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31.
32.
Shankari V. Rajagopal Kurt M. Fujiwara Ruwan Senaratne Kevin Singh Zachary A. Geiger David M. Weld 《Annalen der Physik》2017,529(8)
Ultracold atomic physics experiments offer a nearly ideal context for the investigation of quantum systems far from equilibrium. We describe three related emerging directions of research into extreme non‐equilibrium phenomena in atom traps: quantum emulation of ultrafast atom‐light interactions, coherent phasonic spectroscopy in tunable quasicrystals, and realization of Floquet matter in strongly‐driven lattice systems. We show that all three should enable quantum emulation in parameter regimes inaccessible in solid‐state experiments, facilitating a complementary approach to open problems in non‐equilibrium condensed matter. 相似文献
33.
Xiaotong Zhang Eranda Wanigasekara Zachary S. Breitbach Edra Dodbiba Daniel W. Armstrong 《Rapid communications in mass spectrometry : RCM》2010,24(8):1113-1123
In previous studies, new electrospray ionization mass spectrometry (ESI‐MS) approaches were developed for the highly sensitive detection of singly and doubly charged anions in positive mode ESI‐MS by using specially synthesized dicationic and tricationic ion‐pairing agents, respectively. By detecting the positively charged ion complex in the positive mode, limits of detection (LODs) for the anions can be lowered by several magnitudes. In this work, we used eighteen newly synthesized tetracationic ion‐pairing agents, constructed with different geometries, linkages and cation moieties, for the detection of eighteen triply charged anions of different structural motifs. The LODs for these anions were from ten to several thousand times lower in the positive selective ion monitoring (SIM) mode than in the negative mode. These tetracationic agents also were shown to be useful for the detection of ?1 and ?2 anions. In addition, the LODs for ?3 anions can be further lowered by monitoring the product fragments of the ion‐pairing complexes in the single reaction monitoring (SRM) mode. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
34.
Himo F Demko ZP Noodleman L Sharpless KB 《Journal of the American Chemical Society》2002,124(41):12210-12216
It is well-known that azide salts can engage nitriles at elevated temperatures to yield tetrazoles; however, there is continued debate as to the mechanism of the reaction. Density functional theory calculations with the hybrid functional B3LYP have been performed to study different mechanisms of tetrazole formation, including concerted cycloaddition and stepwise addition of neutral or anionic azide species. The calculations presented here suggest a previously unsuspected nitrile activation step en route to an imidoyl azide, which then cyclizes to give the tetrazole. The activation barriers are found to correlate strongly with the electron-withdrawing potential of the substituent on the nitrile. 相似文献
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36.
Measurements of the partial molar volumes in water at 25°C of the mono-and dihydrochlorides of the ,-diaminoalkanes, up to a chain length of 10 carbon atoms, are reported. Volumes of ionization have been determined and the electrostriction of the solvent calculated. Effects of the substituents are felt up to the -carbon atom, but thereafter are only very weak or nonexistent. 相似文献
37.
E.J Farrell 《Journal of Combinatorial Theory, Series B》1979,26(1):111-122
Let be a family of connected graphs. With each element α ∈ , we can associate a weight wα. Let G be a graph. An F-cover of G is a spanning subgraph of G in which every component belongs to . With every F-cover we can associate a monomial π(C) = Παwα, where the product is taken over all components of the cover. The F-polynomial of G is Σπ(C), where the sum is taken over all F-covers in G. We obtain general results for the complete graph and complete bipartite graphs, and we show that many of the well-known graph polynomials are special cases of more general F-polynomials. 相似文献
38.
Auger spectroscopy has been used to investigate the interactions of oxygen and nitrogen with both the (100) face niobium and with polycrystalline niobium. Sticking coefficients for both gases have been determined as a function of coverage. A temperature and concentration ependent segregation of oxygen at the surface has been observed even under conditions where the solid solubility of the bulk was not exceeded. A model to describe this segregation has been developed and extended to explain discrepancies in earlier investigations f the reaction of oxygen with niobium. 相似文献
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Farrell D Cheng Y McCallum RW Sachan M Majetich SA 《The journal of physical chemistry. B》2005,109(28):13409-13419
The magnetic properties of monodisperse Fe nanoparticles with over 4 orders of magnitude difference in concentration are studied by a combination of ordinary and remanent hysteresis loops, zero field cooled magnetization as a function of temperature, and magnetic relaxation rates. We compare the behavior of dilute dispersions with different concentrations, dispersions, and arrays made from the same particles, and nanoparticle arrays with different particle sizes and separations. The results are related to theoretical predictions and are used to create a unified picture of magnetostatic interactions within the assemblies. 相似文献