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We present new measurements of methane (CH4), nitrogen isotopes (d15N-N2), and total air content (TAC) from the North Greenland Eemian Ice Drilling (NEEM), North Greenland Ice Core Project (NGRIP), and Greenland Ice Sheet Project Two (GISP2) Greenland ice cores from the Last Glacial Maximum through the late Holocene (0 to ~18 thousand years before present [ka BP]). These records provide insight into spatial pattern of Greenland climate evolution across the deglaciation and the Holocene Thermal Maximum. The methane data allow for gas-phase synchronization of ice cores across Greenland and Antarctica, providing empirical delta age reconstructions. The nitrogen isotopic composition data allow for reconstruction of abrupt Greenland surface climate variations, which is provided for all 3 sites. Data are a combination of measurements conducted at Oregon State University, Scripps Institution of Oceanography, and the National Institute for Polar Research using previously established techniques. 

The deposition of dense fibril plaques represents the pathological hallmark for a multitude of human disorders, including many neurodegenerative diseases. Fibril plaques are predominately composed of amyloid fibrils, characterized by their underlying cross beta-sheet architecture. Research into the mechanisms of amyloid formation has mostly focused on characterizing and modeling the growth of individual fibrils and associated oligomers from their monomeric precursors. Much less is known about the mechanisms causing individual fibrils to assemble into ordered fibrillar suprastructures. Elucidating the mechanisms regulating this “secondary” self-assembly into distinct suprastructures is important for understanding how individual protein fibrils form the prominent macroscopic plaques observed in disease. Whether and how amyloid fibrils assemble into either 2D or 3D supramolecular structures also relates to ongoing efforts on using amyloid fibrils as substrates or scaffolds for self-assembling functional biomaterials. Here, we investigated the conditions under which preformed amyloid fibrils of a lysozyme assemble into larger superstructures as a function of charge screening or pH. Fibrils either assembled into three-dimensional gel clusters or two-dimensional fibril sheets. The latter displayed optical birefringence, diagnostic of amyloid plaques. We presume that pH and salt modulate fibril charge repulsion, which allows anisotropic fibril–fibril attraction to emerge and drive the transition from 3D to 2D fibril self-assembly. 

The direction of electron flow in molecular optoelectronic devices is dictated by charge transfer between a molecular excited state and an underlying conductor or semiconductor. For those devices, controlling the direction and reversibility of electron flow is a major challenge. We describe here a novel, single-molecule photodiode. It is based on an internally conjugated, bi-chromophoric dyad with chemically linked (porphyrinato)zinc(II) and bis(terpyridyl)ruthenium(II) groups. On nanocrystalline, degenerately doped indium tin oxide electrodes, the dyad exhibits distinct frequency-dependent, charge-transfer characters. Variations in the light source between red (~ 1.9 eV) and blue (~ 2.7 eV) light excitation for the integrated photodiode result in switching of photocurrents between cathodic and anodic. The origin of the excitation frequency-dependent photocurrents lies in the electronic structure of the chromophore excited states, as shown by the results of theoretical calculations, laser flash photolysis and steady-state spectrophotometric measurements.