Exploring Controls on the Flow Dynamics of Devon Ice Cap using a Basal Friction Inversion

Accurately predicting the future dynamic contribution to mass loss from the ice caps of the High Arctic requires an improved understanding of the basal conditions of these ice bodies. An adjoint method numerical inversion is therefore applied to elucidate the basal and englacial conditions of Devon Ice Cap in the Canadian Arctic Archipelago, which exhibits a variety of changes to flow dynamics in recent years. These include the surge of Southeast1 and Southeast2 Glaciers, which is suggested to be thermally-regulated. A cryo-hydraulic warming feedback may contribute to the acceleration during this surge as an additional source of heat or water is required for the base of sliding areas to reach pressure melting point. During the active phase of the surge, freezing rates increase as the basal temperature gradient increases dramatically, leading to enhanced conductive heat loss which is not countered by additional frictional heating as the weakened till provides less resistance to flow. The termination of this surge could therefore result from water withdrawal from the underlying till without the need for changes to geometry. Glaciers defined as pulsing consistently had lower basal shear stresses when velocities were higher, but different pulses produced different changes to the basal conditions, making it difficult to suggest a mechanism for these events. The cause of the unequal periods of faster and slower flow observed on the Croker Bay Glaciers also remains uncertain. However, changes to water storage in the till layer are far smaller than interannual variability in surface meltwater reaching the bed, suggesting this could play some role in modulating till strength, thus flow speeds. The bed of Belcher Glacier provides very little resistance to flow near the terminus, supporting the hypothesis that its acceleration is a result of the thinning and retreat of the terminus reducing resistive stresses

Geological Insights from the Newly Discovered Granite of Sif Island between Thwaites and Pine Island Glaciers

Large-scale geological structures have controlled the long-term development of the bed and thus the flow of the West Antarctic Ice Sheet (WAIS). However, complete ice cover has obscured the age and exact positions of faults and geological boundaries beneath Thwaites Glacier and Pine Island Glacier, two major WAIS outlets in the Amundsen Sea sector. Here, we characterize the only rock outcrop between these two glaciers, which was exposed by the retreat of slow-flowing coastal ice in the early 2010s to form the new Sif Island. The island comprises granite, zircon U-Pb dated to ~177–174 Ma and characterized by initial ɛNd, 87Sr/86Sr and ɛHf isotope compositions of -2.3, 0.7061 and -1.3, respectively. These characteristics resemble Thurston Island/Antarctic Peninsula crustal block rocks, strongly suggesting that the Sif Island granite belongs to this province and placing the crustal block's boundary with the Marie Byrd Land province under Thwaites Glacier or its eastern shear margin. Low-temperature thermochronological data reveal that the granite underwent rapid cooling following emplacement, rapidly cooled again at ~100–90 Ma and then remained close to the Earth's surface until present. These data help date vertical displacement across the major tectonic structure beneath Pine Island Glacier to the Late Cretaceous

Translocation of isotopically distinct macroalgae : a route to low-cost biomonitoring?

Nitrogen stable isotope ratios (δ15N) in macroalgae are often used to identify sources of nitrogenous pollution in fluvial and estuarine settings. This approach assumes that the macroalgal δ15N is representative of the sources of the pollution averaged over a timespan in the order of days to weeks, but the preferential uptake of a particular nitrogen compound or potential for fractionation in the water column or during uptake and assimilation by the macroalgae could make this assumption invalid. Laboratory studies were therefore performed to investigate the uptake and assimilation of both nitrate and ammonium at a variety of concentrations using the vegetative (non-fertile) tips of the brown macroalgae, Fucus vesiculosus. Nitrate appeared to fractionate at high concentrations, and was found to be taken up more rapidly than ammonia; within 13 days, the macroalgae tips were in isotopic equilibrium with the nitrate solution at 500 μM. These experiments were complemented by an investigation involving the translocation of macroalgae collected from a site enriched in 15N relative to natural levels (Staithes, UK), to the River Tees, Middlesbrough (UK), a site depleted in 15N relative to natural levels. The nitrogen isotope signature shifted 50% within 7 days, with samples deployed nearer the surface subject to greater change. These findings suggest that the translocation of macroalgae with isotopically distinct signatures can be used as a rapid, cost-efficient method for nitrogen biomonitoring in estuarine environments

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Epigenetic regulator genes direct lineage switching in MLL/AF4 leukaemia

The fusion gene MLL/AF4 defines a high-risk subtype of pro-B acute lymphoblastic leukaemia. Relapse can be associated with a lineage switch from acute lymphoblastic to acute myeloid leukaemia resulting in poor clinical outcomes due to resistance towards chemo- and immuno-therapies. Here we show that the myeloid relapses share oncogene fusion breakpoints with their matched lymphoid presentations and can originate from varying differentiation stages from immature progenitors through to committed B-cell precursors. Lineage switching is linked to substantial changes in chromatin accessibility and rewiring of transcriptional programmes, including alternative splicing. These findings indicate that the execution and maintenance of lymphoid lineage differentiation is impaired. The relapsed myeloid phenotype is recurrently associated with the altered expression, splicing or mutation of chromatin modifiers, including CHD4 coding for the ATPase/helicase of the nucleosome remodelling and deacetylation complex, NuRD. Perturbation of CHD4 alone or in combination with other mutated epigenetic modifiers induces myeloid gene expression in MLL/AF4-positive cell models indicating that lineage switching in MLL/AF4 leukaemia is driven and maintained by disrupted epigenetic regulation

Tools & techniques for reduced energy consumption with residential energy system example application

Finite supply and increasing demand characterize our modern energy landscape. Pressure from growing populations, increasing standards of living, and industrializing nations has continued to push energy demand upward. Our societies preferred energy sources are based on fossil fuels that have a finite supply. Although debate continues over the remaining levels of fossil fuel supply it is widely agreed that the sources that are easy to collect are reducing. With the easy to reach sources already in production, sources once thought to be not economically viable due to extreme environments and low-quality or diluted energy are being explored. In the case of the Athabasca oil sands in Alberta Canada, new processes have been developed to extract smaller amounts of oil from larger areas that would have been considered lost in the past. What is happening on the supply side in the Canadian oil sands is also happening on the demand side with cogeneration (using waste heat in power generation) and diurnal cold storage (capturing cold at night for use in day time space cooling). These are examples of getting useful work from previously discarded (cogeneration), unutilized (oil sands), and under-utilized (cold storage) energy sources. This thesis focuses on the demand side of the energy equation in residential buildings. Specifically the paper focuses on conversion and use of energy in residential energy systems; space heating, space cooling, water heating, and refrigeration with the goal to reduce domestic energy consumption by sharing resources and combining components. This research evaluates the feasibility of combining refrigeration and hot water production in a single heat pump system including a steady-state model of a residential vapor-compression refrigerator (heat pump) and energy and exergy analyses. The refrigerant cycle is modeled as steady-state while the cold and hot sink are dynamically modeled. Simulation duration is one day with a time step for dynamic calculations of ten seconds.</p

Clay mineralogy of debris from the basal ice of the Byrd ice core, central West Antarctica

&lt;p&gt;This dataset contains the clay mineral assemblage of debris melted from three intervals of basal ice from the Byrd ice core. Analyses were conducted on the &lt;2 micron fraction. The ice core the debris was extracted from was drilled at 80&lt;i&gt;&lt;strong&gt;°&lt;/strong&gt;&lt;/i&gt;&nbsp;0.1'S, 119&lt;i&gt;&lt;strong&gt;°&lt;/strong&gt;&lt;/i&gt; 31.0'W at Byrd Station, West Antarctica, in January 1968.&lt;/p&gt

Clay Mineralogy of Miocene to recent sediments collected at Site U1521 during International Ocean Discovery Programme (IODP) Expedition 374 to the Ross Sea, Antarctica. NERC EDS National Geoscience Data Centre

International audienc

Clay Mineralogy of Miocene to recent sediments collected at Site U1521 during International Ocean Discovery Programme (IODP) Expedition 374 to the Ross Sea, Antarctica

International audienceThis dataset comprises 35 samples analysed for clay mineralogy from IODP Expedition 374 Site U1521 to the Ross Sea, collected on the RV JOIDES Resolution. Shipboard biostratigraphy and magnetostratigraphy suggests the samples are mainly early Miocene in age (McKay et al., 2019, Proceedings of the International Ocean Discovery Program). The uppermost samples do, however, include younger Plio-Pleistocene sediments