4,226 research outputs found
Forecasting Seasonal UK Consumption Components
Periodic models for seasonal data allow the parameters of the model to vary across the different seasons. This paper uses the components of UK consumption to see whether the periodic autoregressive (PAR) model yields more accurate forecasts than non-periodic models, such as the airline model of Box and Jenkins (1970), and the autoregressive models that pre-test for (seasonal) unit roots. We analyze possible explanations for the relatively poor forecast performance of the periodic models that we find, notwithstanding the apparent support such models receive from the data in-sample.SEASONAL FLUCTUATIONS
On SETAR non- linearity and forecasting
We consider the usefulness of the two-regime SETAR model for out-of-sample forecasting, and compare it with a linear AR model. A range of newly-developed forecast evaluation techniques are employed. Our simulation results show that time-series data need to exhibit a substantial degree of non-linearity before the SETAR model is favoured on some of these criteria. We find only weak evidence that a SETAR model of US GNP provides more accurate forecasts than a linear AR model.SETAR model;linear AR model;out-of-sample forecasting
VLF, magnetic bay and Pi2 substorm signatures at auroral and midlatitude ground stations
A superposed epoch analysis of 100–300 substorms is performed to determine the median size and shape of the substorm-associated VLF chorus, magnetic bay, and Pi2 pulsation burst observed at the near-auroral Halley research station, Antarctica, and at the midlatitude Faraday station at three different local times (2230, 2330, 0130 MLT). The spatial and temporal properties of the magnetic bay signatures are compared with the University of York implementation of the Kisabeth–Rostoker substorm current wedge (SCW) model and the Weimer pulse model, respectively. These constitute the best analytical models of the substorm to date. It is shown that the polarities and relative amplitudes of the observed magnetic bays in the H, D, and Z components at Halley at midnight MLT and at Faraday in the premidnight sector are consistent with the York model for a SCW 3 hours wide in MLT with its westward electrojet at 67°S magnetic latitude. In particular the little-discussed Z component of the bay agrees with the model and is shown to be the clearest substorm signature of the three components, especially at midlatitude. The midnight and postmidnight bays are similar to the premidnight case but progressively smaller and cannot be fully reconciled with the model. The shape of the H and Z bays at Halley and the D bays at Faraday fit a normalized Weimer pulse well, with Weimer's 2 h−1 recovery rate, but the other components do not. The D component at Halley and H at Faraday do fit the Weimer pulse shape but with a faster recovery rate of 4 h−1. It is proposed that this is due to the effect of a decaying current in the SCW combining with the geometrical effect of changing SCW configuration and position relative to the observing station. The Z component at Faraday recovers more slowly than the 2 h−1 Weimer prediction; we cannot explain this. Secondary bays at Halley and Faraday show a clear tendency to recur after 2 hours. Inflection points just prior to onset at Halley and Faraday are argued to be related to reduced convection associated with northward turning of the IMF. The median substorm signature at Halley in the Pi2 frequency band (7–25 mHz) is well correlated with the bay structure, showing that it is part of a broader band, possibly turbulent, spectrum in the substorm-dependent DP2 current. There is evidence of a minor additional narrow band component occurring at substorm onset. This is the dominant signal at Faraday which shows the classic midlatitude substorm signature, a short Pi2 pulsation burst at onset, that decreases progressively in intensity with increasing local time, implying a source region biased to the evening side or else preferred propagation to the east from a near-midnight source
The geology and genesis of the iron skarns of the Turgai belt, northwestern Kazakhstan
The magnetite deposits of the Turgai belt (Kachar, Sarbai and Sokolov), in the Valerianovskoe zone of the southern Urals, Kazakhstan, contain a combined resource of over 3 Gt of iron oxide ore. The deposits are hosted by carbonate sediments and volcaniclastic rocks of the Carboniferous Valerianovka Supergroup, and are spatially related to the gabbroic to granitoid composition intrusive rocks of the Sarbai–Sokolov intrusive series. The magnetite deposits are developed dominantly as metasomatic replacement of limestone, but also, to a lesser extent, of volcanic rocks. Pre-mineralisation metamorphism and alteration resulted in the formation of wollastonite and the silicification of limestone. Magnetite mineralisation is associated with the development of a high temperature skarn assemblage of diopside, grossular–andradite garnet, actinolite, epidote and apatite. Sub-economic copper-bearing sulphide mineralisation overprints the magnetite mineralisation and is associated with deposition of hydrothermal calcite and the formation of an extensive sodium alteration halo dominated by albite and scapolite. Chlorite formation accompanies this stage and further later stage hydrothermal overprints. The replacement has in places resulted in preservation of primary features of the limestone, including fossils and sedimentary structures in magnetite, skarn calc-silicates and sulphides.
Analysis of Re–Os isotopes in molybdenite indicates formation of the sulphide mineral assemblage at 336.2 ± 1.3 Ma, whilst U–Pb analyses of titanite from the skarn alteration assemblage suggests skarn alteration at 326.6 ± 4.5 Ma with re-equilibration of isotope systematics down to ~ 270 Ma. Analyses of mineral assemblages, fluid inclusion microthermometry, O and S isotopes suggest initial mineralisation temperatures in excess of 600 °C from hypersaline brines (45–50 wt.% NaCl eq.), with subsequent cooling and dilution of fluids to around 150 °C and 20 wt.% NaCl eq. by the time of calcite deposition in late stage sulphide-bearing veins. δ18O in magnetite (− 1.5 to + 3.5‰) and skarn forming silicates (+ 5 to + 9‰), δ18O and δ13C in limestone and skarn calcite (δ18O + 5.4 to + 26.2‰; δ13C − 12.1 to + 0.9‰) and δ34S in sulphides (− 3.3 to + 6.6‰) and sulphates (+ 4.9 to + 12.9‰) are all consistent with the interaction of a magmatic-equilibrated fluid with limestone, and a dominantly magmatic source for S. All these data imply skarn formation and mineralisation in a magmatic–hydrothermal system that maintained high salinity to relatively late stages resulting in the formation of the large Na-alteration halo. Despite the reported presence of evaporites in the area there is no evidence for evaporitic sulphur in the mineralising system.
These skarns show similarities to some members of the iron oxide–apatite and iron oxide–copper gold deposit classes and the model presented here may have implications for their genesis. The similarity in age between the Turgai deposits and the deposits of the Magnitogorsk zone in the western Urals suggests that they may be linked to similar magmatism, developed during post-orogenic collapse and extension following the continent–continent collision, which has resulted in the assembly of Laurussian terranes with the Uralide orogen and the Kazakh collage of the Altaids or Central Asian Orogenic Belt. This model is preferred to the model of simultaneous formation of very similar deposits in arc settings at either side of an open tract of oceanic crust forming part of the Uralian ocean
Inhibition of thiol isomerase activity diminishes endothelial activation of plasminogen, but not of protein C
Highlights
•A range of thiol isomerase enzymes were expressed by HMEC-1 endothelial cells.
•Inhibition of thiol isomerases reduced plasminogen activation on HMEC-1 cells.
•Exogenous bovine protein disulphide isomerase increased plasminogen activation in HMEC-1 cells.
•Inhibition of thiol isomerases also reduced fibrin clot lysis, but not via direct effects on tPA.
•HMEC-1 mediated protein C activation was unaffected by thiol isomerase inhibition.
Abstract
Introduction
Cell surface thiol isomerase enzymes, principally protein disulphide isomerase (PDI), have emerged as important regulators of platelet function and tissue factor activation via their action on allosteric disulphide bonds. Allosteric disulphides are present in other haemostasis-related proteins, and we have therefore investigated whether thiol isomerase inhibition has any influence on two endothelial activities relevant to haemostatic regulation, namely activation of protein C and activation of plasminogen, with subsequent fibrinolysis.
Materials and Methods
The study was performed using the human microvascular endothelial cell line HMEC-1. Thiol isomerase gene expression was measured by RT-PCR and activation of protein C and plasminogen by cell-based assays using chromogenic substrates S2366 and S2251, respectively. Cell mediated fibrinolysis was measured by monitoring absorbance at 405 nm following fibrin clot formation on the surface of HMEC-1 monolayers.
Results and Conclusions
A variety of thiol isomerase enzymes, including PDI, were expressed by HMEC-1 cells and thiol reductase activity detectable on the cell surface was inhibited by both RL90 anti-PDI antibody and by the PDI inhibitor quercetin-3-rutinoside (rutin). In cell-based assays, activation of plasminogen, but not of protein C, was inhibited by RL90 antibody and, to a lesser extent, by rutin. Fibrin clot lysis occurring on a HMEC-1 monolayer was also significantly slowed by RL90 antibody and by rutin, but RL90-mediated inhibition was abolished in the presence of exogenous tissue plasminogen activator (tPA). We conclude that thiol isomerases, including PDI, are involved in fibrinolytic regulation at the endothelial surface, although not via a direct action on tPA. These findings broaden understanding of haemostatic regulation by PDI, and may aid in development of novel anti-thrombotic therapeutic strategies targeted via the fibrinolysis system
Investigations to constrain retreat of the Greenland Ice Sheet: glacial geomorphology and sampling for cosmogenic exposure dating of the Centrumsø area, Kronprins Christian Land, northeast Greenland
Over the last few decades atmospheric warming across the Arctic has been far more rapid than elsewhere in the world, contributing to an increase in the sea-level contribution from the Greenland Ice Sheet. Given predictions of continuing atmospheric warming during the 21st century and beyond, it is crucial to understand how the ice sheet has responded to past variations in climate. Kronprins Christian Land lies in a climatically sensitive, yet sparsely studied part of northeast Greenland, in an inter-ice-stream region just north of Nioghalvfjerdsbrae. This paper presents the results of preliminary geomorphological mapping from a 2m spatial-resolution digital elevation model of a 5500km2; region around Centrumsø, as well as a report of sampling for cosmogenic exposure dating, and field observations concerning the extent and nature of palaeo-ice coverage and dynamics. Twenty-one 2kg samples were collected from carefully selected glacial erratics of various lithologies using a hammer and chisel as well as a small angle-grinder.
In general, moraine ridges in the study area are relatively small (2–5m in height) and lack a prominent peak, reflecting limited sediment availability, and suggesting some post-glacial re-mobilization of sediment or deflation caused by melting of the moraines' ice cores. Striated cobbles and boulder-sized clasts were observed at up to 540m a.s.l., sub-rounded erratics (some of which were sampled) at up to 800m a.s.l. and streamlined bedrock at up to 360m a.s.l., all of which indicate sliding between the ice and the bedrock and temperate basal conditions. In addition, several proglacial spillways were noted, along with numerous terraces, commonly situated between lateral moraines and valley sides, which are probably kame terraces formed by glaciofluvial transport and deposition. The prevalence of these landforms indicates significant glaciofluvial action requiring large volumes of meltwater, suggesting this region experienced high-volume melt in short intensive summers during past ice-recession events
Testing the use of marine protected areas to restore and manage tropical multispecies invertebrate fisheries at the Arnavon Islands, Solomon Islands : termination report
This report aimed to determine if the number and size of commercially important invertebrates (e.g. trochus, sea
cucumbers and giant clams) increases as the result of the declaration of the Arnavon Islands Marine
Conservation Area (MCA) relative to fished areas
Technology-Enabled Innovations to Combat Covid-19 Pandemic: A Case Study between Thailand and Taiwan
The COVID-19 pandemic has been disrupting people’s lives for the past two years. Countries worldwide tried to control the number of infections with new and enhanced information technology with varying results. This case study compares the information technologies used to control and combat the COVID-19 pandemic in Thailand and Taiwan. This study aims to identify the contributing factors that make information technology become more effective in controlling the COVID-19 pandemic. This data was gathered retrospectively from December 2019 to August 2021 from 46 subjects in both countries. The results have shown that the category of technology released was inconsistent with entering the stage of transmission of the COVID-19 pandemic. In addition, policy factors such as the rigor of policy, credibility of government or related agencies, including social factors such as the public engagement, communication technology, and the diffusion of innovation, play a key role in enabling the technology to be more efficient for the control of COVID-19 pandemic
On SETAR non- linearity and forecasting
We consider the usefulness of the two-regime SETAR model for out-of-sample forecasting, and compare it with a linear AR model. A range of newly-developed forecast evaluation techniques are employed. Our simulation results show that time-series data need to exhibit a substantial degree of non-linearity before the SETAR model is favoured on some of these criteria. We find only weak evidence that a SETAR model of US GNP provides more accurate forecasts than a linear AR model
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