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    The SPARC Data Initiative - Results of a long journey

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    The influence of air-sea fluxes on atmospheric aerosols during the summer monsoon over the tropical Indian Ocean

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    During the summer monsoon, the western tropical Indian Ocean is predicted to be a hot spot for dimethylsulfide emissions, the major marine sulfur source to the atmosphere, and an important aerosol precursor. Other aerosol relevant fluxes, such as isoprene and sea spray, should also be enhanced, due to the steady strong winds during the monsoon. Marine air masses dominate the area during the summer monsoon, excluding the influence of continentally derived pollutants. During the SO234-2/235 cruise in the western tropical Indian Ocean from July to August 2014, directly measured eddy covariance DMS fluxes confirm that the area is a large source of sulfur to the atmosphere (cruise average 9.1 μmol m−2 d−1). The directly measured fluxes, as well as computed isoprene and sea spray fluxes, were combined with FLEXPART backward and forward trajectories to track the emissions in space and time. The fluxes show a significant positive correlation with aerosol data from the Terra and Suomi-NPP satellites, indicating a local influence of marine emissions on atmospheric aerosol numbers

    Using Chemical Knowledge to Uncover New Biological Function: Discovery of the Cylindrocyclophane Biosynthetic Pathway

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    An understanding of organic chemistry can play a central role in uncovering enzymes with new biochemical functions. We have recently identified the enzymes involved in the biosynthesis of the cylindrocyclophanes, a structurally unique family of natural products, and found that this pathway employs a remarkable macrocyclization event that requires functionalization of an unactivated carbon atom. This work illustrates the potential of using chemically guided approaches for enzyme discovery

    Using Chemical Knowledge to Uncover New Biological Function: Discovery of the Cylindrocyclophane Biosynthetic Pathway

    No full text
    An understanding of organic chemistry can play a central role in uncovering enzymes with new biochemical functions. We have recently identified the enzymes involved in the biosynthesis of the cylindrocyclophanes, a structurally unique family of natural products, and found that this pathway employs a remarkable macrocyclization event that requires functionalization of an unactivated carbon atom. This work illustrates the potential of using chemically guided approaches for enzyme discovery

    Kalsilite-bearing plutonic rocks: The deep-seated Archean Awsard massif of the Reguibat Rise, South Morocco, West African Craton

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    Kalsilite-bearing igneous rocks are extremely rare,most known examples are volcanic. The few previously recorded kalsilite-bearing plutonic rocks are all Phanerozoic and mostly limited to the small ultrapotassic massifs of the Baikal–Stanovoi Rift in the Siberian Craton, the Greenland Batbjerg Massif, and the Kola Peninsula Khibiny Complex. We have found that the Archean to Proterozoic transition in thewestern Reguibat Rise of theWest African Craton is marked by several small massifs predominantly composed of kalsilite syenites, i.e., synnyrites. The largest massif is Awsard, a deep-seated intrusive body mainly composed of 2.46 Ga synnyrites and K-rich nepheline syenites with mantle-like Sr and Nd (whole-rock) and O (zircon) isotope composition. Apart from some superficial resemblance to the Baikal–Stanovoi synnyritiferous complexes, Awsard has no known equivalent in the geological record. It is the oldest, the deepest and the largest known occurrence of synnyrites. Awsard comprises solely felsic syenites with εNd(t) notably more primitive than their Siberian counterparts. The synnyrites contain kalsilite and rare nepheline as primary phases with no leucite or leucite pseudomorphs. Kalsilite and nepheline form large discrete grains that, in places, are accompanied by spectacular Ks–Or or Ne–Or symplectites. The symplectites are magmatic, generated by simultaneous crystallization of the two phases and the imbalance between the growth rate of the feldspar and the diffusivity of silica and alkalis in the melt. To explain why Awsard lacks mafic rocks and associated carbonatites, typical of other synnyrite massifs, we propose that ascending water-poor (H2O b 0.65 wt.%) mafic ultrapotassic magmas solidified at a pressure of 10–16 kbar underneath the already stabilized Archean crust of the region. In these conditions leucite began to crystallize when the temperature dropped to around 1100 °C. As a result of their low density, leucite crystals floated and formed a cap at the top of the intrusion. Then, the chamber was replenished with awater-rich andmore sodic ultrapotassicmagma that originated in the samemetasomatized mantle-source region. After prolonged fractional crystallization this second magma released an aqueous vapor phase that migrated upwards and melted the leucite cap thus producing a low-density hydrous magma of leucite-like, synnyritic, composition. This leucite-like magma, and the late residual melts from the second pulse that replenished the chamber, ascended and intruded the already cratonized lower crust of the western Reguibat Rise. There, the magmas crystallized outside the leucite stability field to produce the synnyrites and the nepheline syenites, respectively. There is no evidence that the metasomatic refertilization of the mantle required to produce the initial ultrapotassic mafic magmas was related to subduction fluids. On the contrary, it seems to have been caused by incompatible-element enriched hydrous fluids released from delaminated lower crustal fragments
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