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81.
Martin J. Lofthouse Evert Ditzel Andrew J. Poole David J. Cole-Hamilton 《Journal of Cluster Science》2006,17(1):27-45
Reaction of CO with hydrogen in the presence of [Ru3(CO)12], KI and N-methylpyrrolidone produces small amounts of methanol under mild conditions. Using D2 the methanol is CD3OD confirming that it is a product of CO hydrogenation. In the presence of added H2O, CH
x
D1-y
OH/D (y=0–3) are produced. Carrying out the same reaction in the presence of MeI water and RhCl3·xH2O (x=3–4) produces ethanoic acid in a slow reaction which continues for at least 64 h. The effects of different reaction parameters
are discussed and labelling using 13CH3I shows that some of the ethanoic acid originates from sources other than MeI whilst labelling with D2, CD3I, and/or D2O suggest that some originates from CO and H2. Electrospray mass spectrometry and high pressure infra-red spectroscopic studies show that the main species present in catalytic
solutions are [HRu3(CO)11]−, [HRu4(CO)13]− and [Ru(CO)3I3]− for methanol carbonylation, [Ru(CO)3I3]− and [RhI2(CO)2]− for ethanoic acid production. A reaction carried out in the absence of [Ru3(CO)12] gave similar results to a reaction in which it was added, suggesting that the entire process may be catalysed by rhodium
complexes alone.
Electronic Supplementary Material Supplementary material for this article is available at and is accessible for authorized users.
相似文献
David J. Cole-HamiltonEmail: |
82.
This paper studies the connections between relational probabilistic models and reference classes, with specific focus on the ability of these models to generate the correct answers to probabilistic queries. We distinguish between relational models that represent only observed relations and those which additionally represent latent properties of individuals. We show how both types of relational models can be understood in terms of reference classes, and that learning such models correspond to different ways of identifying reference classes. Rather than examining the impact of philosophical issues associated with reference classes on relational learning, we directly assess whether relational models can represent the correct probabilities of a simple generative process for relational data. We show that models with only observed properties and relations can only represent the correct probabilities under restrictive conditions, whilst models that also represent latent properties avoids such restrictions. As such, methods for acquiring latent-property models are an attractive alternatives to traditional ways of identifying reference classes. Our experiments on synthetic as well as real-world domains support the analysis, demonstrating that models with latent relations are significantly more accurate than those without latent relations. 相似文献
83.
J. Liu Z.G. Lu P.J. Poole P.J. Barrios D. Poitras Z. Jiao X.P. Zhang 《Optics Communications》2012,285(6):1323-1325
Optical pulses are generated from a coupled-cavity quantum-dot (QD) laser consisting of a short QD-waveguide Fabry–Perot (F–P) cavity and three long external fiber Bragg grating (FBG) cavities. When the laser is biased at low operation current, the feedback from the external cavities dominates and laser pulses have a 1.01 THz repetition rate, determined by the equal frequency difference of the three FBGs. We are thus able to decouple the repetition rate of a mode-locked laser from the cavity length. With much higher bias current, the QD F–P cavity dominates and the repetition rate is switched to 43.8 GHz, defined by the length of the F–P cavity. 相似文献
84.
85.
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers 《Pramana》2001,57(1):195-198
Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy
evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their
contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections
due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier. 相似文献
86.
Yong-X. Hu David Winker Ping Yang Bryan Baum Lamont Poole Lelia Vann 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):569-579
A fast Monte Carlo simulation scheme is developed to assess the impact of multiple scattering on space-based lidar backscattering depolarization measurements. The specific application of our methodology is to determine cloud thermodynamic phase from satellite-based lidar depolarization measurements. Model results indicate that multiple scattering significantly depolarizes backscatter return from water clouds. Multiple scattering depolarization is less significant for non-spherical particles. There are sharp contrasts in the depolarization profile between a layer of spherical particles and a layer of non-spherical particles. Although it is not as obvious as ground-based lidar observations, it is likely that we can identify cloud phase not only for a uniform cloud layer, but also for overlapping cloud layers where one layer contains ice and the other water droplets. 相似文献
87.
Cui-Lian Liu Eduard O. Bobylev Yang Fu David A. Poole III Dr. Koen Robeyns Prof. Dr. Charles-André Fustin Prof. Dr. Yann Garcia Prof. Dr. Joost N. H. Reek Prof. Dr. Michael L. Singleton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(52):11960-11965
Non-covalent interactions are important for directing protein folding across multiple intermediates and can even provide access to multiple stable structures with different properties and functions. Herein, we describe an approach for mimicking this behavior in the self-assembly of metal–organic cages. Two ligands, the bend angles of which are controlled by non-covalent interactions and one ligand lacking the above-mentioned interactions, were synthesized and used for self-assembly with Pd2+. As these weak interactions are easily broken, the bend angles have a controlled flexibility giving access to M2( L1 )4, M6( L2 )12, and M12( L2 )24 cages. By controlling the self-assembly conditions this process can be directed in a stepwise fashion. Additionally, the multiple endohedral hydrogen-bonding sites on the ligand were found to play a role in the binding and discrimination of neutral guests. 相似文献
88.
Simon Rohrbach Andrew J. Smith Jia Hao Pang Darren L. Poole Tell Tuttle Shunsuke Chiba John A. Murphy 《Angewandte Chemie (International ed. in English)》2019,58(46):16368-16388
Recent developments in experimental and computational chemistry have identified a rapidly growing class of nucleophilic aromatic substitutions that proceed by concerted (cSNAr) rather than classical, two‐step, SNAr mechanisms. Whereas traditional SNAr reactions require substantial activation of the aromatic ring by electron‐withdrawing substituents, such activating groups are not mandatory in the concerted pathways. 相似文献
89.
The alternating step generator is a well-known keystream generator consisting of two stop/go clocked LFSRs, LFSR1 and LFSR2, whose clocks are controlled by another LFSR, LFSR3, which is clocked regularly. A probabilistic analysis of this generator is conducted which shows that the posterior probabilites of individual bits of the first derivatives of the regularly clocked LFSR1 and LFSR2 sequences, when conditioned on a given segment of the first derivative of the keystream sequence, can be computed efficiently in a number of probabilistic models of interest. The expected values of these probabilities, for a random keystream sequence, are derived by an approximate theoretical analysis and are also verified by systematic computer experiments. It is pointed out that these posterior probabilities can be enhanced in a resynchronization scenario and thus used for a low-complexity fast correlation attack on the two LFSRs. More generally, it is argued that even without resynchronization these probabilities may be significantly different from one half for fast correlation attacks based on iterative decoding algorithms to be successful, although with incresead complexity. A related method for computing the posterior probabilities of individual bits of the LFSR3 sequence, when conditioned on both the keystream sequence and the LFSR1 and LFSR2 sequences, is also developed. As these posterior probabilities are much more different from one half, they can be used for a low-complexity fast correlation attack on LFSR3, provided that the initial states of LFSR1 and LFSR2 are previously reconstructed. 相似文献
90.
Abstract. A worm ω is a continuous rectifiable arc of unit length in the Cartesian plane. Let W denote the class of all worms. A planar region C is called a cover for W if it contains a copy of every worm in W . That is, C will cover or contain any member ω of W after an appropriate translation and/ or rotation of ω is completed (no reflections). The open problem of determining a cover C of smallest area is attributed to Leo Moser [7], [8]. This paper reduces the smallest known upper bound for this area from
0.275237 [10] to 0.260437. 相似文献