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102. PHOTODETACHMENT AS A DESTRUCTION MECHANISM FOR CN- AND C3N- ANIONS IN CIRCUMSTELLAR ENVELOPES

Author

Kumar, S. S., Hauser, D., Jindra, R., Best, T., Roucka, S., Geppert, Wolf D., Millar, T. J., Wester, R., Kumar, S. S., Hauser, D., Jindra, R., Best, T., Roucka, S., Geppert, Wolf D., Millar, T. J., and Wester, R.

Abstract

Absolute photodetachment cross sections of two anions of astrophysical importance CN- and C3N- were measured to be (1.18 +/- (0.03)(stat)(0.17)(sys)) x 10(-17) cm(2) and (1.43 +/- (0.14)(stat)(0.37)(sys)) x 10(-17) cm(2), respectively, at the ultraviolet (UV) wavelength of 266 nm (4.66 eV). These relatively large values of the cross sections imply that photodetachment can play a major role in the destruction mechanisms of these anions particularly in photon-dominated regions. We have therefore carried out model calculations using the newly measured cross sections to investigate the abundance of these molecular anions in the cirumstellar envelope of the carbon-rich star IRC+10216. The model predicts the relative importance of the various mechanisms of formation and destruction of these species in different regions of the envelope. UV photodetachment was found to be the major destruction mechanism for both CN- and C3N- anions in those regions of the envelope, where they occur in peak abundance. It was also found that photodetachment plays a crucial role in the degradation of these anions throughout the circumstellar envelope., AuthorCount:8

Published
2013
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103. Perchlorophenalenyl radical

Author

Koutentis, Panayiotis Andreas, Chen, Y. Z., Cao, Yun Zhen, Best, T. P., Itkis, M. E., Beer, L., Oakley, R. T., Cordes, A. W., Brock, C. P., Haddon, R. C., and Koutentis, Panayiotis Andreas [0000-0002-4652-7567]

Subjects
crystal structure, Sodium chloride, aromatic compound, reduction, Solid state characterization, percholorophenalenyl radical, chlorine derivative, Biochemistry, Paramagnetism, Crystals, Catalysis, Colloid and Surface Chemistry, Antiferromagnetism, Organic compounds, radical, dimerization, article, ferromagnetic material, Lattice constants, temperature, General Chemistry, monomer, unclassified drug, reaction analysis, chemical structure, Chlorine
Abstract

We report the preparation and solid-state characterization of the perchlorophenalenyl radical (1). The radical is initially obtained as a yellow-green solid by reduction of the perchlorophenalenium salt (12+). This solid sublimes in a sealed tube to give black shiny hexagonal crystals of the perchlorophenalenyl radical (1). The I structure consists of 1-dimensional stacks of the monomeric radical. The peri-chlorine atoms force the phenalenyl system to be strongly nonplanar leading to a large separation between adjacent molecules within the stacks (3.78 Å), and the molecules adopt two distinct stacking motifs (quasisuperimposed and rotated by 60° with respect to neighbors). Because of the packing frustration in the lattice and the large intermolecular spacing, the solid shows Curie paramagnetism in the temperature range 100-400 K, before antiferromagnetic coupling sets in at low temperatures. Due to the narrow bandwidth that results from the isolation of the individual molecules, the solid is a Mott-Hubbard insulator, with a room-temperature conductivity of ρRT = 10-10 S/cm. 123 17 3864 3871 Cited By :99

Published
2001

104. ABSOLUTE PHOTODETACHMENT CROSS-SECTION MEASUREMENTS FOR HYDROCARBON CHAIN ANIONS

Author

Best, T., Otto, R., Trippel, S., Hlavenka, P., von Zastrow, A., Eisenbach, S., Jezouin, S., Wester, R., Vigren, Erik, Hamberg, M., Geppert, Wolf D., Best, T., Otto, R., Trippel, S., Hlavenka, P., von Zastrow, A., Eisenbach, S., Jezouin, S., Wester, R., Vigren, Erik, Hamberg, M., and Geppert, Wolf D.

Abstract

Absolute photodetachment cross sections have been measured for the hydrocarbon chain anions C(n)H(-), n = 2, 4, and 6, which are relevant for an understanding of molecular clouds in the interstellar medium. Data have been obtained for different photon energies within approximately 1 eV of the detachment threshold. With our recently developed method we have achieved a precision of better than 25% on these absolute cross sections. The experiments have been carried out by means of photodetachment tomography of the mass-selected molecular anions in a multipole radio-frequency ion trap. The measured absolute cross sections are in accordance with the empirical scaling law of Millar et al. and have allowed us to determine its free parameters. These results are important for predicting the photostability and thus the abundance of carbon chain anions in planetary atmospheres, in circumstellar envelopes, and in photon-dominated regions of interstellar molecular clouds., authorCount :11

Published
2011
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108. Performance evaluation of PACT Pilot-plant for CO2 capture from gas turbines with Exhaust Gas Recycle.

Author

Akram, M., Ali, U., Best, T., Blakey, S., Finney, K.N., and Pourkashanian, M.

Subjects
CARBON sequestration, GAS turbines, WASTE gases, FLUE gases, ETHANOLAMINES, SOLVENTS
Abstract

Exhaust Gas Recycle (EGR) is one of the technologies used to increase the CO 2 concentration in the gas turbine flue gas. This paper presents the results of an experimental campaign carried out at the Pilot-scale Advanced Capture Technology (PACT) facilities at the UK Carbon Capture and Storage Research Centre (UKCCSRC). A 100 kW e Turbec T100 PH microturbine was integrated with a post combustion CO 2 capture plant that has a CO 2 capture capacity of one ton per day. The impact of different CO 2 concentrations (representing a range of EGR ratios) on the post-combustion CO 2 capture process was experimentally evaluated using 30% (wt.%) Monoethanolamine (MEA) solvent. It was observed that the specific reboiler duty was reduced by around 7.1% per unit percentage increase in CO 2 concentration. Overall, it was seen that the higher the CO 2 concentration, the lower the specific reboiler duty at a fixed capture rate. Both rich and lean solvent loadings increased with increase in flue gas CO 2 concentration. Energy balance on the stripper has shown that steam generation rate and condenser duty increases with increase in CO 2 concentration. The experimental data was used to develop and validate the model for the Pilot-scale amine capture plant using Aspen HYSYS. [ABSTRACT FROM AUTHOR]

Published
2016
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115. Mutants of Arabidopsis thaliana with decreased amplitude in their phototropic response

Author

Khurana, J. P, Ren, Z, Steinitz, B, Parks, B, Best, T. R, and Poff, K. L

Subjects
Life Sciences (General)
Abstract

Two mutants of Arabidopsis thaliana have been identified with decreased phototropism to 450-nanometer light. Fluence-response relationships for these strains (ZR8 and ZR19) to single and multiple flashes of light show thresholds, curve shapes, and fluence for maximum curvature in first positive' phototropism which are the same as those of the wild type. Similarly, there is no alteration from the wild type in the kinetics of curvature or in the optimum dark period separating sequential flashes in a multiple flash regimen. In addition, in both strains, gravitropism is decreased compared to the wild type by an amount which is comparable to the decrease in phototropism. Based on reciprocal backcrosses, it appears that the alteration is due to a recessive nuclear mutation. It is suggested that ZR8 and ZR19 represent alterations in some step analogous to an amplifier, downstream of the photoreceptor pigment, and common to both phototropism and gravitropism.

Published
1989

116. Influence of hook position on phototropic and gravitropic curvature by etiolated hypocotyls of Arabidopsis thaliana

Author

Khurana, J. P, Best, T. R, and Poff, K. L

Subjects
Life Sciences (General)
Abstract

Phototropic and gravitropic curvature by hypocotyls of Arabidopsis thaliana is minimal when the side of the hook with the cotyledons attached is positioned toward the direction of tropistic curvature, and maximal when that side of the hook is positioned away from the direction of tropistic curvature. Based on these data, it is proposed that the position of the hook with attached cotyledons affects curvature and not stimulus perception. A randomly oriented population of plants exhibited considerable heterogeneity in tropistic curvature. This heterogeneity arises at least in part from the dependence of curvature on the position of the hook.

Published
1989

117. The 20 GHz spacecraft IMPATT solid state transmitter

Author

Best, T and Ngan, Y. C

Subjects
Electronics And Electrical Engineering
Abstract

The engineering development of a solid-state transmitter amplifier operating in the 20-GHz frequency range is described. This effort involved a multitude of disciplines including IMPATT device development, circulator design, multiple-diode circuit design, and amplifier integration and test. The objective was to develop a transmitter amplifier demonstrating the feasibility of providing an efficient, reliable, lightweight solid-state transmitter to be flown on a 30 to 20 GHz communication demonstration satellite. The work was done under contract from NASA/Lewis Research Center for a period of three years. The result was the development of a GaAs IMPACT diode amplifier capable of an 11-W CW output power and a 2-dB bandwidth of 300 MHz. GaAs IMPATT diodes incorporating diamond heatsink and double-Read doping profile capable of 5.3-W CW oscillator output power and 15.5% efficiency were developed. Up to 19% efficiency was also observed for an output power level of 4.4 W. High performance circulators with a 0.2 dB inserting loss and bandwidth of 5 GHz have also been developed. These represent a significant advance in both device and power combiner circuit technologies in K-band frequencies.

Published
1986

128. Extravascular Lung Water Measurement.

Author

Vincent, Jean-Louis, Maddison, B., Best, T., and Pearse, R. M.

Abstract

Extravascular lung water (EVLW) is the term used to describe water within the lungs but outside the pulmonary vasculature. Excessive EVLW volume is a common and serious feature of critical illness. However, clinical assessment of the extent of pulmonary capillary leakage is difficult and inconsistent [1, 2]. Traditional methods of reducing EVLW volume include the use of loop diuretics and vasodilator drugs. The choice of these interventions is very much at the discretion of the clinician; pharmacological therapy is titrated to achieve a subjective clinical improvement rather than a quantitative EVLW volume target. The critically ill patient may also require fluid resuscitation to correct hypovolemia and to maintain oxygen delivery to the major organs. However, in the presence of increased pulmonary capillary permeability or impaired myocardial function, the administration of large volumes of intravenous fluid is associated with a significant risk of pulmonary edema. Effective fluid resuscitation, therefore, involves a fine balance between the harmful effects of inadequate tissue oxygen delivery on the one hand and excessive EVLW volume on the other. [ABSTRACT FROM AUTHOR]

Published
2007
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130. Perchlorophenalenyl Radical

Author

Koutentis, P. A., primary, Chen, Y., additional, Cao, Y., additional, Best, T. P., additional, Itkis, M. E., additional, Beer, L., additional, Oakley, R. T., additional, Cordes, A. W., additional, Brock, C. P., additional, and Haddon, R. C., additional

Published
2001
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150. Walking Track Analysis

Author

Hare, G. M. T., primary, Evans, P. J., additional, Mackinnon, S. E., additional, Best, T. J., additional, Bain, J. R., additional, Szalai, J. P., additional, and Hunter, D. A., additional

Published
1992
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