Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

Activities within the period from July 1, 1992 through December 31, 1992 by Georgia Tech researchers in millimeter and submillimeter wavelength tropospheric remote sensing have been centered around the calibration of the Millimeter-wave Imaging Radiometer (MIR), preliminary flight data analysis, and preparation for TOGA/COARE. The MIR instrument is a joint project between NASA/GSFC and Georgia Tech. In the current configuration, the MIR has channels at 90, 150, 183(+/-1,3,7), and 220 GHz. Provisions for three additional channels at 325(+/-1,3) and 8 GHz have been made, and a 325-GHz receiver is currently being built by the ZAX Millimeter Wave Corporation for use in the MIR. Past Georgia Tech contributions to the MIR and its related scientific uses have included basic system design studies, performance analyses, and circuit and radiometric load design, in-flight software, and post-flight data display software. The combination of the above millimeter wave and submillimeter wave channels aboard a single well-calibrated instrument will provide unique radiometric data for radiative transfer and cloud and water vapor retrieval studies. A paper by the PI discussing the potential benefits of passive millimeter and submillimeter wave observations for cloud, water vapor and precipitation measurements has recently been published, and is included as an appendix

Investigation of passive atmospheric sounding using millimeter and submillimeter wavelength channels

Activities within the period from January 1, 1992 through June 30, 1992 by Georgia Tech researchers in millimeter and submillimeter wavelength tropospheric remote sensing have been centered around the integration and initial data flights of the MIR on board the NASA ER-2. Georgia Tech contributions during this period include completion of the MIR flight software and implementation of a 'quick-view' graphics program for ground based calibration and analysis of the MIR imagery. In the current configuration, the MIR has channels at 90, 150, 183 +/- 1,3,7, and 220 GHz. Provisions for three additional channels at 325 +/-1,3 and 9 GHZ have been made, and a 325-GHz receiver is currently being built by the ZAX Millimeter Wave Corporation for use in the MIR. The combination of the millimeter wave and submillimeter wave channels aboard a single well-calibrated instrument will provide the necessary aircraft radiometric data for radiative transfer and cloud and water vapor retrieval studies. A paper by the PI discussing the potential benefits of passive millimeter and submillimeter wave observations for cloud, water vapor and precipitation measurements has recently been accepted for publication (Gasiewski, 1992), and is included as Appendix A. The MIR instrument is a joint project between NASA/GSFC and Georgia Tech. Other Georgia Tech contributions to the MIR and its related scientific uses have included basic system design studies, performance analyses, and circuit and radiometric load design

Microbial controls on net production of nitrous oxide in a denitrifying woodchip bioreactor

Denitrifying woodchip bioreactors are potential low-cost technologies for the removal of nitrate (NO3-) in water through denitrification. However, if environmental conditions do not support microbial communities performing complete denitrification, other N transformation processes will occur, resulting in the export of nitrite (NO2-), nitrous oxide (N2O), or ammonium (NH4+). To identify the factors controlling the relative accumulation of NO2-, N2O, and/or NH4+ in denitrifying woodchip bioreactors, porewater samples were collected over two operational years from a denitrifying woodchip bioreactor designed for removing NO3- from mine water. Woodchip samples were collected at the end of the operational period. Changes in the abundances of functional genes involved in denitrification, N2O reduction, and dissimilatory NO3- reduction to NH4+ were correlated with porewater chemistry and temperature. Temporal changes in the abundance of the denitrification gene nirS were significantly correlated with increases in porewater N2O concentrations and indicated the preferential selection of incomplete denitrifying pathways ending with N2O. Temperature and the total organic carbon/NO3- ratio were strongly correlated with NH4+ concentrations and inversely correlated with the ratio between denitrification genes and the genes indicative of ammonification (sigma nir/nrfA), suggesting an environmental control on NO3- transformations. Overall, our results for a denitrifying woodchip bioreactor operated at hydraulic residence times of 1.0-2.6 d demonstrate the temporal development in the microbial community and indicate an increased potential for N2O emissions with time from the denitrifying woodchip bioreactor

On Spatial Consensus Formation: Is the Sznajd Model Different from a Voter Model?

In this paper, we investigate the so-called ``Sznajd Model'' (SM) in one dimension, which is a simple cellular automata approach to consensus formation among two opposite opinions (described by spin up or down). To elucidate the SM dynamics, we first provide results of computer simulations for the spatio-temporal evolution of the opinion distribution $L(t)$, the evolution of magnetization $m(t)$, the distribution of decision times $P(\tau)$ and relaxation times $P(\mu)$. In the main part of the paper, it is shown that the SM can be completely reformulated in terms of a linear VM, where the transition rates towards a given opinion are directly proportional to frequency of the respective opinion of the second-nearest neighbors (no matter what the nearest neighbors are). So, the SM dynamics can be reduced to one rule, ``Just follow your second-nearest neighbor''. The equivalence is demonstrated by extensive computer simulations that show the same behavior between SM and VM in terms of $L(t)$, $m(t)$, $P(\tau)$, $P(\mu)$, and the final attractor statistics. The reformulation of the SM in terms of a VM involves a new parameter $\sigma$, to bias between anti- and ferromagnetic decisions in the case of frustration. We show that $\sigma$ plays a crucial role in explaining the phase transition observed in SM. We further explore the role of synchronous versus asynchronous update rules on the intermediate dynamics and the final attractors. Compared to the original SM, we find three additional attractors, two of them related to an asymmetric coexistence between the opposite opinions.Comment: 22 pages, 20 figures. For related publications see http://www.ais.fraunhofer.de/~fran

STM and Electrochemical Investigation of Homoepitaxial Boron-Doped CVD Diamond Films

Homoepitaxial growth of boron-doped CVD diamond films was carried out on (100) and (111) oriented substrates. Atomic resolution images were obtained for both (100) and (111) surfaces using scanning tunneling microscopy. STM images reveal the presence of a 2x1-monohydride reconstruction for the untreated (100) surface and a lxl reconstruction for the untreated (111) surface. No other atomically resolved reconstructions were observed under a wide range of growth conditions. Non-aqueous electrochemical investigations were carried out on the films exhibiting atomically resolved reconstructions. Evidence for potential-induced surface-reconstruction and surface chemical modification of the (100) 2xl-monohydride surface has been observed

Chemical Vapor Deposited Diamond Films for Self-Referencing Fiber Optic Raman Probes [Erratum]

Diamond thin films grown by the microwave plasma enhances chemical vapor deposition (CVD) process have been investigated as an internal reference in fiber optic remote Raman sensing. The growth parameters have been optimized for diamond thin films on quarts substrates using a gas mixture of methane, carbon dioxide, and hydrogen. The resulting films exhibit essentially no Raman spectral background while exhibiting a strong Raman peak at 1332 cm-¹. The films are used as an internal reference in the quantitative measurement of chemical concentration using remote fiber optic Raman sensing. Internal referencing is accomplished by normalizing all spectral intensities of the chemical species to the integrated area of the CVD diamond reference peak at 1332 cm-¹ and verified using ethanol/water solutions. It is shown that the measurement is independent of laser power fluctuations

Chemical Vapor Deposited Diamond Films for Self-Referencing Fiber Optic Raman Probes

Diamond thin films grown by the microwave plasma enhances chemical vapor deposition (CVD) process have been investigated as an internal reference in fiber optic remote Raman sensing. The growth parameters have been optimized for diamond thin films on quarts substrates using a gas mixture of methane, carbon dioxide, and hydrogen. The resulting films exhibit essentially no Raman spectral background while exhibiting a strong Raman peak at 1332 cm-¹. The films are used as an internal reference in the quantitative measurement of chemical concentration using remote fiber optic Raman sensing. Internal referencing is accomplished by normalizing all spectral intensities of the chemical species to the integrated area of the CVD diamond reference peak at 1332 cm-¹ and verified using ethanol/water solutions. It is shown that the measurement is independent of laser power fluctuations

Microwave Plasma Chemical Vapor Deposited Diamond Tips for Scanning Tunneling Microscopy

Diamond microparticles were grown on etched tungsten wires using a microwave plasma-assisted chemical vapor deposition process. The apexes on cubo-octahedral particles bound by {100} and {111} facets were effectively used as tunneling tips for scanning tunneling microscopy. The atomically resolved surface image of highly oriented pyrolytic graphite was acquired. Tunneling characteristics revealed a higher electron emission from the diamond tips than that from the platinum–iridium tips. The same diamond tips were used to produce surface indentation and its image. © 1997 American Institute of Physics