7,544 research outputs found
A FIRST-PRINCIPLES STUDY OF LI-METAL ADSORPTION ON A SI(100) SURFACE
No full textWe present the results of self-consistent ab initio pseudopotential calculations for the equilibrium structure of Li adsorbed Si(100) surfaces. The stable adsorption sites ale determined for a wide range of Li coverage (Theta=1/2-2). At half-monolayer coverage, the 2x2 structure with Li atoms occupied at the interdimer bridge sites is found to be most stable, while at one-monolayer coverage Li atoms are adsorbed at both the pedestal and cave sites, exhibiting a 2x1 structure where the Si dimers are symmetric. At Theta=2, we find the most stable phase to be the 1x1 structure, which is formed by breaking all the Si dimers of the substrate. From the calculated formation energies, we suggest that the saturation coverage is Theta=2
Atomic and electronic structure of Li-adsorbed Si(100) surfaces
No full textWe investigate the atomic and electronic structure of Li-adsorbed Si(100) surfaces through first-principles pseudopotential calculations. We find that Li adatoms interact mainly with the dangling-bond orbitals of Si dimers, however, no hydrogenlike directional bonds exist between the Li and substrate Si atoms, based on calculated scanning tunneling microscopy images. The analysis of charge densities demonstrates a large charge transfer from the Li adatom to a dangling-bond orbital of a Si dimer, which is responsible for a large decrease of work function at submonolayer coverages. The Li atoms form linear chains either by occupying the interdimer bridge sites along the dimer row direction or the dimer bridge and cave sites perpendicular to the dimer row. As Li coverage (Theta) increases, repulsive interactions between the adatoms in the chains are also found to increase. Thus, at 1-ML Li coverage, the stable adsorptions sites are changed to either the cave and pedestal sites or the valley-bridge and pedestal sites, with all the Si dimers symmetric, resulting in a 2x1 structure. From the calculated formation energies, we find a 1x1 phase to be thermodynamically stable at Theta=2, in contrast to other alkali-metal adsorptions.
Microstructures of explosively consolidated rapidly solidified aluminum and Al-Li alloy powders
Full text linkThe microstructures and the characteristics of water-atomized, nitrogen gas-atomized Al powders and ultrasonic argon gas-atomized Al-Li alloy powder were investigated by means of metallography, SEM, Auger electron spectroscopy and X-ray diffraction techniques. Rapidly solidified powders were explosively consolidated into different sized cylinders under various explosive parameters. The explosively consolidated compacts have been tested and analysed for density microhardness, retention of rapidly solidified microstructures, interparticle bonding, fractography and lattice distortion. It is shown that the explosive consolidation technique is an effective method for compacting rapidly solidified powders. The characteristics of surface layers play a very important role in determining the effectiveness of the joints sintered, and the Al-Li alloy explosive compacts present an abnormal softening appearance compared to the original powder
Knee proprioception in patients with osteosarcoma around the Knee after modular endoprosthetic reconstruction
No full text
Synthesis of the possible metabolites of quinocetone in animals
No full textThe possible metabolites of quinocetone in animals had been prepared with different selective reagent by three synthetic routes. It was their principal reaction that Na2S2O4 reduced quinoxaline-1,4-dioxide derivatives to quinoxaline derivatives, H(2)O(2 s)oxidized 2-carboxyl-quinoxaline derivatives to 2-carboxyl-quinoxaline-1-oxide ones and P(OCH3)(3) reduced 2-carboxyl- quinoxaline-1,4-dioxide derivatives to 3-carboxyl-quinoxaline-1-oxide ones. The title compounds ware confirmed with NMR, UV, FAB-MS, et al
1,3-dipolar cycloaddition of azides with electron-deficient alkynes under mild condition in water
No full textWe report a simple synthetic protocol for the 1,3-dipolar cycloaddition of azides with electron-deficient alkynes. Alkyne with at least one neighboring electron-withdrawing group proceeds with the cycloaddition successfully without any catalysts at room temperature in water. Under this simple condition, we evaluated a series of small molecule model reactions and then coupled an azido-DNA molecule with electron-deficient alkynes for the formation of [1,2,3]-triazole heterocycle, providing a potential method for introducing functional groups to DNA under biological conditions. (C) 2004 Elsevier Ltd. All rights reserved.The National Scinece Foundation (sensing and Imaging Initiative Grant 0097793), and a Center of Excellence in Genomic Science Grant (P50 HG002806) from the National Institutes of Healt
Additional role of nicotinic acid hydroxylase for the transformation of 3-succinoyl-pyridine by Pseudomonas sp. JY-Q
No full textApplied Environmental Microbiology, 87, e02740-20Note : if this item contains full text it may be a preprint, author manuscript, or a Gold OA copy that permits redistribution with a license such as CC BY. The final version is available through the publisher’s platform.Nicotine and nicotinic acid (NA) are both considered to be representatives of N-heterocyclic aromatic compounds, and their degradation pathways have been revealed in Pseudomonas species. However, the cooccurrence of these two pathways has only been observed in Pseudomonas sp. strain JY-Q. The nicotine pyrrolidine catabolism pathway of strain JY-Q consists of the functional modules Nic1, Spm, and Nic2. The module enzyme, 3-succinoylpyridine monooxygenase (Spm), catalyzes transformation of 3-succinoyl-pyridine (SP) to 6-hydroxy-3-succinoyl-pyridine (HSP). There exist two homologous but not identical Spm enzymes (namely, Spm1 and Spm2) in JY-Q. However, when spm1 and spm2 were both in-frame deleted, the mutant still grew well in basic salt medium (BSM) supplemented with nicotine as the sole carbon/nitrogen nutrition, suggesting that there exists an alternative pathway responsible for SP catabolism in JY-Q. NicAB, an enzyme accounting for NA hydroxylation, contains reorganized domains similar to those of Spm. When the JY-Q_nicAB gene (nicAB in strain JY-Q) was introduced into another Pseudomonas strain, one that is unable to degrade NA, the resultant recombinant strain exhibited the ability to transform SP to HSP, but without the ability to metabolize NA. Here, we conclude that NicAB in strain JY-Q exhibits an additional role in SP transformation. The other genes in the NA cluster, NicXDFE (Nic2 homolog), then also exhibit a role in subsequent HSP metabolism for energy yield. This finding also suggests that the cooccurrence of nicotine and NA degradation genes in strain JY-Q represents an advantage for JY-Q, making it more effective and flexible for the degradation of nicotine.China Postdoctoral Science Foundationhttps://login.libproxy.rpi.edu/login?url=https://doi.org/10.1128/AEM.02740-2
Transformation of Dion-Jacobson-type layered oxyfluorides into new anion-deficient pyrochlore-type oxides, ASrNb(2)O(6.5) (A = Li and Na)
No full textNew pyrochlore-type oxides, ASrNb(2)O(6.5) (A = Li and Na), were prepared from Dion-Jacobson-type layered perovskite oxyfluorides, ASrNb(2)O(6)F. The prototype layered perovskite phases are transformed into anion-deficient pyrochlore-type oxides by heating above 600 degreesC in air. The ASrNb(2)O(6)F (A = Rb and K) and RbCaNb2O6F compounds have the layered perovskite structure, whereas the pyrochlore structure is found to be more stable than the layered perovskite in the AF-SrNb2O6 (A = Li and Na) and KF-CaNb2O6 systems
Photoemission studies of oxygen adsorbed on a LiAl(110) alloy surface: Role of Li segregation
No full textWe investigated that the effect of the number of segregated Li atoms on the rate of oxidation on a LiAl alloy surface. Oxygen molecules adsorbed on the LiAl alloy react with the surface atoms to form stable oxides. The segregated Li atoms at reconstructed surfaces (c(2 x 2) and (2 x 1)) enhance the oxidation rate and form stable LiAlO, and Li2O. The degree of enhancement of oxidation by segregated Li atoms varies as a function Of 02 exposure and annealing temperature, where the latter is directly related to the mode of surface reconstruction by Li segregation. (c) 2005 Elsevier B.V. All rights reserved.KOSEF through the Center for Nanotubes and Nanostructured Composites, the Brain Korea 21 Project, the Advanced Backbone IT Technology Development Project, and the National R & D Project for Nano Science and Technolog
- …
