Connecting the Greenland Ice Sheet and the ocean : a case study of Helheim Glacier and Sermilik Fjord

Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 4 (2016): 34–45, doi:10.5670/oceanog.2016.97.The rapid ice loss from the Greenland Ice Sheet that began in the late 1990s sparked an interest in glacier/ocean exchanges both because an increase in submarine melting of the glacier is a potential trigger of glacier retreat and because the increasing freshwater discharge can affect the regional ocean’s circulation and ecosystems. An interdisciplinary field project focused on the Helheim Glacier-Sermilik Fjord system began in 2008 and has continued to date. We found that warm, Atlantic Water flows into the fjord, drives melting of the glacier, and is regularly replenished through shelf-forced and glacier-driven circulations. In summer, the release of surface melt at the base of the glacier has a pronounced impact on local ocean circulation, the properties of the glacier, and its melt rate. Measurements taken in the fjord indicate that it is virtually impossible to derive submarine melt rates from hydrographic (including moored) data due to the fjord’s pronounced water mass variability and uncertain contribution from iceberg melt. Efforts to correlate glacier behavior with ocean forcing on seasonal and interannual time scales yield no straightforward connections, likely because of a dependence on a wider range of parameters, including subglacial discharge and bedrock geometry. This project emphasizes the need for sustained long-term measurements of multiple glacier/ocean/atmosphere systems to understand the different dynamics that control their evolution.This work has been supported directly or indirectly by the National Science Foundation; NASA; the Woods Hole Oceanographic Institution; the universities of Kansas, Maine, and Oregon; the Kerr, Clark, and Haas Foundations; and Greenpeace

Comparison of AlSi10Mg and Al 6061 Processed through DMLS

Direct Metal Laser Sintering (DMLS) processing of aluminum alloys has been primarily limited to a casting grade of aluminum, AlSi10Mg. The reasons for the choice of AlSi10Mg by machine manufacturers are presently unknown; however, it is suspected that the reduced coefficient of thermal expansion (CTE) due to the presence of Silicon may enhance DMLS processability. Aluminum 6061 (Al 6061) is a commonly used alloy across a wide range of industries and applications, and Harvest has observed a high interest in DMLS-manufactured Al 6061 products. However, the higher CTE value potentially presents greater challenges in controlling the shrinkage-induced warp common during DMLS. The work presented in this paper was performed in an effort to understand differences in manufacturability as well as mechanical properties of DMLS-processed AlSi10Mg and Al 6061.Mechanical Engineerin

Iceberg properties and distributions in three Greenlandic fjords using satellite imagery

Icebergs calved from tidewater glaciers represent about one third to one half of the freshwater flux from the Greenland ice sheet to the surrounding ocean. Using multiple satellite datasets, we quantify the first fjord-wide distributions of iceberg sizes and characteristics for three fjords with distinct hydrography and geometry: Sermilik Fjord, Rink Isbræ Fjord and Kangerlussuup Sermia Fjord. We estimate average total iceberg volumes in summer in the three fjords to be 6.4 ± 1.5, 1.7 ± 0.40 and 0.16 ± 0.09 km3, respectively. Iceberg properties are influenced by glacier calving style and grounding line depth, with variations in size distribution represented by exponents of power law distributions that are −1.95 ± 0.06, −1.87 ± 0.05 and −1.62 ± 0.04, respectively. The underwater surface area of icebergs exceeds the subsurface area of glacial termini by at least one order of magnitude in all three fjords, underscoring the need to include iceberg melt in fjord freshwater budgets. Indeed, in Sermilik Fjord, we calculate summertime freshwater flux from iceberg melt of 620 m3 s−1 (±140 m3 s−1), similar in magnitude to subglacial discharge. The method developed here can be extended across Greenland to assess relationships between glacier calving, iceberg discharge and freshwater production.NNX12AP50G55223

Additively-manufactured piezoelectric devices

A low-cost micro-stereolithography technique with the ability to additively manufacture dense piezoelectric ceramic components is reported. This technique enables the layer-wise production of functional devices with a theoretical in-plane resolution of ∼20 μm and an out-of-plane resolution of <1 μm without suffering a significant reduction in the piezoelectric properties when compared to conventionally produced ceramics of the same composition. The ability to fabricate devices in complex geometries and with different material properties means that conventional limits of manufacturing are not present. A hollow, spherical shell of the piezoelectric material 0.65Pb(Mg⅓Nb⅔)O3–0.35PbTiO3, built without tooling or recourse to additional equipment or processes, is shown generating ultrasound in the MHz range

Using a magnetite/thermoplastic composite in 3D printing of direct replacements for commercially available flow sensors

Flow sensing is an essential technique required for a wide range of application environments ranging from liquid dispensing to utility monitoring. A number of different methodologies and deployment strategies have been devised to cover the diverse range of potential application areas. The ability to easily create new bespoke sensors for new applications is therefore of natural interest. Fused deposition modelling is a 3D printing technology based upon the fabrication of 3D structures in a layer-by-layer fashion using extruded strands of molten thermoplastic. The technology was developed in the late 1980s but has only recently come to more wide-scale attention outside of specialist applications and rapid prototyping due to the advent of low-cost 3D printing platforms such as the RepRap. Due to the relatively low-cost of the printers and feedstock materials, these printers are ideal candidates for wide-scale installation as localized manufacturing platforms to quickly produce replacement parts when components fail. One of the current limitations with the technology is the availability of functional printing materials to facilitate production of complex functional 3D objects and devices beyond mere concept prototypes. This paper presents the formulation of a simple magnetite nanoparticle-loaded thermoplastic composite and its incorporation into a 3D printed flow-sensor in order to mimic the function of a commercially available flow-sensing device. Using the multi-material printing capability of the 3D printer allows a much smaller amount of functional material to be used in comparison to the commercial flow sensor by only placing the material where it is specifically required. Analysis of the printed sensor also revealed a much more linear response to increasing flow rate of water showing that 3D printed devices have the potential to at least perform as well as a conventionally produced sensor

Ratcheting synthesis

Synthetic chemistry has traditionally relied on reactions between reactants of high chemical potential and transformations that proceed energetically downhill to either a global or local minimum (thermodynamic or kinetic control). Catalysts can be used to manipulate kinetic control, lowering activation energies to influence reaction outcomes. However, such chemistry is still constrained by the shape of one-dimensional reaction coordinates. Coupling synthesis to an orthogonal energy input can allow ratcheting of chemical reaction outcomes, reminiscent of the ways that molecular machines ratchet random thermal motion to bias conformational dynamics. This fundamentally distinct approach to synthesis allows multi-dimensional potential energy surfaces to be navigated, enabling reaction outcomes that cannot be achieved under conventional kinetic or thermodynamic control. In this Review, we discuss how ratcheted synthesis is ubiquitous throughout biology and consider how chemists might harness ratchet mechanisms to accelerate catalysis, drive chemical reactions uphill and programme complex reaction sequences.<br/

Cancer bioimprinting and cell shape recognition for diagnosis and targeted treatment

Cancer incidence and mortality have both increased in the last decade and are predicted to continue to rise. Diagnosis and treatment of cancers are often hampered by the inability to specifically target neoplastic cells. Bioimprinting is a promising new approach to overcome shortfalls in cancer targeting. Highly specific recognition cavities can be made into polymer matrices to mimic lock-and-key actions seen in in vivo biological systems. Early studies concentrated on molecules and were inhibited by template size complexity. Surface imprinting allows the capture of increasingly complex motifs from polypeptides to single cell organisms and mammalian cells. Highly specific cell shape recognition can also be achieved by cell interaction with imprints that can be made into polymer matrices to mimic biological systems at a molecular level. Bioimprinting has also been used to achieve nanometre scale resolution imaging of cancer cells. Studies of bioimprint-based drug delivery on cancer cells have been recently trialled in vitro and show that this approach can potentially improve existing chemotherapeutic approaches. This review focuses on the possible applications of bioimprinting with particular regards to cancer understanding, diagnosis and therapy. Cell imprints, incorporated into biosensors can allow the limits of detection to be improved or negate the need for extensive patient sample processing. Similar cell imprinting platforms can be used for nanoscale imaging of cancer morphology, as well as to investigate topographical signalling of cancer cells in vitro. Lastly, bioimprints also have applications as selective drug delivery vehicles to tumours with the potential to decrease chemotherapy-related side effects

Complete genome sequence of Streptococcus agalactiae strain 01173, isolated from Kuwaiti wild fish

© 2020 Santi et al. Here, we report the complete genome of piscine Streptococcus agalactiae 01173 serotype Ia, which was generated using long-read sequencing technology. The bacteria were isolated from wild fish displaying signs of streptococcosis, from a fish kill incident in Kuwait

Towards a fullerene-based quantum computer

Molecular structures appear to be natural candidates for a quantum technology: individual atoms can support quantum superpositions for long periods, and such atoms can in principle be embedded in a permanent molecular scaffolding to form an array. This would be true nanotechnology, with dimensions of order of a nanometre. However, the challenges of realising such a vision are immense. One must identify a suitable elementary unit and demonstrate its merits for qubit storage and manipulation, including input / output. These units must then be formed into large arrays corresponding to an functional quantum architecture, including a mechanism for gate operations. Here we report our efforts, both experimental and theoretical, to create such a technology based on endohedral fullerenes or 'buckyballs'. We describe our successes with respect to these criteria, along with the obstacles we are currently facing and the questions that remain to be addressed.Comment: 20 pages, 13 figs, single column forma