Determining calcium bioavailability is important in establishing dietary calcium requirements. In infants and small children, previously conducted mass balance studies have largely been replaced by stable isotope-based studies. The ability to assess calcium absorption using a relatively short 24-hour urine collection without the need for multiple blood samples or fecal collections is a major ad...

A method that uses the intensity of the absorption of the oxidized cell uloses at 5.S microns as a measure of their carboxyl content is described. The analyses are canied out on mineral oil slurries of 1:1 mixtures of fine ly divided polystyrene and cellulose. The absorption of the polystyrene at 6.2 microns is used as a reference band, t hus obviating the necessity of accurately controlling th...

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amo...

This study determined the effect of long-term administration of 4(G)-beta-D-galactosylsucrose (lactosucrose; LS) on intestinal calcium absorption. In a randomized, single-blind, parallel-group study, LS (n=9, 6.0 g twice daily) or a placebo (maltose; n=8, 6.0 g twice daily) was administered to healthy young women for 92 wk: the study also included a 4-wk post-administration period. All particip...

IMPORTANCE Experts debate optimal 25-hydroxyvitamin D (25[OH]D) levels for musculoskeletal health. OBJECTIVE To compare the effects of placebo, low-dose cholecalciferol, and high-dose cholecalciferol on 1-year changes in total fractional calcium absorption, bone mineral density, Timed Up and Go and five sit-to-stand tests, and muscle mass in postmenopausal women with vitamin D insufficiency. ...

The relative impermeability of the surfaces of leaves to water and mineral ions in solution is a condition upon which the life of terrestrial higher plants depends. However, for the investigator this feature imposes difficulties on attempts to make quantitative studies of the process of ion absorption by leaf tissue. The importance of this absorption process in the physiology of leaf cells has ...

Reflectance spectra of carbonate minerals in the shortwave infrared (SWIR) and thermal infrared (TIR) wavelength regions contain a number of diagnostic absorption features. The shape of these features depends on various physical and chemical parameters. To accurately identify carbonate minerals or rocks in pure and mixed form, it is necessary to analyze the effects of the parameters on spectral...