Pyrolysis and thermal hydrogasification of hydrocarbons

Imperial Users onl

Semantic variation operators for multidimensional genetic programming

Multidimensional genetic programming represents candidate solutions as sets of programs, and thereby provides an interesting framework for exploiting building block identification. Towards this goal, we investigate the use of machine learning as a way to bias which components of programs are promoted, and propose two semantic operators to choose where useful building blocks are placed during crossover. A forward stagewise crossover operator we propose leads to significant improvements on a set of regression problems, and produces state-of-the-art results in a large benchmark study. We discuss this architecture and others in terms of their propensity for allowing heuristic search to utilize information during the evolutionary process. Finally, we look at the collinearity and complexity of the data representations that result from these architectures, with a view towards disentangling factors of variation in application.Comment: 9 pages, 8 figures, GECCO 201

Inactivation of Escherichia coli ATCC 25922 and Saccharomyces cerevisiae IMR-R-L 962 in grapefruit [Citrus paradisi (Macf.)] juice by UV-C light: changes in bioactive compounds and quality characteristics

The viability of UV-C treatment (0.0-2.36 J/cm²) at 254 nm as a non-thermal preservation process for grapefruit juice on microbial inactivation, the organic acids and individual flavonoids, as well as the quality characteristics (pH, ºBrix, titratable acidity, colour, total phenolics and antioxidant capacity) was evaluated. Additionally, pectin methylesterase (PME) activity was also measured. The effects of UV-C on microbial inactivation were assessed by kinetic studies on the inactivation of inoculated grapefruit juice with one strain of Escherichia coli ATCC 25922 and one strain of Saccharomyces cerevisiae IMR-R-L 962. The suitability of Weibull distribution and modified Gompertz models was analysed to characterise the UV-C inactivation kinetics for E. coli and S. cerevisiae in freshly squeezed grapefruit juice. Likewise, the changes after UV-C treatment in citric (CA), malic (MA), ascorbic (AA) and tartaric (TA) acids, as well as naringin (NAR), hesperidin (HES) and neohesperidin (NEO), were quantified by HPLC, whereas the total phenolics and antioxidant capacity (DPPH? and ABTS?+) were quantified by spectrophotometric methods. Nonlinear inactivation curves were successfully fitted with Weibull-type and modified Gompertz models. However, the Gompertz model allowed a better fit and more accurate estimation of the parameters. UV-C treatment at 1.83 J/cm² achieved a 5.18 ± 0.01 and 2.7 ± 0.15 log CFU/mL reduction in E. coli and S. cerevisiae, respectively, whereas no significant changes occurred in CA, MA, TA, NAR, HES, NEO, total phenolics, ABTS?+, pH, ºBrix, titratable acidity and colour of the grapefruit juices (p>0.05). However, PME was partially inhibited and the AA level and DPPH? decreased significantly after treatment, with losses up to 15.9 and 8% (at 1.83 J/cm²), respectively, which were associated with the UV-C dose intensity.Fil: la Cava, Enzo Luciano Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Química Básica y Aplicada del Nordeste Argentino. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas Naturales y Agrimensura. Instituto de Química Básica y Aplicada del Nordeste Argentino; ArgentinaFil: Sgroppo, Sonia Cecilia. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentin

Credit supply shocks in the US housing market

The aim of my thesis is to study the impact of three different types of credit supply shocks on the US economy during the recent boom-bust cycle. I apply rigourous identification strategies using a comprehensive mortgage loan-application level dataset that spans two decades to identify the causal effect of each shock on the US housing market { the market at the epicentre of the recent global financial crisis. The first chapter examines how shocks to the geographic distance between borrowers and lenders affected the quality of loans originated by US banks. I show that US banks that originated loans at relatively long distances recorded relatively high shares of delinquent mortgages, which suggests that geographic distance hampers a bank's ability to screen bor- rowers. The second chapter assesses how the supply of mortgage credit was affected by the closure of the private-label securitisation market in 2007. By impairing lender financing conditions, I demonstrate that the shock to the securitisation market caused US mortgage lenders to curtail new lending and that this adversely affected the aggregate level of new mortgage credit. The third chapter explores whether shocks to bank lending standards affect household borrowing and spending. I show that the introduction of US state anti-predatory lending laws, by tightening lending standards, caused a decline in the level of household mortgage credit, although this had little subsequent impact on household spending

Ocular manifestations of Sturge–Weber syndrome: pathogenesis, diagnosis, and management

Sturge-Weber syndrome has been included in the group of phakomatoses that is characterized by hamartomas involving the brain, skin, and eyes. The characteristic facial port-wine stain, involving the first branch of the trigeminal nerve and the embryonic vasculature distribution in this area, leads to several ocular complications of the anterior segment and can involve the eyelids and conjunctiva. The posterior segment of the eyes is also affected with diffuse choroidal hemangiomas. However, the most frequent ocular comorbidity is glaucoma with a prevalence rate ranging from 30%-70%. Glaucoma is related to anterior chamber malformations, high episcleral venous pressure (EVP), and changes in ocular hemodynamics. Glaucoma can be diagnosed at birth, but the disease can also develop during childhood and in adults. The management of glaucoma in Sturge-Weber syndrome patients is particularly challenging because of early onset, frequently associated severe visual field impairment at the time of diagnosis, and unresponsiveness to standard treatment. Several surgical approaches have been proposed, but long-term prognosis for both intraocular pressure control and visual function remains unsatisfactory in these patients. Choroidal hemangiomas may also lead to visual impairment thorough exudative retinal detachment and macular edema. Treatment of exudative hemangioma complications is aimed at destructing the tumor or decreasing tumor leakage