Using Shuttle Radar Topography to map ancient water channels in Mesopotamia

The Shuttle Radar Topography Mission (SRTM) is currently producing a digital elevation model of most of the world's surface. Here the authors assess its value in mapping and sequencing the network of water channels that provided the arterial system for Mesopotamia before the petrol engine

SUMOylation Is Required for Glycine-Induced Increases in AMPA Receptor Surface Expression (ChemLTP) in Hippocampal Neurons

yesMultiple pathways participate in the AMPA receptor trafficking that underlies long-term potentiation (LTP) of synaptic transmission. Here we demonstrate that protein SUMOylation is required for insertion of the GluA1 AMPAR subunit following transient glycine-evoked increase in AMPA receptor surface expression (ChemLTP) in dispersed neuronal cultures. ChemLTP increases co-localisation of SUMO-1 and the SUMO conjugating enzyme Ubc9 and with PSD95 consistent with the recruitment of SUMOylated proteins to dendritic spines. In addition, we show that ChemLTP increases dendritic levels of SUMO-1 and Ubc9 mRNA. Consistent with activity dependent translocation of these mRNAs to sites near synapses, levels of the mRNA binding and dendritic transport protein CPEB are also increased by ChemLTP. Importantly, reducing the extent of substrate protein SUMOylation by overexpressing the deSUMOylating enzyme SENP-1 or inhibiting SUMOylation by expressing dominant negative Ubc9 prevent the ChemLTP-induced increase in both AMPAR surface expression and dendritic SUMO-1 mRNA. Taken together these data demonstrate that SUMOylation of synaptic protein(s) involved in AMPA receptor trafficking is necessary for activity-dependent increases in AMPAR surface expression.Medical Research Council, the European Research Council and the Wellcome Trus

Spatial Stability of Incompressible Attachment-Line Flow

Linear stability analysis of incompressible attachment-line flow is presented within the spatial framework. The system of perturbation equations is solved using spectral collocation. This system has been solved in the past using the temporal approach and the current results are shown to be in excellent agreement with neutral temporal calculations. Results amenable to direct comparison with experiments are then presented for the case of zero suction. The global solution method utilized for solving the eigenproblem yields, aside from the well-understood primary mode, the full spectrum of least-damped waves. Of those, a new mode, well separated from the continuous spectrum is singled out and discussed. Further, relaxation of the condition of decaying perturbations in the far-field results in the appearance of sinusoidal modes akin to those found in the classical Orr-Sommerfeld problem. Finally, the continuous spectrum is demonstrated to be amenable to asymptotic analysis. Expressions are derived for the location, in parameter space, of the continuous spectrum, as well as for the limiting cases of practical interest. In the large Reynolds number limit the continuous spectrum is demonstrated to be identical to that of the Orr-Sommerfeld equation

Endothelial cells form transient Notch-dependent NO-containing cystic structures during zebrafish cerebrovascular development

Endothelial cell behaviour during blood vessel formation is highly complex and dynamic. Transgenic zebrafish have provided many new insights into these processes, due to their ability to provide detailed in vivo imaging. We here report a previously undescribed endothelial cell behaviour during zebrafish embryonic development. Endothelial cells of the cerebral vessels of 3-5d post fertilisation embryos extruded large membranous spherical structures. These were only found on the cerebral vessels, and did not detach from the parent vessel, instead regressing back into the endothelial cell. These structures did not communicate with the vessel lumen, exhibited periodic oscillations in size and shape, and were enriched with filamentous actin at their neck. Due to their unknown nature and spherical appearance we termed these structures kugeln (German for sphere). Pharmacological inhibition of vascular endothelial growth factor (VEGF) signalling significantly increased kugel number while Notch inhibition significantly reduced both kugel number and diameter. Kugeln contain little cytoplasm, but are highly positive for nitric oxide (NO) reactivity, suggesting they represent a novel NO containing organelle specific to the cerebral vessels

Asymmetric Hapln1a drives regionalized cardiac ECM expansion and promotes heart morphogenesis in zebrafish development

Aims Vertebrate heart development requires the complex morphogenesis of a linear tube to form the mature organ, a process essential for correct cardiac form and function, requiring coordination of embryonic laterality, cardiac growth, and regionalized cellular changes. While previous studies have demonstrated broad requirements for extracellular matrix (ECM) components in cardiac morphogenesis, we hypothesized that ECM regionalization may fine tune cardiac shape during heart development. Methods and results Using live in vivo light sheet imaging of zebrafish embryos, we describe a left-sided expansion of the ECM between the myocardium and endocardium prior to the onset of heart looping and chamber ballooning. Analysis using an ECM sensor revealed the cardiac ECM is further regionalized along the atrioventricular axis. Spatial transcriptomic analysis of gene expression in the heart tube identified candidate genes that may drive ECM expansion. This approach identified regionalized expression of hapln1a, encoding an ECM cross-linking protein. Validation of transcriptomic data by in situ hybridization confirmed regionalized hapln1a expression in the heart, with highest levels of expression in the future atrium and on the left side of the tube, overlapping with the observed ECM expansion. Analysis of CRISPR-Cas9-generated hapln1a mutants revealed a reduction in atrial size and reduced chamber ballooning. Loss-of-function analysis demonstrated that ECM expansion is dependent upon Hapln1a, together supporting a role for Hapln1a in regionalized ECM modulation and cardiac morphogenesis. Analysis of hapln1a expression in zebrafish mutants with randomized or absent embryonic left–right asymmetry revealed that laterality cues position hapln1a-expressing cells asymmetrically in the left side of the heart tube. Conclusion We identify a regionalized ECM expansion in the heart tube which promotes correct heart development, and propose a novel model whereby embryonic laterality cues orient the axis of ECM asymmetry in the heart, suggesting these two pathways interact to promote robust cardiac morphogenesis

The range and level of impurities in CO2 streams from different carbon capture sources

For CO2 capture and storage deployment, the impact of impurities in the gas or dense phase CO2 stream arising from fossil fuel power plants, or large scale industrial emitters, is of fundamental importance to the safe and economic transportation and storage of the captured CO2. This paper reviews the range and level of impurities expected from the main capture technologies used with fossil-fuelled power plants in addition to other CO2 emission-intensive industries. Analysis is presented with respect to the range of impurities present in CO2 streams captured using pre-combustion, post-combustion and oxy-fuel technologies, in addition to an assessment of the different parameters affecting the CO2 mixture composition. This includes modes of operation of the power plant, and different technologies for the reduction and removal of problematic components such as water and acid gases (SOx/NOx). A literature review of data demonstrates that the purity of CO2 product gases from carbon capture sources is highly dependent upon the type of technology used. This paper also addresses the CO2 purification technologies available for the removal of CO2 impurities from raw oxy-fuel flue gas, such as Hg and non-condensable compounds. CO2 purities of over 99% are achievable using post-combustion capture technologies with low levels of the main impurities of N2, Ar and O2. However, CO2 capture from oxy-fuel combustion and integrated gasification combined cycle power plants will need to take into consideration the removal of non-condensables, acid gas species, and other contaminants. The actual level of CO2 purity required will be dictated by a combination of transport and storage requirements, and process economics

Dual control of fault intersections on stop-start rupture in the 2016 Central Italy seismic sequence

Large continental earthquakes necessarily involve failure of multiple faults or segments. But these same critically-stressed systems sometimes fail in drawn-out sequences of smaller earthquakes over days or years instead. These two modes of failure have vastly different implications for seismic hazard and it is not known why fault systems sometimes fail in one mode or the other, or what controls the termination and reinitiation of slip in protracted seismic sequences. A paucity of modern observations of seismic sequences has hampered our understanding to-date, but a series of three Mw>6 earthquakes from August to November 2016 in Central Italy represents a uniquely well-observed example. Here we exploit a wealth of geodetic, seismological and field data to understand the spatio-temporal evolution of the sequence. Our results suggest that pre-existing fault structures controlled the extent and termination of rupture in each event in the sequence, and that fluid diffusion, channelled along these same structures, may have also determined the timing of rupture reinitiation. This dual control of subsurface structure on the stop-start rupture in seismic sequences may be common; future efforts should focus on investigating its prevalence