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A new method for assessing the similarity of material compositions is described. A similarity measure is important for the classification and clustering of compositions. The similarity of the material compositions is calculated utilizing a data-mined ionic substitutional similarity based upon the probability with which two ions will substitute for each other within the same structure prototype. The method is validated via the prediction of crystal structure prototypes for oxides from the Inorganic Crystal Structure Database, selecting the correct prototype from a list of known prototypes within five guesses 75% of the time. It performs particularly well on the quaternary oxides, selecting the correct prototype from a list of known prototypes on the first guess 65% of the time.
The intramolecular addition of beta-ketoesters to unactivated alkynes under neutral conditions and at room temperature is described. The method employs triphenylphosphinegold(I) cation as a catalyst for the formation of exo-methylenecycloalkanes. Both monocyclic and bicyclic cyclopentanes and cyclohexanes can be formed in excellent yields and with good diastereoselectivity.
The field of reticular chemistry is rapidly expanding and, as is true for any emerging field, there exists ‘folklores’ that permeate through the scientific discourse. It is within this context that we seek to address these ‘folklores’ in order to provide the realities of reticular chemistry.
This paper presents a general theory of organizational response to regulation, a theory that integrates adaptation and mutual selection perspectives. Two major forms of regulation in the hospital industry, certificate of need and rate review, are examined. Hypotheses are derived concerning the nature and timing of the various adjustments hospitals make both in internal organizational arrangements and in patterns of interorganizational activity in the face of regulatory constraints. Suggestions and data sources for testing the theory are presented.
We introduce a practical, new, face-centered-cubic dielectric structure which simultaneously solves two of the outstanding problems in photonic band structure. In this new ``photonic crystal'' the atoms are nonspherical, lifting the degeneracy at the W point of the Brillouin zone, and permitting a full photonic band gap rather than a pseudogap. Furthermore, this fully three-dimensional fcc structure lends itself readily to microfabrication on the scale of optical wavelengths. It is created by simply drilling three sets of holes 35.26\ifmmode^\circ\else\textdegree\fi{} off vertical into the top surface of a solid slab or wafer, as can be done, for example, by chemical-beam-assisted ion etching.
Entanglement properties of excited eigenstates (or of thermal mixed states) are difficult to study with conventional analytical methods. We approach this problem for random spin chains using a recently developed real-space renormalization group technique for excited states ("RSRG-X"). For the random $XX$ and quantum Ising chains, which have logarithmic divergences in the entanglement entropy of their (infinite-randomness) critical ground states, we show that the entanglement entropy of excited eigenstates retains a logarithmic divergence while the mutual information of thermal mixed states does not. However, in the $XX$ case the coefficient of the logarithmic divergence extends from the universal ground-state value to a universal interval due to the degeneracy of excited eigenstates. These models are noninteracting in the sense of having free-fermion representations, allowing strong numerical checks of our analytical predictions.
Abstract Die Insertion ungesättigter Liganden in M‐C‐ oder M‐H‐Bindungen verläuft über eine migratorische Insertion, die eine fundamentale metallorganische Reaktion ist. Jüngste Berichte bestätigen migratorische Insertionen von Alkenen in M‐O‐ und M‐N‐Bindungen im Verlauf von Alkenalkoxylierungen bzw. Alkenaminierungen. Wir geben hier einen Überblick über den Stand der Literatur und wollen außerdem betrachten, wie diese jüngsten Studien mit klassischen Experimenten der Bildung von C‐O‐ und C‐N‐Bindungen mit Alkenkomplexen später Übergangsmetalle zusammenhängen.
