomized to 2000 IU day?1 of vitamin D3 or placebo for 1 year, with 25‐hydroxyvitamin D (25(OH)D) being measured at baseline and every 4 months. Based on participant's place of residence, daily ambient UVB dose at wavelengths that can induce vitamin D synthesis (D‐UVB) was obtained. Cumulative and weighted ambient D‐UVB (cw‐D‐UVB) exposure prior to each blood draw was calculated for each participant. Linear regression analysis and multilevel modeling were used to examine the association between UVB exposure, supplementation and 25(OH)D concentration. There was considerable annual variation in D‐UVB, cw‐D‐UVB and 25(OH)D. Both supplementation and cw‐D‐UVB were found to be strongly associated with 25(OH)D: in multilevel model, an increase of approximately 6 nmol L?1 for every 100 kJ m?2 in cw‐D‐UVB was found, among those receiving placebo and supplementation (P < 0.0001). Treatment was associated with increase of 23 nmol L?1 (P < 0.0001). Sunshine is an important determinant of 25(OH)D concentration, even in those who are taking high‐dose vitamin D supplements and reside at a higher mid‐latitude location. 相似文献
69.
Highly Efficient Triplet Photosensitizers: A Systematic Approach to the Application of IrIII Complexes containing Extended Phenanthrolines
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Yue Lu Dr. Niamh McGoldrick Dr. Frances Murphy Dr. Brendan Twamley Xiaoneng Cui Dr. Colm Delaney Dr. Gearóid M. Ó Máille Junsi Wang Prof. Dr. Jianzhang Zhao Prof. Dr. Sylvia M. Draper 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(32):11349-11356
A series of IrIII complexes, based on 1,10‐phenanthroline featuring aryl acetylene chromophores, were prepared and investigated as triplet photosensitizers. The complexes were synthesized by Sonogashira cross‐coupling reactions using a “chemistry‐on‐the‐complex” method. The absorption properties and luminescence lifetimes were successfully tuned by controlling the number and type of light‐harvesting group. Intense UV/Vis absorption was observed for the IrIII complexes with two light‐harvesting groups at the 3‐ and 8‐positions of the phenanthroline. The asymmetric IrIII complex (with a triphenylamine (TPA) and a pyrene moiety attached) exhibited the longest lifetime. Red emission was observed for all the complexes in deaerated solutions at room temperature. Their emission at low temperature (77 K) and nanosecond time‐resolved transient difference absorption spectra revealed the origin of their triplet excited states. The singlet‐oxygen (1O2) sensitization and triplet‐triplet annihilation (TTA)‐based upconversion were explored. Highly efficient TTA upconversion (ΦUC=28.1 %) and 1O2 sensitization (ΦΔ=97.0 %) were achieved for the asymmetric IrIII complex, which showed intense absorption in the visible region (λabs=482 nm, ?=50900 m ?1 cm?1) and had a long‐lived triplet excited state (53.3 μs at RT). 相似文献
70.