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Your search keyword '"Woolard, D."' showing total 146 results
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146 results on '"Woolard, D."'

11. Terahertz generation in submicron GaN diodes within the limited space-charge accumulation regime.

Author

Sokolov, V. N., Kim, K. W., Kochelap, V. A., and Woolard, D. L.

Subjects
ELECTRON transport, DIODES, NITRIDES, ELECTRON distribution, OSCILLATIONS
Abstract

The conditions for microwave power generation with hot-electron transport are investigated in a submicron GaN diode when it operates in the limited space-charge accumulation (LSA) mode. Applying a transport model based on the local quasistatic approximation, the analysis shows that the nitride diodes can support the LSA mode of oscillation in the terahertz-frequency range. For a 100 nm n-GaN diode with a cross section of 500 μm2 and the electron density of 1×1017 cm-3, the generated microwave power is estimated to be as high as ≈0.6 W with the corresponding dc-to-rf conversion efficiency of ≈9% and the negative differential resistance of ≈-1.3 Ω; which thus provides an efficient mechanism to achieve very high-frequency microwave generation in the nitrides. [ABSTRACT FROM AUTHOR]

Published
2005
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12. Submillimeter-wave Fourier transform spectroscopy of biological macromolecules.

Author

Globus, T. R., Woolard, D. L., Samuels, A. C., Gelmont, B. L., Hesler, J., Crowe, T. W., and Bykhovskaia, M.

Subjects
*FOURIER transform spectroscopy, *BIOMACROMOLECULES
Abstract

In this article we report experimental results on Fourier-transform infrared spectroscopy of deoxyribonucleic acid (DNA) macromolecules and related biological materials in the submillimeter range (i.e., ∼10–500 cm-1). Film samples made from commercial DNA fibers, polyadenylic acid potassium salt, and cellular agents such as the spore form of Bacillus subtillis have been prepared and measured. A broad series of measurements carried out in the low frequency region (10–50 cm-1) with a higher resolution of 0.2 cm-1 revealed fine features—multiple dielectric resonances in the submillimeter-wave spectra obtained from DNA samples. These long-wave absorption features are shown to be intrinsic properties of biological materials determined by phonon modes. The emphasis is on reproducibility of experimental spectra and on receiving reliable results. The effects of differences in sample preparation, including sample geometry, orientation, and aging are studied and separated from the phonon effects that determine the fine structure of transmission spectra. A direct comparison of spectra between different DNA samples reveals a large number of modes and a reasonable level of sequence-specific uniqueness. A theoretical study of two double helical DNA fragments has applied a normal mode analysis to predict spectra in the far infrared. Most of the modes determined by long-distance interactions are at frequencies below 220 cm-1, with the density higher than one mode per cm-1, which is approximately what was observed experimentally. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2002
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13. Simulation of resonant tunneling structures: Origin of the I-V hysteresis and plateau-like...

Author

Zhao, Peiji and Woolard, D.

Subjects
*QUANTUM tunneling, *HYSTERESIS
Abstract

Focuses on a study that simulated hysteresis and plateau-like behavior of the current-voltage curves of a double-barrier resonant tunneling structure (RTS) in the negative differential resistance region. Numerical technique for modeling the RTS; Numerical results and analysis; Conclusion.

Published
2000
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14. On the different physical roles of hysteresis and intrinsic oscillations in resonant tunneling structures.

Author

Woolard, D. L., Buot, F. A., Rhodes, D. L., Lu, X. J., Lux, R. A., and Perlman, B. S.

Subjects
*PHYSICS, *HYSTERESIS, *QUANTUM tunneling, *DIODES
Abstract

Deals with a study which delineated the physics responsible for hysteresis and that of the high-frequency oscillations for intrinsic resonant tunneling diode structures. Background theory; Nonlinear equivalent circuit model study; Conclusions.

Published
1996
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15. Construction of higher-moment terms in the hydrodynamic electron-transport model.

Author

Woolard, D. L., Tian, H., Littlejohn, M. A., Kim, K. W., Trew, R. J., Ieong, M. K., and Tang, T. W.

Subjects
*HYDRODYNAMICS, *MONTE Carlo method
Abstract

Presents a study which considered the accurate closure relations and microscopic electron dynamics in the development of hydrodynamic transport models using the Monte Carlo method. Discussion on the microscopic dynamics of electron motion in submicron devices; Characteristics of the model; Establishment of a set of suitable closure relations.

Published
1993
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16. Laboratory-acquired Vaccinia virus infection--Virginia, 2008

Author

Davies, E., Peake, L., Woolard, D., Novak, C., Hall, K., Leonard, R.T., Allen, R., Reynolds, M., Davidson, W., Hughes, C., Olson, V., Smith, S., Zhao, H., Li, Y., Karem, K., Damon, I., MacNeil, A., and Roess, A.

Subjects
United States. Centers for Disease Control and Prevention -- Powers and duties, Virginia. Department of Health -- Powers and duties, Vaccinia -- Properties, Sentinel health events -- 2008 AD, Smallpox vaccine -- Properties, Virus diseases -- 2008 AD
Abstract

Vaccinia virus (VACV) is the live viral component of smallpox vaccine. Inadvertent exposure to VACV can result in infection, and severe complications can occur in persons with underlying risk factors [...]

Published
2009

17. Outbreak of histoplasmosis among travelers returning from El Salvador--Pennsylvania and Virginia, 2008

Author

Warren, K.A., Weltman, A., Hanks, C., LaFountain, T., Lowery, E., Woolard, D., Armstrong, C., Patel, A.S., and Kurkjian, K.M.

Subjects
Company distribution practices, Histoplasmosis -- Distribution, Histoplasmosis -- Statistics, Histoplasmosis -- Causes of, Medical geography -- Analysis, Occupational health and safety -- Statistics, Travelers -- Health aspects
Abstract

Histoplasmosis is a fungal disease caused by infection with Histoplasma capsulatum. Histoplasmosis, which can be acquired from soil contaminated with bird or bat droppings, occurs worldwide and is one of [...]

Published
2008

18. USE OF S-ABSCISIC ACID (CONTEGOTM SL) IN VEGETABLE PRODUCTION

Author

Racsko, J., primary, Marmor, F., additional, Hopkins, C.R., additional, Petracek, P., additional, Silverman, F.P., additional, Fritts Jr., R., additional, Liu, X., additional, Woolard, D., additional, Lopez, J., additional, Leep, D., additional, and Pienaar, J., additional

Published
2014
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36. Submillimeter-wave phonon modes in DNA macromolecules

Author

Woolard, D. L., primary, Globus, T. R., additional, Gelmont, B. L., additional, Bykhovskaia, M., additional, Samuels, A. C., additional, Cookmeyer, D., additional, Hesler, J. L., additional, Crowe, T. W., additional, Jensen, J. O., additional, Jensen, J. L., additional, and Loerop, W. R., additional

Published
2002
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