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111.
112.
AbstractHigh performance and high temperature polymers are a class of polymeric materials exhibiting high thermal stability and their resistance to fire makes them valuable assets for many applications. Those applications include as typical examples high temperature gas separation membranes, automotive and aerospace industry as well as the construction industry. The high performance polymers have been synthesized since the early 1960s, and have developed rapidly over the past few decades. Most high performance polymers comprise a highly aromatic backbone, linear chains, and strong inter-chain interactions. This review deals mostly with commercial polymeric materials. Studies regarding their thermal behavior, degradation mechanism and their reaction to fire have been synthetically combined in order to bring out potential insight concerning the effect of the thermal decomposition and thermal behavior on the fire properties of those polymers. 相似文献
113.
114.
A. L. Tolstikhina R. V. Gaĭnutdinov M. L. Zanaveskin K. L. Sorokina N. V. Belugina Yu. V. Grishchenko 《Crystallography Reports》2007,52(5):894-900
Particular artifacts of atomic-force microscopy (AFM) images of dielectrics, which are related to the presence of a static charge on the surface, are described. Artificial climate control with the use of a TRACKPORE ROOM-02 climatic box during measurements makes it possible to remove the static charge, owing to which the quality of AFM images and reliability of measured metric surface characteristics increase. Comparative analysis of the surface roughness measured under conventional conditions of microscope operation (static charge is present on a dielectric surface) and under the conditions of controlled artificial climate (static charge is completely removed) is performed. It is established that, in the presence of a static charge on the surface, roughness measurements may yield both overestimated and underestimated values; the largest increase in error is observed in measurements of micro-and nanosized surface areas. 相似文献
115.
Zdzisław Wawrzak Paweł Grochulski Zdzisław Gałdecki William L. Duax Phyllis D. Strong D. N. Kirk 《Journal of chemical crystallography》1991,21(5):649-652
The title compound crystallizes in space groupP212121 with lattice constantsa=16.253(3),b=17.107(3), andc=8.486(2) Å. The A ring has 1,2-half-chair conformation. The calculated steric energy of a 6-methyl-17-ester progesterone molecule is lower by about 4 kJ/mol for the normal A-ring conformation. The progesterone side chain has typical conformation for 17-ester steroids; the C(16)-C(17)-C(20)-O(20) torsion angle is –24.9(4)°. 相似文献
116.
N. N. Novikova S. I. Zheludeva N. D. Stepina A. L. Tolstikhina R. V. Gaĭnutdinov A. I. Erko W. Haase Yu. G. Galyametdinov 《Crystallography Reports》2006,51(6):1041-1047
The molecular organization of Langmuir-Blodgett films based on the liquid crystal europium complex has been studied by the X-ray standing-wave method at the synchrotron radiation source BESSY (Germany). Analysis of the experimental data obtained made it possible to determine the composition of the organic multilayer nanosystems and localize the position of metal ions incorporated in organic layers from the aqueous subphase during film deposition. It is shown that, despite the low content of metal ions in the aqueous subphase (no higher than 10?7 mol/l), their incorporation into the Langmuir layer affects the molecular film organization significantly. 相似文献
117.
Paweł Grochulski Zdzisław Wawrzak Zdzisław Gałdecki Andrzej Szyczewski 《Journal of chemical crystallography》1991,21(1):33-37
The X-ray crystal structure of 4-methoxy-4-cholesten-3-one, C28H46O2, has been determined. Final agreement factors wereR=0.057 andR
w
=0.057 for 2912 reflections. TheA ring has a sofa-half-chair conformation, and the C4 side chain is turned under the steroid skeleton. The cholesterol side chain is fully extended, with agauche, trans conformation of the terminal C26 and C27 methyl groups. 相似文献
118.
Zdzisław Gałdecki Paweł Grochulski Zdzisław Wawrzak William L. Duax Phyllis D. Strong 《Journal of chemical crystallography》1989,19(3):561-568
The crystal and molecular structure of 3,12-dihydroxy-2-morpholino-5-pregnan-20-one, C25H41O4N, has been determined:M
r
=419.6,P21,a=13.5778(8),b=14.4340(8),c=5.8943(5) Å,=94.32(1)°,V
c
=1151.9(3) Å3,Z=2,D
x
=1.21 g cm–3,
(CuK) = 1.5418 Å, =5.6 cm–1,F(000)=460,R=0.039,R
w
=0.040 for 2421 unique observed reflections. All six-membered rings have chair conformations, and theD ring has a 13-envelope conformation. The progesterone side chain has an unusual conformation, and the C16-C17-C20-O20 torsion angle, which defines the conformation, is –152.6(3)°. The unusual conformation seems to be forced by the intramolecular hydrogen bond between the hydroxyl group at C12 and the O20 atom from the side-chain. 相似文献
119.
A new pd-catalyzed cascade reaction for the synthesis of strained aromatic polycycles 总被引:1,自引:0,他引:1
Two new palladium catalyzed cascade reactions involving a 4-exo-dig cyclocarbopalladation are described. These processes are shown to convert bromoenediynes and bromodienynes into strained aromatic compounds in a single step. 相似文献
120.
Derrien G Charnay C Zajac J Jones DJ Rozière J 《Chemical communications (Cambridge, England)》2008,(27):3118-3120
Copper-containing mesoporous silica spheres of size in the colloidal range with perfect conservation of pore-ordering, shape and monodispersity and high intra-pore metal dispersion were prepared via a new one-step synthesis and functionalisation route. 相似文献