Layered nanoscale amorphous solid films of methanol and ethanol undergo complete intermixing prior to the onset of measurable desorption at 120 K. This intermixing precedes and inhibits crystallization. Subsequent desorption of the film is described quantitatively by a kinetic model describing evaporation from a continuously mixed ideal binary liquid solution. This occurs at temperatures below the melting point of the binary mixture, indicating ideal behavior for the supercooled liquid solution. This approach provides a new method for preparing and examining deeply supercooled solutions. 相似文献
Engineering proteins to bind small molecules presents a challenge as daunting as drug discovery, for both hinge upon our understanding of receptor-ligand molecular recognition. However, powerful techniques from combinatorial molecular biology can be used to rapidly select artificial receptors. While traditionally researchers have relied upon antibody technologies as a source of new binding proteins, the lipocalin scaffold has recently emerged as an adaptable receptor for small molecule binding. 'Anticalins', engineered lipocalin variants, offer some advantages over traditional antibody technology and illuminate features of molecular recognition between receptors and small molecule ligands. 相似文献
We prove that a diffeomorphism possessing a homoclinic point with a topological crossing (possibly with infinite order contact) has positive topological entropy, along with an analogous statement for heteroclinic points. We apply these results to study area-preserving perturbations of area-preserving surface diffeomorphisms possessing homoclinic and double heteroclinic connections. In the heteroclinic case, the perturbed map can fail to have positive topological entropy only if the perturbation preserves the double heteroclinic connection or if it creates a homoclinic connection. In the homoclinic case, the perturbed map can fail to have positive topological entropy only if the perturbation preserves the connection. These results significantly simplify the application of the Poincaré-Arnold-Melnikov-Sotomayor method. The results apply even when the contraction and expansion at the fixed point is subexponential.The first author was partially supported by a Sloan Foundation Fellowship and an N.S.F. grant. The second author was partially supported by a National Science Foundation Postdoctoral Research Fellowship. Both authors would like to thank MSRI for their support during the period that much of this paper was written. 相似文献
The preparation, properties and spectroscopic investigation (IR, 1H NMR, 31P NMR, MS) of η3-allyl[1,2-bis(diphenylphosphino)ethan]tricarbonylvanadium(0) compounds are reported. 相似文献
Metal Sulphur Nitrogen Compounds. 17. Compounds HgN2S · NH3 and Hg(NH3)2I2 · S4N4 The crystal and molecular structures of the known compounds HgN2S · NH3 and of the new inclusion compound 2Hg(NH3)2I2 · S4N4 are reported. HgN2S · NH3 is orthorhombic, space group Pbca with a = 5.548, b = 10.158, c = 14.919 Å, Z = 8. In the dimeric molecules two Hg atoms are bridged to form eight-membered rings . In addition, each Hg is coordinated by an NH3 molecule and by an N atom of an adjacent ring. This results in a two-dimensional network. 2Hg(NH3)2I2 · S4N4 is tetragonal, space group P42/nmc, a = 8.948, c = 13.188 Å, Z = 2. It is an inclusion compound with S4N4 molecules in the holes of the lattice of the large Hg(NH3)2I2 tetrahedra. 相似文献