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J. L. Whitton 《辐射效应与固体损伤》2013,168(3)
Proceedings of the second conference on surface effects in controlled fusion devices, San Francisco, USA, February 1976. (Eds. W. Bauer, C. R. Finfgeld and M. Kaminsky). North Holland (Amsterdam), 534 pages. US $120.50. 相似文献
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Abstract A systematic investigation of the dechanneling of protons in tungsten has been completed for the <111> axial direction and also for the (110) plane. Measurements at room temperature have been made at energies of 0.5, 2.0, 3.5, 8.0 and 12.0 MeV; at 2.0 MeV, the effect of target temperature has been investigated over the range 77–873°K. In the axial case, the dechanneling rate increases strongly with the vibrational amplitude ρ, but not as strongly as the ρ2 dependence reported by the Catania group (Refs. 4–7) for silicon and germanium. Also, unlike silicon and germanium, the tungsten axial data exhibit practically no energy dependence and so cannot be fitted by the zρ2/E scaling parameter suggested by the Catania group. On the other hand, the planar dechanneling data in tungsten exhibit the predicted (E ?1)dependence and relatively littie temperature dependence, in good agreement with previous work. 相似文献
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Arborescent micelles: Dendritic poly(γ‐benzyl l‐glutamate) cores grafted with hydrophilic chain segments 下载免费PDF全文
Greg Whitton Mario Gauthier 《Journal of polymer science. Part A, Polymer chemistry》2016,54(9):1197-1209
Amphiphilic copolymers were obtained by grafting arborescent poly(γ‐benzyl l ‐glutamate) (PBG) cores of generations G1–G3 with polyglycidol, poly(ethylene oxide) (PEO), or poly(l ‐glutamic acid) (PGA) chain segments. The PBG substrates were synthesized by two methods: (1) subjecting PBG samples with a dispersity ? = Mw/Mn < 1.1 to partial acidolysis of the benzyl ester groups, to produce randomly distributed carboxylic acid functionalities, and (2) using PBG chains containing a glutamic acid di‐tert‐butyl ester initiator fragment in the last grafting cycle of the PBG core synthesis, and selective acidolysis of the tert‐butyl ester groups to obtain substrates with carboxylic acid termini. Linear polymers with ? < 1.20 and a primary amine terminus were also synthesized to serve as hydrophilic shell materials: Polyglycidol and PEO by anionic polymerization, and PGA by N‐carboxyanhydride ring‐opening polymerization. These polymers, combined with the two different PGB substrate types, allowed the evaluation of the usefulness of random versus chain‐end grafting in producing arborescent copolymers useful as unimolecular micelles in organic and aqueous media. Size exclusion chromatography served to determine the grafting yield, molar mass, dispersity, and branching functionality of the copolymers. Dynamic light scattering measurements provided information on their aggregation behavior in aqueous environments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1197–1209 相似文献
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K. Yoganathan Shugeng Cao Sharon C. Crasta Srinivasulu Aitipamula Stephen R. Whitton Siewbee Ng Antony D. Buss Mark S. Butler 《Tetrahedron》2008,64(44):10181-10187
Bioassay-guided isolation using an MRSA whole cell assay yielded four novel benzophenone dimers, microsphaerins A–D (1–4), from two Singapore isolates of the soil anamorph Microsphaeropsis sp. The structures of 1–4 were elucidated on the basis of spectral data and the structures of 1 and 4 were confirmed by X-ray crystallographic analyses. 相似文献
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Nagaraja TN Nagesh V Ewing JR Whitton PA Fenstermacher JD Knight RA 《Magnetic resonance imaging》2007,25(3):311-318
A rat model of transient suture occlusion of one middle cerebral artery (MCA) was used to create a unilateral reperfused cerebral ischemic infarct with blood-brain barrier (BBB) opening. Opening of the BBB was visualized and quantitated by magnetic resonance (MR) contrast enhancement with a Look-Locker T(1)-weighted sequence either following an intravenous bolus injection (n=7) or during a step-down infusion (n=7) of gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA). Blood levels of Gd-DTPA after either input were monitored via changes in sagittal sinus relaxation rate. Blood-to-brain influx constants (K(i)) were calculated by Patlak plots. On the basis of the MRI parameters and lesion size, the ischemic injury was determined to be similar in the two groups. The bolus injection input produced a sharp rise in blood levels of Gd-DTPA that declined quickly, whereas the step-down infusion led to a sharp rise that was maintained relatively constant for the period of imaging. Visual contrast enhancement and signal-to-noise (S/N) ratios were better with the step-down method (S/N=1.8) than with bolus injection (S/N=1.3). The K(i) values were not significantly different between the two groups (P>.05) and were around 0.005 ml/(g min). The major reason for the better imaging of BBB opening by the step-down infusion was the higher amounts of Gd-DTPA in plasma and tissue during most of the experimental period. These results suggest that step-down MR contrast agent (MRCA) administration schedule may be more advantageous for detection and delineation of acute BBB injury than the usually used bolus injections. 相似文献
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Silicon single crystals were implanted at room temperature with Xe and I ions in the energy range 20 to 150 keV and with 20 to 50 keV P ions. The lattice disorder induced by these implants was measured by a combination of the channeling and Rutherford backscattering techniques. The disorder produced by implanting I and Xe ions exhibited a similar relationship with implantation energy to that previously established for bismuth implants. The P ion implants induced less lattice disorder per incident ion in the energy range studied. Integral depth distributions of the implanted ions and of the lattice disorder were obtained by combining a layer removal technique with radiotracer implants of 110 keV 133Xe and 40 keV 32P. The depth distributions showed that in both cases the ions penetrate deeper into the crystal than the damage they produce but that the separation is significantly greater for the P implant than for the Xe implant. 相似文献
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The possibility of using ion implantation to form high concentration junctions in semiconductors has been explored for the specific case of sulphur in GaAs, GaP and Ge. The effects of ion dose, ion energy, crystal orientation and target temperature have been investigated by means of radiotracers and sectioning techniques. It is shown that high concentration junctions can be formed using an incident ion having high electronic stopping cross-section and implanted along the <110< channeling directions of the crystals. A large increase in junction concentration may be obtained when the GaAs and GaP crystals are maintained at 150 °C during the implantation process, but this is not the case with Ge. Rutherford back-scattering of 1 MeV He+ ions has been used to measure the ion-bombardment induced damage in the crystals and to show how this damage can be annealed by heating the crystal during the implantation. The annealing, at temperatures up to 150 °C, is most effective in GaAs and least effective in Ge. 相似文献
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Carter G. Nobes M. J. Whitton J. L. 《Applied Physics A: Materials Science & Processing》1985,38(2):77-95
The generation and development of surface features by ion bombardment induced sputtering erosion of f.c.c. metals is reviewed. Studies with polycrystalline substrates reveal the plethora of individual features, both etch pits and cones and the repetitive features, such as ripple trains, which form differently on different crystallite surfaces. Studies with well defined single crystals clarify the origins of such features and the relative independence of their habit on ion species and substrate material. 相似文献