Labile low-valent tin azides: syntheses, structural characterization, and thermal properties.

The first two examples of the class of tetracoordinate low-valent, mixed-ligand tin azido complexes, Sn(N3)2(L)2, are shown to form upon reaction of SnCl2 with NaN3 and SnF2 with Me3SiN3 in either pyridine or 4-picoline (2, L = py; 3, L = pic). These adducts of Sn(N3)2 are shock- and friction-insensitive and stable at r.t. under an atmosphere of pyridine or picoline, respectively. A new, fast, and efficient method for the preparation of Sn(N3)2 (1) directly from SnF2, and by the stepwise de-coordination of py from 2 at r.t., is reported that yields 1 in microcrystalline form, permitting powder X-ray diffraction studies. Reaction of 1 with a nonbulky cationic H-bond donor forms the salt-like compound {C(NH2)3}Sn(N3)3 (4) which is comparably stable despite its high nitrogen content (55%) and the absence of bulky weakly coordinating cations that are conventionally deemed essential in related systems of homoleptic azido metallates. The spectroscopic and crystallographic characterization of the polyazides 1-4 provides insight into azide-based H-bonded networks and unravels the previously unknown structure of 1 as an important lighter binary azide homologue of Pb(N3)2. The atomic coordinates for 1 and 2-4 were derived from powder and single crystal XRD data, respectively; those for 1 are consistent with predictions made by DFT-D calculations under periodic boundary conditions

Pressure-induced structural changes in methylamine borane and dimethylamine borane

Methylamine borane and dimethylamine borane have been studied under compression to 3 GPa using Raman spectroscopy and synchrotron powder X-ray diffraction. Both undergo reversible pressure-induced structural changes in this pressure range. The structural changes in the case of methylamine borane may be indicative of a second-order phase transition, taking place between ca. 0.8-1.2 GPa, which does not result in a change of spacegroup symmetry. In the case of dimethylamine borane, however, a reversible, reconstructive phase transition (monoclinic → orthorhombic) occurs below 0.7 GPa. This new high-pressure phase was successfully indexed, with a possible space group assignment of Pccn or Pbcn

Regularity of Cauchy horizons in S2xS1 Gowdy spacetimes

We study general S2xS1 Gowdy models with a regular past Cauchy horizon and prove that a second (future) Cauchy horizon exists, provided that a particular conserved quantity $J$ is not zero. We derive an explicit expression for the metric form on the future Cauchy horizon in terms of the initial data on the past horizon and conclude the universal relation A\p A\f=(8\pi J)^2 where A\p and A\f are the areas of past and future Cauchy horizon respectively.Comment: 17 pages, 1 figur

A922 Sequential measurement of 1 hour creatinine clearance (1-CRCL) in critically ill patients at risk of acute kidney injury (AKI)

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Genetic Studies of Winter Hardiness in Barley

An important obstacle toward the development of winter barley varieties with a higher level of winter hardiness has been the deficiency of genetic information on this character. The primary objective of these studies was to obtain information on the genetics of the winter hardiness of a group of 18 winter barley varieties which originated from widely different geographic areas of the world. It was hoped that this information might be helpful in determining whether or not it would be possible for barley breeders to combine different genetic sources of winter hardiness and attain a higher level of hardiness than presently exists

The low-temperature and high-pressure crystal structures of cyclobutanol (C4H7OH)

The title compound, (C6H14N2)[Cu(C2O4)(2)(H2O)].2H(2)O, crystallizes in the space group P (1) over bar. In the solid state, the [Cu(ox)(2)(H2O)](2-) units (ox is oxalate, C2O4) dimerize to give a tetragonally distorted CuO6 coordination environment. Extensive hydrogen bonding between the oxalate, the coordinated water, the 1,4-diazoniabicyclo[2.2.2]octane dications ([dabcoH(2)](2+)) and the water of crystallization determines the crystal packing