Long-term chemical and biological trends in Scottish streams and lochs

Between 1975 and 1985 several catchments in Scotland were established as reference sites to determine short-term (hours, days, weeks) and long-term (years, decades) changes in major physical, chemical and biological variables. The initial selection criteria included catchment size, land-use and deposition loading. Changes in fish status of lochs were determined by systematic netting while quantitative estimates of fish populations were made at stream sites. Egg survival and year class distribution assisted interpretation. Historical changes in pH based on stratigraphical changes in diatom assemblages are compared with recent measured changes which have occurred during the past 20 years when SO₂ emissions declined. Significant chemical and biological trends due to changes in pollutant loading are best detected in sensitive lochs which are unmanaged and with low organic content and acid neutralising capacity (ANC) close to zero. Significant trends are less apparent in lochs with managed (forested) catchments. Many stream sites also reveal long-term improvements in pH, sulphate (SO₄) Alkalinity (Alk) etc, but the significance of these trends is much less because of the greater inherent chemical variability. Stream sites close to ANC=0 provide the most wide-ranging evidence of ecological change, ie, increase in Alk, decrease in SO₄ and increase in numbers of juvenile salmonids. Measured chemical changes are compared with predicted estimates, based on critical load calculations and problems in interpretation are discussed.     

Venus: absence of a phase effect at a 2-centimeter wavelength

Observations of Venus made during 1967 and 1968 at a frequency of 15.4 gigahertz set an upper limits of 5 percent for the variation of brightness temperature with phase. This negative result appears to contradict earlier detections of a phase effect. By comparison with Virg A (3C 274), which has an assumed flux density of 29 x 10(-26) watt per square meter per hertz, the brightness temperature of Venus at this frequency is 485 + 60, -40 degrees K (mean error).     

Lactoperoxidase: identification and isolation from Harderian and lacrimal glands

Investigation of bovine lacrimal and harderian glands revealed the presence of the enzyme lactoperoxidase, which was isolated and purified. A nonheme, iron-containing protein was identified at the same time. Both proteins are present in milk, mammary glands, and salivary glands. Their roles are discussed: The lactoperoxidase may be important in controlling bacterial flora.     

Imaging of intermittency in ripple-wave turbulence

The dynamics of a fluid surface filled with high-amplitude ripples were studied with a technique (diffusing light photography) that resolves the height at all locations instantaneously. Even when nonlinearities are strong enough to generate a (Kolmogorov) cascade from long wavelength (where energy is input) to shorter wavelength, the resulting turbulent state contains large coherent spatial structures. The appearance of these structures in a thermal equilibrium state (with the same average energy) would be highly improbable.     

Ancient use and manipulation of landscape in the Yalahau region of the northern Maya lowlands

The tropical lowlands of southern Mexico and Central America are composed of a complex mosaic of landscapes that presented a variety of possibilities and challenges to the subsistence practices of the ancient Maya. The Yalahau Regional Human Ecology Project has been investigating ancient Maya agricultural practices and use of resources in a unique fresh-water wetland zone located in the northeast corner of the Yucatán Peninsula. While containing only a sparse population today, the Yalahau region once supported numerous Maya communities and civic-ceremonial centers, particularly during the Late Preclassic and Early Classic periods, between approximately 100 B.C. and A.D. 450. Our investigations have developed evidence that the ancient Maya manipulated and cultivated the wetland landscape of the region, used soil or algae from the wetlands to enrich upland garden plots, and cultivated trees within their communities. We suggest that the study of ancient Maya agricultural practices can contribute to sustainable development of the area today and in the future.     

Magnetometer Evidence of a Structure within the La Venta Pyramid

The pyramid at La Venta, Tabasco, Mexico, was surveyed in May 1969 with a high-sensitivity difference magnetometer. The general pattern of the magnetic map is one of low (10-gamma) radial anomalies, which reflect the ridge and gully topography of the pyramid, with a larger magnetic high area (+30 gammas) centered 25 meters south and 10 meters east of the center of the pyramid. The anomalous region near the top has been interpreted with the aid of computer-calculated anomalies from three-dimensional rectangular blocks. The major high is probably associated with a basalt structure that rises to within 1 to 2 meters of the surface. A possible form for this structure was found to be a 10-meter-square horizontal platform with walls along its northern and eastern margin.