Dynamics of continental accretion Moresi, L; Betts, P G; Miller, M S ...
Nature (London),
04/2014, Letnik:
508, Številka:
7495
Journal Article
Recenzirano
Subduction zones become congested when they try to consume buoyant, exotic crust. The accretionary mountain belts (orogens) that form at these convergent plate margins have been the principal sites ...of lateral continental growth through Earth's history. Modern examples of accretionary margins are the North American Cordilleras and southwest Pacific subduction zones. The geologic record contains abundant accretionary orogens, such as the Tasmanides, along the eastern margin of the supercontinent Gondwana, and the Altaïdes, which formed on the southern margin of Laurasia. In modern and ancient examples of long-lived accretionary orogens, the overriding plate is subjected to episodes of crustal extension and back-arc basin development, often related to subduction rollback and transient episodes of orogenesis and crustal shortening, coincident with accretion of exotic crust. Here we present three-dimensional dynamic models that show how accretionary margins evolve from the initial collision, through a period of plate margin instability, to re-establishment of a stable convergent margin. The models illustrate how significant curvature of the orogenic system develops, as well as the mechanism for tectonic escape of the back-arc region. The complexity of the morphology and the evolution of the system are caused by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonally to the convergence direction. We find geological and geophysical evidence for this process in the Tasmanides of eastern Australia, and infer that this is a recurrent and global phenomenon.
► High dust accumulation on PV modules reduces its performance. ► Increased tilt angle reduces the losses due to dust accumulation. ► Varying the tilt angle introduces non-uniform distribution of ...dust which increases the risk of hotspot formation. ► Horizontal installation configuration of PV modules has the highest risk of forming hotspots.
A spatially-resolved 3 dimensional model is developed utilising the circuit analysis software PSPICE to investigate the effect of inhomogeneously deposited dust on the performance of Cadmium–Telluride photovoltaic (PV) thin film modules. CdTe devices are wide band gap materials and typically have a non-ohmic back contact, which are major differences to other technologies which might impact of the effects of dust on device performance. The effects of dust concentration and tilt angle on the PV module’s performance are investigated by simulating the effect of patterns created on the module’s surface during long- and short-term exposure. This deposition is inhomogeneous and it is shown that severe localised mismatch can occur. The PSPICE model is then used to investigate the likelihood of localised hot-spot formation in different installation orientations. The model crucially considers the impact of dust on the spectrum seen by the PV module, which is shown to be critical when modelling the performance of wide band-gap devices such as CdTe. It is shown that performance continuously deteriorates with increasing dust concentration, with operating efficiencies decreasing by 34% in only 90days. The tilt angle of the installation will have a significant effect on the overall dust accumulation, which, as shown in the paper, will change over time. It is shown that the module orientation impacts on the risk of hot-spot formation and the worst case for this is a horizontal orientation of the devices. The non-ohmic back contact of the Cadmium–Telluride modules does not appear to increase the risk of hot-spot formation in comparison to ‘normal’ back contacts.
In the high mountains of Asia, ongoing glacier retreat threatens human and ecological systems through reduced water availability. Rock glaciers are climatically more resistant than glaciers and ...contain valuable water volume equivalents (WVEQ). Across High Mountain Asia (HMA) the WVEQ of rock glaciers is poorly quantified, and thus their hydrological significance versus glaciers is unknown. Here we present the first systematic assessment of Himalayan rock glaciers, totalling ~25,000 landforms with an areal coverage of ~3747 km2. We calculate the WVEQ of Himalayan rock glaciers to be 51.80 ± 10.36 km3. Their comparative importance versus glaciers (rock glacier: glacier WVEQ ratio) is 1:25, which means that they constitute hydrologically valuable long-term water stores. In the context of climate-driven glacier recession, their relative hydrological value will likely increase. These cryospheric stores should be included in future scenario modelling to understand their role in sustainable water management for HMA.
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•We present the first Himalayan rock glacier inventory, derived using Google Earth.•Approx. 25,000 rock glaciers, covering an estimated 3747 km2, were identified.•Himalayan rock glaciers contain an estimated water volume equivalent of 51.80 km3.•Himalayan rock glacier to ice glacier water storage ratio is 1:25.•Under future climate warming, Himalayan rock glaciers are hydrologically valuable.
Siglec-9 is an MHC-independent inhibitory receptor expressed on a subset of natural killer (NK) cells. Siglec-9 restrains NK cytotoxicity by binding to sialoglycans (sialic acid-containing glycans) ...on target cells. Despite the importance of Siglec-9 interactions in tumor immune evasion, their role as an immune evasion mechanism during HIV infection has not been investigated. Using in vivo phenotypic analyses, we found that Siglec-9+ CD56dim NK cells, during HIV infection, exhibit an activated phenotype with higher expression of activating receptors and markers (NKp30, CD38, CD16, DNAM-1, perforin) and lower expression of the inhibitory receptor NKG2A, compared to Siglec-9- CD56dim NK cells. We also found that levels of Siglec-9+ CD56dim NK cells inversely correlate with viral load during viremic infection and CD4+ T cell-associated HIV DNA during suppressed infection. Using in vitro cytotoxicity assays, we confirmed that Siglec-9+ NK cells exhibit higher cytotoxicity towards HIV-infected cells compared to Siglec-9- NK cells. These data are consistent with the notion that Siglec-9+ NK cells are highly cytotoxic against HIV-infected cells. However, blocking Siglec-9 enhanced NK cells' ability to lyse HIV-infected cells, consistent with the known inhibitory function of the Siglec-9 molecule. Together, these data support a model in which the Siglec-9+ CD56dim NK subpopulation is highly cytotoxic against HIV-infected cells even whilst being restrained by the inhibitory effects of Siglec-9. To harness the cytotoxic capacity of the Siglec-9+ NK subpopulation, which is dampened by Siglec-9, we developed a proof-of-concept approach to selectively disrupt Siglec/sialoglycan interactions between NK and HIV-infected cells. We achieved this goal by conjugating Sialidase to several HIV broadly neutralizing antibodies. These conjugates selectively desialylated HIV-infected cells and enhanced NK cells' capacity to kill them. In summary, we identified a novel, glycan-based interaction that may contribute to HIV-infected cells' ability to evade NK immunosurveillance and developed an approach to break this interaction.
Our current knowledge of human memory CD8
T cells is derived largely from studies of the intravascular space. However, emerging data are starting to challenge some of the dogmas based on this work, ...suggesting that a conceptual revision may be necessary. In this review, we provide a brief history of the field and summarize the biology of circulating and tissue-resident memory CD8
T cells, which are ultimately responsible for effective immune surveillance. We also incorporate recent findings into a biologically integrated model of human memory CD8
T cell differentiation. Finally, we address how future innovative human studies could improve our understanding of anatomically localized CD8
T cells to inform the development of more effective immunotherapies and vaccines, the need for which has been emphasized by the global struggle to contain severe acute respiratory syndrome coronavirus 2.
The interspecies exchange of metabolites plays a key role in the spatiotemporal dynamics of microbial communities. This raises the question of whether ecosystem-level behavior of structured ...communities can be predicted using genome-scale metabolic models for multiple organisms. We developed a modeling framework that integrates dynamic flux balance analysis with diffusion on a lattice and applied it to engineered communities. First, we predicted and experimentally confirmed the species ratio to which a two-species mutualistic consortium converges and the equilibrium composition of a newly engineered three-member community. We next identified a specific spatial arrangement of colonies, which gives rise to what we term the “eclipse dilemma”: does a competitor placed between a colony and its cross-feeding partner benefit or hurt growth of the original colony? Our experimentally validated finding that the net outcome is beneficial highlights the complex nature of metabolic interactions in microbial communities while at the same time demonstrating their predictability.
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•Microbial community dynamics can be inferred from intracellular metabolism•Metabolic interactions drive engineered microbial consortia to predictable equilibria•Spatial organization shapes the dynamics of mutualism in a metabolic eclipse scenario•Computation of Microbial Ecosystems in Time and Space (COMETS): a flexible tool
Microbes can interact with the environment and with each other through the uptake and secretion of metabolites. Here, Harcombe et al. ask whether mathematical modeling of the metabolic network of individual species can help forecast the spatiotemporal behavior of two- and three-species engineered microbial ecosystems. In addition to accurately predicting colony growth rates and equilibrium community compositions, their approach sheds new light on the complex nature of cooperation and competition in spatially structured environments.
The anomalous metallic state in the high-temperature superconducting cuprates is masked by superconductivity near a quantum critical point. Applying high magnetic fields to suppress superconductivity ...has enabled detailed studies of the normal state, yet the direct effect of strong magnetic fields on the metallic state is poorly understood. We report the high-field magnetoresistance of thin-film La
Sr
CuO
cuprate in the vicinity of the critical doping, 0.161 ≤
≤ 0.190. We find that the metallic state exposed by suppressing superconductivity is characterized by magnetoresistance that is linear in magnetic fields up to 80 tesla. The magnitude of the linear-in-field resistivity mirrors the magnitude and doping evolution of the well-known linear-in-temperature resistivity that has been associated with quantum criticality in high-temperature superconductors.
Chronic HIV infection causes persistent low-grade inflammation that induces premature aging of the immune system including senescence of memory and effector CD8 T cells. To uncover the reasons of ...gradually diminished potency of CD8 T cells from people living with HIV, here we expose the T cells to planar lipid bilayers containing ligands for T-cell receptor and a T-cell integrins and analyze the cellular morphology, dynamics of synaptic interface formation and patterns of the cellular degranulation. We find a large fraction of phenotypically naive T cells from chronically infected people are capable to form mature synapse with focused degranulation, a signature of a differentiated T cells. Further, differentiation of aberrant naive T cells may lead to the development of anomalous effector T cells undermining their capacity to control HIV and other pathogens that could be contained otherwise.
Although critical illness has been associated with SARS-CoV-2-induced hyperinflammation, the immune correlates of severe COVID-19 remain unclear. Here, we comprehensively analyzed peripheral blood ...immune perturbations in 42 SARS-CoV-2 infected and recovered individuals. We identified extensive induction and activation of multiple immune lineages, including T cell activation, oligoclonal plasmablast expansion, and Fc and trafficking receptor modulation on innate lymphocytes and granulocytes, that distinguished severe COVID-19 cases from healthy donors or SARS-CoV-2-recovered or moderate severity patients. We found the neutrophil to lymphocyte ratio to be a prognostic biomarker of disease severity and organ failure. Our findings demonstrate broad innate and adaptive leukocyte perturbations that distinguish dysregulated host responses in severe SARS-CoV-2 infection and warrant therapeutic investigation.
Recent improvements to the Hadley Centre climate model include the introduction of a new land surface scheme called "MOSES" (Met Office Surface Exchange Scheme). MOSES is built on the previous ...scheme, but incorporates in addition an interactive plant photosynthesis and conductance module, and a new soil thermodynamics scheme which simulates the freezing and melting of soil water, and takes account of the dependence of soil thermal characteristics on the frozen and unfrozen components. The impact of these new features is demonstrated by comparing 1×CO^sub 2^ and 2×CO^sub 2^ climate simulations carried out using the old (UKMO) and new (MOSES) land surface schemes. MOSES is found to improve the simulation of current climate. Soil water freezing tends to warm the high-latitude land in the northern Hemisphere during autumn and winter, whilst the increased soil water availability in MOSES alleviates a spurious summer drying in the mid-latitudes. The interactive canopy conductance responds directly to CO^sub 2^, supressing transpiration as the concentration increases and producing a significant enhancement of the warming due to the radiative effects of CO^sub 2^ alone.PUBLICATION ABSTRACT
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