Human impact on mid- and late Holocene vegetation in south Cumbria, UK

The use of 9 pollen sampling sites and 56 14C dates has identified hitherto unsuspected or poorly-defined sequences of mid- to late Holocene (late Neolithic to post-Medieval) anthropogenic vegetation changes in south Cumbria, U.K. A series of small-scale, but significant woodland clearance episodes are recorded throughout the Bronze Age, followed by a marked recession in activity during the early Iron Age. The late Iron Age-Roman periods witnessed the first major clearance of woodland in the region which was succeeded by woodland regeneration in the post-Roman/early Medieval period. Woodland clearance intensified in the later Medieval period culminating in large areas of permanently open landscape. The results show that high-resolution, independently date pollen analysis is necessary to reveal regional evidence of small, temporary Bronze Age clearances. A well-documented prehistoric wooden trackway from Foulshaw Moss is shown to be significantly older than previously thought, dating to the mid-Bronze Age, ca. 1550–1250 cal B.C. Pre-Roman cereal cultivation in the area is also confirmed.The Department of Earth Sciences     

High‐Voltage Photogeneration Exclusively via Aggregation‐Induced Triplet States in a Heavy‐Atom‐Free Nonplanar Organic Semiconductor

The electron–hole recombination kinetics of organic photovoltaics (OPVs) are known to be sensitive to the relative energies of triplet and charge‐transfer (CT) states. Yet, the role of exciton spin in systems having CT states above 1.7 eV—like those in near‐ultraviolet‐harvesting OPVs—has largely not been investigated. Here, aggregation‐induced room‐temperature intersystem crossing (ISC) to facilitate exciton harvesting in OPVs having CT states as high as 2.3 eV and open‐circuit voltages exceeding 1.6 V is reported. Triplet excimers from energy‐band splitting result in ultrafast CT and charge separation with nonradiative energy losses of <250 meV, suggesting that a 0.1 eV driving force is sufficient for charge separation, with entropic gain via CT state delocalization being the main driver for exciton dissociation and generation of free charges. This finding can inform engineering of next‐generation active materials and films for near‐ultraviolet OPVs with open‐circuit voltages exceeding 2 V. Contrary to general belief, this work reveals that exclusive and efficient ISC need not require heavy‐atom‐containing active materials. Molecular aggregation through thin‐film processing provides an alternative route to accessing 100% triplet states on photoexcitation.     

Activities of SOD and the ascorbate-glutathione cycle enzymes in subcellular compartments in leaves and roots of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii

The activities of the ascorbate-glutathione cycle enzymes ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione reductase (GR) and SOD were studied in cell organelles of the cultivated tomato Lycopersicon esculentum (M82) and its wild salt-tolerant related species Lycopersicon pennellii (Lpa). All four enzymes of the ascorbate-glutathione cycle were present in chloroplasts/plastids, mitochondria and peroxisomes of leaf and root cells of both tomato species. In all leaf and root organelles of both species, the activity of MDHAR was similar to, or higher than, that of APX, while the activity of DHAR was one order of magnitude lower than that of MDHAR. Based on these results, it is suggested that in the organelles of both tomato species, ascorbate is regenerated mainly by MDHAR. In both tomato species, GR activity, and to a lesser extent DHAR activity, was found to reside in the soluble fraction of all leaf and root cell organelles, while APX and MDHAR activities were distributed between the membrane and soluble fractions. A higher SOD to APX activity ratio in all Lpa organelles was the major difference between the two tomato species. It is possible that this higher ratio contributes to the inherently better protection of Lpa from salt stress, as was previously reported.     

Syntheses and preliminary pharmacological evaluation of the two epimers of the 5-F2t-isoprostane.

The total synthesis of the 5-F2t-isoprostane 1 and its 5-epimer 2 from diacetone-D-glucose is described. We report preliminary data on the vascular properties of these compounds.     

A functional fragment of Tau forms fibers without the need for an intermolecular cysteine bridge

We study the aggregation of a fragment of the neuronal protein Tau that contains part of the proline rich domain and of the microtubule binding repeats. When incubated at 37 °C with heparin, the fragment readily forms fibers as witnessed by Thioflavin T fluorescence. Electron microscopy and NMR spectroscopy show bundled ribbon like structures with most residues rigidly incorporated in the fibril. Without its cysteines, this fragment still forms fibers of a similar morphology, but with lesser Thioflavin T binding sites and more mobility for the C-terminal residues.     

Correction to: Preliminary insights into the population characteristics and distribution of reef (Mobula alfredi) and oceanic (M. birostris) manta rays in French Polynesia

Coral Reefs - This erratum has been initiated as many corrections which were submitted during proofing were overlooked by vendor.     

Cutting edge: T cells respond to lipopolysaccharide innately via TLR4 signaling

LPS, a molecule produced by Gram-negative bacteria, is known to activate both innate immune cells such as macrophages and adaptive immune B cells via TLR4 signaling. Although TLR4 is also expressed on T cells, LPS was observed not to affect T cell proliferation or cytokine secretion. We now report, however, that LPS can induce human T cells to adhere to fibronectin via TLR4 signaling. This response to LPS was confirmed in mouse T cells; functional TLR4 and MyD88 were required, but T cells from TLR2 knockout mice could respond to LPS. The human T cell response to LPS depended on protein kinase C signaling and involved the phosphorylation of the proline-rich tyrosine kinase (Pyk-2) and p38. LPS also up-regulated the T cell expression of suppressor of cytokine signaling 3, which led to inhibition of T cell chemotaxis toward the chemokine stromal cell-derived factor 1alpha (CXCL12). Thus, LPS, through TLR4 signaling, can affect T cell behavior in inflammation.     

Frequency-dependent conspecific attraction to food patches

In many ecological situations, resources are difficult to find but become more apparent to nearby searchers after one of their numbers discovers and begins to exploit them. If the discoverer cannot monopolize the resources, then others may benefit from joining the discoverer and sharing their discovery. Existing theories for this type of conspecific attraction have often used very simple rules for how the decision to join a discovered resource patch should be influenced by the number of individuals already exploiting that patch. We use a mechanistic, spatially explicit model to demonstrate that individuals should not necessarily simply join patches more often as the number of individuals exploiting the patch increases, because those patches are likely to be exhausted soon or joining them will intensify future local competition. Furthermore, we show that this decision should be sensitive to the nature of the resource patches, with individuals being more responsive to discoveries in general and more tolerant of larger numbers of existing exploiters on a patch when patches are resource-rich and challenging to locate alone. As such, we argue that this greater focus on underlying joining mechanisms suggests that conspecific attraction is a more sophisticated and flexible tactic than currently appreciated.