The deglaciation of coastal areas of southeast Greenland

Large marine-terminating glaciers around the margins of the Greenland Ice Sheet have retreated, accelerated and thinned over the last two decades. Relatively little is known about the longer term behaviour of the Greenland Ice Sheet, yet this information is valuable for assessing the significance of modern changes. We address this by reporting 11 new beryllium-10 (10Be) exposure ages from previously uninvestigated coastal areas across southeast Greenland. The new ages are combined with existing data from the region to assess the timing of glacier retreat after the Last Glacial Maximum. The results show that deglaciation occurred first in the north of the region (~68°N) and progressed southwards. This north–south progression is attributed to the influence of the warm Irminger Current on the ice margin. Areas in the south of the region were isolated from the warm waters by the shallow bathymetry of the continental shelf. This demonstrates that oceanographic forcing paced the deglaciation of southeast Greenland through the Younger Dryas and early Holocene. In most areas of southeast Greenland bedrock ages are systematically older than their counterpart boulder samples; this offset is likely the result of inherited 10Be content in bedrock surfaces. This suggests that subglacial erosion during the last glacial cycle was insufficient to completely remove pre-existing 10Be content. Alternatively, this pattern may be the signature of a substantial retreat and advance cycle prior to final Holocene deglaciation

Tracking molecular resonance forms of donor-acceptor push-pull molecules by single-molecule conductance experiments

The ability of molecules to change colour on account of changes in solvent polarity is known as solvatochromism and used spectroscopically to characterize charge-transfer transitions in donor–acceptor molecules. Here we report that donor–acceptor-substituted molecular wires also exhibit distinct properties in single-molecule electronics under the influence of a bias voltage, but in absence of solvent. Two oligo(phenyleneethynylene) wires with donor–acceptor substitution on the central ring (cruciform-like) exhibit remarkably broad conductance peaks measured by the mechanically controlled break-junction technique with gold contacts, in contrast to the sharp peak of simpler molecules. From a theoretical analysis, we explain this by different degrees of charge delocalization and hence cross-conjugation at the central ring. Thus, small variations in the local environment promote the quinoid resonance form (off), the linearly conjugated (on) or any form in between. This shows how the conductance of donor–acceptor cruciforms is tuned by small changes in the environment

CCHamide-2 Is an Orexigenic Brain-Gut Peptide in <i>Drosophila</i>

<div><p>The neuroendocrine peptides CCHamide-1 and -2, encoded by the genes <i>ccha1</i> and <i>-2</i>, are produced by endocrine cells in the midgut and by neurons in the brain of <i>Drosophila melanogaster</i>. Here, we used the CRISPR/Cas9 technique to disrupt the <i>ccha1</i> and <i>-2</i> genes and identify mutant phenotypes with a focus on <i>ccha-2</i> mutants. We found that both larval and adult <i>ccha2</i> mutants showed a significantly reduced food intake as measured in adult flies by the Capillary Feeding (CAFE) assay (up to 72% reduced food intake compared to wild-type). Locomotion tests in adult flies showed that <i>ccha2</i> mutants had a significantly reduced locomotor activity especially around 8 a.m. and 8 p.m., where adult <i>Drosophila</i> normally feeds (up to 70% reduced locomotor activity compared to wild-type). Reduced larval feeding is normally coupled to a delayed larval development, a process that is mediated by insulin. Accordingly, we found that the <i>ccha2</i> mutants had a remarkably delayed development, showing pupariation 70 hours after the pupariation time point of the wild-type. In contrast, the <i>ccha-1</i> mutants were not developmentally delayed. We also found that the <i>ccha2</i> mutants had up to 80% reduced mRNA concentrations coding for the <i>Drosophila</i> insulin-like-peptides-2 and -3, while these concentrations were unchanged for the <i>ccha1</i> mutants. From these experiments we conclude that CCHamide-2 is an orexigenic peptide and an important factor for controlling developmental timing in <i>Drosophila</i>.</p></div