Impacts of agriculture on the parasite communities of northern leopard frogs (Rana pipiens) in southern Quebec, Canada.

Given that numerous amphibians are suffering population declines, it is becoming increasingly important to examine the relationship between disease and environmental disturbance. Indeed, while many studies relate anthropogenic activity to changes in the parasitism of snails and fishes, little is known of the impact on the parasites of amphibians, particularly from agriculture. For 2 years, the parasite communities of metamorphic northern leopard frogs from 7 agricultural wetlands were compared with those from 2 reference wetlands to study differences in parasite community diversity and abundance of various species under pristine conditions and 3 categories of disturbance: only agricultural landscape, only pesticides, and agricultural landscape with pesticides. Agricultural (and urban) area was negatively related to species richness, and associated with the near absence of adult parasites and species that infect birds or mammals. We suggest that agriculture and urbanization may hinder parasite transmission to frogs by limiting access of other vertebrate hosts of their parasites to wetlands. The only parasite found at all localities was an unidentified echinostome infecting the kidneys. This parasite dominated communities in localities surrounded by the most agricultural land, suggesting generalist parasites may persist in disrupted habitats. Community composition was associated with dissolved organic carbon and conductivity, but few links were found with pesticides. Pollution effects may be masked by a strong impact of land use on parasite transmission.

Multiresidue methods using solid-phase extraction techniques for monitoring priority pesticides, including triazines and degradation products, in ground and surface waters.

The review describes the use of solid-phase extraction (SPE) techniques for monitoring priority pesticides in ground and surface waters. The focus is on triazine herbicides and their degradation products. Data concerning the fate, occurrence, properties and extraction of triazines and their degradation products using different SPE techniques are tabulated and discussed.

Oxygen isotopes and emerald trade routes since antiquity

Oxygen isotopic compositions of historical emerald artifacts from the Gallo-Roman period to the 18th century indicate that during historical times, artisans worked emeralds originating from deposits supposedly discovered in the 20th century. In antiquity, Pakistani and Egyptian emeralds were traded by way of the Silk Route. Together with Austrian stones, they were the only source of gem-quality emeralds. Immediately after the discovery of the Colombian mines by Spaniards in the 16th century, a new trade route was established, first via Spain to Europe and India and then directly via the Philippines to India. Since then, Colombian emeralds have dominated the emerald trade, and most of the high-quality emeralds cut in the 18th century in India originated from Colombia.

Mercury distribution in relation to iron and manganese in the waters of the St. Lawrence river.

Waters entering the St. Lawrence River from Lake Ontario and from the Ottawa River have been sampled on a quaternary basis between March 1995 and October 1996. Mercury, iron, manganese, organic carbon and other chemical parameters have been determined in the filtered water (< 0.5 micron) and suspended particles (> 0.5 micron). Average total mercury concentrations (+/- standard deviation, number of determinations) in filtered samples were 1.3 +/- 0.9 pM (39) at the mouth of Lake Ontario and 4.0 +/- 2.3 pM (54) at the outlet of the Ottawa River. The respective average concentrations in suspended particles were 1.1 +/- 0.4 (39) and 0.6 +/- 0.2 (55) nmol g-1. Partial correlation analyses reveal that in the fraction < 0.5 micron--which seems to consist of a significant fraction of colloids--mercury was significantly linked to iron, while in the particulate phase, mercury was related to manganese. Mercury was not correlated with organic carbon. A sorption model on iron and manganese hydroxides is proposed to explain these observations.

Twin Block appliance. Part II.

The main purpose of the Twin Block is to advance the mandible and to correct moderate to severe overjets. When the first molars are encouraged to erupt, the Twin Block also results in a partial correction of the overbite. The Rick-A-Nator or Rick-A-Nator 2 Appliances are utilized to hold the mandible in a forward position and also to help erupt the bicuspids to complete the orthopedic correction of the overbite. It is vital that the total treatment time for the active phase with the Twin Block and the support phase with the Rick-A-Nator be a minimum of 15 to 18 months to allow for permanent muscular, skeletal and dental changes to be accomplished.

Class II malocclusion in mixed dentition.

The primary goal of early treatment is to correct the existing muscular, skeletal and dental imbalances before the eruption of the permanent teeth. When early treatment is instituted, 80% of the malocclusion can be treated with orthopedic appliances and the remaining 20% solved with the straight wire appliances. This approach ensures that in excess of 95% of the cases can be treated non-extraction and non-surgically.