Air pollution: sensitive detection of ten pollutant gases by carbon monoxide and carbon dioxide lasers

Detection sensitivities of a few parts per billion for ten gaseous pollutants have been evaluated by measuring the strength of the absorption of infrared radiation from carbon monoxide and carbon dioxide lasers. Ethylene concentrations as small as 5 parts per billion have been detected in air. The measured absorption strengths indicate that in mixtures of pollutants, such as nitrogen dioxide and water vapor, the sensitivity is reduced by overlapping absorption bands. However, calculations indicate that it should be possible to detect nitrogen dioxide concentrations of 0.01 part per million in the presence of water vapor concentrations of 105 parts per million.     

Spawning success and early life history of longnose suckers in Great Lakes tributaries

Fish eggs and larvae are often subject to very high mortality, and variation in early life survival can be important for population dynamics. Although longnose suckers (Catostomus catostomus) are widespread in northern North America, little is known about their early life history. We examined fecundity and early larval survivorship during sucker spawning events in three small Lake Michigan tributaries. Although egg deposition varied 25% among spawning events, estimated larval export to the lake varied over 25,000‐fold from around 1000 to 26 million. Based on variation in environmental conditions across years, it appears that spring flow and temperature may be important determinants of egg survival to larval outmigration. Larval age data suggest that most individuals that survived to outmigration hatched during a 2‐day period despite adult spawning across at least 10 days. Most larvae spent <2 weeks in the stream and emigrated around the time of transition from endogenous to exogenous feeding before substantial growth occurred. In two of three cases, larvae drifted exclusively at night; however, high drift rates occurred during both day and night in the case where larvae were very abundant, suggesting density‐dependent drift behaviour. Our results indicate that survival in tributary streams from egg deposition to larval export is highly variable in longnose suckers. These large differences in early life survival may translate into variability in recruitment, thereby influencing population structure and dynamics.     

Odor stimuli trigger influx of calcium into olfactory neurons of the channel catfish

Olfactory transduction is thought to be mediated by a G protein-coupled increase in intracellular adenosine 3',5'-monophosphate (cAMP) that triggers the opening of cAMP-gated cation channels and results in depolarization of the plasma membrane of olfactory neurons. In olfactory neurons isolated from the channel catfish, Ictalurus punctatus, stimulation with olfactory stimuli (amino acids) elicits an influx of calcium that leads to a rapid increase in intracellular calcium. In addition, in a reconstitution assay a plasma membrane calcium channel has been identified that is gated by inositol-1,4,5-trisphosphate (IP3), which could mediate this calcium influx. Together with previous studies indicating that stimulation with olfactory stimuli leads to stimulation of phosphoinositide turnover in olfactory cilia, these data suggest that an influx of calcium triggered by odor stimulation of phosphoinositide turnover may be an alternate or additional mechanism of olfactory transduction.     

Ostwald ripening of clays and metamorphic minerals

Analyses of particle size distributions indicate that clay minerals and other diagenetic and metamorphic minerals commonly undergo recrystallization by Ostwald ripening. The shapes of their particle size distributions can yield the rate law for this process. One consequence of Ostwald ripening is that a record of the recrystallization process is preserved in the various particle sizes. Therefore, one can determine the detailed geologic history of clays and other recrystallized minerals by separating, from a single sample, the various particle sizes for independent chemical, structural, and isotopic analyses.     

Carbon monoxide measurements in the troposphere

During the second flight of the space shuttle, the measurement of air pollution from satellites (MAPS) experiment in the OSTA-1 payload acquired approximately 35 hours of radiometric measurements of the carbon monoxide mixing ratio in the middle troposphere, upper troposphere, and lower stratosphere. A gas filter radiometer operating in the 4.67-micrometer band was used to acquire the data over the region from 38 degrees N to 38 degrees S during both daytime and nighttime. The performance of the measurement system was excellent. The data reduced to date indicate the presence of significant gradients in the middle tropospheric carbon monoxide mixing ratio with both latitude and longitude over the North Atlantic, the Mediterranean Sea, and the Middle East. On the basis of comparisons with directly measured values, the accuracy of the measurements is approximately 15 percent. Comparisons of data taken on successive orbits over the same geographic region indicate that the repeatability of the measurements is approximately 5 percent.