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192 results on '"Herron N"'

4. Phosphatovanadium chemistry: new compounds, including an example of 'Tenne's prospect', and oxidation of cyclohexadiene

Author

Thorn, D.L., Harlow, R.L., and Herron, N.

Subjects
Chemistry, Inorganic -- Research, Vanadium -- Research, Phosphorus compounds -- Research, Complex compounds -- Research, Metal halides -- Research, Chemistry
Abstract

Several phosphatovanadium cluster compounds with embedded halide ions were investigated. They include the chloride (VO)6(O3POSiMe3)8Cl and the fluoride Et4P (sup +) (V2O3)2(O3PPh)4F (sup -) and the methylphosphato and butyl phosphato analogues of the fluoride compound. Both enable the oxidation of 1,4-cyclohexadiene to benzene in hot pyridine mixture. In addition, both have only three oxygen atoms per phosphorus for cluster bonding, thus allowing the phosphorus centers to serve as sites of positive Gaussian curvature.

Published
1995

8. Crystal structure and optical properties of CD32S14 (SC6H5)36, DMF4, a cluster with a 15 angstom CdS core

Author

Herron, N., Calabrese, J.C., Farneth, W.E., and Wang, Y.

Subjects
Pyridine -- Research, Crystals -- Research, Science and technology, Research
Abstract

Recrystallization of the solid [[Cd.sub.10][S.sub.4][([SC.sub.6][H.sub5]).sub.12] from a solution of pyridine and N, N-dimethylformamide (DMF) results in the formation of the cluster [Cd.sub.32][S.sub.14] [([SC.sub.16][H.sub.5]).sub.36][center dot][DMF.sub.4] as pale yellow cubes. The structure consists of an 82-atom CdS core that is a roughly spherical piece of the cubic sphalerite lattice 12 angstroms in diameter. The four corners of the lattice are capped by hexagonal wurtzite-like CdS units, which results in an overall tetrahedral cluster 15 angstroms in diameter. This cluster dissolves intact in tetrahydrofuran where its absorption spectrum reveals a sharp peak at 358 nanometers at room temperature and its emission spectra show a strong broad band at 500 nanometers., The use of very small molecular clusters as synthetic precursors to bulk, extended solids interests both the physics[1] and chemistry [2] communities. In the particular case of semiconductor materials, the [...]

Published
1993

10. Investing for Impact: Constructing a Better Built Environment

Author

Keith D. Hampson, Judy A. Kraatz, Adriana X. Sanchez, Naomi A. Herron, Hampson, Keith D., Sanchez, A., Kraatz, J., Herron, N., Keith D. Hampson, Judy A. Kraatz, Adriana X. Sanchez, Naomi A. Herron, Hampson, Keith D., Sanchez, A., Kraatz, J., and Herron, N.

Published
2013

11. Impacts of meso-scale Watershed Development in Andhra Pradesh (India) and their implications for designing and implementing improved WSD policies and programs

Author

Croke, Barry, Herron, N., Pavelic, P., Ahmed, S., Reddy, V.R., Ranjan, R., Syme, Geoff, Samad, M., Rao, K.V., Croke, Barry, Herron, N., Pavelic, P., Ahmed, S., Reddy, V.R., Ranjan, R., Syme, Geoff, Samad, M., and Rao, K.V.

Abstract

Watershed Development (WSD) programs in rainfed dryland agriculture in India have been introduced in an effort to promote more sustainable management of the surface and groundwater resources, and to improve the livelihoods of farmers. This paper outlines

Published
2012

15. Geomorphic controls on the physical and hydrologic properties of soils in a valley floor

Author

Wilson, Colin J, Herron, N F, Greene, Richard, Cunningham, Ross, Wilson, Colin J, Herron, N F, Greene, Richard, and Cunningham, Ross

Abstract

The distribution of soil hydraulic and physical properties strongly influences runoff processes in landscapes. Although much work has been done to quantify and predict the properties of hillslope soils, far less is known about the distribution of soil properties in valley floors. A technique that links the estimation and distribution of soil hydraulic properties in valleys, with easily identified geomorphic features, was developed along a 2 km length of a valley at Brooks Creek in New South Wales, Australia. Soil physical and hydraulic property data were collected across a set of floodplain and fan features within the valley and analysed statistically to determine if soil properties varied significantly between geomorphic features and stratigraphic layers. The results show that the depth-averaged saturated hydraulic conductivity, K(s), of the soil varies significantly with landform: fan units have K(g) values that are twice that of floodplains and colluvial toeslope deposits have K(s) values four times higher than floodplains. Given the notorious variability of K(s) values in space, the strong statistical separation of soil properties by landform, backed up by strong separation of soil particle size by landform, suggests a way forward in understanding the distribution of soil properties in valleys and their influence on catchment hydrology.

Published
2000

47. A microprocessor controlled gearbox for use in electric and hybrid-electric vehicles.

Author

Masding, P.W., Bumby, J.R., and Herron, N.

Abstract

This paper describes the automation and control of a 'manual'synchromesh gearbox in a form suitable for use in an electric or hybrid-electric vehicle. Such a computer controlled transmission system allows full integration and control of the drive train leading to improved vehicle performance. The automation process is described, and a full description given, of the computer control algorithms necessary to ensure smooth and reliable operation of the transmission system. It is shown that an up-change can be achieved in 1.4 seconds and a down-change in 1.2 seconds. These times are shown to represent maximum gear change times and details of how they can be reduced substantially are discussed. [ABSTRACT FROM PUBLISHER]

Published
1988
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48. The DuPont Powder Challenge:  The Crystal Structure of [C<INF>5</INF>NH<INF>6</INF>][Al<INF>3</INF>F<INF>10</INF>]&sbd;A Cautionary Tale

Author

Harlow, R. L., Herron, N., Li, Z., Vogt, T., Solovyov, L., and Kirik, S.

Abstract

A compound previously reported as HAlF4 has been shown to be [pyridinium][Al3F10]. The structure of this phase was solved and refined using a combination of synchrotron X-ray and neutron powder diffraction techniques in association with a number of other analytical techniques. The structure consists of [Al3F10]n- sheets containing both corner-sharing (common) and edge-sharing (unusual) AlF6 octahedra. The sheets are separated by pyridinium cations oriented perpendicular to the sheets. The final crystallographic data are as follows:  monoclinic, space group C2/m, a = 8.2706(3), b = 6.1998(3), c = 10.525(1) Å, β = 103.38(1)°, V = 525.0(1) Å3, and Z = 2. This compound appears to be another example of a layered “clay-like” aluminum fluoride.

Published
1999

50. Linear- and nonlinear-optical properties of semiconductor clusters

Author

Wang, Ying, Herron, N., Mahler, W., and Suna, A.

Abstract

CdS and PbS clusters with sizes ranging from a few angstroms to 150 Å can be synthesized in polymers. The dependence of the band gap on the cluster size deviates from the prediction of a simple particle-in-a-box model owing to the breakdown of the effective-mass approximation. Instead, the dependence can be described by a simple tight-binding cluster model. The optical nonlinearity, expressed as α_2/α_0, of 50-Å CdS clusters in Nafion film is determined to be −6.1 × 10^−7 cm^2 W^−1 at 480 nm. The nonlinearity originates from the bleaching of the excitonic absorption owing to the presence of trapped carriers on the cluster surfaces. By passivating the CdS surfaces with ammonia, we have shown that the nonlinearity can be controlled by surface chemistry. We have determined that the presence of one trapped electron–hole pair can bleach the excitonic absorption of the whole CdS cluster. This efficient bleaching can be understood by using a model that considers the shifting of the exciton resonance and weakening of its oscillator strength in the presence of a trapped electron or hole. We also discuss two new classes of material: superclusters in zeolites and surface-capped clusters. Both represent our first steps toward the systematic synthesis of clusters of controlled surfaces and sizes.

Published
1989

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