Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores

Orbital tuning is central for ice core chronologies beyond annual layer counting, available back to 60 ka (i.e. thousands of years before 1950) for Greenland ice cores. While several complementary orbital tuning tools have recently been developed using δ¹⁸Oatm, δO₂⁄N₂ and air content with different orbital targets, quantifying their uncertainties remains a challenge. Indeed, the exact processes linking variations of these parameters, measured in the air trapped in ice, to their orbital targets are not yet fully understood. Here, we provide new series of δO₂∕N₂ and δ¹⁸Oatm data encompassing Marine Isotopic Stage (MIS) 5 (between 100 and 160 ka) and the oldest part (340–800 ka) of the East Antarctic EPICA Dome C (EDC) ice core. For the first time, the measurements over MIS 5 allow an inter-comparison of δO₂∕N₂ and δ¹⁸Oatm records from three East Antarctic ice core sites (EDC, Vostok and Dome F). This comparison highlights some site-specific δO₂∕N₂ variations. Such an observation, the evidence of a 100 ka periodicity in the δO₂∕N₂ signal and the difficulty to identify extrema and mid-slopes in δO2∕N2 increase the uncertainty associated with the use of δO₂∕N₂ as an orbital tuning tool, now calculated to be 3–4 ka. When combining records of δ¹⁸Oatm and δO₂∕N₂ from Vostok and EDC, we find a loss of orbital signature for these two parameters during periods of minimum eccentricity (∼ 400 ka, ∼ 720–800 ka). Our data set reveals a time-varying offset between δO₂∕N₂ and δ¹⁸Oatm records over the last 800 ka that we interpret as variations in the lagged response of δ¹⁸Oatm to precession. The largest offsets are identified during Terminations II, MIS 8 and MIS 16, corresponding to periods of destabilization of the Northern polar ice sheets. We therefore suggest that the occurrence of Heinrich–like events influences the response of δ¹⁸Oatm to precession.

Vegetables and their cultivation; the history, cultivation, and forcing of culinary vegetables, saladings, and herbs, for home use and exhibitions; also the formation of the vegetable garden; the management of soils; manures and their uses; and the eradication of injurious insect and fungoid pests, etc. ...

Mode of access: Internet.

Forcing regression through a given point using any familiar computational routine /

"March 1983."

Steam warfare in the Parana: a narrative of operations, by the combined squadrons of England and France, in forcing a passage up that river,

Sketches of South America, illustrative of allusions in the foregoing narrative, to the geography, natural history, inhabitants, etc., of that part of the world. Extracts translated from Felix de Azara's Voyages dans l'Amérique Méridionale... v.2, p. [121]-287.

The kitchen gardener's instructor : containing a catalogue of garden and herb seed, with practical directions under each head for the cultivation of culinary vegetables and herbs : with a calendar, showing the work necessary to be done in a kitchen garden ... : also, directions for forcing or forwarding vegetables out of the ordinary season : the whole adapted to the climate of the United States /

Advertisement: 1 p. (at end).

The American kitchen-gardener : containing complete practical directions for the cultivation of culinary vegetables and herbs, together with instructions for forcing or forwarding vegetables out of the ordinary season /

Mode of access: Internet.

Coercive air strategy : forcing a bureaucratic shift /

Originally presented as Thesis--School of Advanced Airpower Studies, Air University, 1993-94.

The illustrated strawberry culturist : containing the history, sexuality, field and garden culture of strawberries, forcing or pot culture, how to grow from seed, hybridizing, and all other information neccessary to enable everybody to raise their own strawberries, together with a description of new varieties and a list of the best of the old sorts -- /

Includes index.

The kitchen gardener's instructor : containing a catalogue of garden and herb seeds, with practical directions under each head, for the cultivation of culinary vegetables & herbs : with a calendar, showing the work necessary to be done in a kitchen garden, in every month throughout the season : also, directions for forcing or forwarding vegetables out of the ordinary season /

Includes index.

The Scotch forcing and kitchen gardener; : being a second edition with extensive additions, of The Scotch forcing gardener: compre[he]nding the forcing of asparagus, cucumbers, cherries ... together with the management of the green-house--culture of wall and orchard fruits--kitchen vegetables, sallads and herbs ... /

Errata: p. [xiii].

The orchard: including the management of wall and standard fruit trees, and the forcing pit; with selected lists and synonymes of the most choice varieties.

"Head gardener to His Grace the Duke of Buccleuch, at Dalkeith."

Evidence for energy relaxation via a radiative cascade in surface-passivated PbS quantum dots

Multiple emission peaks have been observed from surface passivated PbS nanocrystals displaying strong quantum confinement. The emission spectra are shown to be strongly dependent on the excited-state parity. We also find that intraband energy relaxation from initial states excited far above the band-edge is nearly three orders of magnitude slower than that found in other nanocrystal quantum dots, providing evidence of inefficient energy relaxation via phonon emission. The initial-state parity dependence of the photoluminescent emission properties suggests that energy relaxation from the higher excited states occurs via a radiative cascade, analogous to energy relaxation in atomic systems. Such radiative cascade emission is possible from ideal zero-dimensional semiconductors, where electronic transitions can be decoupled from phonon modes.

Radiative relaxation in synthetic pheomelanin

We report a detailed photoluminescence study of cysteinyldopa-melanin ( CDM), the synthetic analogue of pheomelanin. Emission spectra are shown to be a far more sensitive probe of CDM's spectroscopic behavior than are absorption spectra. Although CDM and dopa-melanin ( DM, the synthetic analogue of eumelanin) have very similar absorption spectra, we find that they have very different excitation and emission characteristics; CDM has two distinct photoluminescence peaks that do not shift with excitation wavelength. Additionally, our data suggest that the radiative quantum yield of CDM is excitation energy dependent, an unusual property among biomolecules that is indicative of a chemically disordered system. Finally, we find that the radiative quantum yield for CDM is similar to 0.2%, twice that of DM, although still extremely low. This means that 99.8% of the energy absorbed by CDM is dissipated via nonradiative pathways, consistent with its role as a pigmentary photoprotectant.