10 research outputs found
Modeling buoyancy-driven circulation in an idealized tidewater glacier fjord
No full textTidewater glacier fjords are narrow, deep inlets connecting marine-terminating glaciers with the continental shelf sea. Over the recent years, the rapid mass loss of the Greenland Ice Sheet has sparked interest in these fjords due to their impacts on submarine glacier melting as well as coastal ocean circulation. In tidewater glacier fjords, subglacial discharge is an important source of buoyancy, which drives the exchange flow and controls salt and heat transports between fjord and the coastal sea. However, due to the difficulty in acquiring field data in the ice-packed environments, direct observations of the oceanographic condition are rare, and the general circulation in these fjords are poorly understood.
Numerical model is an alternative approach to explore the buoyancy driven exchange in tidewater glacier fjords. This dissertation uses a coupled ocean/plume model to study the circulation and heat transports in idealized fjord basins and discusses the impacts on submarine melting of the glacier front.
Firstly, in order to better represent the subglacial discharge, we developed a new model framework, ROMS-ICEPLUME, to parameterize the rising and initial outflowing stage of the subglacial discharge plume in vicinity of the glacier/ocean boundary. The coupled model is tested for sensitivities over various model configurations and validated with field observations using a quasi-realistic setup. We find that the modeled circulation is very sensitive to the choices of outflow parameterization and coupling method. This model is able to reproduce the strong outflowing plume and its spatial structure observed in a Greenlandic fjord. Results from this part provides an important tool in advancing our understanding of the exchange processes in tidewater glacier fjords.
Secondly, using the coupled model framework, the circulation and heat exchange driven by subglacial discharge are simulated in a series of idealized conditions. The buoyancy-driven plume travels along the southside of the fjord channel, and to a great extent resembles the structure of a coastal current. The physical properties of outflowing plume are estimated using model fields and compared with that derived from a shallow water model. We find that the outflow structure is dependent on the location of subglacial river, and plume properties are better predicted by the shallow water model when discharge enters from the southside of the channel. Heat budgets analysis highlights the role of discharge-driven exchange flow in removing submarine melt water from glacier front. This mechanism in theory enhances submarine melting, but it is not well reflected in the modeled melt rates due to limitation of the melting parameterization.Ph.D.Includes bibliographical reference
Meltwater‐Enhanced Nutrient Export From Greenland's Glacial Fjords: A Sensitivity Analysis
No full textAuthor Posting. © American Geophysical Union, 2020. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 125(7), (2020): e2020JC016185, doi:10.1029/2020JC016185.As mass loss from the Greenland Ice Sheet accelerates, this modeling study considers how meltwater inputs to the ocean can impact marine ecosystems using a simplified fjord scenario. At marine‐terminating glaciers in Greenland fjords, meltwater can be delivered far below the sea surface, both as subglacial runoff (from atmosphere‐driven surface melt) and as basal melt (from ocean heat). Such delivery can result in buoyancy‐driven upwelling and the upward entrainment of nutrient‐rich deep water, which can support phytoplankton growth in fjord surface waters. For this study, we use an idealized fjord‐scale model to investigate which properties of glaciers and fjords govern the transport of buoyantly upwelled nutrients from fjords. We model the influence of fjord geometry, hydrology, wind, tides, and phytoplankton growth within the fjord on meltwater‐driven nutrient export to the ocean. We use the Regional Ocean Modeling System (ROMS) coupled to a buoyant plume model and a biogeochemical model to simulate physical and biogeochemical processes within an idealized tidewater glacial fjord. Results show that meltwater‐driven nutrient export increases with larger subglacial discharge rates and deeper grounding lines, features that are both likely to change with continued ice sheet melting. Nutrient export decreases with longer residence times, allowing greater biological drawdown. While the absence of a coastal current in the model setup prevents the downstream advection of exported nutrients, results suggest that shelf‐forced flows could influence nutrient residence time within fjords. This simplified model highlights key uncertainties requiring further observation to understand ecological impacts of Greenland mass loss.This project was supported by a University of Georgia Presidential Scholarship and NSF Graduate Research Fellowship (GRFP) (to HO), NASA‐IDS NNX14AD98G, and by NASA Physical Oceanography program (80NSSC18K0766).2020-12-2
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Psychopathic tendencies are selectively associated with reduced emotional awareness in the context of early adversity
No full textIt is unclear at present whether psychopathic tendencies are associated with lower or higher levels of emotional awareness (EA). Given that psychopathy includes a proficiency for manipulating others, one might expect an elevated ability to identify and use information about others’ emotions. On the other hand, empathic deficits in psychopathy could arise from reduced emotional awareness. Further, heterogeneity in psychopathy may also play a role, wherein ‘secondary’ psychopathy is associated with early adversity and high negative affect, while ‘primary’ psychopathy is not. In this paper, we tested the relationship between EA and psychopathic tendencies in 177 undergraduate students (40 males) who completed the levels of emotional awareness scale (LEAS), the triarchic psychopathy measure (TPM), the affective (empathy-related) subscales of the interpersonal reactivity index (IRI), and two measures of early adversity: the childhood experiences of care and abuse questionnaire (CECA) and the childhood trauma questionnaire (CTQ). We found that lower LEAS scores were associated with higher TPM and lower IRI empathy scores, but these relationships were primarily present in those with early adversity and high negative affect. This suggests that lower EA may be selectively associated with higher levels of secondary psychopathy, while those with higher levels of primary psychopathy remain capable of higher EA. © 2022 Smith et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Targeted release of a bispecific fusion protein SIRPα/Siglec-10 by oncolytic adenovirus reinvigorates tumor-associated macrophages to improve therapeutic outcomes in solid tumors
No full textBackground The pleiotropic roles of tumor-associated macrophages (TAMs) render them attractive targets in antitumor drug development. CD47/SIRPα (signal regulatory protein alpha) and CD24/Siglec-10 (sialic acid-binding immunoglobulin-like lectin 10) signaling pathways have been found to suppress macrophage phagocytosis of malignant cells. Systemic blockade of CD47/SIRPα has shown severe side effects. Intratumoral delivery of a CD47 inhibitor by oncolytic viruses (OVs) may circumvent this hurdle.Methods To identify the characteristics of recombinant adenovirus (AdV)-SIRPα/Siglec-10, we conducted CCK8 assay, quantitative PCR, western blot, competitive binding assay, in vitro cytotoxicity assay, ELISA and phagocytosis assay. We investigated the antitumor immune responses of AdV-SIRPα/Siglec-10 using flow cytometry, various tumor-bearing mouse models, humanized tumor-bearing mouse models, immune cell depletion, RNA sequencing, and in vitro T cell activation assay.Results Here, we developed a novel AdV encoding a fusion protein composed of the extracellular domains of murine or human SIRPα and Siglec-10 (SIRPα/Siglec-10), termed AdV-mSS or AdV-huSS. The SIRPα/Siglec-10 was effectively secreted by cells infected with AdV-mSS and functioned as a dual blocker of CD47 and CD24, thereby significantly enhancing macrophage phagocytosis. In a series of tumor models, including subcutaneous and ascitic H22 hepatocellular carcinoma (HCC), subcutaneous Hepa1-6 HCC, MC38 colorectal carcinoma, and Lewis lung carcinoma, AdV-mSS treatment markedly enhanced antitumor efficacy. Mechanistically, AdV-mSS reprogrammed TAMs toward an antitumor phenotype and enhanced the expression of major histocompatibility complex (MHC)-I/II, promoting CD8+T cell proliferation and activation. Depletion of either macrophages or CD8+T cells abrogated the antitumor efficacy of AdV-mSS. Similarly, in a humanized LM3 HCC mouse model, AdV-huSS significantly inhibited tumor growth and prolonged survival.Conclusions Dual SIRPα/Siglec-10 inhibitor delivered intratumorally by AdV not only reinvigorated the TAM-CD8+T cell axis but also potentially reduced the risk of off-target effects. Further investigation of AdV-huSS in patients with cancer is warranted in the near future
Research on burnout fault of moulded case circuit breaker based on finite element simulation
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Wave attenuation by flattened vegetation (Scirpus mariqueter)
No full textWith the capacity to reduce wave energy and trap sediment, Scirpus mariqueter has become an important native species of annual grass for ecology restoration at the Yangtze Estuary in eastern China. Due to seasonal variances of biophysical characteristics, S. mariqueter usually bends and breaks in winter, resulting in flattened stems that may reduce its wave attenuation capacity. To investigate the effects of vegetation flattening on wave attenuation, a set of flume experiments were conducted for flattened and standing vegetation under different wave conditions. The model vegetation was designed to represent the wilted S. mariqueter collected in winter with dynamic similarity. Results showed that the wave damping coefficient for flattened vegetation (βF) was 33.6%-72.4% of that for standing vegetation (βS) with the same vegetation length. Both βF and βS increased with wave height but decreased with water depth. A wave attenuation indicator (WAI) was defined to generate empirical formulas for βS and βF as well as their ratio βF/βS. The empirical formulas were then applied to modify the existing standing vegetation-based wave attenuation model for flattened vegetation and performed successfully. Understanding the wave attenuation characteristics of flattened vegetation is essential for the management of ecological restoration and coastal protection.</p
