Nanodiamonds in the Younger Dryas boundary sediment layer.

We report abundant nanodiamonds in sediments dating to 12.9 +/- 0.1 thousand calendar years before the present at multiple locations across North America. Selected area electron diffraction patterns reveal two diamond allotropes in this boundary layer but not above or below that interval. Cubic diamonds form under high temperature-pressure regimes, and n-diamonds also require extraordinary conditions, well outside the range of Earth's typical surficial processes but common to cosmic impacts. N-diamond concentrations range from approximately 10 to 3700 parts per billion by weight, comparable to amounts found in known impact layers. These diamonds provide strong evidence for Earth's collision with a rare swarm of carbonaceous chondrites or comets at the onset of the Younger Dryas cool interval, producing multiple airbursts and possible surface impacts, with severe repercussions for plants, animals, and humans in North America.

Three-millennium antiquity of the lithokelyphos variety of lithopedion.

Identification of a 3100-year-old lithopedion in the Archaic Southwest antedates its first clinical notation by 2100 years. It was only the "autopsy" of time (excavation of the site) that allowed its presence to be brought to light.

A new protocol for assessing viseme perception in sentence context: the lipreading discrimination test.

Forty-six hearing-impaired young adults were tested with a newly developed instrument that requires a discrimination response to assess viseme perception as a component of lipreading performance. Stimuli were videotaped sentences that differed on half of the trials from a captioned target sentence by one viseme embedded in the middle of the sentence. Discrimination within six visual categories was tested: gross syllable pattern, consonant articulation--lips, consonant articulation--tongue, vowel articulation--extreme lip shapes, vowel articulation--graded lip shapes, and vowel articulation--jaw movement. Test data were analyzed using an item response theory model. The results indicated that the test data conformed to the expectations of the Rasch model for person measurement. Relationships among subjects' test scores and communication characteristics also were examined. The data provide evidence that the test protocol, at this early stage of development, is useful for assessing at least one perceptual component of lipreading performance.