962 resultados para Ce^3
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The database reported here is derived using the Combinatorial Extension (CE) algorithm which compares pairs of protein polypeptide chains and provides a list of structurally similar proteins along with their structure alignments. Using CE, structurestructure alignments can provide insights into biological function. When a protein of known function is shown to be structurally similar to a protein of unknown function, a relationship might be inferred; a relationship not necessarily detectable from sequence comparison alone. Establishing structurestructure relationships in this way is of great importance as we enter an era of structural genomics where there is a likelihood of an increasing number of structures with unknown functions being determined. Thus the CE database is an example of a useful tool in the annotation of protein structures of unknown function. Comparisons can be performed on the complete PDB or on a structurally representative subset of proteins. The source protein(s) can be from the PDB (updated monthly) or uploaded by the user. CE provides sequence alignments resulting from structural alignments and Cartesian coordinates for the aligned structures, which may be analyzed using the supplied Compare3D Java applet, or downloaded for further local analysis. Searches can be run from the CE web site, http://cl.sdsc.edu/ce.html, or the database and software downloaded from the site for local use.
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Mode of access: Internet.
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Mode of access: Internet.
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Plates partially hand colored.
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<p>In this work, Pr<sub>0.6</sub>Sr<sub>0.4</sub>FeO<sub>3- </sub>-Ce<sub>0.9</sub>Pr<sub>0.1</sub>O<sub>2- </sub> (PSFO-CPO) nanofibers were synthesized by a one-step electrospin technique for use in intermediate-temperature solid oxide fuel cell (IT-SOFC) applications. PSFO-CPO nanofibers were produced with a diameter of about 100nm and lengths exceeding tens of microns. The thermal expansion coefficient (TEC) matches with standard GDC electrolytes and the resulting conductivity also satisfies the needs of IT-SOFCs cathodes. EIS analysis of the nanofiber structured electrode gives a polarization resistance of 0.072cm<sup>2</sup> at 800C, smaller than that from the powdered cathode with the same composition. The excellent electrochemical performance can be attributed to the well-constructed microstructure of the nanofiber structured cathode, which promotes surface oxygen diffusion and charge transfer processes. All the results imply that the one-step electrospin method is a facile and practical way of improving the cathode properties and that PSFO-CPO is a promising cathode material for IT-SOFCs.</p>
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He II photoelectron spectra of La, Ce and Yb show features which cannot be explained in terms of single electron excitations. It is proposed that these are due to formation of electron-hole paris.
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Ce(3d) and (4d) core level XPS spectra of CeX = Fe, Co, Ni and Cu) suggest that the mean valence of Ce was as well as 4f hybridization strength decrease systematically from Fe to Cu. This observation is in agreement with the results of Bremstrahlung Isochromat Spectroscopy (BIS), but in disagreement with LIII-edge data reported earlier.
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The supramolecular structures of eight aryl protected ethyl-6-methyl-4-phenyl-2-thioxo-1,2,3,4 tetrahydropyrimidine-5-carboxyl ates were analyzed in order to understand the effect of variations in functional groups on molecular geometry, conformation and packing of molecules in the crystalline lattice. It is observed that the existence of a short intra-molecular C-H center dot center dot center dot pi interaction between the aromatic hydrogen of the aryl ring with the isolated double bond of the six-membered tetrahydropyrimidine ring is a key feature which imparts additional stability to the molecular conformation in the solid state. The compounds pack via the cooperative involvement of both N-H center dot center dot center dot S=C and N-H center dot center dot center dot O=C intermolecular dimers forming a sheet like structure. In addition, weak C-H center dot center dot center dot O and C-H center dot center dot center dot pi intermolecular interactions provide additional stability to the crystal packing.
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The supramolecular structures of eight aryl protected ethyl-6-methyl-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine- 5-carboxylates have been analyzed to determine the role of different functional groups on the molecular geometry, conformational characteristics and the packing of these molecules in the crystal lattice. Out of these the para fluoro substituted compound on the aryl ring exhibits conformational polymorphism, due to the different conformation of the ester moiety. This behaviour has been characterized using both powder and single-crystal X-ray diffraction, optical microscopy and differential scanning calorimetry performed on both these polymorphs. The compounds pack via the cooperative interplay of strong N-H center dot center dot center dot O=C intermolecular dimers and chains forming a sheet like structure. In addition, weak C-H center dot center dot center dot O=C and C-H center dot center dot center dot pi interactions impart additional stability to the crystal packing.
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Scheelite type solid electrolytes, Li(0.5)Ce(0.5-x)Ln(x)MoO(4) (x = 0 and 0.25, Ln = Pr, Sm) have been synthesized using a solid state method. Their structure and ionic conductivity (a) were obtained by single crystal X-ray diffraction and ac-impedance spectroscopy, respectively. X-ray diffraction studies reveal a space group of I4(1)/a for Li(0.5)Ce(0.5-x)Ln(x)MoO(4) (x = 0 and 0.25, Ln = Pr, Sm) scheelite compounds. The unsubstituted Li0.5Ce0.5MoO4 showed lithium ion conductivity similar to 10(-5)-10(-3) Omega(-1)cm(-1) in the temperature range of 300-700 degrees C (sigma = 2.5 x 10(-3) Omega(-1) cm(-1) at 700 degrees C). The substituted compounds show lower conductivity compared to the unsubstituted compound, with the magnitude of ionic conductivity being two (in the high temperature regime) to one order (in the low temperature regime) lower than the unsubstituted compound. Since these scheelite type structures show significant conductivity, the series of compounds could serve in high temperature lithium battery operations.
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In this study we analyzed climate and crop yields data from Indian cardamom hills for the period 1978-2007 to investigate whether there were significant changes in weather elements, and if such changes have had significant impact on the production of spices and plantation crops. Spatial and temporal variations in air temperatures (maximum and minimum), rainfall and relative humidity are evident across stations. The mean air temperature increased significantly during the last 30 years; the greatest increase and the largest significant upward trend was observed in the daily temperature. The highest increase in minimum temperature was registered for June (0.37A degrees C/18 years) at the Myladumpara station. December and January showed greater warming across the stations. Rainfall during the main monsoon months (June-September) showed a downward trend. Relative humidity showed increasing and decreasing trends, respectively, at the cardamom and tea growing tracts. The warming trend coupled with frequent wet and dry spells during the summer is likely to have a favorable effect on insect pests and disease causing organisms thereby pesticide consumption can go up both during excess rainfall and drought years. The incidence of many minor pest insects and disease pathogens has increased in the recent years of our study along with warming. Significant and slight increases in the yield of small cardamom (Elettaria cardamomum M.) and coffee (Coffea arabica), respectively, were noticed in the recent years.; however the improvement of yield in tea (Thea sinensis) and black pepper (Piper nigrum L.) has not been seen in our analysis.