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Assessment of dust size retrievals based on AERONET: a case study of radiative closure from visible‐near‐infrared to thermal infrared
Get PDFSuper‐coarse dust particles (diameters >10 μm) are evidenced to be more abundant in the atmosphere than model estimates and contribute significantly to the dust climate impacts. Since super‐coarse dust accounts for less dust extinction in the visible‐to‐near‐infrared (VIS‐NIR) than in the thermal infrared (TIR) spectral regime, they are suspected to be underestimated by remote sensing instruments operates only in VIS‐NIR, including Aerosol Robotic Networks (AERONET), a widely used data set for dust model validation. In this study, we perform a radiative closure assessment using the AERONET‐retrieved size distribution in comparison with the collocated Atmospheric Infrared Sounder (AIRS) TIR observations with comprehensive uncertainty analysis. The consistently warm bias in the comparisons suggests a potential underestimation of super‐coarse dust in the AERONET retrievals due to the limited VIS‐NIR sensitivity. An extra super‐coarse mode included in the AERONET‐retrieved size distribution helps improve the TIR closure without deteriorating the retrieval accuracy in the VIS‐NIR
Avoiding breakdown in incomplete factorizations in low precision arithmetic
Get PDFThe emergence of low precision floating-point arithmetic in computer hardware has led to a resurgence of interest in the use of mixed precision numerical linear algebra. For linear systems of equations, there has been renewed enthusiasm for mixed precision variants of iterative refinement. We consider the iterative solution of large sparse systems
using incomplete factorization preconditioners. The focus is on the robust computation of such preconditioners in half precision arithmetic and employing them to solve symmetric positive definite systems to higher precision accuracy; however, the proposed ideas can be applied more generally.
Even for well-conditioned problems, incomplete factorizations can break down when small entries occur on the diagonal during the factorization. When using half precision arithmetic, overflows are an additional possible source of breakdown. We examine how breakdowns can be avoided and we implement our strategies within new half precision Fortran sparse incomplete Cholesky factorization software. Results are reported for a range of problems from practical applications. These demonstrate that, even for highly ill-conditioned problems, half precision preconditioners can potentially replace double precision preconditioners, although unsurprisingly this may be at the cost of additional iterations of a Krylov solver
Contradictory forces: Ezra Pound’s Italian correspondence 1925-45
Get PDFThis thesis examines the letters written by Ezra Pound between 1925 when he settled in
Rapallo, Italy and his repatriation to stand trial for treason in late 1945. While they do not
provide the raw material to create a reliable chronology of the poet’s work, feelings and
activities, the letters offer another interpretative lens. The fragments of opinion,
experience, prejudice and polemic in the correspondence expose a series of contradictions:
the poet utilises the most personal of literary forms—the letter—and yet does so in a
largely impersonal way; seeks to create literary groups and yet is an individualist; wishes to
re-invent civilisation but chooses isolation from centres of power; with correspondence
essential to pursuing his expanding agendas, as well as overcoming isolation, writes in a
way that is often unintelligible; preaches collaboration and is a generous networker, but is
dictatorial in what people should read and think; emphasises clearly stated beliefs and
action while embracing the vague and inconsistent abstractions of fascism; has a high
opinion of his own power and ability to connect to the powerful, yet his influence is largely
illusory; and regards literary knowledge as something acquired diligently, but announces
himself a master of other disciplines.
The contradictions offer an alternative chronology which allows for an understanding of
Pound according to his preoccupations, passions and objectives repeated over decades. In
so doing, this exploration of his correspondence suggests a significant disconnect with
biographies of the poet.
The letters dominated Pound’s time in the 1930s and the dramatis personae, style and tone
of the letters specifically influenced The Pisan Cantos. This thesis concludes by exploring
the relationship between the contradictions in Pound’s Rapallo correspondence and the
precarious equilibrium of The Pisan Cantos
Innovation under constraints: the role of open innovation in Ghana
Get PDFThis paper analyses Low-Income Country (LICs) firms’ use of open innovation (OI) in overcoming various innovation constraints. We disaggregate local and foreign sources of innovation using a new measure of international openness. A survey of 501 manufacturing firms in Ghana reveals that OI is employed to address cost, knowledge, management, and market barriers. Knowledge and cost constraints lead to a broader and deeper search whereas cost barriers lead to a greater domestic search. Firms that faced market barriers significantly search more internationally while those facing infrastructure barriers tend to search less broadly and deeply for external knowledge. The substantial informal sector in Ghana hampers OI. Results also indicate an inverted-U-shaped relationship between the breadth of openness and innovation performance. This paper contributes to the literature by providing the first large firm-level survey-based evidence of OI in a LICs context, and by introducing a new measure of international innovation openness
4-(3-((Pyridin-4-ylmethyl)amino)-[1,2,4]triazolo[4,3-b][1,2,4]triazin-6-yl)phenol: an improved anticancer agent in hepatocellular carcinoma and a selective MDR1/MRP modulator
Get PDFHepatocellular carcinoma is the most common type of primary liver cancer. However, multidrug resistance (MDR) is a major obstacle to the effective chemotherapy of cancer cells. This report documents the rational design, synthesis and biological evaluation of a novel series of triazolotriazines substituted with CH2NH-linked pyridine for use as dual c-Met/MDR inhibitors. The compound 12g with IC50 of 3.06 μM on HepG2 cells showed more potency than crizotinib (IC50 = 5.15 μM) in MTT assay. In addition, 12g inhibited c-Met kinase at low micromolar level (IC50 = 0.052 μM). 12g significantly inhibited Pgp and MRP1/2 efflux pumps in both cancerous HepG2 and BxPC3 cells starting from the lower concentrations of 3 and 0.3 µM, respectively. 12g did not inhibit MDR1 and MRP1/2 in noncancerous H69 cholangiocytes up to the concentration of 30 and 60 µM, respectively. Current results highlighted that cancerous cells were more susceptible to the effect of 12g than normal cells, in which the inhibition occurred only at the highest concentrations, suggesting a further interest in 12g as a selective anticancer agent. Overall, 12g, as a dual c-Met and P-gp/MRP inhibitor, is a promising lead compound for developing a new generation of the anticancer agents
Climate change and the politicisation of ESG in the US
Get PDFESG, or environmental, social, and governance, is seen by some as an instrument to tackle climate change, and by others as a tool to allow investors to assess climate change risks and opportunities. It has been widely politicised in the US, where Republican critics have characterised it as an attempt by the liberal financial elite to impose a leftist decarbonising mission on the US economy through an investment risk back door. The current paper explores the way in which ESG has become a, perhaps unlikely, object of politicisation by the political right. In doing so, it analyses the meaning of politicisation in an ESG context and the various forms it has taken, both discursive and substantive. The paper also seeks to explain why it is that ESG politicisation has occurred at particular junctures
and draws on political opportunity theory from social movement studies to account for this. It further examines various reactions to the politicisation of ESG that have sought to depoliticise it
Mathematical modeling of PI3K/Akt pathway in microglia
No full textThe motility of microglia involves intracellular signaling pathways that are predominantly controlled by changes in cytosolic Ca2+ and activation of PI3K/Akt (phosphoinositide-3-kinase/protein kinase B). In this letter, we develop a novel biophysical model for cytosolic Ca2+ activation of the PI3K/Akt pathway in microglia where Ca2+ influx is mediated by both P2Y purinergic receptors (P2YR) and P2X purinergic receptors (P2XR). The model parameters are estimated by employing optimization techniques to fit the model to phosphorylated Akt (pAkt) experimental modeling/in vitro data. The integrated model supports the hypothesis that Ca2+ influx via P2YR and P2XR can explain the experimentally reported biphasic transient responses in measuring pAkt levels. Our predictions reveal new quantitative insights into P2Rs on how they regulate Ca2+ and Akt in terms of physiological interactions and transient responses. It is shown that the upregulation of P2X receptors through a repetitive application of agonist results in a continual increase in the baseline [Ca2+], which causes the biphasic response to become a monophasic response which prolongs elevated levels of pAkt
Modelling of collagen receptor clustering and signalling
Get PDFPlatelets play a crucial role in haemostasis and thrombosis, and their activation is
regulated by various agonists and intracellular signalling pathways. This PhD thesis aims to
investigate the complex interplay between platelet receptors, signalling pathways, and
intracellular calcium dynamics using mathematical modelling approaches. We present an
agent-based model (ABM) to investigate the dimerisation of GPVI and the role of glycolipid-enriched raft-like domains in regulating receptor diffusion. We introduce an ordinary
differential equation (ODE) model to unravel the regulatory mechanisms of GPVI signalling
from Syk phosphorylation to releasing inositol trisphosphate (IP3) into the platelet cytosol via
LAT signalosome. To fulfil the signalling complexity more completely than has previously been
possible, a mathematical model of phosphoinositide (PI) metabolism in human platelets in
response to GPVI activation was developed and calibrated against experimental data capturing
transient time-course changes in phosphoinositide positional isomers. Finally, two machine
learning models, a non-linear autoregressive network with exogenous inputs (NARX) and a
partial least square (PLS) regression model, were developed to investigate how different
agonists and inhibitors impact on intracellular calcium dynamics in platelets.
The findings from this thesis provide valuable insights into the complex regulatory
mechanisms of platelet activation and intracellular calcium dynamics and how they are
influenced by various agonists and inhibitors. These mathematical modelling approaches have
the potential to be used in the development of simulation frameworks for studying
spatiotemporal concentrations of ligands and inhibitors in platelets. The results of this thesis
may have implications for the development of targeted therapies for platelet-related diseases,
such as thrombosis and haemostasis disorders. The models also have wide applicability to
other cell systems. Overall, this PhD thesis contributes to our understanding of platelet biology
and provides novel insights into platelet signalling and calcium dynamics using mathematical
modelling approaches
Barriers to BIM implementation in the HVAC industry: an exploratory study
Get PDFIn recent times, the rise of urbanization, industrialization, population growth, food security, and the COVID-19 pandemic have led to an increased demand for indoor spaces with efficient air conditioning systems. As a result, there is a growing interest in creating more complex HVAC systems to improve indoor spaces. Building information modeling (BIM) offers numerous benefits to the HVAC industry, such as clash detection, budget and time reductions, and increased efficiency. However, its implementation is currently hindered by various challenges. This research aims to identify the major barriers to BIM implementation in the HVAC industry in Turkey, using a questionnaire survey of 224 domain experts working in 42 different companies across various fields of the HVAC industry. The study utilized several statistical analyses to categorize and prioritize the most critical barriers, including reliability tests, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), the Kaiser–Meyer–Olkin (KMO) test, Bartlett’s test, and ranking of factors (IRI). The results indicate that the “Deficiencies of Infrastructure and Lack of Qualified Personnel (DIP)” factor group constituted the most significant barrier, followed by “Lack of Documentation and Specifications (LDS)”, “Deficiencies of Case Studies and Project Drawings (DCP)”, and “Lack of Motivation and Resistance to BIM (LMR)”. Moreover, our research revealed that 60% of the participants’ companies allocate less than 40% of their budgets to technological infrastructure, which hinders the adoption of BIM. To promote BIM in the HVAC sector, we recommend enhancing personnel capacity building, improving skills and knowledge about BIM, promoting guidelines, and providing free access to documentation for practitioners