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40 results on '"Heaps, David A."'

2. News and Notes

Author

Heaps, David, David, Henry, and Walton, Janie

Published
1952

3. Nonchromatographic 'Stir and Filter approach' (SAFA) for isolating [Sc.sub.3]N at the rate of [C.sub.80] metallofullerenes

Author

Stevenson, Steven, Harich, Kim, Hua Yu, Stephen, Ryan R., Philips, J. Paige, Heaps, David, and Coumbe, Curtis

Subjects
Nitrides -- Chemical properties, Chromatography -- Methods, Cyclopentadiene -- Chemical properties, Chemistry
Abstract

The use of cyclopentadienyl (CPD) and amino functionalized silica to selectively bind contaminant fullerenes is reported. This 'Stir and Filter Approach' (SAFA) provides purified metallic nitride fullerene samples at ambient and reflux conditions.

Published
2006

4. Reduction of detection limits of the direct deposition GC/FT-IR interface by surface-enhanced infrared absorption

Author

Heaps, David A. and Griffiths, Peter R.

Subjects
Molecules -- Research, Mass spectrometry -- Research, Gas chromatography -- Research, Isomerization -- Research, Chemistry
Abstract

Even though the interface of gas chromatography (GC) and mass spectrometry (MS) is by far the most popular way of identifying molecules eluting from a GC in real time, the identification of compositional isomers by MS is equivocal at best. Much better results would be found by infrared spectrometry (IR) if the sensitivity of the GC/IR interface could be improved. In this paper, we show how the smallest quantity of molecules injected into a GC for which an identifiable infrared spectrum can be measured on-line has been reduced by a factor of 10 below the detection limit of the most sensitive current technique. A commercial direct deposition interface between a GC and a Fourier transform infrared spectrometer was modified by vapor-depositing an island film of silver on the surface of the zinc selenide substrate. Band intensities in the spectra of molecules located within ~4 nm of the surface of the silver islands were increased by at least 1 order of magnitude through surface-enhanced infrared absorption (SEIRA). The effectiveness of this approach was illustrated by comparing the limits of identification of butylbenzene isomers measured with and without the silver film. Comparison with the spectra of the same molecules measured by mass spectrometry showed the increased sensitivity and specificity of the GC/SEIRA interface.

Published
2005

7. The SLA battleground: Mobile operators will need to deliver on attractive service level agreements (SLAs) if they are to give their 2.5G and 3G services a competitive edge. (Profitable Carrier Strategies)

Author

Dobson, Rob and Heaps, David

Subjects
Telecommunications services industry, Wireless telecommunications service, Wireless voice/data service, Market trend/market analysis, Quality of service, Cellular telephone services industry -- Services -- Forecasts and trends, Telecommunications services industry -- Services -- Forecasts and trends, Wireless communication systems -- Services, Communications industry -- Services -- Forecasts and trends
Abstract

Service quality was a relatively straightforward concept in the 2G world. Admittedly it was difficult to implement in the first network rollouts, but 2G operators in the early 1990s only […]

Published
2002

8. Feasibility study of terahertz time-domain measurement to monitor individual layer thickness of bilayer tablets

Author

Wang, Yifan, Muzzio, Fernando, Cuitino, Alberto, and Heaps, David

Abstract

Individual layer weight control is a critical issue for bilayer tablets during manufacturing process. Despite its importance for ensuring product content uniformity, few studies have investigated the possibility of developing a process analytical technology (PAT) tool to monitor the individual layer control. We introduced the use of Terahertz time-domain measurement because of its fast measurement to be inline/online. Its feasibility was then investigated to measure individual layer thickness for bilayer tablets. The design of experiment included API concentration, excipient type, and layer weight ratio. Tablets were scanned in Terahertz region and refractive index was measured. The predicted values from the measurement were compared to the reference. This study has shown that successful measurements are statistically consistent with the reference for each individual layer and accuracy can be even higher if measurements were taken both sides. Measurement failure scenario is also presented. Based on results, the potential possibility for Terahertz time-domain measurement to be a PAT tool for bilayer tablets is discussed.

Published
2014

14. Newsletter

Author

Esmonde-White, Francis W.L., primary and Heaps, David A., additional

Published
2011
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15. Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc3N@C80(CF3)n (n = 2−16) and Their Radical Anions

Author

Shustova, Natalia B., primary, Peryshkov, Dmitry V., additional, Kuvychko, Igor V., additional, Chen, Yu-Sheng, additional, Mackey, Mary A., additional, Coumbe, Curtis E., additional, Heaps, David T., additional, Confait, Bridget S., additional, Heine, Thomas, additional, Phillips, J. Paige, additional, Stevenson, Steven, additional, Dunsch, Lothar, additional, Popov, Alexey A., additional, Strauss, Steven H., additional, and Boltalina, Olga V., additional

Published
2011
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31. The democracy placebo

Author

Heaps, David

Subjects
United States. Department of State -- International relations, International relations -- Political aspects, Democracy -- International aspects, Political reform -- International aspects, Somalia -- Political aspects, Haiti -- Political aspects
Published
1994

32. Fighting the good fight

Author

Heaps, David

Subjects
Amnesty International -- Reports, Human rights workers -- Services, Human rights -- International aspects
Published
1990

36. OVEREXTENDED.

Author

Heaps, David

Subjects
*LETTERS to the editor
Abstract

Presents a letter in reference to the article "Just Following Orders," published in the October 3, 1988 issue, related to the content of a speech by political advisor Frank Mankiewicz.

Published
1988

37. CREDITING CARTER.

Author

Heaps, David

Subjects
*LETTERS to the editor, *HUMAN rights
Abstract

Presents a letter to the editor commenting on the article "The New Republic And Its Times" that was published in the December 10, 1984 issue of the periodical.

Published
1985

38. Rats.

Author

Heaps, David

Subjects
*LETTERS to the editor, *CONSERVATIVES
Abstract

Presents a letter to the editor related to the article "Conservatives for Clinton," published in the November 2, 1992 issue.

Published
1992

39. Opinion.

Author

Burt, Daniel, Banks, John, Johnson, Chris, White, Margaret, Downie, Ian, Heaps, David, and Szpiro, Oded

Subjects
LETTERS to the editor, INCOME inequality, COMPUTER science, COMPUTER training, TRAFFIC safety
Abstract

Presents several letters to the editor in reference to articles and topics that were discussed in the previous issues. Comparison of the salaries of women with their male counterparts; Analysis of the curriculum of computer science in schools; Need for accuracy in the British government's road-pricing plan.

Published
2005

40. Nonchromatographic "Stir and Filter Approach" (SAFA) for Isolating Sc3N @ C80 Metallofullerenes.

Author

Stevenson, Steven, Harich, Kim, Hua Yu, Stephen, Ryan R., Heaps, David, Coumbe, Curtis, and Phillips, J. Paige

Subjects
*NITRIDES, *HEAT resistant alloys, *METALS, *FULLERENES, *FILTERS & filtration, *CHEMICAL research
Abstract

Separation difficulties have led to a paucity of purified metallic nitride fullerenes (MNFs). Fundamental research and application development has been hampered with limited sample availability. Separation techniques designed to remove contaminant empty-cage fullerenes (e.g., C60, C70…C20) and classical metallofullerenes (e.g., non-MNFs) traditionally require expensive and tedious chromatographic methods. Our motivation is an alternative purification approach to minimize dependence on HPLC. Herein we report the use of cyclopentadienyl (CPD) and amino functionalized silica to selectively bind contaminant fullerenes. This ‘Stir and Filter Approach› (SAFA) provides purified MNF samples at ambient and reflux conditions. Under reflux conditions, purified MNFs (80% recovery, 41 h) are obtained using CPD silica. However, at room temperature, there is an equilibrium established between fullerenes and CPD silica, and no purified MNF samples are obtained using SAFA. In contrast, purified MNF samples (99+%) are readily obtained at room temperature using amino, diamino, and triamino silica at recoveries of 93% (11 h), 76% (9 h), and 50% (6 h), respectively. [ABSTRACT FROM AUTHOR]

Published
2006
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