Early warning systems for sovereign debt crises: The role of heterogeneity

Sovereign default models that differ in their treatment of unobservable country, regional and time heterogeneities are systematically compared. The analysis is based on annual data over the 1983-2002 period for 96 developing economies. Inference-based criteria and parameter plausibility overwhelmingly favour more complex models that allow the link between the probability response and the fundamentals to vary over time and across countries. However, out-of-sample forecast evaluation using several loss functions and equal-predictive-ability tests suggests that simplicity beats complexity. Parsimonious pooled logit models produce the most accurate sovereign default forecasts and outperform the naive benchmarks.     

Evaluation of energy integration aspects for IGCC-based hydrogen and electricity co-production with carbon capture and storage

Integrated Gasification Combined Cycle (IGCC) is a power generation technology in which the solid feedstock is partially oxidized with oxygen and steam to produce syngas. In a conventional IGCC design without carbon capture, the syngas is purified for dust and hydrogen sulphide removal and then sent to a Combined Cycle Gas Turbine (CCGT) for power generation. Carbon capture technologies are expected to play an important role in the coming decades for reducing the greenhouse gas emissions. In a modified IGCC design for carbon capture, the syngas is catalytically shifted to maximize the hydrogen level and to concentrate the carbon species in the form of carbon dioxide which can be later captured in a pre-combustion arrangement. After carbon dioxide capture, the hydrogen-rich syngas can be either purified in a Pressure Swing Adsorption (PSA) unit and exported to the external customers (e.g., chemical industry, PEM fuel cells) or used in a CCGT for power generation.     

Evaluation of iron based chemical looping for hydrogen and electricity co-production by gasification process with carbon capture and storage

Integrated Gasification Combined Cycle (IGCC) is one of power generation technologies having the highest potential for carbon capture with low penalties in efficiency and cost. Syngas produced by gasification can be decarbonised using chemical looping methods in which an oxygen carrier (usually a metallic oxide) is recycled between the syngas oxidation reactor (fuel reactor) and the chemical agent oxidation reactor (steam reactor). In this way, the resulted carbon dioxide is inherently separated from the other products of combustion and the syngas energy is transferred to an almost pure hydrogen stream suitable to be used not only for power generation but also for transport sector (PEM fuel cells).     

Use of lower grade coals in IGCC plants with carbon capture for the co-production of hydrogen and electricity

This paper investigates the potential use of lower grade coals in an IGCC-CCS plant that generates electricity and produces hydrogen simultaneously with carbon dioxide capture and storage. The paper underlines one of the main advantages of gasification technology, namely the possibility to process lower grade coals, which are more widely available than the high-grade coals normally used in European power plants. Based on a proposed plant concept that generates about 400 MW net electricity with a flexible output of 0–50 MW_th hydrogen and a carbon capture rate of at least 90%, the paper develops fuel selection criteria for coal fluxing and blending of various types of coal for optimizing plant performance e.g. oxygen consumption, hydrogen production potential, specific syngas energy production per tonne of oxygen consumed, etc. These performance indicators were calculated for a number of case studies through process flow simulations. The main conclusion is that blending of coal types of higher and lower grade is more beneficial in terms of operation and cost performance than fluxing high-grade coals.     

Assessment of hydrogen and electricity co-production schemes based on gasification process with carbon capture and storage

Through gasification, a solid feedstock is partially oxidized with oxygen and steam to produce syngas which can be used for conversion into different valuable compounds (e.g. hydrogen) or to generate power in a combined cycle gas turbine (CCGT). Integrated gasification combined cycle (IGCC) is one of power generation technologies having the highest potential for carbon capture with low penalties in efficiency and cost.     

Transparent plasmonic nanocontainers protect organic fluorophores against photobleaching

Numerous research efforts are investigating the possibility of using light interactions with metallic nanoparticles to improve the fluorescence properties of nearby molecules. Few investigations have considered the encapsulation of molecules in metallic nanocavities. In this paper, we present the optical properties of new hybrid nanoparticles consisting of gold nanoshells and fluorescent organic dyes in their liquid cores. Microspectroscopy on single nanoparticle demonstrates that the extinction spectra are in good agreement with Mie's theory. Finite difference time domain (FDTD) calculations reveal that excitation and emission radiations are efficiently transmitted through the thin gold nanoshells. Thus, they can be considered as transparent plasmonic nanocontainers for photoactive cores. In agreement with FDTD calculations, measurements show that fluorophores encapsulated in gold nanoshells keep their brightness, but they show fluorescence lifetimes 1 order of magnitude shorter. As a salient consequence, the photoresistance of encapsulated organic dyes is also improved by an order of magnitude. This unusual ultraviolet photoresistance results from the reduced probability of triplet-singlet conversion that eventually exposes dyes to singlet oxygen photodegradation.     

Candida glabrata Ste20 is involved in maintaining cell wall integrity and adaptation to hypertonic stress, and is required for wild-type levels of virulence

The conserved family of fungal Ste20 p21-activated serine-threonine protein kinases regulate several signalling cascades. In Saccharomyces cerevisiae Ste20 is involved in pheromone signalling, invasive growth, the hypertonic stress response, cell wall integrity and binds Cdc42, a Rho-like small GTP-binding protein required for polarized morphogenesis. We have cloned the STE20 homologue from the fungal pathogen Candida glabrata and have shown that it is present in a single copy in the genome. Translation of the nucleotide sequence predicts that C. glabrata Ste20 contains a highly conserved p21-activated serine-threonine protein kinase domain, a binding site for G-protein beta subunits and a regulatory Rho-binding domain that enables the kinase to interact with Cdc42 and/or Rho-like small GTPases. C. glabrata Ste20 has 53% identity and 58% predicted amino acid similarity to S. cerevisiae Ste20 and can complement both the nitrogen starvation-induced filamentation and mating defects of S. cerevisiae ste20 mutants. Analysis of ste20 null and disrupted strains suggest that in C. glabrata Ste20 is required for a fully functional hypertonic stress response and intact cell wall integrity pathway. C. glabrata Ste20 is not required for nitrogen starvation-induced filamentation. Survival analysis revealed that C. glabrata ste20 mutants, while still able to cause disease, are mildly attenuated for virulence compared to reconstituted STE20 cells.     

Trade-off in emissions of acid gas pollutants and of carbon dioxide in fossil fuel power plants with carbon capture

This paper investigates the impact of capture of carbon dioxide (CO₂) from fossil fuel power plants on the emissions of nitrogen oxides (NO_X) and sulphur oxides (SO_X), which are acid gas pollutants. This was done by estimating the emissions of these chemical compounds from natural gas combined cycle and pulverized coal plants, equipped with post-combustion carbon capture technology for the removal of CO₂ from their flue gases, and comparing them with the emissions of similar plants without CO₂ capture. The capture of CO₂ is not likely to increase the emissions of acid gas pollutants from individual power plants; on the contrary, some NO_X and SO_X will also be removed during the capture of CO₂. The large-scale implementation of carbon capture is however likely to increase the emission levels of NO_X from the power sector due to the reduced efficiency of power plants equipped with capture technologies. Furthermore, SO_X emissions from coal plants should be decreased to avoid significant losses of the chemicals that are used to capture CO₂. The increase in the quantity of NO_X emissions will be however low, estimated at 5% for the natural gas power plant park and 24% for the coal plants, while the emissions of SO_X from coal fired plants will be reduced by as much as 99% when at least 80% of the CO₂ generated will be captured.