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211.
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H. D. Hochheimer E. Gmelin W. Bauhofer Ch. von Schnering-Schwarz H. G. von Schnering J. Ihringer W. Appel 《Zeitschrift für Physik B Condensed Matter》1988,73(2):257-263
The real part of the dielectric constant , the heat capacityc
p, the infrared reflectivity, and the X-ray diffraction of TlGaSe2 have been measured in the temperature range from 12 K (30K) to 300 K. Both andc
p show two anomalies at about 110 K and 120 K. A study of the hysteresis loop as well as an investigation of the dielectric dispersion in the microwave region show that the phase below 110 K is ferroelectric. The crystal structure remains nearly unchanged in the course of the phase transition. The loss of the
symmetry (C2/cCc) results from small positional shifts of the T1 atoms in the ab plane accompanied by a discontinuity in the axial ratios. We suggest, that the ferroelectricity is caused by the stereochemically active electron lone pair configuration of the Tl+ ion. Thus TlGaSe2 may provide the first example for ferroelectricity caused by this mechanism. 相似文献
214.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Duboscq JE Elliot JR Escobar CO Gibney MC Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Ong P Pinfold J Punkar G Purohit MV Ross WR Santoro AF Shoup AL Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundzia AB Witherell MS 《Physical review D: Particles and fields》1992,46(1):R1-R5
215.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Duboscq JE Elliott JR Escobar CO Gibney MC Hartner GF Huber J Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Pinfold J Punkar G Purohit MV Ross WR Santoro AF Schmidt DM Shoup AL Sliwa K Sokoloff MD Souza MH Sperka D Spalding WJ Streetman ME Stundzia AB Witherell MS 《Physical review D: Particles and fields》1992,46(5):1941-1950
216.
Anjos JC Appel JA Bean A Bracker SB Browder TE Cremaldi LM Duboscq JE Elliott JR Escobar CO Gibney MC Hartner GF Karchin PE Kumar BR Losty MJ Luste GJ Mantsch PM Martin JF McHugh S Menary SR Morrison RJ Nash T Nauenberg U Ong P Pinfold J Punkar G Purohit MV Santoro AF Sidhu JS Shoup AL Sliwa K Sokoloff MD Souza MH Spalding WJ Streetman ME Stundzia AB Witherell MS 《Physical review D: Particles and fields》1990,41(9):2705-2708
217.
Tricyclic analogs 2a and 8 were prepared by four-step routes. The key step was an intermolecular hetero Diels-Alder reaction involving a quinone methide. 相似文献
218.
The MELANIE project: from a biopsy to automatic protein map interpretation by computer. 总被引:3,自引:0,他引:3
R D Appel D F Hochstrasser M Funk J R Vargas C Pellegrini A F Muller J R Scherrer 《Electrophoresis》1991,12(10):722-735
The goals of the MELANIE project are to determine if disease-associated patterns can be detected in high resolution two-dimensional polyacrylamide gel electrophoresis (HR 2D-PAGE) images and if a diagnosis can be established automatically by computer. The ELSIE/MELANIE system is a set of computer programs which automatically detect, quantify, and compare protein spots shown on HR 2D-PAGE images. Classification programs help the physician to find disease-associated patterns from a given set of two-dimensional gel electrophoresis images and to form diagnostic rules. Prototype expert systems that use these rules to establish a diagnosis from new HR 2D-PAGE images have been developed. They successfully diagnosed cirrhosis of the liver and were able to distinguish a variety of cancer types from biopsies known to be cancerous. 相似文献
219.
Experimental data conclusively shows that the weak van der Waals interactions between alkane molecules, <1.5% the strength of covalent bonding on a per carbon atom basis, modify the carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectrum significantly in ordered solids, both in intensity, spectral shape, peak position, and dichroic signature. This constitutes a further breakdown of the ‘building block’ model, or, more precisely, even a molecular model in interpreting NEXAFS spectra. These observations have significant implications for the interpretation and use of NEXAFS spectra from any crystalline or semi-crystalline macromolecules, small molecules, or other weakly interacting systems. 相似文献
220.
The enthalpies of reaction of the complexes (acac)M(olefin)2 (acac=acetyl-acetonate, M=Rh(I), Ir(I); olefin=ethylene, propene, vinyl chloride, vinyl acetate, methyl acrylate and styrene) with 1,5-cyclooctadiene in n-heptane, according to the reaction [(acac)M(olefin)2 + 1,5COD → (acac)M(1,5COD) + 2 olefin]n.heptane have been determined by solution calorimetry. From these results the influence of substituent R in the olefin CH2CHR on the M---(CH2CHR) displacement enthalpy has been derived. It is concluded that π back-bonding is slightly more important in the Ir---olefin bond than in the Rh---olefin bond. Furthermore, the data show that, as a result of steric factors which inhibit the approach of solvent molecules, solvation enthalpies are not additive. 相似文献