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11.
RD Harris WS Baker Van Stipdonk MJ RM Crooks EA Schweikert 《Rapid communications in mass spectrometry : RCM》1999,13(14):1374-1380
A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Richard D. Foust Jr. Brandon Cruickshank Michael Stringer Julie Olander 《The Chemical Educator》1999,4(3):108-111
Four semesters of student evaluations of an environmental chemistry class have been analyzed for differences that can be attributed to Web-based enhancements. The enhancements included Web-based lecture notes, reading and problem assignments, bookmark files, and videotaped lectures. We developed these materials as part of a larger project to provide university-level technical courses over the Internet. Student perceptions of the course improved significantly (α = 0.10) after adding Web-based enhancements. Student’s opinion of the instructor improved, but the change is not significant at the 90% confidence level. The student responses to “Was the course challenging?” “Was my interest stimulated?” and “Was the instructor concerned?” were unchanged in the two groups of students. Drop rates were unchanged between the two student groups. The grade-average was nearly identical for the two student groups (82.9% vs. 83.5%), but the grade-distribution changed significantly. The percentage of A’s decreased slightly when Web-based enhancements were added, but the number of B’s increased from 22% to 40%. The percentage of C’s, D’s and F’s decreased for the students with access to Web-based enhancements. These results indicate that Web-based materials helped weaker students improve their performance and, therefore, their opinion of the class and of the instructor was more favorable. 相似文献
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Aderholz M Aggarwal MM Akbari H Allport PP Badyal SK Ballagh HC Barth M Baton JP Bingham HH Brucker EB Burnstein RA Campbell JR Cence RJ Chatterjee TK Clayton EF Corrigan G Coutures C DeProspo D Devanand De Wolf EA Faulkner PJ Foeth H Fretter WB Gupta VK Hanlon J Harigel G Harris FA Jabiol MA Jacques P Jain V Jones GT Jones MD Kafka T Kalelkar M Kasper P Kohli JM Koller EL Krawiec RJ Lauko M Lys JE Marage P Milburn RH Miller DB Mittra IS Mobayyen MM Moreels J Morrison DR Myatt G Nailor P 《Physical review D: Particles and fields》1992,45(7):2232-2243
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Collision-induced dissociation of the ions [ArS]?, [ArSO]? and [ArSO2]? has uncovered a rich and varied ion chemistry. The major fragmentations of [ArS]? are complex and occur without prior ring hydrogen scrambling: for example, [C6H5S]?→[C2HS]? and [HS]?; [p-CD3C6H4S]?→[C6H4S]?˙, [CD3C4S]? and [C2HS]?. In contrast, all decompositions of [C6H5CH2S]? are preceded by specific benzylic and phenyl hydrogen interchange reactions. [ArSO2]? and [ArSO2]? ions undergo rearrangement, e.g. [C6H5SO]?→[C6H5O]? and [C6H5S]?; [C6H5SO2]?→[C6H5O] ?. The ion [C6H5CH2SO]? eliminates water, this decomposition is preceded by benzylic and phenyl hydrogen exchange. 相似文献
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Acyl transfer from p-nitrophenyl trimethylacetate to hydrogen peroxide in millimolar aqueous solutions of an amphiphilic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer slows down as the temperature is raised due to partitioning of the hydrophobic ester into heat-induced micelles. 相似文献
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Brian E. Mann Bernard L. Shaw Allan J. Stringer 《Journal of organometallic chemistry》1974,73(1):129-130
One of the sets of hydride 1H NMR patterns for the isothiocyanato/thiocyanato mixture trans- [PtH(SCN) (PEt3)2] is broad. Previously there had been disagreement on the cause of this broadening. It is now shown to be due to the 14N quadrupole by double resonance. 相似文献