The UK is rich in heat-producing granites, especially in the county of Cornwall, suggesting the potential for energy production with low environmental footprint. The United Downs Deep Geothermal Power (UDDGP) project aims to demonstrate the technical and commercial viability to produce electricity from the Cornish geothermal resource, exploiting the natural permeability of a significant deep structural fracture zone known as the Porthtowan Fault Zone. Drilling of the first well started at the end of 2018, and the plant is expected to be operational by mid-2020. A relevant question is whether deep geothermal energy is truly environmentally benign. This article presents a comprehensive and detailed Life Cycle Assessment study that i) identifies the main life-cycle sources of environmental impacts for the production of electricity in the UDDGP plant; ii) investigates the effects on the environmental impacts of significant uncertainties surrounding the project, such as availability of geothermal fluid and configuration of the power plant, and iii) compares the performance of the UDDGP operation, and by extension of the putative geothermal energy production in the UK, with other key energy sources in the country. The life cycle inventory relies on a combination of site-specific data for wells construction and literature data for above-surface facilities and stimulation techniques. We validated our model by comparing climate change impacts of UDDGP with those reported by other studies on enhanced geothermal systems. Our results show that the greatest portion of environmental impacts originates from the construction phase (primarily due to steel for wells casing and diesel used during drilling), whilst the scenario analysis demonstrates that increasing installed capacity and cogenerating heat and power are the most effective strategies for improving the environmental performance. Our analysis also suggests that the environmental impacts may increase by ~35% if stimulation techniques are required to increase the geothermal wells productivity. Compared to alternative energy sources, in the category climate change, UDDGP performs better than solar energy and is comparable with wind and nuclear. It is shown that the environmental benefits of geothermal energy are not straightforward and that a number of trade-offs needs to be considered when other impact categories are quantified.
New semi-aromatic bio-based copolyamides PA 4T/4Y and PA 6T/6Y were successfully synthesized in bulk by direct solid-state polycondensation in which hydrophobic bio-based dicarboxylic acids sebacic acid, octadecanedioic or hydrogenated dimer fatty acid (Y = C10, C18 or C36) alternate with terephthalic acid T. The absence of a polymerization solvent and the possibility of performing the polymerization on the dicarboxylic acid make it an interesting route for future production of alternating copolyamides. A stepwise synthetic approach is taken where first terephthalic acid-based diamide diamines of the linear C4 or C6 diamines 4T4 or 6T6 are prepared, followed by preparation of solid salts with the above aliphatic dicarboxylic acids and subjecting the salts to a solidstate post-condensation. The alternation is achieved by the interlocking of the 4T4 or 6T6 units in the salts with the bio-based dicarboxylic acids and polymerizing these salts below the melt temperature of the terephthalamide-based core. During the polycondensation, the transamidation reaction of the terephthalamide moiety is prevented and with that the randomization of the polyamide. Especially the diaminobutane-based PA 4T/4Y copolyamides show strict alternation, leading to interesting properties like high crystallinity and high melting points of 250 to 318°C supported by a randomness value of 2, determined using 13 C NMR spectroscopy. The special alternating feature becomes especially clear when heating the polymer in the melt state, when the transamidation of the terephthalamide moieties is no longer prevented by the interlocking principle, leading to lowering of the randomness value and therewith the melting point and crystallinity.
Little is known about the effect of human immunodeficiency virus (HIV) infection on the Central American healthcare system. We describe HIV-related admissions in a Guatemalan medical service. The study was conducted at Guatemala City's largest public hospital. Data were derived from standardized data collection sheets maintained by the HIV testing service and by HIV clinic physicians. Data were collected for 295 medicine admissions of 257 HIV-infected adults during an 18-month period in 1999 and 2000; 30% of the patients were women. Average age was 33 years. Only 12.5% of the patients had been diagnosed with HIV infection prior to 1999 and nearly all had symptomatic AIDS. 60.3% of the patients were diagnosed with HIV infection during their hospitalization. The most common discharge diagnoses were tuberculosis (13.9%), toxoplasmosis, diarrhoea, candida and other fungal infections, and meningitis. Mean length of stay for HIV-positive patients was 17 days. 23.7% of the patients died during their hospitalization; this was double the mortality of non-HIV patients. HIV-infected patients represented 5.8% of the total admissions of the general medical wards. In a country where HIV prevalence is thought to be less than 1%, AIDS is now responsible for over 5% of admissions to a large medical service at a cost of $500,000 per year. These findings underline the importance of HIV infection in Central America and demonstrate the utility of tracking hospital admission data as a method of surveillance.
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