"It's an isolated case," said Peter Constantakes, a spokesman for the State Department of Environmental Conservation, adding that bear attacks in New York generally occurred only about once every 5 to 10 years.
Until recently, astronomers thought that significant impacts on Jupiter should occur only about once in a decade.
He estimates that the mutation occurred only about 1000 years ago in the Mossi and that the allele is now spreading rapidly among South Africans.
According to NASA, total solar eclipses occur only about once a year because the moon and the sun don't orbit in the exact same plane.
As the moon and sun don't orbit in the exact same plane, total solar eclipses occur only about once a year.
Our studies indicate that the partial coat protein genes of potyviruses have an evolutionary rate of about 1.15×10−4 nucleotide substitutions/site/year, and the initial radiation of the potyviruses occurred only about 6,600 years ago, and hence coincided with the dawn of agriculture.
We chose 15mers because, by chance, any one 15mer should occur only about once in a genome of this size, making high-copy 15mers extremely infrequent by chance and thus indicative of repetitive elements (Gu et al. 2008).
In the volvocine algae the development from unicellular species, which were similar to the present species Chlamydomonas reinhardtii[ 5], to multicellular species and its relatives occurred only about 200 million years ago [ 1].
For most of its distribution, B. integrifolia occurs only within about 50 kilometres (30 mi) of the coast, where it typically occurs on poor quality sandy soils derived from sandstone.
