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11.
Irradiation of 3,3'-[ethane-1,2-diyl]bis-[1,2,4-triazolo-[4,3-a]pyridine] at 300 nm gave the cisoid-fused cyclobutane dimer 5aα,5bα-10bα,10cα-tetrahydro-1,10-ethano-2,3,8,9,10a,10d-hexaazadicyclopenta[a,i]biphenylene. Under the same conditions 3,3'-[propane-1,3-diyl]bis-[1,2,4-triazolo[4,3-a]pyridine] gave the corresponding cyclobutane dimer, 5aα,5bα,10bα,10cα-tetrahydro-1,10-propano-2,3,8,9,10a,10d-hexaazadicyclopenta[a,i]biphenylene whereas at 254 nm the photoproduct obtained had the “cage-like” structure 3b,3c,3d,3e,6b,6c,6d,6e-octahydro-3, 4-propano-1,2,3a,3f,5,6-hexaazadicyclobuta[def,jkl]dicyclopenta[b,h]biphenylene. Replacement of the hydrocarbon linkage with the oxybis(methylene) or a thiobis(methylene) unit and irradiation at 300 nm gave the corresponding cisoid-fused, cyclobutane dimers only. The effect of methyl substituents in the pyridine ring of the bicyclic system on the dimerization process was also studied. 相似文献
12.
L. H. Dunlap 《Journal of Polymer Science.Polymer Physics》1966,4(5):673-684
Specific heats of plasticized poly(vinyl chloride) can be readily obtained by means of the thin foil calorimeter when the polymer is fabricated into sheet or film. The effects of temperature and plasticizer content on the specific heat and of the plasticizer content on the glass temperature are readily observed. The data may be used to estimate the glass temperatures of plasticizers where those temperatures are not readily reached by normal techniques. The specific heat at the glass temperature is approximately 0.255 for the ranges of 0–30 phr plasticizer. A definite glass transition is not observed with 60 phr plasticizer. No other transitions were observed between 200 and 400°K. The previous history of the polymer is important, as it can change the specific heat of the polymer noticeably, especially above the glass temperature. Comparison of the values listed here with those obtained by others should be made with the understanding that these samples were fabricated by extrusion and were free of observable strain. The degree of crystallinity of these polymers is very small, probably less than 10%, since none was found by x-ray diffraction. The plasticizing effect of some stabilizers was noted. 相似文献
13.
N. Rösch P. Sandl P. Knappe A. Görling B. I. Dunlap 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1989,12(1-4):547-550
LCGTO Xα model cluster calculations have been carried out to rationalize the shape of the CO 1π band of the chemisorption system CO/Ni(111) observed in angular resolved photoemission. The splitting induced by substrate interaction at twofold bridging sites (0.4 eV) is much smaller than the value deduced from experiment (1.2 eV). From calculations on (CO) n clusters lateral adsorbate interaction is estimated to cause a sizable broadening of the 1π band (1.2eV, in satisfactory agreement with experiment), but essentially no splitting (?0.1 eV). Therefore, rehybridisation due to local interaction does not seem to suffice as an explanation for the observed shape of the CO 1π band. 相似文献
14.
R.L. Rasera G.K. Shenoy B.D. Dunlap D.G. Westlake 《Journal of Physics and Chemistry of Solids》1979,40(1):75-77
Time-differential perturbed γ-ray angular correlation experiments have been carried out on 181Ta impurities in ?-phase zirconium hydride over the temperature range from 20 to 588 K. A static, slightly asymmetric electric quadripole interaction is found at all temperatures. The static nature of the pattern indicates the absence of significant hydrogen diffusion at these temperatures on the time scale of the experiment (0.1 μsec). The temperature dependence of the static quadrupole frequency is given by the relation vq(t) = 130[1 ? (1.9 × 10?5)T1.5] MHz. 相似文献
15.
The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe). 相似文献
16.
17.
D. Niarchos P.J. Viccaro G.K. Shenoy B.D. Dunlap J.K. Yakinthos 《Journal of Physics and Chemistry of Solids》1983,44(4):307-309
The values of the magnetic moments and the electric field gradient in TmNi3 and TmCo3 are obtained from 169Tm Mössbauer spectroscopy. These values are compared to those from crystal field model based on point charge calculations for these intermetallics. 相似文献
18.
Part I. Chromatography using ultra-stable metal oxide-based stationary phases for HPLC 总被引:1,自引:0,他引:1
The first part of the review contrasts the main drawbacks of silica-based packings such as their relative thermal and chemical instability with excellent stability of metal oxides. The paper concerns mainly ZrO2, TiO2 and Al2O3. Methods of preparation of spherical particles for HPLC are described. Surface chemistry of the oxides is, however, very different from that of silica. Ability of the oxides to ion- and ligand exchange is discussed from a chromatographic point of view. 相似文献
19.
Yuehai Liang B. Dabrowski C. W. Kimball Weimin Peng
B. D. Dunlap
《Physica C: Superconductivity and its Applications》1992,190(4):415-426Mössbauer studies on 57Fe-doped superconducting REBa2Cu3O7+δ (RE=Er, Dy) were made as a function of temperature for x=0.15 and 0.30. The magnetic behavior of the 3d dopants, which mainly occupy Cu(1) sites, undergoes antiferromagnetic ordering which is coexistent with superconductivity at low temperature. The dimensionality of the magnetic interaction changes from 2D to 3D when the rare earth changes from Er to Dy. the line-widths of the Mössbauer subspectra are characteristic of magnetic fluctuation behavior in the vicinity of a phase transition. Combining these results with those of Fe-doped Y-123 (pseudo 1D) and Gd (3D), the magnitude of the rare earth moments appears to be strongly correlated with the dimensionality of the magnetic interaction of Fe dopants in these compounds. However, the Mössbauer spectrum for 155Gd in GdBa2Cu2.85Fe0.15O7+δ (TN(Fe) 14 K) shows no magnetic order at 4.9 K. 相似文献
20.
Ritesh Sachan Abhinav Malasi Sagar Yadavali Blake Griffey John Dunlap Gerd Duscher Ramki Kalyanaraman 《Particle & Particle Systems Characterization》2015,32(4):476-482
Currently, one of the challenges in high‐resolution transmission electron microscopy (TEM) studies of nanomaterials is to make contamination‐free materials in a simple and time‐efficient way. Here, a method is demonstrated that combines nanosecond‐pulsed laser dewetting of thin films with a film float‐off technique to realize nanostructures (NSs) on electron‐transparent substrates in a robust and rapid manner. NSs of metal (Ag) and bimetals (AgCo, AuCo) ranging from 20 to 150 nm are synthesized on thin carbon film deposited on mica substrates. The NS/carbon system is subsequently transferred onto TEM grids by a float‐off process resulting from debonding of the carbon from mica due to their contrasting hydrophobic nature. This process enables the fabrication of different NSs on flexible and electron‐transparent substrates. 相似文献