18 research outputs found
Red, green and blue lasing enabled by single-exciton gain in colloidal quantum dot films
Selective Versus Comprehensive Neck Dissection after Chemoradiation for Advanced Oropharyngeal Squamous Cell Carcinoma
Surface recombination and charged exciton in nanocrystal quantum dots on photonic crystals under two-photon excitation
Utilizing computed tomography as a road map for designing selective and superselective neck dissection after chemoradiotherapy
Past extreme warming events linked to massive carbon release from thawing permafrost
Between about 55.5 and 52 million years ago, Earth experienced a
series of sudden and extreme global warming events (hyperthermals)
superimposed on a long-term warming trend1. The first and largest
of these events, the Palaeocene–Eocene Thermal Maximum (PETM),
is characterized by a massive input of carbon, ocean acidification2
and an increase in global temperature of about 5 6C within a few
thousand years3. Although various explanations for the PETM have
been proposed4–6, a satisfactory model that accounts for the source,
magnitude and timing of carbon release at the PETM and successive
hyperthermals remains elusive. Here we use a new astronomically
calibrated cyclostratigraphic record from central Italy7 to show that
the Early Eocene hyperthermals occurred during orbits with a com-
bination of high eccentricity and high obliquity. Corresponding
climate–ecosystem–soil simulations accounting for rising concen-
trations of background greenhouse gases8 and orbital forcing show
that the magnitude and timing of the PETM and subsequent
hyperthermals can be explained by the orbitally triggered de-
composition of soil organic carbon in circum-Arctic and
Antarctic terrestrial permafrost. This massive carbon reservoir
had the potential to repeatedly release thousands of petagrams
(1015 grams) of carbon to the atmosphere–ocean system, once a
long-term warming threshold had been reached just before the
PETM. Replenishment of permafrost soil carbon stocks following
peak warming probably contributed to the rapid recovery from each
event9, while providing a sensitive carbon reservoir for the next
hyperthermal10. As background temperatures continued to rise
following the PETM, the areal extent of permafrost steadily
declined, resulting in an incrementally smaller available carbon
pool and smaller hyperthermals at each successive orbital forcing
maximum. A mechanism linking Earth’s orbital properties with
release of soil carbon from permafrost provides a unifying model
accounting for the salient features of the hyperthermals