Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in Whycocomagh Bay, a Canadian estuary in the Bras d\u27Or Lake system

Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production (NOP) and gross oxygen production (GOP) using near-continuous measurements of the O2∕Ar gas ratio and discrete measurements of the triple isotopic composition of O2, during the transition from ice-covered to ice-free conditions, in Whycocomagh Bay, an estuary in the Bras d\u27Or Lake system in Nova Scotia, Canada. The volumetric gross oxygen production was 5.4+2.8-1.6 role= presentation \u3e5.4+2.8−1.6 mmol O2 m−3 d−1, similar at the beginning and end of the time series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt. We performed the first field-based dual tracer release experiment in ice-covered water to quantify air–water gas exchange. The gas transfer velocity at \u3e90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs are active in Whycocomagh Bay during spring while it is covered in ice

Unified Structural Representation of the southern California crust and upper mantle

We present a new, 3D description of crust and upper mantle velocity structure in southern California implemented as a Unified Structural Representation (USR). The USR is comprised of detailed basin velocity descriptions that are based on tens of thousands of direct velocity (Vp, Vs) measurements and incorporates the locations and displacement of major fault zones that influence basin structure. These basin descriptions were used to developed tomographic models of crust and upper mantle velocity and density structure, which were subsequently iterated and improved using 3D waveform adjoint tomography. A geotechnical layer (GTL) based on Vs30 measurements and consistent with the underlying velocity descriptions was also developed as an optional model component. The resulting model provides a detailed description of the structure of the southern California crust and upper mantle that reflects the complex tectonic history of the region. The crust thickens eastward as Moho depth varies from 10 to 40 km reflecting the transition from oceanic to continental crust. Deep sedimentary basins and underlying areas of thin crust reflect Neogene extensional tectonics overprinted by transpressional deformation and rapid sediment deposition since the late Pliocene. To illustrate the impact of this complex structure on strong ground motion forecasting, we simulate rupture of a proposed M 7.9 earthquake source in the Western Transverse Ranges. The results show distinct basin amplification and focusing of energy that reflects crustal structure described by the USR that is not captured by simpler velocity descriptions. We anticipate that the USR will be useful for a broad range of simulation and modeling efforts, including strong ground motion forecasting, dynamic rupture simulations, and fault system modeling. The USR is available through the Southern California Earthquake Center (SCEC) website (http://www.scec.org)

Prophylactic corticosteroid use in patients receiving axicabtagene ciloleucel for large B-cell lymphoma

ZUMA-1 (NCT02348216) examined the safety and efficacy of axicabtagene ciloleucel (axi-cel), an autologous CD19-directed chimaeric antigen receptor (CAR)-T cell therapy, in refractory large B-cell lymphoma. To reduce treatment-related toxicity, several exploratory safety management cohorts were added to ZUMA-1. Specifically, cohort 6 investigated management of cytokine release syndrome (CRS) and neurologic events (NEs) with prophylactic corticosteroids and earlier corticosteroid and tocilizumab intervention. CRS and NE incidence and severity were primary end-points. Following leukapheresis, patients could receive optional bridging therapy per investigator discretion. All patients received conditioning chemotherapy (days -5 through -3), 2 × 106 CAR-T cells/kg (day 0) and once-daily oral dexamethasone [10 mg, day 0 (before axi-cel) through day 2]. Forty patients received axi-cel. CRS occurred in 80% of patients (all grade ≤2). Any grade and grade 3 or higher NEs occurred in 58% and 13% of patients respectively. Sixty-eight per cent of patients did not experience CRS or NEs within 72 h of axi-cel. With a median follow-up of 8·9 months, objective and complete response rates were 95% and 80% respectively. Overall, prophylactic corticosteroids and earlier corticosteroid and/or tocilizumab intervention resulted in no grade 3 or higher CRS, a low rate of grade 3 or higher NEs and high response rates in this study population

Currents and convection cause enhanced gas exchange in the ice-water boundary layer

The presence of sea ice acts as a physical barrier for air-sea exchange. On the other hand it creates additional turbulence due to current shear and convection during ice formation. We present results from a laboratory study that demonstrate how shear and convection in the ice-ocean boundary layer can lead to significant gas exchange. In the absence of wind, water currents beneath the ice of 0.23m s-1 produced a gas transfer velocity (k) of 2.8m d-1, equivalent to k produced by a wind speed of 7m s-1 over the open ocean. Convection caused by air-sea heat exchange also increased k of as much as 131%compared to k produced by current shear alone. When wind and currents were combined, k increased, up to 7.6m d-1, greater than k produced by wind or currents alone, but gas exchange forcing by wind produced mixed results in these experiments. As an aggregate, these experiments indicate that using a wind speed parametrisation to estimate k in the sea ice zone may underestimate k by ca. 50 % for wind speeds \u3c 8m s-1

Validation de nouvelles conditions aux limites pour la restauration géomécanique 3D: exemple d'un modèle analogique.

International audienceGeomechanical restoration methods are dependent on boundary conditions to ensure geological consistency of the restored model in terms of geometry and strain. Classical restoration boundary conditions, such as attening a datum horizon, may lead to inconsistent displacement and strain elds. We restore a laboratory structural sandbox model with known deformation history in order to develop guidelines for denition of boundary conditions that produce improved results from geomechanical restorations. The sandbox model has a basal silicone layer, includes syn-kinematic deposition, and is characterized by structures analogous to those found in supra-salt extensional environments. The deformed geometry is interpreted from 3D tomography imaging, and a time-series of cross-section tomography images provides a benchmark to quantify restoration error and inform boundary conditions. We conrm that imposing a lateral displacement equal and opposite to far-eld tectonic shortening or extension provides a more accurate restoration. However, the amount of displacement may not be known in real cases. We therefore test several established methods, using only the unrestored geometries, to assess the amount of shortening that should be used to guide geomechanical restorations. An accurate estimation is provided by the area-depth method and potentially by a dilatation analysis. Additionally, novel fault compliance boundary conditions produce improved results in the vicinity of crossing and branching faults. Application of similar methods should produce improved restoration of natural geologic structures

Fluorescein Analogue Xanthene-9-Carboxylic Acid: A Transition-Metal-Free CO Releasing Molecule Activated by Green Light

6-Hydroxy-3-oxo-3<i>H</i>-xanthene-9-carboxylic acid is introduced as the first transition-metal-free carbon monoxide releasing molecule activated by visible light (photoCORM). This water-soluble fluorescein analogue releases carbon monoxide in both water and methanol upon irradiation at 500 nm. When selectively irradiated in the presence of hemoglobin (Hb) under physiological conditions, released CO is quantitatively trapped to form carboxyhemoglobin (COHb). The reaction progress can be accurately monitored by characteristic absorption and emission properties of the reactants and products

Defining Proper Boundary Conditions in 3-D Structural Restoration: A Case Study Restoring a 3-D Forward Model of Suprasalt Extensional Structures

International audienceTo overcome the non-physical limitations to 2D structural restoration tools, efforts are being made toward developing 3D mechanics-based methods, which respect both mass and linear momentum conservations. 3D methods remove many common assumptions in 2D techniques that are often violated in nature, such as line-length and area conservation or constant boundary condition (BC) displacement. However, 3D restorations have challenges of their own that must be overcome to produce accurate, physical representations of rock deformation. One of the greatest challenges is choosing geologically and physically reasonable BCs. These are often based on accepted geometric assumptions, such as flattening and unfolding a datum horizon while simultaneously removing fault offset. However, these BCs, as based on kinematic hypotheses, may lead to unphysical configurations. In addition, non-physical BCs are often required in order to ensure numerical convergence (e.g. fixing degrees of freedom), adding uncertainty to the result. Understanding the forward deformation process is crucial for defining proper BCs and accurate interpretations of a restoration. In this study, we perform a 3D restoration on the structures formed from a 3D analog model. Restoring a forward model provides a priori knowledge of viable BCs to guide our restorations without adding unknown uncertainty to the result. The analog experiment was a 3D forward model of a gravity-driven extensional system with sand layers above a ductile zone, no pre-existing fault architecture and a 1.5° basinward dip. Sedimentary layers were added as growth strata throughout the forward model, recording the timing and kinematics of fault activity and fold growth. The analog model produced two prominent grabens, several half-grabens, salt welds and secondary fault structures. Using BCs defined from knowledge of the undeformed and deformed states, we perform a sequential 3D restoration of this extensional system. These BCs at each time-step are constrained by video capturing the complete forward deformation sequence. These findings are the first to document how accurate BCs add value to 3D restoration techniques. Moreover, restoring the complex structures in our model provides fundamental insight into the temporal evolution of 3D extensional structures, akin to natural suprasalt basins like GOM, Brazil and Angola. This clears the path for increasing accuracy in strain evaluation and assessment of paleo-basin geometry

Fluorescein Analogues as Photoremovable Protecting Groups Absorbing at ∼520 nm

International audienceA new photoremovable protecting group, (6-hydroxy-3-oxo-3H-xanthen-9-yl)methyl (1), with a molar absorption coefficient ε of ∼4 × 104 m–1 cm–1 at ∼520 nm for the release of carboxylates or phosphates is reported. Three derivatives of 1 (diethyl phosphate, acetate, and bromide) were isolated as complexes with DDQ and shown to release the ligands with quantum yields ≤2.4% in aqueous solution