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Retreat, lowering and persistent supraglacial streams at the Barnes Ice Cap, Baffin Island, Canada
Get PDFSignificant and widespread surface melt is prevalent across glaciers and ice caps, and such surface melt is transmitted through complex supraglacial pathways. The efficiency with which this water transits across glaciers and ice caps is important since it is by these networks that water is removed from the system, constituting mass loss. Here, we use remote sensing to explore mass loss of the Barnes Ice Cap in Arctic Canada since the 1980s alongside a detailed investigation of supraglacial drainage evolution, focussing on the central-southern outlet which is the fastest moving part of the ice-cap. The Barnes Ice Cap is almost entirely covered in a network of supraglacial channels from the highest to lowest elevations. These channels exhibit extraordinary stability over many years and are re-used annually. We also observe significant and widespread surface lowering across most of the Barnes Ice Cap, yet erosion by flowing water in these channels is of sufficient magnitude to ensure they persist rather than re-establishing anew each year. As a result, efficient routing of water across and off the ice cap is likely re-initiated quickly each year, removing large volumes of water from the glacier system
Polymerization from Lipid Membranes.
Get PDFIn living cells, lipid bilayer membranes can be asymmetrically functionalized with brush-like layers of macromolecules. Here, we describe a lipid membrane-initiated polymerization reaction for the growth of thick and dense polymer brushes directly from one side of lipid membranes. By incorporating a novel lipid-based polymerization initiator into lipid bilayers, we grew poly( -isopropylacrylamide) (PNIPAM) brushes from supported lipid bilayers (SLBs), small unilamellar vesicles (SUVs), and giant unilamellar vesicles (GUVs), via aqueous atom transfer radical polymerization (ATRP). We used quartz crystal microbalance with dissipation monitoring (QCM-D) and dynamic light scattering (DLS) to quantify growth kinetics from SLBs and SUVs. The resulting polymer brushes were up to 70 nm thick. Growth from GUVs led to the spontaneous transformation of spheroidal vesicles into dense, bush-like networks of "strings of pearls". Broadly speaking, this approach could offer improved performance for biomedical applications and a valuable in vitro model for the biophysics of asymmetric lipid membranes
Local equivalence and refinements of Rasmussen's s-invariant
No full textInspired by the notions of local equivalence in monopole and Heegaard Floer homology, we introduce a version of local equivalence that combines odd Khovanov homology with equivariant even Khovanov homology into an algebraic package called a local even-odd (LEO) triple. We get a homomorphism from the smooth concordance group C to the resulting local equivalence group CLEO of such triples. We give several versions of the s-invariant that descend to CLEO, including one that completely determines whether the image of a knot K in CLEO is trivial. We discuss computer experiments illustrating the power of these invariants in obstructing sliceness, both statistically and for some interesting knots studied by Manolescu-Piccirillo. Along the way, we explore several variants of this local equivalence group, including one that is totally ordered
Urban resilience in Ancient Mesopotamia: insights into the socioeconomic system of the Bronze and Iron Age Khabur Valley
No full textThe ability of urban centres to grow and persist through crises is often assessed qualitatively in archaeology but quantitative assessment is more elusive. Here, the authors explore urban resilience in ancient Mesopotamia by applying an adaptive cycle framework to the settlement dynamics of the Bronze and Iron Age Khabur Valley (c. 3000–600 BC). Using an integrated dataset of settlements and hollow ways, they identify patterns of growth, conservation, release and reorganisation across six periods, demonstrating the value of coupling archaeological data with resilience theory and network analysis to understand the adaptive capacities of complex archaeological societies
Creative Political Geography
Get PDFThis chapter examines creative approaches to political geography and geopolitics. It situates these approaches within feminist political geography’s contributions to the subdiscipline; in particular around disrupting common sense geopolitical narratives and critically reflecting on the power relations inherent in knowledge production. Traditionally the purview of cultural geography and geohumanities, creative methods and approaches have been central also in geopolitical research. I suggest that arts-based methods need to be understood alongside creative storytelling, and I insist that these advances cannot be understood separately from the concerns of postcolonial and decolonial work. The chapter is divided into three sections. First, I discuss art, performance, and their relationship with political geography. Second, I look to narrative, storytelling, and creative writing of geography as otherwise, and how this creative practice is indebted to postcolonial and Black theory. Finally, I end with some pointers and considerations for those wishing to collaborate with artists and creative writers in their geographical research
International High-Tech Cross-Border Acquisitions and Long-Term Employment Growth in Foreign Target Firms: Are EMNEs Catching up by Hiring in Foreign Technological Clusters?
Get PDFDo emerging market (E)MNEs, compared with developed market (D)MNEs, engage in more post-acquisition hiring when acquiring foreign high-tech firms? Drawing on the concepts of ‘home base augmentation’ and ‘catching up by hiring’ and extending them to high-tech cross-border M&As, we argue that EMNEs use post-acquisition hiring to access knowledge and embed themselves in world leading innovation networks to build innovation related dynamic capabilities. Using a large, matched sample of cross-border acquisitions, we find that EMNE acquisitions are associated with significantly higher post-acquisition employment growth than DMNE acquisitions. This effect is especially strong when targets are located in developed market technological clusters. These findings suggest that employment growth is not merely a by-product of acquisition, but a deliberate strategy through which EMNEs develop technological capabilities
The Limits of Equity and the Claim of Justice: Theological Implications of a Move from "Equality" to "Equity" within Christian Organising
No full textIn recent years, there has been a shift in focus within the UK-based charitable sector’s EDI agendas from equality to equity. Although equality is not altogether absent, it is equity that is now most often emphasised within organisational policies. This is most likely attributable to the way equality is understood within the sector. Nevertheless, when organisations whose practice is underpinned by Christian theology adopt this shift towards equity without interrogating the implications of so doing, there is a danger of losing both the richness and challenge that theological understandings of equality can contribute to organisational practice. Focusing specifically on the international development sector in the UK, this article therefore explores how theological understandings of equality and equity can be brought together with sectoral understandings to positively shape organisational practice. The article is rooted in Catholic Social Teaching, since this offers a helpful theological framework for faith-based organisations underpinned by Christian theology to understand the significance of the ‘E’ in EDI
Cosmological dressing rules
Get PDFThe basic observables in cosmology are known as in-in correlators. Recent calculations have revealed that in-in correlators in four dimensional de Sitter space exhibit hidden simplicity stemming from a close relation to scattering amplitudes in flat space. In this paper we explain how to make this property manifest by dressing flat space Feynman diagrams with certain auxiliary propagators. These dressing rules are derived for conformally coupled and massless scalar theories and we show that they reproduce the same infrared divergences predicted by the Schwinger-Keldysh formalism
Dendrochronology and remote sensing reveal beaver occupancy and colonization dynamics in an expanding Arctic population
Get PDFThe North American beaver (Castor canadensis) is expanding its distribution in the Arctic tundra. Due to the species' capacity to engineer ecosystems, they can transform surface water dynamics and biogeochemistry, permafrost stability, vegetation composition, and impact Indigenous subsistence practices. Understanding past temporal occupancy dynamics of beavers is essential for assessing beaver colonization dynamics and impacts on ecosystems and people, but in the absence of historical data, new methods are required to address such knowledge gaps. By felling vegetation, beavers leave a clear historical signal of their occupancy and by damming rivers, they can also create a hydrological signal of their colonization. We combined dendrochronological techniques with satellite image time‐series analysis to infer beaver colonization and associated hydrological impacts at their northern range edge in the Inuvialuit Settlement Region in Arctic Canada. Over an ~130‐km transect, we recorded 60 detected beaver lodge and/or dam sites. At three focal sites across a latitudinal gradient, we collected 94 Salix and Alnus shrub stems with browsing scars. To reconstruct browsing histories and infer past beaver occupancy, we cross‐dated these against regional shrub‐ring chronologies spanning 1973–2023 (Salix) and 1968–2023 (Alnus), formed from 99 unbrowsed shrubs collected across the survey transect. The browsing histories provide evidence of beaver colonization in the region starting in 2008. The northern site record indicates occupancy between 2008 and 2022, the central site between 2015 and 2022, and the southern site between 2011 and 2023. We compared findings at one lodge–dam complex site with a remote sensing‐based time‐series decomposition method for the detection and characterization of surface water changes. Abrupt change in surface water extent was detected directly upstream of dams between 2015 and 2019, aligning with beaver browsing activity between 2015 and 2021. Convergent results across two independent novel methods give strength to the approach used and provide a link between browsing activity and hydrological impacts. Our findings indicate that combined dendrochronology and satellite image time‐series analysis may be applied elsewhere in the Arctic to gain insights into northward beaver range expansion and hydrological impacts in the understudied northern margins of their range
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