Isolating silkworm genomic DNA without liquid nitrogen suitable for marker studies

Genomic DNA was isolated from posterior silk gland of silkworms, Antheraea assama. Absolute alcohol was used as tissue fixing solution instead of grinding in liquid nitrogen, which yielded high molecular weight DNA (>40 kb). Samples yielded similar amount of DNA when fixed in absolute alcohol (400 μmg/g of silk gland tissue) and ground in liquid nitrogen (456 μmg/g of silk gland tissue). RAPD profile of the isolated DNA revealed high degree of polymorphism. The silkworms were analysed using 50 random primers among which 36 polymorphic primers gave 309 amplicons. The average amplicons per primer found to be 8.58 and 94.82% amplicons were polymorphic. Cluster analysis based on Jaccard’s similarity coefficients resulted in the formation of two main clusters with S9 on one cluster and the remaining strains on the other cluster. Jaccard’s similarity coefficients ranged from 0.122 to 0.863 indicating a high level of genetic diversity within muga silkworm collection. Isolated DNA was also suitable for cloning and restriction enzyme digestion. This method does not require liquid nitrogen for fixation, grinding or storage at -80°C, making it advantageous over other common protocols.Key words: Genomic, silkworms, muga, molecular breeding

Chemical characteristics of air from different source regions during the second Pacific Exploratory Mission in the Tropics (PEM-Tropics B)

Ten-day backward trajectories are used to determine the origins of air parcels arriving at locations of airborne DC-8 chemical measurements during NASA's second Pacific Exploratory Mission in the Tropics B that was conducted during February-April 1999. Chemical data at sites where the trajectories had a common geographical origin and transport history are grouped together, and statistical measures of chemical characteristics are computed. Temporal changes in potential temperature are used to determine whether trajectories experienced a significant convective influence during the 10-day period. Trajectories describing the aged marine Southern Hemispheric category remain over the South Pacific Ocean during the 10-day period, and their corresponding chemical signature indicates very clean air. The category aged marine air in the Northern Hemisphere is found to be somewhat dirtier. Subdividing its trajectories based on the direction from which the air had traveled is found to be important in explaining the various chemical signatures. Similarly, long-range northern hemispheric trajectories passing over Asia are subdivided depending on whether they had followed a mostly zonal path, had originated near the Indian Ocean, or had originated near Central or South America and subsequently experienced a stratospheric influence. Results show that the chemical signatures of these subcategories are different from each other. The chemical signature of the southern hemispheric long-range transport category apparently exhibits the effects of pollution from Australia, southern Africa, and South America. Parcels originating over Central and northern South America are found to contain the strongest pollution signature of all categories, due to biomass burning and other sources. The convective category exhibits enhanced values of nitrogen species, probably due to emissions from lightning associated with the convection. Values of various species, including peroxides and acids, confirm that parcels were influenced by the removal of soluble gas and particle species due to precipitation. Finally, current results are compared with those from the first PEM-Tropics mission that was conducted in the same region during the southern hemispheric dry season (August-October 1996) when extensive biomass burning occurred. Results show that air samples during PEM-Tropics B are considerably cleaner than those of its dry season counterpart. Copyright 2001 by the American Geophysical Union

Photochemistry of HOx in the upper troposphere at northern midlatitudes

The factors controlling the concentrations of HOx radicals (= OH + peroxy) in the upper troposphere (8-12 km) are examined using concurrent aircraft observations of OH, HO2, H2O2, CH3OOH, and CH2O made during the Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX) at northern midlatitudes in the fall. These observations, complemented by concurrent measurements of O3, H2O, NO, peroxyacetyl nitrate (PAN), HNO3, CH4, CO, acetone, hydrocarbons, actinic fluxes, and aerosols, allow a highly constrained mass balance analysis of HOx and of the larger chemical family HOy (= HOx + 2 H2O2 + 2 CH3OOH + HNO2 + HNO4). Observations of OH and HO2 are successfully simulated to within 40% by a diel steady state model constrained with observed H2O2 and CH3OOH. The model captures 85% of the observed HOx variance, which is driven mainly by the concentrations of NOx (= NO + NO2) and by the strength of the HOx primary sources. Exceptions to the good agreement between modeled and observed HOx are at sunrise and sunset, where the model is too low by factors of 2-5, and inside cirrus clouds, where the model is too high by factors of 1.2-2. Heterogeneous conversion of NO2 to HONO on aerosols (γNO2=10-3) during the night followed by photolysis of HONO could explain part of the discrepancy at sunrise. Heterogeneous loss of HO2 on ice crystals (γice_HO2=0.025) could explain the discrepancy in cirrus. Primary sources of HOx from O(1D)+H2O and acetone photolysis were of comparable magnitude during SONEX. The dominant sinks of HOy were OH+HO2 (NOx<50 parts per trillion by volume (pptv)) and OH+HNO4 (NOx>50 pptv). Observed H2O2 concentrations are reproduced by model calculations to within 50% if one allows in the model for heterogeneous conversion of HO2 to H2O2 on aerosols (γHO2=0.2). Observed CH3OOH concentrations are underestimated by a factor of 2 on average. Observed CH2O concentrations were usually below the 50 pptv detection limit, consistent with model results; however, frequent occurrences of high values in the observations (up to 350 pptv) are not captured by the model. These high values are correlated with high CH3OH and with cirrus clouds. Heterogeneous oxidation of CH3OH to CH2O on aerosols or ice crystals might provide an explanation (γice_CH3OH∼0.01 would be needed). Copyright 2000 by the American Geophysical Union

A case study of transport of tropical marine boundary layer and lower tropospheric air masses to the northern midlatitude upper troposphere

Low-ozone (<20 ppbv) air masses were observed in the upper troposphere in northern midlatitudes over the eastern United States and the North Atlantic Ocean on several occasions in October 1997 during the NASA Subsonic Assessment, Ozone and Nitrogen Oxide Experiment (SONEX) mission. Three cases of low-ozone air masses were shown to have originated in the tropical Pacific marine boundary layer or lower troposphere and advected poleward along a warm conveyor belt during a synoptic-scale disturbance. The tropopause was elevated in the region with the low-ozone air mass. Stratospheric intrusions accompanied the disturbances. On the basis of storm track and stratospheric intrusion climatologies, such events appear to be more frequent from September through March than the rest of the year. Copyright 2000 by the American Geophysical Union

Factors controlling tropospheric O3, OH, NOx, and SO2 over the tropical Pacific during PEM-Tropics B

Observations over the tropical Pacific during the Pacific Exploratory Mission (PEM)-Tropics B experiment (March-April 1999) are analyzed. Concentrations of CO and long-lived nonmethane hydrocarbons in the region are significantly enhanced due to transport of pollutants from northern industrial continents. This pollutant import also enhances moderately O3 concentrations but not NOx concentrations. It therefore tends to depress OH concentrations over the tropical Pacific. These effects contrast to the large enhancements of O3 and NOx concentrations and the moderate increase of OH concentrations due to biomass burning outflow during the PEM-Tropics A experiment (September-October 1996). Observed CH3I concentrations, as in PEM-Tropics A, indicate that convective mass outflux in the middle and upper troposphere is largely independent of altitude over the tropical Pacific. Constraining a one-dimensiohal model with CH3I observations yields a 10-day timescale for convective turnover of the free troposphere, a factor of 2 faster than during PEM-Tropics A. Model simulated HO2, CH2O, H2O2, and CH3OOH concentrations are generally in agreement with observations. However, simulated OH concentrations are lower (∼25%) than observations above 6 km. Whereas models tend to overestimate previous field measurements, simulated HNO3 concentrations during PEM-Tropics B are too low (a factor of 2-4 below 6 km) compared to observations. Budget analyses indicate that chemical production of O3 accounts for only 50% of chemical loss; significant transport of O3 into the region appears to take place within the tropics. Convective transport of CH3OOH enhances the production of HOx and O3 in the upper troposphere, but this effect is offset by HOx loss due to the scavenging of H2O2. Convective transport and scavenging of reactive nitrogen species imply a necessary source of 0.4-1 Tg yr-1 of NOx in the free troposphere (above 4 km) over the tropics. A large fraction of the source could be from marine lightning. Oxidation of DMS transported by convection from the boundary layer could explain the observed free tropospheric SO2 concentrations over the tropical Pacific. This source of DMS due to convection, however, would imply in the model free tropospheric concentrations much higher than observed. The model overestimate cannot be reconciled using recent kinetics measurements of the DMS-OH adduct reaction at low pressures and temperatures and may reflect enhanced OH oxidation of DMS during convection. Copyright 2001 by the American Geophysical Union

OH and HO2 chemistry in the North Atlantic free troposphere

Interactions between atmospheric hydrogen oxides and aircraft nitrogen oxides determine the impact of aircraft exhaust on atmospheric chemistry. To study these interactions, the Subsonic Assessment: Ozone and Nitrogen Oxide Experiment (SONEX) assembled the most complete measurement complement to date for studying HO(x) (OH and HO2) chemistry in the free troposphere. Observed and modeled HO(x) agree on average to within experimental uncertainties (±40%). However, significant discrepancies occur as a function of NO and at solar zenith angles >70°. Some discrepancies appear to be removed by model adjustments to HO(x)-NO(x) chemistry, particularly by reducing HO2NO2 (PNA) and by including heterogeneous reactions on aerosols and cirrus clouds

On the origin of tropospheric ozone and NOx over the tropical South Pacific

The budgets of ozone and nitrogen oxides (NOx = NO + NO2) in the tropical South Pacific troposphere are analyzed by photochemical point modeling of aircraft observations at 0-12 km altitude from the Pacific Exploratory Mission-Tropics A campaign flown in September-October 1996. The model reproduces the observed NO2/NO concentration ratio to within 30% and has similar success in simulating observed concentrations of peroxides (H2O2, CH3OOH), lending confidence in its use to investigate ozone chemistry. It is found that chemical production of ozone balances only half of chemical loss in the tropospheric column over the tropical South Pacific. The net loss is 1.8 x 1011 molecules cm-2 s-1. The missing source of ozone is matched by westerly transport of continental pollution into the region. Independent analysis of the regional ozone budget with a global three-dimensional model corroborates the results from the point model and reveals the importance of biomass burning emissions in South America and Africa for the ozone budget over the tropical South Pacific. In this model, biomass burning increases average ozone concentrations by 7-8 ppbv throughout the troposphere. The NOx responsible for ozone production within the South Pacific troposphere below 4 km can be largely explained by decomposition of peroxyacetylnitrate (PAN) transported into the region with biomass burning pollution at higher altitudes. Copyright 1999 by the American Geophysical Union