Relative Importance of Gas-Phase Diffusive and Advective Trichloroethene (TCE) Fluxes in the Unsaturated Zone under Natural Conditions

2002 ◽  
Vol 36 (14) ◽  
pp. 3157-3164 ◽  
Author(s):  
Jee-Won Choi ◽  
Fred D. Tillman ◽  
James A. Smith
Keyword(s):  
Gas Phase ◽  
Unsaturated Zone ◽  
Relative Importance ◽  
Natural Conditions

The relative importance of bladder versus neotenic stages of Polystoma marmorati and P. umthakathi in natural frog populations in South Africa

1998 ◽  
Vol 72 (2) ◽  
pp. 117-121 ◽  
Author(s):  
L.H. Du Preez ◽  
D.J. Kok
Keyword(s):  
South Africa ◽  
Significant Contribution ◽  
Relative Importance ◽  
Natural Conditions ◽  
High Prevalence ◽  
Low Prevalence ◽  
Very High

AbstractInfection levels of Polystoma marmorati (Polystomatidae: Monogenea) in the painted reed frog, Hyperolius marmoratus, and P. umthakathi in the kloof frog, Natalobatrachus bonebergi, were studied under natural conditions. The recorded prevalence for P. marmorati was generally high in adult frogs and low in tadpoles. In the case of P. umthakathi, the opposite was found with a low prevalence in adult frogs and a very high prevalence in tadpoles. Based on these findings, the hypothesis is presented that for P. marmorati the neotenic stage does not play a determining role and the population is maintained by bladder parasites. For P. umthakathi the neotenic stage appears to be more important than the bladder parasite and the population can probably survive without any significant contribution from bladder parasites.

scholarly journals Boron abundances in diffuse interstellar clouds

2009 ◽  
Vol 5 (S268) ◽  
pp. 237-242
Author(s):  
Adam M. Ritchey ◽  
S. R. Federman ◽  
Y. Sheffer ◽  
D. L. Lambert
Keyword(s):  
Gas Phase ◽  
Massive Star ◽  
Galactic Halo ◽  
Galactic Disk ◽  
Cosmic Ray ◽  
Secondary Process ◽  
Relative Importance ◽  
Interstellar Clouds ◽  
Comprehensive Survey ◽  
Spiral Arm

AbstractWe present a comprehensive survey of B abundances in diffuse interstellar clouds from HST/STIS observations along 56 Galactic sight lines. Our sample is the result of a complete search of archival STIS data for the B II λ1362 resonance line, with each detection confirmed by the presence of absorption from other dominant ions at the same velocity. The data probe a range of astrophysical environments including both high-density regions of massive star formation as well as low-density paths through the Galactic halo, allowing us to clearly define the trend of B depletion onto interstellar grains as a function of gas density. Many extended sight lines exhibit complex absorption profiles that trace both local gas and gas associated with either the Sagittarius-Carina or Perseus spiral arm. Our analysis indicates a higher B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of the Sun, which may suggest that B production in the current epoch is dominated by a secondary process. The average gas-phase B abundance in the warm diffuse ISM [log ϵ(B) = 2.38±0.10] is consistent with the abundances determined for a variety of Galactic disk stars, but is depleted by 60% relative to the solar system value. Our survey also reveals sight lines with enhanced B abundances that potentially trace recent production of 11B either by cosmic-ray or neutrino-induced spallation. Such sight lines will be key to discerning the relative importance of the two production routes for 11B synthesis.

Pollination of Banksia ericifolia Smith: Birds, Mammals and Insects as Pollen Vectors

1985 ◽  
Vol 33 (3) ◽  
pp. 271 ◽  
Author(s):  
DC Paton ◽  
V Turner
Keyword(s):  
Native Bees ◽  
Relative Importance ◽  
Natural Conditions ◽  
Natural Rate ◽  
Coastal Heath ◽  
Multiple Cross ◽  
Pollen Vectors ◽  
Banksia Ericifolia ◽  
Exclusion Experiments ◽  
Native Birds

In coastal heath, 12 km north of Sydney, Banksia ericifolia set fruit after cross-pollination but not after controlled self-pollination. Animals removed nectar and pollen from inflorescences during the day but not overnight. Introduced honeybees (Apis mellifera) and native birds (Meliphagidae, Zosteropidae) visited flowers frequently during the day, carried pollen on their body surfaces and were likely to transfer pollen between plants. Native bees, nocturnal moths and ants also visited flowers but were too infrequent, did not move between plants or foraged inappropriately to be important pollinators. No mammals were seen visiting flowers and the small mammals we caught carried no pollen. Exclusion experiments confirmed that pollination occurred during the day and not at night, but the experiments were insufficient to determine the relative importance of honeybees versus birds as pollinators. Only about 3% of the flowers of Banksia ericifolia developed follicles under natural conditions. Follicle production in this species was limited by resources and not by pollinators, since multiple cross- pollinations of flowers did not increase follicle production above the natural rate.

scholarly journals INFLUENCE OF PROOXIDANT NATURE ON EVOLUTION OF FORMALDEHYDE FROM OXO-DEGRADABLE POLYETHYLENE

2019 ◽  
Vol 62 (2) ◽  
pp. 101-107
Author(s):  
Vladimir I. Korchagin ◽  
Alena M. Surkova ◽  
Lubov N. Studenikina ◽  
Artem V. Protasov
Keyword(s):  
Gas Phase ◽  
Oxidative Degradation ◽  
Degradation Process ◽  
Thermal Oxidative Degradation ◽  
Degradation Index ◽  
Natural Conditions ◽  
Iron Copper ◽  
Destructive Processes ◽  
Technical Solutions ◽  
Degree Of Isolation

In the article, methods of oxo-destruction of polyethylene modified with pro-oxidants of various nature are considered taking into account ecotoxicological aspects. A comparative evaluation of the indexes of degradation of polyethylene under the influence of air oxygen under accelerated thermal aging and under natural conditions is presented. It was revealed that the degradation index rises in the series "iron <copper <cobalt". The amount of formaldehyde in the gas-air extraction of oxo-degradable polyethylene modified with iron, cobalt and copper stearate is determined with accelerated thermal-oxidative degradation. The degree of isolation of formaldehyde increases in the series "copper <iron <cobalt", which indicates different periods of induction of the degradation process initiated by prooxidates, as well as the presence of side processes that affect the depth of destructive processes. It has been established that a polyethylene film modified with cobalt stearate contributes to the increase in formaldehyde emissions, while the formaldehyde content in the gas phase is 0.065 mg / m3 (per 1 g of sample), which exceeds MAC m.o.t by 1.3 times. The content of formaldehyde precipitates in the gas phase is reduced by 3.25 times, with the use of ferrous sterate. Individual carcinogenic risks (ICR) for oxo-degradable films based on iron, copper and cobalt stearates are predicted to equal 6.593·10-5, 5.595·10-5 2.864·10-4, respectively. A comparative analysis of prooxidants allows us to conclude that the use of iron and copper stearates contributes to a slower degradation of polyethylene and reduces its ecotoxicological hazard, the use of cobalt based pro-oxidants contributes to a faster and deeper destruction, but is accompanied by increased release of formaldehyde in the oxodegradation of modified polyethylene. Of interest is the further study of complex prooxidants on the basis of iron with trace amounts of cobalt as highly effective and environmentally friendly modifiers of polyolefins, contributing to their accelerated oxidation in the environment, as well as the development of technical solutions to reduce the risk in the case of cobalt stearate as an effective prooxidant.

Licvd of Cr(C,O) Films from Cr(CO)6 at 248 NM: Gas-Phase and Surface Processes

1988 ◽  
Vol 129 ◽  
Author(s):  
R. Nowak ◽  
L. Konstantinov ◽  
P. Hess
Keyword(s):  
Carbon Monoxide ◽  
Gas Phase ◽  
Laser Fluence ◽  
Film Deposition ◽  
Surface Processes ◽  
Minor Role ◽  
Relative Importance ◽  
Experimental Conditions ◽  
Krf Excimer Laser ◽  
A Minor

ABSTRACTThe influence of laser fluence and carbon monoxide partial pressure on the deposition rate of thin Cr(C,O) films was investigated. The films were deposited from Cr(CO)6 mixtures with CO and Ar using a KrF excimer laser. The observed results are discussed with respect to the relative importance of gasphase and surface processes. The results reveal that under the present experimental conditions chromium atoms produced in the gas phase play only a minor role as direct film precursors in KrF laser-induced film deposition.

Photolysis of SO2 in the Presence of Foreign Gases. VI. Acetylene and Allene

1974 ◽  
Vol 52 (20) ◽  
pp. 3451-3453 ◽  
Author(s):  
Menachem Luria ◽  
Julian Heicklen
Keyword(s):  
Triplet State ◽  
Gas Phase ◽  
Triplet States ◽  
Relative Importance ◽  
Excited Singlet ◽  
Singlet States ◽  
Excited Singlet States ◽  
Allene System

The photolysis of SO2 at 3130 Å and 25 °C in the presence of C2H2 leads to CO, and, in the presence of allene to CO and C2H4 as gas phase products. In the C2H2 system, the CO comes from the two non-emitting triplet states of SO2, 57% from SO2** and 43% from SO2≠. In the allene system, the two excited singlet states of SO2, and possibly the emitting triplet state, also participate. The relative importance of the contributions from each state can be estimated to be >35% from 1SO2, <16% from 3SO2, 8% from SO2*, 12% from SO2**, and 29% from SO2≠.

Gas-phase photolysis of spiropentane at 147.0 nm

1985 ◽  
Vol 63 (12) ◽  
pp. 3593-3596 ◽  
Author(s):  
M. Paller ◽  
R. D. Doepker
Keyword(s):  
Nitric Oxide ◽  
Hydrogen Sulfide ◽  
Gas Phase ◽  
Hydrogen Iodide ◽  
Radical Scavenger ◽  
Relative Importance ◽  
Molecular Processes ◽  
Primary Reaction ◽  
Reaction Channels

The gas-phase photolysis of spiropentane has been investigated using xenon (147.0 nm) resonance radiation. Major products observed in order of decreasing importance are ethylene, aliène, methylacetylene, 1,2-butadiene, acetylene, propylene, and vinylacetylene. Nitric oxide was used as a radical scavenger while hydrogen sulfide and hydrogen iodide were employed as radical interceptors in the determination of the relative importance of radical and molecular processes. CH3/CH2 and CH3C=C• radicals were identified and quantified. Seven primary reaction channels were postulated of which those involving the "elimination" of ethylene were the most predominant accounting for 71% of the photodecomposition.

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