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91.
Vaman C Andreoiu C Bazin D Becerril A Brown BA Campbell CM Chester A Cook JM Dinca DC Gade A Galaviz D Glasmacher T Hjorth-Jensen M Horoi M Miller D Moeller V Mueller WF Schiller A Starosta K Stolz A Terry JR Volya A Zelevinsky V Zwahlen H 《Physical review letters》2007,99(16):162501
Rare isotope beams of neutron-deficient 106,108,110Sn from the fragmentation of 124Xe were employed in an intermediate-energy Coulomb excitation experiment. The measured B(E2,0(1)(+)-->2(1)(+)) values for 108Sn and 110Sn and the results obtained for the 106Sn show that the transition strengths for these nuclei are larger than predicted by current state-of-the-art shell-model calculations. This discrepancy might be explained by contributions of the protons from within the Z = 50 shell to the structure of low-energy excited states in this region. 相似文献
92.
Angus Campbell Dr. Ian Mat Som Dr. Claire Wilson Prof. Dr. J. Stephen Clark 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):1155-1160
Six members of the asbestinin family of marine diterpene natural products have been synthesized in an efficient and stereoselective manner from a single oxa-bridged intermediate. Five of these natural products have not been synthesized previously and the structures of four of them have been confirmed as those proposed originally or following revisions to the original structures. The fifth natural product—asbestinin-21—has been shown to be a diastereomer of the compound that had been proposed previously. 相似文献
93.
Sinu C. Rajappan Dillon R. McCarthy Joseph P. Campbell Jonathon B. Ferrell Mona Sharafi Ona Ambrozaite Jianing Li Severin T. Schneebeli 《Angewandte Chemie (International ed. in English)》2020,59(38):16668-16674
Selective monofunctionalization of substrates with distant, yet equally reactive functional groups is difficult to achieve, as it requires the second functional group to selectively modulate its reactivity once the first functional group has reacted. We now show that mechanically interlocked catalytic rings can effectively regulate the reactivity of stoppering groups in rotaxanes over a distance of about 2 nm. Our mechanism of communication is enabled by a unique interlocked design, which effectively removes the catalytic rings from the substrates by fast dethreading as soon as the first reaction has taken place. Our method not only led to a rare example of selective monofunctionalization, but also to a “molecular if function”. Overall, the study presents a way to get distant functional groups to communicate with each other in a reaction‐history‐dependent manner by creating linkers that can ultimately perform logical operations at the molecular level. 相似文献
94.
The paper reports the results of work on the construction of LISP programs for various symbolic operations in complex analysis, including the evaluation of integrals around closed contours by the use of Cauchy's Theorem. It is concluded that the only difficulty in the way of the preparation of programs for all of the important and useful textbook calculations in complex analysis is that large amounts of fast storage in the computer are needed. 相似文献
95.
E.E.B. Campbell K. Hoffmann I.V. Hertel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):345-348
The timescale for the coupling of electronic and vibrational excitation in isolated fullerenes is determined by recording
positive ion time-of-flight mass spectra on excitation with ultrashort laser pulses at 790 nm of the same fluence but different
pulse durations. The coupling leads to the onset of a delayed ionisation “tail” on the parent fullerene ion peak. This occurs
for a pulse duration of 500-1000 fs, depending on laser fluence.
Received 20 October 2000 相似文献
96.
The application of non‐destructive imaging to characterizing samples has become more important as the costs of samples increase. Imaging a sample via X‐ray techniques is preferable when altering or even touching the sample affects its properties, or when the sample is fielded after characterization. Two laboratory‐based X‐ray techniques used at Los Alamos include micro X‐ray computed tomography (MXCT) and confocal micro X‐ray fluorescence (confocal MXRF). Both methods create a 3D rendering of the sample non‐destructively. MXCT produces a high‐resolution (sub‐µm voxel) rendering of the sample based upon X‐ray absorption; the resulting model is a function of density and does not contain any elemental information. Confocal MXRF produces an elementally specific 3D rendering of the sample, but at a lower (30 × 30 × 65 µm) resolution. By combining data from these two techniques, scientists provided a more comprehensive method of analysis. We will describe a MATLAB routine written to render each of these data sets individually and/or within the same coordinate system. This approach is shown in the analysis of two samples: an integrated circuit surface mounted resistor and a machined piece of polystyrene foam. The samples chosen provide an opportunity to compare and contrast the two X‐ray techniques, identify their weaknesses and show how they are used in a complementary fashion. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
97.
We study the multiplicative structure of rings of coinvariants for finite groups. We develop methods that give rise to natural
monomial bases for such rings over their ground fields and explicitly determine precisely which monomials are zero in the
ring of coinvariants. We apply our methods to the Dickson, upper triangular and symmetric coinvariants. Along the way, we
recover theorems of Steinberg [17] and E. Artin [1]. Using these monomial bases we prove that the image of the transfer for
a general linear group over a finite field is a principal ideal in the ring of invariants.
This research is supported in part by the Natural Sciences and Engineering Research Council of Canada 相似文献
98.
Michael Campbell Yatao Yang Peter A. Wallace A. Sheila Holmes-Smith 《Optical Review》1997,4(1):A111-A113
This paper reports the development and characterisation of a multipoint quasi-distributed optical fiber sensor for pH measurement. The system is based on a 170 m length of 200 μm core diameter plastic cladding silica fiber where sections of cladding have been removed and replaced with dye immobilised sol-gel glass to form sensing points. Evanescent wave excitation of a dye, immobilised within 2 mm long sections of cladding, enables the pH value of any spillage material to be determined by optical time domain reflectometry along the length of the fiber. The results suggest a spatial resolution of better than 2.5 meters for this fiber system and indicate that this arrangement could form the basis of a practical sensor/actuator system for chemical spillage, provided that suitable dye/analyte combinations are available. 相似文献
99.
We discuss several examples of synchronous dynamical phenomena in
coupled cell networks
that are unexpected from symmetry considerations, but are natural
using a theory developed by Stewart, Golubitsky, and Pivato. In particular
we demonstrate patterns of synchrony in networks with small numbers of cells
and in lattices (and periodic arrays) of cells that cannot readily be
explained by conventional symmetry considerations. We also show that
different types of dynamics can coexist robustly in single solutions of
systems of coupled identical cells. The examples include a
three-cell system exhibiting equilibria, periodic, and quasiperiodic states
in different cells; periodic $2n\times 2n$ arrays of cells that generate
$2^n$ different patterns of synchrony from one symmetry-generated solution;
and systems exhibiting multirhythms (periodic solutions with rationally
related periods in different cells). Our theoretical results include the
observation that reduced equations on a center manifold of a skew product
system inherit a skew product form. 相似文献
100.
The high-temperature cubic phase of non-stoichiometric strontium ferrite SrFeOx (2.5≤x≤3.0) has been studied by in situ neutron powder diffraction in air over the temperature range 300-1273 K. The composition of SrFeOx changes within the range 2.56≤x≤2.81 from 1273 to 673 K, respectively.Rietveld refinements of the diffraction patterns show that the high-temperature cubic phase of SrFeOx is consistent with a face-centred Fm3c structure. This structure leads to agreement with previous density measurements. This cell allows the high-temperature structure of SrFeOx to be described in terms of a solid solution of the composition end members. Cubic SrFeOx at high temperature is found to closely obey Vegard's law. The density of cubic SrFeOx is also found to exhibit a linear relationship with composition. 相似文献