1,721,135 research outputs found
Single step purification of a synthetic peptide fragment of neurofilaments by preparative high performance liquid-chromatography
No full textIt was recently shown that fragment Lys-Ser-Pro-Val (1,2) is the major site in vivo neurofilament phosforilation. A suitable method for the preparation of this peptide was therefore studied paying particular attention to the purification step. Even thought solubility of this peptide in methyl t-butil ether does not allow the standard purification. It is possible achieve a good separation in a single step by HPLC, after a simple extraction with acidic water.It was recently shown that fragment Lys-Ser-Pro-Val (1,2) is the major site in vivo neurofilament phosforilation. A suitable method for the preparation of this peptide was therefore studied paying particular attention to the purification step. Even thought solubility of this peptide in methyl t-butil ether does not allow the standard purification. It is possible achieve a good separation in a single step by HPLC, after a simple extraction with acidic water. © 1989, Taylor & Francis Group, LLC. All rights reserved
STRUCTURAL INVESTIGATION OF THE CR/SI INTERFACE
No full textWe have studied the short range order around Cr atoms deposited on Si(111) surface by means of the surface electron energy loss fine structure (SEELFS) technique above the L2,3 edges of chromium. The weak oscillations superimposed on the high energy side of the edges have been analyzed using the extended X-ray absorption fine structure (EXAFS) formula. Different evaporations of very clean chromium films have been analyzed. The radial distribution function indicates the formation of a Cr/Si interface for very thin deposits (equivalent thicknesses of about 3 and 5 angstrom) of chromium. We have found that the first nearest neighbour distance Cr-Si is 2.46 +/- 0.05 angstrom supporting the formation of a CrSi2 interface at room temperature
Cerium oxide nanoparticles reduce the accumulation of autofluorescent deposits in light-induced retinal degeneration: Insights for age-related macular degeneration
No full textEXTENDED ELECTRON ENERGY-LOSS FINE-STRUCTURE AND SELECTED-AREA ELECTRON-DIFFRACTION STUDIES OF SMALL PALLADIUM CLUSTERS
No full textExtended electron energy-loss fine structure (EXELFS) and selected-area electron diffraction (SAED) techniques have both been applied to the study of the crystalline structure of Pd clusters of average diameters ranging from bulk to 24 angstrom. The combined use of these techniques gives complementary information about the crystalline structure of Pd clusters. Both techniques show the same lattice parameter expansion, about 4% for the smallest Pd cluster, with respect to the bulk. The EXELFS analysis performed on the Pd-M4,5 edge shows a sizeable increase of structural disorder in the smallest cluster. SAED gives additional information about the Pd bulk sample, showing the occurrence of crystalline regions about 50 angstrom in diameter
XPS, LEED and AFM investigation of the Si(100) surface after the deposition and annealing of tellurium thin films
No full textIn this study the structural properties and the morphology of the Te/Si(100) 2 X 1 system after an annealing process have been investigated. Several Te/Si(100) samples have been annealed at different temperatures. Up to about 150 degrees C no changes are observed in the samples. At about 200 degrees C the tellurium films evaporate from the silicon substrate leaving one monolayer of Te on the Si(100) surface indicating a higher strength in the Te-Si bonds with respect to the Te-Te one. The remaining monolayer of Te on Si(100) induces a 1 X 1 reconstruction of the surface. The annealing procedure performed at higher temperatures (more than about 400-500 degrees C), leads to the complete removal of the tellurium. The resulting silicon surface is 2 X 1 reconstructed with a different morphology with respect to the one observed before the Te film deposition. Repeating several times the deposition of Te and the annealing procedure, at temperatures higher than about 400 degrees C, a picturesque morphology of the silicon surface is observed
Study of Different Phases in a-C:H:N Thin Films Deposited by Plasma- Enhanced Chemical Vapour Deposition: A comparision Between Theoretical and Experimental Data
No full textThe electronic structure of amorphous carbon nitride (a-C:H:N) thin films prepared by radiofrequency (rf) plasma decomposition of CH4/N2 mixture was determined by soft x-ray photoe1ectron spectroscopy by the mean of synchrotron radiation source. On increasing N2 fraction, the valence band shows profound changes. The new features are identified by a comparison of the experimental spectra with theoretically weighted density of the states of graphite and C3N4 structures
XPS analysis on SiO2 sol-gel thin films
No full textThe X-ray Photoelectron Spectroscopy has been applied to study the composition and the electronic structure of thin SiO2 films prepared using the sol-gel technique on silicon substrates. Samples prepared using different amount of tetraethoxysilane and methyltriethoxysilane have been annealed at various temperatures. The valence band, the Si 2p and KL(23)L(23) Auger features have been followed as a function of the preparation conditions. The Si Auger parameter has been used to determine the attendance of different C-H and OH groups. The presence of Si-C bonds, observed in the valence band spectra, strongly decreases as the annealing temperature grows, showing the loss of methyl groups
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