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41.
Optically active 4-demethoxyanthracyclinoiies (39a-g) bearing a variety of substituents at the 9position have been synthesised by an analogous route to that previously employed by us for (+)-4-demethoxydaunomycinone (5). These novel anthracyclinones have been prepared in sufficient quantity for subsequent glycosidation and biological evaluation. 相似文献
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43.
When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data. 相似文献
44.
Gareth W. Harbottle Neil Feeder Karl R. Gibson Mel Glossop Graham N. Maw William A. Million Florence F. Morel Simon Osborne Cedric Poinsard 《Tetrahedron letters》2007,48(24):4293-4296
The syntheses of 6-fluoropyrido[3,4-d]pyrimidin-4-ylamine derivatives is reported herein. Methods for generating C, N and O linked analogues under microwave irradiation are described. 相似文献
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46.
Hiroshi Shinotsuka Shigeo Tanuma Cedric J. Powell 《Surface and interface analysis : SIA》2022,54(5):534-560
We have calculated inelastic mean free paths (IMFPs) for 14 organic compounds (26-n-paraffin, adenine, β-carotene, diphenyl-hexatriene, guanine, Kapton, polyacetylene, poly (butene-1-sulfone), polyethylene, polymethylmethacrylate, polystyrene, poly(2-vinylpyridine), thymine, and uracil) and liquid water for electron energies from 50 eV to 200 keV with the relativistic full Penn algorithm including the correction of the bandgap effect in insulators. These calculations were made with energy-loss functions (ELFs) obtained from measured optical constants and from calculated atomic scattering factors for X-ray energies. Our calculated IMFPs could be fitted to a modified form of the relativistic Bethe equation for inelastic scattering of electrons in matter from 50 eV to 200 keV. The average root-mean-square (RMS) deviation in these fits was 0.17%. The IMFPs were also compared with a relativistic version of our predictive Tanuma–Powell–Penn (TPP-2M) equation. The average RMS deviation in these comparisons was 7.2% for energies between 50 eV and 200 keV. This average RMS deviation is smaller than that found in a similar comparison for our group of 41 elemental solids (11.9%) and for our group of 42 inorganic compounds (10.7%) for the same energy range. We found generally satisfactory agreement between our calculated IMFPs and values from other calculations for energies between 200 eV and 10 keV. We also found reasonable agreement between our IMFPs for organic compounds and measured IMFPs for energies between 50 eV and 200 keV. Substantial progress for IMFP measurements for liquid water has been made in recent years through the invention of liquid water microjet photoelectron spectroscopy and droplet photoelectron imaging. We found that the IMFPs from these experiments and the associated analyses were larger than our IMFPs by factors between two and four for energies between about 30 eV and 1000 eV. The energy dependences of the measured IMFPs are, however, similar to that of our IMFPs in the same energy range. Since IMFPs calculated from the same algorithm for a number of inorganic compounds agree reasonably well with measured IMFPs for energies between 100 eV and 200 keV, the large differences between IMFPs for water from recent experiments and our results are surprising and need to be resolved with additional experiments. 相似文献
47.
L. Laiarinandrasana T. F. Morgeneyer H. Proudhon C. Regrain 《Journal of polymer science. Part A, Polymer chemistry》2010,48(13):1516-1525
In this study an attempt is made to link the damage and microstructural evolution of semicrystalline polymers, in particular polyamide 6, to the macroscopic material behavior during tensile and creep tests. Tensile specimens, removed before failure were seen to have undergone striction. They were examined using synchrotron radiation tomography. These samples showed elongated axisymmetric columns of voids separated by thin ligaments of material. These observations were confirmed and refined through a cryofractography experiment of a different tensile sample, stopped before failure. An attempt was made to obtain quantitative data about void volume fraction and morphology through image analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1516–1525, 2010 相似文献
48.
Schwab DE Tard C Brecht E Peters JW Pickett CJ Szilagyi RK 《Chemical communications (Cambridge, England)》2006,(35):3696-3698
X-ray absorption spectroscopic measurements and density functional calculations suggest that the hydrogenase H-cluster is best described as an electronically inseparable 6Fe-cluster due to extensive delocalization of frontier molecular orbitals of the iron centres, sulfide and the non-innocent dithiolate ligands. 相似文献
49.
Two-terminal thin films of poly(3-hexylthiophene) (P3HT) with a wide electrode separation (150 m) has been studied using current-voltage characteristics at different temperatures. Space-charge-limited conduction (SCLC) with high injection barriers (1.3 eV) has been observed at all temperatures in the low electric field regime. A possible transition from SCLC to injection-limited conduction (ILC) is reported. The experimental results have been compared with the disorder-controlled injection model proposed by Arkhipov et al. [V.I. Arkhipov, H. von Seggern, E.V. Emilianova, Appl. Phys. Lett. 83 (2003) 5074; V.I. Arkhipov, E.V. Emilianova, Y.-H. Tak, H. Bässler, J. Appl. Phys. 84 (1998) 848; V.I. Arkhipov, U. Wolf, H. Bässler, Phys. Rev. B 59 (1999) 7514]. 相似文献
50.
Mezzenga R Meyer C Servais C Romoscanu AI Sagalowicz L Hayward RC 《Langmuir : the ACS journal of surfaces and colloids》2005,21(8):3322-3333
We have investigated the rheological properties of lyotropic liquid crystals (LCs) formed by self-assembled neutral lipids and water, their relationship with the topology of the structure, and their dependence on temperature and water content. The phase diagram of a representative monoglyceride-water system, determined by combining cross-polarized optical microscopy and small-angle X-ray scattering (SAXS), included four structures: lamellar, hexagonal, gyroid bicontinuous cubic (Ia3d), and double diamond bicontinuous cubic (Pn3m), as well as several regions of two-phase coexistence of some of the above structures. Rheology in the linear viscoelastic regime revealed a specific signature that was characteristic of the topology of each structure considered. The order-order transitions lamellar-to-cubic and cubic-to-hexagonal, as well as the order-disorder transitions from each LC to an isotropic fluid, were easily identified by following the development of the storage and loss moduli, G' and G', respectively. The viscoelastic properties of both bicontinuous cubic phases were shown to be strongly frequency-dependent, following a pseudo-Maxwell behavior, with multiple relaxation times. Cubic-to-cubic transitions were nicely captured by scaling the longest relaxation time, tau, with either temperature or water volume fraction. Therefore, the set of the three main parameters used to establish the rheological behavior of the structure, that is, G', G', and relaxation time, tau, constitutes a consistent ensemble to identify the structures of the liquid crystal. Finally, relaxation spectra, extracted for all liquid crystalline phases, allowed an additional possible identification criterion of the various structures considered. 相似文献