MAGNESIUM | De-icing salts help
keep our roads safe by preventing ice
from freezing on roads and bridge
decks. But that safety comes with a
price, since the 17 million tons of
de-icing salts applied annually to
U.S. roadways greatly contribute to
their decay. Comparing three different
salts, researchers with Purdue’s Joint
Transportation Research Program
found that all three strongly interacted
with the concrete to which they are
applied, producing additional phases
and phase changes that, when expansive
in nature, can cause additional cracking
and damage to the concrete. And while
magnesium chloride is considered
more effective at lower temperatures,
sodium chloride appears more benign
than either magnesium chloride or
calcium chloride when reacting
with the concrete substrate.
Understanding Culture from Ancient Dental Enamel
STRONTIUM | Rising at dawn when they hear the mosque’s call for prayer, Michele
Buzon and her crew eat a light snack, then head for a burial site more than 3,500 years
old. After excavating for a few hours in the northern Sudan desert, they return to their
house for breakfast, then dig again until mid-afternoon, when they return home to
Buzon’s bioarcheology team has traveled to Tombos five winters to examine strontium in
the dental enamel of human remains to learn about migration in the Nile Valley, where
ancient Nubian and Egyptian cultures once coexisted.
With more than 200 remains excavated from individual and group tombs, they have
covered about one-third of the site, says Buzon, associate professor of anthropology.
Differences in strontium ratios, along with skeletal and mortuary analyses, reveal that
biologically and ethnically mixed people lived there, fueling insights on sociopolitical
activities and biocultural effects of environmental stress and cultural change.
“These people lived good lives. They have relatively few signs of ill health, nutritional
deficiencies, infection or signs of hard labor,” she says. “They also show almost no
violent injuries in their bones, and appear to have lived in peace in their multicultural
community.” | K.M.
© 2015 Theodore Gray periodictable.c