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91.
92.
S. R. Elliott B. Beck P. Beiersdorfer D. Church D. DeWitt D. K. Knapp R. E. Marrs D. Schneider L. Schweikhard 《Hyperfine Interactions》1993,81(1-4):151-159
The LLNL electron beam ion trap provides the world's only source of stationary highly charged ions up to bare U. This unique capability makes many new atomic and nuclear physics experiments possible. 相似文献
93.
94.
Melissa D'Ascenzio Kathryn M. Pugh Rebecca Konietzny Georgina Berridge Cynthia Tallant Shaima Hashem Octovia Monteiro Jason R. Thomas Markus Schirle Stefan Knapp Brian Marsden Oleg Fedorov Chas Bountra Benedikt M. Kessler Paul E. Brennan 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(4):1019-1024
95.
Shan Z Knapp JA Follstaedt DM Stach EA Wiezorek JM Mao SX 《Physical review letters》2008,100(10):105502
In situ tensile straining transmission electron microscopy tests have been carried out on nanocrystalline Ni. Grain agglomerates (GAs) were found to form very frequently and rapidly ahead of an advancing crack with sizes much larger than the initial average grain size. High-resolution electron microscopy indicated that the GAs most probably consist of nanograins separated by low-angle grain boundaries. Furthermore, both inter- and intra-GA fractures were observed. The observations suggest that these newly formed GAs may play an important role in the formation of the dimpled fracture surfaces of nanocrystalline materials. 相似文献
96.
97.
Ö. Nilgün Akkuş Andreas Decken Carsten Knapp Jack Passmore 《Journal of chemical crystallography》2006,36(5):321-329
[Zn(SO2)2][AsF6]2 (1) has been prepared from zinc metal and AsF5 in liquid sulfur dioxide, and crystallized from sulfur dioxide giving crystals of [Zn(SO2)4(AsF6)2] (1a). The compound 1 forms the homoleptic complexes [Zn(NCR)6](AsF6)2 (R: CH3 (2a), C6H5 (3a), C6F5 (3b)) with the corresponding nitriles. In these complexes, the metal center is octahedrally surrounded by six ligands (average Zn–N 2.13 ?). Reaction of 1 with the weaker ligand F3CCN results in dicoordination at the metal center complemented by a two-dimensional polymeric network (2b) containing bridging AsF6
− anions. [Zn(SO2)4(AsF6)2] (1a): monoclinic, P21/c, a=8.5176(8) ?, b=13.5787(14) ?, c=14.7661(15) ?, β=99.296(2)°; [Zn(NCCH3)6][AsF6]2
(2a): rhombohedral, R-3, a=11.2225(8) ?, b=11.2225(8) ?, c=16.9393(14) ?; [Zn (NCCF3)2][μ-FAsF5)2( (2b): monoclinic, P21/c, a=11.226(3) ?, b=6.6147(19) ?, c=10.460(3) ?, β=104.028(5)°; [Zn(NCC6H5)6][AsF6]2 (3a): monoclinic, P21/n, a=13.7968(10) ?, b=19.8861(15) ?, c=16.1692(12) ?, β=91.563(2)°; [Zn(NCC6F5)6][AsF6]2·2SO2 (3b): monoclinic, P21/n, a=10.8448(9) ?, b=154456(13) ?, c=17.5206(15) ?, β=104.158(1)°. 相似文献
98.
Andreas?Decken Carsten?Knapp Jack?PassmoreEmail author 《Journal of chemical crystallography》2005,35(9):697-700
The first metal complex of carbonyl cyanide [Ag{NCC(O)CN}2]n [SbF6]n was synthesized and characterized by X-ray crystallography. The silver(I) centers are bridged by the cyanide groups of the carbonyl cyanides giving a two-dimensional layer structure. The SbF6− anions are embedded in the cationic framework to neutralize the charge with only very weak contacts to the Ag+. The compound crystallizes in the monoclinic space group C2/c with a = 11.8737(13) Å, b = 10.2497(13) Å, c = 10.5883(13) Å, β = 90.183(3)∘. 相似文献
99.
In an earlier paper, we constructed all finite, planar, semimodular lattices in three simple steps from the direct product
of two finite chains. In this note we prove that one of the three steps can be eliminated.
The research of the first author was supported by the NSERC of Canada. 相似文献
100.
The crystal structure of the ammonia transport (Amt) protein AmtB at 1.4 Angstrom resolution revealed four ammonia/ammonium (NH(3)/NH(4)(+)) binding sites along the approximately 20 Angstrom narrow pore. It is an open question whether the bound NH(3)/NH(4)(+) are neutral (NH(3)) or cationic (NH(4)(+)). On the basis of the AmtB crystal structure, we calculated the pK(a) of these four NH(3)/NH(4)(+) by solving the Poisson-Boltzmann equation. Except for one NH(3)/NH(4)(+) binding site (Am1) at the entry point of the Amt pore, binding sites are occupied by NH(3) due to lack of energy contributions from solvation, eliminating an existence of charged form NH(4)(+) and, inevitably, its potential cation-pi interaction. The only two titratable residues in the pore, His168 and His318, are in the neutral charge state. The NH(4)(+) charge state at the Am1 site is stabilized by Ser219 functioning as an H-bond acceptor. However, when involving explicit crystal water nearby, the NH(3) charge state is stabilized by the reorientation of Ser219-OH group. This H-bond donor Ser219 significantly decreases the pK(a) of NH(3)/ NH(4)(+) at the Am1 site to approximately 1. The flip/flop H-bond of Ser219 may play a dual role first in binding and subsequently in deprotonating NH(4)(+), which is a prerequisite to conduct NH(3) through the Amt pore across the membrane. 相似文献