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Natural organic matter plays an important role in oceanic hydrothermal systems through a combination of geological and chemical processes. However, identifying the hydrothermal pathways of organic compounds is still quite limited, preventing us from understanding how organic matter is transformed in hydrothermal systems. In this study, we focus on the reaction pathways of alkenes, which represent a key functional group intermediate linking the most abundant hydrocarbons in seafloor hydrothermal environments. Three major pathways are observed for alkenes under mild hydrothermal conditions, including hydration, oxidation, and dimerization. The pathway distributions of alkenes can be affected by the presence of dissolved metal salts; hydration of alkenes is driven by metal ions via the change of solution pH, while alkene dimerization is controlled by pH and the type of metal cations and complexes. Overall, this study identifies alkene hydrothermal pathways and highlights the important roles of metal salts in controlling hydrothermal transformations.

 

Estimating the pose of a camera with respect to a 3D reconstruction or scene representation is a crucial step for many mixed reality and robotics applications. Given the vast amount of available data nowadays, many applications constrain storage and/or bandwidth to work efficiently. To satisfy these constraints, many applications compress a scene representation by reducing its number of 3D points. While state-of-the-art methods use K-cover-based algorithms to compress a scene, they are slow and hard to tune. To enhance speed and facilitate parameter tuning, this work introduces a novel approach that compresses a scene representation by means of a constrained quadratic program (QP). Because this QP resembles a one-class support vector machine, we derive a variant of the sequential minimal optimization to solve it. Our approach uses the points corresponding to the support vectors as the subset of points to represent a scene. We also present an efficient initialization method that allows our method to converge quickly. Our experiments on publicly available datasets show that our approach compresses a scene representation quickly while delivering accurate pose estimates. 

Abstract. A system of subglacial lakes drained on Thwaites Glacier from 2012–2014. To improve coverage for subsequent drainage events, we extended theelevation and ice-velocity time series on Thwaites Glacier through austral winter 2019. These new observations document a second drainage cycle in2017/18 and identified two new lake systems located in the western tributaries of Thwaites and Haynes glaciers. In situ and satellite velocityobservations show temporary < 3 % speed fluctuations associated with lake drainages. In agreement with previous studies, these observationssuggest that active subglacial hydrology has little influence on thinning and retreat of Thwaites Glacier on decadal to centennial timescales. 

Glyco-immune checkpoint receptors, molecules that inhibit immune cell activity following binding to glycosylated cell-surface antigens, are emerging as attractive targets for cancer immunotherapy. Defining biologically relevant ligands that bind and activate such receptors, however, has historically been a significant challenge. Here, we present a CRISPRi genomic screening strategy that allowed unbiased identification of the key genes required for cell-surface presentation of glycan ligands on leukemia cells that bind the glyco-immune checkpoint receptors Siglec-7 and Siglec-9. This approach revealed a selective interaction between Siglec-7 and the mucin-type glycoprotein CD43. Further work identified a specific N-terminal glycopeptide region of CD43 containing clusters of disialylated O-glycan tetrasaccharides that form specific Siglec-7 binding motifs. Knockout or blockade of CD43 in leukemia cells relieves Siglec-7-mediated inhibition of immune killing activity. This work identifies a potential target for immune checkpoint blockade therapy and represents a generalizable approach to dissection of glycan–receptor interactions in living cells.

 

Multivalued decision diagrams are an excellent technique to study the behavior of discrete-state systems such as Petri nets, but their variable order (mapping places to MDD levels) greatly affects efficiency, and finding an optimal order even just to encode a given set is NP-hard. In state-space generation, the situation is even worse, since the set of markings to be encoded keeps evolving and is known only at the end. Previous heuristics to improve the efficiency of the saturation algorithm often used in state-space generation seek a variable order minimizing a simple function of the Petri net, such as the sum over each transition of the top variable position (SOT) or variable span (SOS). This, too, is NP-hard, so we cannot compute orders that minimize SOT or SOS in most cases but, even if we could, it would have limited effectiveness. For example, SOT and SOS can be led astray by multiple copies of a transition (giving more weight to it), or transitions with equal inputs and outputs (giving weight to transitions that should be ignored). These anomalies inspired us to define SOUPS, a new heuristic that only takes into account the \emph{unique} and \emph{productive} portion of each transition. The SOUPS metric can be easily computed, allowing us to use it in standard search techniques like simulated annealing to find good orders. Experiments show that SOUPS is a much better proxy for the quantities we really hope to improve, the memory and time for MDD manipulation during state-space generation. 

Abstract. The Reference Elevation Model of Antarctica (REMA) is thefirst continental-scale digital elevation model (DEM) at a resolution ofless than 10&thinsp;m. REMA is created from stereophotogrammetry with submeterresolution optical, commercial satellite imagery. The higher spatial andradiometric resolutions of this imagery enable high-quality surfaceextraction over the low-contrast ice sheet surface. The DEMs are registeredto satellite radar and laser altimetry and are mosaicked to provide acontinuous surface covering nearly 95&thinsp;% the entire continent. The mosaicincludes an error estimate and a time stamp, enabling change measurement.Typical elevation errors are less than 1&thinsp;m, as validated by thecomparison to airborne laser altimetry. REMA provides a powerful newresource for Antarctic science and provides a proof of concept forgenerating accurate high-resolution repeat topography at continentalscales.

 

Abstract. Ocean-induced basal melting is directly and indirectly responsible for much of the Amundsen Sea Embayment ice loss in recent decades, but the total magnitude and spatiotemporal evolution of this melt is poorly constrained. To address this problem, we generated a record of high-resolution Digital Elevation Models (DEMs) for Pine Island Glacier (PIG) using commercial sub-meter satellite stereo imagery and integrated additional 2002&ndash;2015 DEM/altimetry data. We implemented a Lagrangian elevation change (Dh/Dt) framework to estimate ice shelf basal melt rates at 32&ndash;256-m resolution. We describe this methodology and consider basal melt rates and elevation change over the PIG shelf and lower catchment from 2008&ndash;2015. We document the evolution of Eulerian elevation change (dh/dt) and upstream propagation of thinning signals following the end of rapid grounding line retreat around 2010. Mean full-shelf basal melt rates for the 2008&ndash;2015 period were ~82&ndash;93&thinsp;Gt/yr, with ~&thinsp;200&ndash;250&thinsp;m/yr basal melt rates within large channels near the grounding line, ~&thinsp;10&ndash;30&thinsp;m/yr over the main shelf, and ~&thinsp;0&ndash;10&thinsp;m/yr over the North and South shelves, with the notable exception of a small area with rates of ~&thinsp;50&ndash;100&thinsp;m/yr near the grounding line of a fast-flowing tributary on the South shelf. The observed basal melt rates show excellent agreement with, and provide context for, in situ basal melt rate observations. We also document the relative melt rates for km-scale basal channels and keels at different locations on the shelf and consider implications for ocean circulation and heat content. These methods and results offer new indirect observations of ice-ocean interaction and constraints on the processes driving sub-shelf melting beneath vulnerable ice shelves in West Antarctica.