Monolith formation and ring-stain suppression in low-pressure evaporation of poly(ethylene oxide) droplets

When droplets of dilute suspensions are left to evaporate the final dry residue is typically the familiar coffee-ring stain, with nearly all material deposited at the initial triple line (Deegan et al, Nature, vol. 389, 1997, pp. 827-829). However, aqueous poly(ethylene oxide) (PEO) droplets only form coffee-ring stains for a very narrow range of the experimental parameters molecular weight, concentration and drying rate. Instead, over a wide range of values they form either a flat disk or a very distinctive tall central monolith via a four-stage deposition process which includes a remarkable bootstrap-building step. To predict which deposit will form, we present a quantitative model comparing the effects of advective build-up at the triple line to diffusive flux and use this to calculate a dimensionless number χ. By experimentally varying concentration and flux (using a low-pressure drying chamber), the prediction is tested over nearly two orders of magnitude in both variables and shown to be in good agreement with the boundary between disks and monoliths at χ ≈ 1.6

Prevalence of Coxiella burnetii in clinically healthy German sheep flocks

<p>Abstract</p> <p>Background</p> <p>Current epidemiological data on the situation of <it>Coxiella (C.) burnetii </it>infections in sheep are missing, making risk assessment and the implementation of counteractive measures difficult. Using the German state of Thuringia as a model example, the estimated sero-, and antigen prevalence of <it>C. burnetii </it>(10% and 25%, respectively) was assessed at flock level in 39/252 randomly selected clinically healthy sheep flocks with more than 100 ewes and unknown abortion rate.</p> <p>Results</p> <p>The CHECKIT™ Q-fever Test Kit identified 11 (28%) antibody positive herds, whereas real-time PCR revealed the presence of <it>C. burnetii </it>DNA in 2 (5%) of the flocks. Multiple-locus variable number of tandem repeats analysis of 9 isolates obtained from one flock revealed identical profiles. All isolates contained the plasmid QpH1.</p> <p>Conclusions</p> <p>The results demonstrate that <it>C. burnetii </it>is present in clinically inconspicuous sheep flocks and sporadic flare-ups do occur as the notifications to the German animal disease reporting system show. Although <it>C. burnetii </it>infections are not a primary veterinary concern due to the lack of significant clinical impact on animal health (with the exception of goats), the eminent zoonotic risk for humans should not be underestimated. Therefore, strategies combining the interests of public and veterinary public health should include monitoring of flocks, the identification and culling of shedders as well as the administration of protective vaccines.</p

Characterization and Geological Implications of Precambrian Calcite-hosted Phosphate

Constraints on marine phosphate availability and cycling directly inform our understanding of long-term biological evolution. However, early Earth phosphate records are sparse, biased toward siliciclastic samples, and are susceptible to post-depositional modification. Well-preserved shallow marine inorganic carbonate precipitates provide a complementary yet understudied record of phosphate cycling. We combined micro-X-ray Fluorescence mapping, X-ray absorption and Nuclear Magnetic Resonance spectroscopy on samples of Precambrian syndepositional herringbone calcite and microspar to characterize phosphorus speciation and distribution in these carbonate fabrics. Phosphorus spectroscopy from synthetic calcite, herringbone calcite and microspar, are qualitatively consistent with a disordered distribution of phosphate. These characteristics are diagnostic of calcite-hosted phosphate, which is pervasive at low concentrations in herringbone calcite and microspar. This study provides evidence that ancient, well-preserved carbonate fabrics retain phosphate sourced from seawater and highlights the potential for an unaltered archive of marine phosphate concentration over geologic time.Leverhulme Trust Grant PLP-2015-28

Characterization and Geological Implications of Precambrian Calcite-hosted Phosphate

Constraints on marine phosphate availability and cycling directly inform our understanding of long-term biological evolution. However, early Earth phosphate records are sparse, biased toward siliciclastic samples, and are susceptible to post-depositional modification. Well-preserved shallow marine inorganic carbonate precipitates provide a complementary yet understudied record of phosphate cycling. We combined micro-X-ray Fluorescence mapping, X-ray absorption and Nuclear Magnetic Resonance spectroscopy on samples of Precambrian syndepositional herringbone calcite and microspar to characterize phosphorus speciation and distribution in these carbonate fabrics. Phosphorus spectroscopy from synthetic calcite, herringbone calcite and microspar, are qualitatively consistent with a disordered distribution of phosphate. These characteristics are diagnostic of calcite-hosted phosphate, which is pervasive at low concentrations in herringbone calcite and microspar. This study provides evidence that ancient, well-preserved carbonate fabrics retain phosphate sourced from seawater and highlights the potential for an unaltered archive of marine phosphate concentration over geologic time.Leverhulme Trust Grant PLP-2015-28

Tonian carbonates record phosphate-rich shallow seas

The early-middle Neoproterozoic is thought to have witnessed significant perturbations to marine P cycling, in turn facilitating the rise of eukaryote-dominated primary production. However, with few robust constraints on aqueous P concentrations, current understanding of Neoproterozoic P cycling is generally model-dependent. To provide new geochemical constraints, we combined microanalytical datasets with solid-state NMR, synchrotron-based XANES spectroscopy, and micro-XRF imaging to characterise the speciation and distribution of P in Tonian shallow-water carbonate rocks. These data reflect shallow water phosphate concentrations 10-100x higher than modern systems, supporting the hypothesis that tectonically-driven influxes in P periodically initiated kinetically-controlled CaCO3 deposition, in turn destabilising marine carbonate chemistry, climate, and nutrient inventories. Alongside these observations, a new compilation and statistical analysis of mudstone geochemistry data indicates that, in parallel, Corg and P burial increased across later Tonian continental margins until becoming decoupled at the close of the Tonian, implicating widespread N-limitation triggered by increasing atmospheric O2

New Caledonia obducted Peridotite Nappe: offshore extent and implications for obduction and post-obduction processes

One of the largest ophiolitic peridotite masses in the world covers a quarter of the island of Grande Terre, New Caledonia. The Peridotite Nappe was obducted during the Eocene, is weakly deformed and corresponds to the highest of a structurally simple pile of thrust nappes. We present new marine seismic data that allows us to track the offshore continuation of the Peridotite Nappe along‐strike for a distance of more than 500 km south of New Caledonia, and to image its pre‐, syn‐ and post‐obduction sedimentary records. Offshore, the Peridotite Nappe underlies a c. 150‐km wide and 2 km‐deep basin. Flat‐topped horsts of peridotite are clearly bounded by major normal faults; in contrast faults are obscure onland. To the east, the Peridotite Nappe roots along the eastern margin of the Félicité Ridge (new name), a c. 300 x 25 km dome‐shaped ridge, which we interpret as being the southern extension of the HP/LT metamorphic core complex observed in New Caledonia. Two alternative tectonic models address the relative timing and relationships between Peridotite Nappe emplacement, uplift of a metamorphic core complex, and extensional tectonics. These models provide new ideas for the understanding the formation of the eastern margin of the Zealandia continent. Our results contribute to an understanding of how oceanic mantle is emplaced onto continental margins

Stratigraphy and Tectonics of the Continental Norfolk Ridge, SW Pacific Ocean.

International audienceThe Norfolk Ridge is a north-south trending ca. 1000 x 80 km bathymetric high located along the easternmost edge of the Zealandia continent at ca. 1 km water-depth. It lies in a key tectonic position which marks the boundary between Neogene subduction-related arcs and backarc basins to the east (e.g. 3-4 km deep Norfolk Basin) and Mesozoic to Paleogene continental basins to the west (e.g. 2-3 km deep New Caledonia and Reinga basins). The ridge is emergent in New Caledonia and New Zealand where obduction is known to have occurred in the late Paleogene to early Neogene. It is also hypothesized to be proximal to where the Tonga Kermadec Subduction initiated. Yet, the structure, geology and stratigraphy of the Norfolk Ridge remain largely unknown. New geophysical and geological data from the TECTA and VESPA voyages acquired in 2015 onboard RV L’Atalante reveal the structural style and stratigraphy of the ridge. It is composed of a thick sedimentary succession perched between the Norfolk and New Caledonia basins. Two main seismic units are observed. The lower unit (NR1) is thick (> 2 s twt), tilted east towards the Norfolk Basin and its top is marked by a major erosional unconformity. The upper unit (NR2) is thinner (1 km) that in the Eocene-Oligocene, but – surprisingly – without evidences for contraction. These events were closely followed by, or synchronous with, a volcanic episode and normal faulting that formed the ridge’s present-day morphology. This calls into question the modalities of the induced subduction initiation model that is proposed for the region