The Structure of Yttrium Cobaltate from Neutron Diffraction

The crystal structure of YCoO₃has been determined from Rietveld analysis of the powder neutron diffraction data at 17, 100, and 300 K. At each temperature, the structure is a distorted perovskite with orthorhombic symmetry, space groupPbnm(Z=4). The lattice parameters, at 300 K, are 5.1388(5)× 5.4191(5)×7.3658(7) Å. Structural analysis indicates that the formal valence of cobalt in YCoO₃is +3. Analysis of the Co–O distances and the absence of magnetic structure indicates that the majority of the Co³⁺ions in YCoO₃are in the low-spin (i.e.t⁶_2ge⁰_g) state. The data also show that perhaps 10% of the Co³⁺ions at 300 K (but insignificant fractions at 100 and 17 K) are in the high-spin state.     

A Bayesian tutorial for data assimilation

Data assimilation is the process by which observational data are fused with scientific information. The Bayesian paradigm provides a coherent probabilistic approach for combining information, and thus is an appropriate framework for data assimilation. Viewing data assimilation as a problem in Bayesian statistics is not new. However, the field of Bayesian statistics is rapidly evolving and new approaches for model construction and sampling have been utilized recently in a wide variety of disciplines to combine information. This article includes a brief introduction to Bayesian methods. Paying particular attention to data assimilation, we review linkages to optimal interpolation, kriging, Kalman filtering, smoothing, and variational analysis. Discussion is provided concerning Monte Carlo methods for implementing Bayesian analysis, including importance sampling, particle filtering, ensemble Kalman filtering, and Markov chain Monte Carlo sampling. Finally, hierarchical Bayesian modeling is reviewed. We indicate how this approach can be used to incorporate significant physically based prior information into statistical models, thereby accounting for uncertainty. The approach is illustrated in a simplified advection–diffusion model.     

Samarium Barbier reactions of alpha-iodomethyloxazoles and thiazoles with aliphatic aldehydes

[reaction: see text] The reductive coupling of substituted alpha-iodomethyloxazoles and thiazoles with aliphatic aldehydes under Barbier conditions provides an effective method for the direct incorporation of intact heterocyclic systems.     

Untersuchung von Getreide, Mehl und Bachwaren

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Schwefel

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Literatur

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Über zwei neue projektive natürliche Geometrien

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Lipid-Polypeptid-Wechselwirkung an der Grenzfl?che Luft-Wasser

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Sum List Coloring Graphs

Let G=(V,E) be a graph with n vertices and e edges. The sum choice number of G is the smallest integer p such that there exist list sizes (f(v):v ∈ V) whose sum is p for which G has a proper coloring no matter which color lists of size f(v) are assigned to the vertices v. The sum choice number is bounded above by n+e. If the sum choice number of G equals n+e, then G is sum choice greedy. Complete graphs K_n are sum choice greedy as are trees. Based on a simple, but powerful, lemma we show that a graph each of whose blocks is sum choice greedy is also sum choice greedy. We also determine the sum choice number of K_2,n, and we show that every tree on n vertices can be obtained from K_n by consecutively deleting single edges where all intermediate graphs are sc-greedy.