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Parts molded from reground BPA polycarbonate (PC) resin recovered from used objects do not always give the desired physical properties as parts molded from virgin resin. This loss of properties appears due to a surface hydrolysis of the PC which results in a reduction in molecular weight and formation of bis-phenol-A (BPA). The hydrolysis appears to be aided by exposure to uv-light and humidity. If the surface of the PC is washed with caustic solution, BPA and low MW oligomers are removed and many of the physical properties of the PC are restored. 相似文献
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Bruce T. Bolon M.A. HaugenA. Abin-Fuentes J. DeneenC.B. Carter C. Leighton 《Journal of magnetism and magnetic materials》2007
We have used ferromagnet/antiferromagnet/ferromagnet trilayers and ferromagnet/antiferromagnet multilayers to probe the grain size dependence of exchange bias in polycrystalline Co/Fe50Mn50. X-ray diffraction and transmission electron microscopy show that the Fe50Mn50 (FeMn) grain size increases with increasing FeMn thickness in the Co (30 Å)/FeMn system. Hence, in Co(30 Å)/FeMn(tAF Å)/Co(30 Å) trilayers the two Co layers sample different FeMn grain sizes at the two antiferromagnet/ferromagnet interfaces. For FeMn thicknesses above 100 Å, where simple bilayers have a thickness-independent exchange bias, we are therefore able to deduce the influence of FeMn grain size on the exchange bias and coercivity (and their temperature dependence) simply by measuring trilayer and multilayer samples with varying FeMn thicknesses. This can be done while maintaining the (1 1 1) orientation, and with little variation in interface roughness. Increasing the average grain size from 90 to 135 Å results in a fourfold decrease in exchange bias, following an inverse grain size dependence. We interpret the results as being due to a decrease in uncompensated spin density with increasing antiferromagnet grain size, further evidence for the importance of defect-generated uncompensated spins. 相似文献
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Nuclear systematics and the abundance of elements and isotopes in meteorites, in planets, in the solar photosphere, in the solar wind, and in solar flares are used to estimate the abundance of elements in the Sun. The results indicate that 56Fe, the decay product of doubly-magic 56Ni, is the Sun"s most abundant nuclide. The next most abundant nuclide is the doubly-magic 16O. The most abundant elements – Fe, Ni, O, Si, S, Mg, and Ca – are the even-Z elements that Harkins1 found to comprise -99% of ordinary meteorites. The least abundant elements have loosely bound nucleons (Li, Be and B) further confirming the proposed link1 between abundance and nuclear structure, with one conspicuous and important exception. Diffusion enriches light-weight nuclides at the solar surface, hiding the link of abundance to nuclear stability beneath the Sun"s H-rich exterior. 相似文献
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Al-Hashimi HM Bolon PJ Prestegard JH 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,142(1):153-158
Dipole-dipole couplings between pairs of spin 12 nuclei, which can be measured from NMR spectra in field-ordered media, offer useful constraints on the orientation of various fragments in molecular systems. However, the orientation of fragments relative to a molecule fixed reference frame is often key to complete structure determination. Here, we demonstrate that the symmetry properties of molecular complexes can aid in the definition of a reference frame. It is shown that a threefold rotational symmetry axis dictates the direction and symmetry of the experimentally determined order tensor for alpha-methyl-mannose in fast exchange among the three symmetry-related binding sites of mannose binding protein. This approach facilitates studies of the geometry of the ligand in the protein-ligand complex and also may provide a novel route to structure determination of a homomultimeric protein. 相似文献
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O. Manuel C. Bolon Prashanth Jangam 《Journal of Radioanalytical and Nuclear Chemistry》2002,251(3):417-422
The nuclear energy surface is presented as three-dimensional (3-D) plots of mass or atomic number versus charge density versus average energy per nucleon. These plots reveal a trough or cradle of the nuclides. Stable and long-lived nuclides are located in the valley. Those that are radioactive or are easily destroyed by fusion or fission occupy higher positions. Separate modes of nucleosynthesis fill the cradle from different directions and produce distinct occupancy levels, i.e., different abundance patterns. The cradle can be used to estimate the properties of nuclear matter that cannot be studied in the laboratory. 相似文献
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Arunmozhiarasi Armugam Charmian DN Cher KaiYing Lim Dawn CI Koh David W Howells Kandiah Jeyaseelan 《BMC neuroscience》2009,10(1):120
Background
Phospholipase A2 liberates free fatty acids and lysophospholipids upon hydrolysis of phospholipids and these products are often associated with detrimental effects such as inflammation and cerebral ischemia. The neuroprotective effect of neutral phospholipase from snake venom has been investigated. 相似文献9.
J.F. Martin C. Bolon R.C. Lanza D. Luckey L.S. Osborne D.G. Roth G.J. Feldman G. Hanson D.E. Lyon M.L. Perl T. Pun J.T. Dakin 《Physics letters. [Part B]》1976,65(5):483-486
We present a high statistics study of particle ratios in electroproduction of forward hadrons. The π+/π? ratios for a proton target rise monotonically to a value of 2.4 ± 0.2 at Q2 of 3 (GeV/c)2 and for a neutron target average 1.16 ± 0.04 from Q2 of 0.35 to 3 (GeV/c)2. We report the first data on electroproduction of , and measure the cross sections of K±, p, and relative to pions as a function of Q2. 相似文献
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