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At least 595 records · Page 33Linked to original sources
PubMed1995

The use of stable tracers to study intestinal calcium absorption. The Italian Society of Osteoporosis.

This paper represents the final document released by the Italian Society of Osteoporosis (S.I.OP.), on the occasion of its fifth annual meeting held in Padova, Italy (November 30-December 3, 1993). The S.I.OP. has in fact planned to periodically organize a conference on still-debated, controversial issues. After an exhaustive discussion of the various aspects of the problem by qualified experts in the field, a solution will be proposed by the members of the Society. The problems related to the use of radioactive tracers to study intestinal calcium absorption and the possible ways to over-come them were the issues discussed last year, by four panelists (R. P. Heaney, C. Gennari, G. Mioni, and S. Minisola) coordinated by G. F. Mazzuoli.

Calcium↗
PubMed2004

Use of 87Sr/86Sr and delta11B to identify slag-affected sediment in southern Lake Michigan.

Slag is a ubiquitous byproduct of the iron-smelting industry and influences geochemistry and water quality in adjacent geologic units, ground and surface water. Despite extensive slag deposition along the Indiana shoreline of Lake Michigan, definitive evidence that slag has affected lakebed sediments has not been established. Concerns for the protection of water and ecosystem resources in the Great Lakes motivated this study to determine if strontium and boron isotopes could be used to identify and delineate slag-affected bed sediment in Lake Michigan. Sixty-five samples of bed sediment were acquired from the southern lobe of Lake Michigan and analyzed for 87Sr/86Sr and deltat11B. Samples immediately offshore from Indiana steel mills and slag-disposal sites contained higher median 87Sr/86Sr values (0.70881) than shoreline sediments collected elsewhere in the basin (0.70847) and uniquely decreased with increasing distance from the shoreline. The highest delta11B values occurred in sediments from the Indiana shoreline (+12.9 to 16.4/1000) but were also elevated in sediments collected offshore from three Lake Michigan cities (+11.7 to 12.7/1000). Contoured isotope data indicated that 82-154 km2 of bed sediment along the Indiana shoreline had elevated 87Sr/86Sr and delta11B values relative to shoreline sediments elsewhere in southern Lake Michigan.

Boron↗
PubMed1968

Relation between simultaneous Ca and Sr transport rates in isolated segments of vetch, barley, and pine roots.

Root segments of vetch, barley, and pine were exposed to a nutrient solution containing (85)Sr and (45)Ca tracers. Translocation was measured from solutions containing stable ions at concentrations of 2.5 mm Ca, and at either 0.5 mm or 2.5 mm Sr. Polar transport was established between 12 and 18 hr in barley, and between 16 and 22 hr in vetch. Acropetal transport remained below 5% of basipetal transport of tracer during these intervals. Transport in both vetch and barley usually declined before an elapsed time of 24 hr unlike corn, which maintained its steady state beyond 24 hr. Pine was radically different in that it showed no difference between acropetal and basipetal transport rates and had very low rates. Sr transport in all plants studied to date paralleled that of Ca and the ratio Sr:Ca transported was equal to the ratio Sr:Ca in the nutrient. In vetch, stable Ca transport was reduced to one-fifth when Sr concentration was increased from 0.5 mm to 2.5 mm. Yet stable Sr transport did not change, indicating that the effect on transport was not due to competitive inhibition. A similar effect was less pronounced in barley, but could not be detected in pine. The magnitude of the transport rates varied considerably among the various species, corn having the greatest followed by barley, vetch, and pine in decreasing order. Transport did not correlate with root weight or surface area; it amounted to from 0.03 to 0.60 nanomoles per hr in these experiments as compared to 7 nanomoles per hr previously established in corn (in all cases, 55 mm segments, sectioned 10 mm from apex).

Calcium↗
PubMed1997

Accretion rates of meteorites and cosmic dust in the Early Ordovician.

Abundant fossil meteorites in marine, condensed Lower Ordovician limestones from Kinnekulle, Sweden, indicate that accretion rates of meteorites were one to two orders of magnitude higher during an interval of the Early Ordovician than at present. Osmium isotope and iridium analyses of whole-rock limestone indicate a coeval enhancement of one order of magnitude in the influx rate of cosmic dust. Enhanced accretion of cosmic matter may be related to the disruption of the L chondrite parent body around 500 million years ago.

Calcium Carbonate↗