The effect of carbide precipitate morphology on fracture toughness in low-tempered steels containing Ni.

Nickel is known to increase the resistance to cleavage fracture of iron and decrease a ductile-to-brittle transition temperature. The medium-carbon, low-alloy martensitic steels attain the best combination of properties in low-tempered condition, with tempered martensite, retained austenite and transition carbides in the microstructure. This paper is focused on the influence of Ni addition (from 0.35 to 4.00%) on the microstructure and fracture toughness of structural steels after tempering. In this research, four model alloys of different concentration of Ni and constant concentration of carbon and other elements were used. All samples were in as-quenched and tempered conditions. Quenching was performed in oil at room temperature. After quenching, samples were tempered at 200 degrees C for 2 h. The microstructure of the investigated steels was analyzed using JEM200CX transmission electron microscope. An increase of nickel content in the investigated structural steels causes a decrease of epsilon carbide concentration in their microstructure after tempering. In these steels, cementite precipitates independently in the boundaries of martensite needles and in the twin boundaries in the areas where the Fe(2.4)C carbide has been dissolved. These results will be used to design new technologies of tempering of structural steels with nickel addition.

Atmospheric heavy metal deposition accumulated in rural forest soils of southern Scandinavia.

Thirty-three years of measurements of atmospheric heavy metal (HM) deposition (bulk precipitation) in Denmark combined with European emission inventories form the basis for calculating a 50-year accumulated atmospheric input to a remote forest plantation on the island of Laesoe. Soil samples taken in two depths, 0-10 cm and 10-20 cm, at eight forest sites at the island were used to determine the increase in HM content in the eolian deposited top soils of the plantation. Concentrations of lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), vanadium (V), nickel (Ni) and arsenic (As) were determined in atmospheric deposition and in soils. The accumulated atmospheric deposition is of the same magnitude as the increase of these metals in the top soil.

Survival of rotavirus antibody activity derived from bovine colostrum after passage through the human gastrointestinal tract.

BACKGROUND: Rotavirus is a major cause of infectious diarrhea in infants and young children. Several studies have shown that hyperimmune bovine colostrum, derived from cows immunized with rotavirus, can prevent rotavirus diarrhea when given passively. The objective of this study was to determine whether colostral antibody activity survived transit through the gut by measuring the level of rotavirus antibody activity in the feces. METHODS: Hyperimmune colostrum containing different levels of rotavirus antibody was administered to 105 children attending nine Adelaide childcare centres. Subjects were asked to drink 100 ml of whole milk supplemented with colostrum 3 times a day, for a period of 6 days. Stool samples were collected from the subjects before, during, and after consumption of the study product. Rotavirus activity was determined using a novel virus reduction enzyme-linked immunosorbent assay (ELISA) and a virus neutralization assay. RESULTS: Rotavirus antibody activity was detected in 521 (86%) of 602 fecal specimens obtained during the study using the virus reduction ELISA. The antibody activity was detected as early as 8 hours after ingestion of hyperimmune colostrum and up to 72 hours after consumption had ceased. There was a strong relation (r = 0.81) between the titer of rotavirus antibody administered to subjects and the level of antibody activity detected in the feces. CONCLUSIONS: The results show that antirotavirus activity survived passage through the gut. Therefore, passive immunotherapy may be used to prevent or treat infectious diseases that affect the entire length of the gastrointestinal tract.

Use of alpha-, beta- and gamma-hexachlorocyclohexane in Europe, 1970-1996.

Data on current and historical usage of alpha, beta, and gamma-hexachlorocyclohexane (HCH) in Europe are presented. The data were collected and estimated as a part of a project studying the regional cycling of persistent organic pollutants (POPs) in the Baltic environment (Popcycling-Baltic). Better data on sources, environmental discharges and atmospheric emissions of HCH and other POPs are needed to study, and hopefully reduce, the impact of these pollutants on the environment. Substantial uncertainties are assigned to the estimated data for individual countries and years, but it seems likely that the general trend of usage in Europe is captured. The quality of the estimates is thought to improve in general throughout the period, thus, reflecting the availability of reliable data. The results suggest that 382,000 t of technical HCH and 81,000 t of lindane were used in Europe from 1970 to 1996. This is equivalent to an estimated cumulative usage of 259,000 t alpha-HCH, 235,000 t gamma-HCH and 20,000 t beta-HCH. The usage of technical HCH was the major source of gamma-HCH until the late 1970s, and thereafter lindane became the dominating source of this isomer. The use of gamma-HCH in 1996 was estimated to still be nearly one-third of the European usage in 1970. The pattern of decreasing concentrations in biota follows the pattern of reductions in usage for the studied period within the Baltic area.

A study on the potential sources of air pollutants observed at Tjörn, Sweden.

The Potential Source Contribution Function (PSCF) receptor model combines both chemical and meteorological information. In this study, PSCF was employed to identify the potential source emission regions for aerosol compositions measured at Tjörn, Sweden (58.01 ∘N, 11.36 ∘E). PSCF was for the first time applied on a European scale. One hundred and fifty-two four-day air parcel backward trajectories were combined with concentrations of sixteen elements determined in 33 coarse and fine aerosol samples. The observations were made between February 17 and March 26, 1985. The modeling results of the heavy metals V, Pb, Zn, and As are presented and compared with available emission inventory data. A number of known industrialized regions in the former USSR and Europe are found of high potential to be the emission source areas. These areas are in good agreement with the known emission information. The PSCF maps of total sulfur, Non-Seasalt-Sulfur (N.S.S.) and chlorine are also presented. High potential regions in the Arctic area exist in the PSCF map for total sulfur wheres they do not occur in that for N.S.S.

Quantitative assessment of worldwide contamination of air, water and soils by trace metals.

Calculated loading rates of trace metals into the three environmental compartments demonstrate that human activities now have major impacts on the global and regional cycles of most of the trace elements. There is significant contamination of freshwater resources and an accelerating accumulation of toxic metals in the human food chain.