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  • 1
    Publication Date: 1993-01-01
    Description: An introduced whitefly species, responsible for over a half billion dollars in damage to U.S. agricultural production in 1991, is morphologically indistinguishable from Bemisia tabaci (Gennadius). However, with the use of polymerase chain reaction-based DNA differentiation tests, allozymic frequency analyses, crossing experiments, and mating behavior studies, the introduced whitefly is found to be a distinct species. Recognition of this new species, the silverleaf whitefly, is critical in the search for management options.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Perring, T M -- Cooper, A D -- Rodriguez, R J -- Farrar, C A -- Bellows, T S Jr -- New York, N.Y. -- Science. 1993 Jan 1;259(5091):74-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Entomology, University of California, Riverside 92521.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8418497" target="_blank"〉PubMed〈/a〉
    Keywords: Alleles ; Animals ; Base Sequence ; Crosses, Genetic ; DNA/genetics ; Diptera/*classification/genetics/*physiology ; Enzymes/genetics ; Female ; Genetic Linkage ; Male ; Molecular Sequence Data ; Oligodeoxyribonucleotides ; Polymerase Chain Reaction ; Polymorphism, Genetic ; Sexual Behavior, Animal ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-08-19
    Description: Ionospheric modification using photochemically reactive vapors is studied with a one-dimensional, multiion, fluid model of plasma flow along magnetic field lines. The magnitudes of ion and electron density changes are determined by considering both chemical processes (i.e., photoionization, ion-molecule reactions, dissociative recombination, electron attachment) and transport processes (i.e., multispecies diffusion, electric currents, ambipolar electric fields). The numerical treatment in the model is not specific to any type of release or any interaction chemistry. It has been used to simulate releases of Ba, CO2, and CF3Br in the ionosphere, but generalization to other species may be easily accomplished. The results of the calculations are found to be in good agreement with experimental observations. The feasibility of modifying the parallel current paths in the auroral F region is examined.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 13
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  • 3
    Publication Date: 2019-06-28
    Description: This report documents progress to date in an ongoing study to analyze and model emissions leaving a proposed High Speed Civil Transport (HSCT) from when the exhaust gases leave the engine until they are deposited at atmospheric scales in the stratosphere. Estimates are given for the emissions, summarizing relevant earlier work (CIAP) and reviewing current propulsion research efforts. The chemical evolution and the mixing and vortical motion of the exhaust are analyzed to track the exhaust and its speciation as the emissions are mixed to atmospheric scales. The species tracked include those that could be heterogeneously reactive on the surfaces of the condensed solid water (ice) particles and on exhaust soot particle surfaces. Dispersion and reaction of chemical constituents in the far wake are studied with a Lagrangian air parcel model, in conjunction with a radiation code to calculate the net heating/cooling. Laboratory measurements of heterogeneous chemistry of aqueous sulfuric acid and nitric acid hydrates are also described. Results include the solubility of HCl in sulfuric acid which is a key parameter for modeling stratospheric processing. We also report initial results for condensation of nitric acid trihydrate from gas phase H2O and HNO3.
    Keywords: GEOPHYSICS
    Type: NASA-CR-189688 , NAS 1.26:189688 , ARI-RR-902
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: Progress to date in an ongoing study to analyze and model emissions leaving a proposed High Speed Civil Transport (HSCT) from when the exhaust gases leave the engine until they are deposited at atmospheric scales in the stratosphere is documented. A kinetic condensation model was implemented to predict heterogeneous condensation in the plume regime behind an HSCT flying in the lower stratosphere. Simulations were performed to illustrate the parametric dependence of contrail droplet growth on the exhaust condensation nuclei number density and size distribution. Model results indicate that the condensation of water vapor is strongly dependent on the number density of activated CN. Incorporation of estimates for dilution factors into a Lagrangian box model of the far-wake regime with scale-dependent diffusion indicates negligible decrease in ozone and enhancement of water concentrations of 6-13 times background, which decrease rapidly over 1-3 days. Radiative calculations indicate a net differential cooling rate of the plume about 3K/day at the beginning of the wake regime, with a total subsidence ranging between 0.4 and 1 km. Results from the Lagrangian plume model were used to estimate the effect of repeated superposition of aircraft plumes on the concentrations of water and NO(y) along a flight corridor. Results of laboratory studies of heterogeneous chemistry are also described. Kinetics of HCl, N2O5 and ClONO2 uptake on liquid sulfuric acid were measured as a function of composition and temperature. Refined measurements of the thermodynamics of nitric acid hydrates indicate that metastable dihydrate may play a role in the nucleation of more stable trihydrates PSC's.
    Keywords: GEOPHYSICS
    Type: NASA-CR-191495 , NAS 1.26:191495 , ARI-RR-1006
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  • 5
    Publication Date: 2019-07-13
    Description: 48.5 kHz signals from a transmitter in Silver Creek, Nebraska, propagating to Huntsville (HU), Alabama over a approximately 1200 km Great Circle Path (GCP) exhibit characteristic amplitude changes which appear within 20 ms of cloud-to-ground (CG) flashes located within 50 km of the path. Data are consistent with the heating of ionospheric electrons by the electromagnetic (EM) pulse from lightning producing ionization changes in the D-region over the thunderstorm.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 20; 21; p. 2355-2358
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  • 6
    Publication Date: 2019-07-12
    Description: The relationships among cloud-to-ground (CG) lightning, sferics, whistlers, VLF amplitude perturbations, and other ionospheric phenomena occurring during substorm events were investigated using data from simultaneous ground-based observations of narrow-band and broad-band VLF radio waves and of CG lightning made during the 1987 Wave-Induced Particle Precipitation campaign conducted from Wallops Island (Virginia). Results suggest that the data collected on ionospheric phenomena during this event may represent new evidence of direct coupling of lightning energy to the lower ionosphere, either in conjunction with or in the absence of gyroresonant interactions between whistler mode waves and electrons in the magnetosphere.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; 65-75
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  • 7
    Publication Date: 2019-07-12
    Description: The decline in stratospheric ozone at northern midlatitudes in wintertime may be caused by chlorine photochemistry that has been enhanced by heterogeneous reactions. The possibility that the heterogeneous reaction of N2O5 on sulfate aerosols is the cause of this decadal ozone decline is examined by comparing ClO and O3 measurements made in the lower stratosphere during February, 1988, with results from a 2D model. At midlatitudes, the abundances, latitudinal, and seasonal gradients of the observed ClO are similar to the results of a model with heterogeneous chemistry, but are in strong disagreement with the results from the model with only gas-phase chemistry. At low latitudes, agreement is best with the results of the model with only gas-phase chemistry. Limited observations indicate that the amount of reactive chlorine is being enhanced, and that heterogeneous chemistry is a likely cause.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 18; 2273-227
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  • 8
    Publication Date: 2019-08-14
    Description: Attention is given to a simple formulation of the propagation and absorption in a magnetized collisional plasma of EM pulses from lightning which describes the effect of discharge orientation and radiated electric field on the structure and magnitude of heating and secondary ionization in the D region. Radiation from most lightning discharges can heat substantially, but only the most intense (not less than 20 V/m) are likely to cause ionization enhancements not less than 10 percent of the ambient in a single ionization cycle. This dependence on the radiated electric field is modified by the discharge radiation pattern: a horizontal cloud discharge tends to cause larger heating and ionizaton maxima while a vertical return stroke causes disturbances of a larger horizontal extent.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 20; p. 2067-2070.
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  • 9
    Publication Date: 2019-08-28
    Description: Modification of the nighttime D region electron density (N(sub e)) due to heating by very-low-frequency (VLF) transmitters is investigated theoretically using a four-species model of the ion chemistry. The effects of a 100 kW, a 265 kW, and a 1000 kW VLF transmitter are calculated for three ambient N(sub e) profiles. Results indicate that N(sub e) is reduced by up to 26% at approximately 80 km altitude over a 1000 kW transmitter.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 2; p. 93-96
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  • 10
    Publication Date: 2019-08-28
    Description: Detectable heating of the nightime D region by a 28.5 kHz signal is observed in 16 out of 144 cases with events occurring under conditions of moderate to low D region electron densities as represented by the unperturbed VLF signal levels. Three dimensional modeling of the effects of NAU heating on a probe VLF signal predicts values in general agreement with observations and suggests that maximum effects should occur under tenuous D region conditions.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 19; 20; p. 2071-2074.
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