Statistical methods for the identification and control of multivariate stochastic systems

Imperial Users onl

Fishing for solutions. Environmental and operational assessment of selected Galician fisheries and their products

Fishing is the only hunting activity which is still maintained on an industrial level to sustain worldwide food demand. Currently, worldwide fisheries are suffering a series of hazards linked to overexploitation and increasing human demand for protein, causing a wide range of environmental impacts on marine ecosystems, such as stock depletion or ecosystem disruption. Moreover, the fishing industry has grown to an extent where the environmental burdens associated with on board and on land operational activities, such as fuel consumption by vessels or wastewater generated by canning factories, are also becoming important environmental concerns. From a regional perspective, Galicia (NW Spain), the main fishing region in the European Union (EU) in terms of landed fish and economic turnover, does not escape these global threats. Additionally, Galicia supplies the rest of Spain and other EU countries with important amounts of fresh and processed seafood

Genetic heterogeneity of residual variance in broiler chickens

Aims were to estimate the extent of genetic heterogeneity in environmental variance. Data comprised 99 535 records of 35-day body weights from broiler chickens reared in a controlled environment. Residual variance within dam families was estimated using ASREML, after fitting fixed effects such as genetic groups and hatches, for each of 377 genetically contemporary sires with a large number of progeny ($>$100 males or females each). Residual variance was computed separately for male and female offspring, and after correction for sampling, strong evidence for heterogeneity was found, the standard deviation between sires in within variance amounting to 15–18% of its mean. Reanalysis using log-transformed data gave similar results, and elimination of 2–3% of outlier data reduced the heterogeneity but it was still over 10%. The correlation between estimates for males and females was low, however. The correlation between sire effects on progeny mean and residual variance for body weight was small and negative (-0.1). Using a data set bigger than any yet presented and on a trait measurable in both sexes, this study has shown evidence for heterogeneity in the residual variance, which could not be explained by segregation of major genes unless very few determined the trait

Review of Life-Cycle Approaches Coupled with Data Envelopment Analysis: Launching the CFP + DEA Method for Energy Policy Making

Life-cycle (LC) approaches play a significant role in energy policy making to determine the environmental impacts associated with the choice of energy source. Data envelopment analysis (DEA) can be combined with LC approaches to provide quantitative benchmarks that orientate the performance of energy systems towards environmental sustainability, with different implications depending on the selected LC + DEA method. The present paper examines currently available LC + DEA methods and develops a novel method combining carbon footprinting (CFP) and DEA. Thus, the CFP + DEA method is proposed, a five-step structure including data collection for multiple homogenous entities, calculation of target operating points, evaluation of current and target carbon footprints, and result interpretation. As the current context for energy policy implies an anthropocentric perspective with focus on the global warming impact of energy systems, the CFP + DEA method is foreseen to be the most consistent LC + DEA approach to provide benchmarks for energy policy making. The fact that this method relies on the definition of operating points with optimised resource intensity helps to moderate the concerns about the omission of other environmental impacts. Moreover, the CFP + DEA method benefits from CFP specifications in terms of flexibility, understanding, and reporting

Virulence of malaria is associated with differential expression of Plasmodium falciparum var gene subgroups in a case-control study

Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) is a major pathogenicity factor in falciparum malaria that mediates cytoadherence. PfEMP1 is encoded by approximately 60 var genes per haploid genome. Most var genes are grouped into 3 subgroups: A, B, and C. Evidence is emerging that the specific expression of these subgroups has clinical significance. Using field samples from children from Papua New Guinea with severe, mild, and asymptomatic malaria, we compared proportions of transcripts of var groups, as determined by quantitative polymerase chain reaction. We found a significantly higher proportion of var group B transcripts in children with clinical malaria (mild and severe), whereas a large proportion of var group C transcripts was found in asymptomatic children. These data from naturally infected children clearly show that major differences exist in var gene expression between parasites causing clinical disease and those causing asymptomatic infections. Furthermore, parasites forming rosettes showed a significant up-regulation of var group A transcripts

Participation and Deliberation in Networked Publics: The Case of Social Network Sites.

Online social network sites have become an important source of news and political information for many people. At the same time, these sites have transformed the way users encounter and engage with this type of content. This thesis investigates the democratic implications of this trend. Specifically, it estimates the extent to which the relationship between news consumption and political behaviour is mediated by the unique technological affordances of social network sites. It explores how, and to what extent, social network sites transform the way users encounter and engage with news content and how this, in turn, shapes their subsequent political behaviour. This thesis comprises a series of original comparative research papers. Paper 1 sets out to establish evidence of a relationship between everyday social network site use and political participation. Using nationally representative data collected by the UK Oxford Internet Institute, it establishes evidence to suggest that social network site use has the potential to increase political participation, but only when it comes to certain activities. Building on this analysis, Paper 2 estimates the extent to which social network site use indirectly influences political participation, through inadvertently exposing users to news content and information. It finds that although the everyday use of social network sites positively predicts inadvertent news and information exposure, such exposure does not translate into widespread political participation. Since a growing body of research indicates that the effects of news and information on participatory behaviour is largely channeled through interpersonal communication, Paper 3 and Paper 4 focus on the communicative processes that are typically thought to precede participation. Specifically, these papers analyse a unique set of data to investigate the extent to which social network sites shape the way users discuss the news content they consume on these sites. Paper 3 compares the deliberative quality of user comments left on social network sites with those left on news websites. Paper 4 adopts an identical methodological approach to compare the level of civility and politeness in user comments across platforms. The findings suggest that while social network sites are conducive to civil political discussion, they do not appear to encourage comments of superior deliberative quality

THE GATING OF THE BACTERIAL MECHANOSENSITIVE CHANNEL MSCS REFLECTS ITS FUNCTION AS A SENSOR OF BOTH CROWDING AND LATERAL PRESSURE AS WELL AS ITS ROLE IN OSMOREGULATION

The mechanosensitive channel MscS is a ubiquitous bacterial membrane valve that opens by increased tension in the event of osmotic down-shock, releasing small internal osmolytes and thus preventing the cell from excessive hydration and possible lysis. This osmolyte release is accompanied by a reduction of osmotic pressure and volume of the cell, which simultaneously increases crowding. The large catalogue of MscS homologs in both prokaryotes and eukaryotes makes the study of this channel enticing to the field of physical biochemistry. Here are the results of three different studies, two of which focus on the gating of MscS in the presence of large osmolytes and amphipathic compounds and a third which describes the first electrophysiological examination of the inner membrane of the facultative pathogen Vibrio cholerae. The first study in Chapter 2 describes the sensitivity of gating transitions in MscS to large intracellular macromolecules. This sensitivity originates at the cytoplasmic cage domain and the perceived crowding alters the rate of opening, closing and inactivation. Chapter 3 details the utilization of MscS as a sensor for changes in the lateral pressure profile of native bilayers and how this technique can be used to resolve the potential of antibacterial agents to partition into the membrane. The third and final study describes our development of a procedure to generate giant spheroplasts of Vibrio cholerae and the subsequent characterization of its two major mechanosensitive channels in terms of gating, inactivation, conductivity, and compatible osmolyte sensitivity as well as the durability of the pathogen in response to osmotic shock. These contributions to the field of mechanobiology and channel biophysics suggest that environmental feedback during osmoregulation is recognized by the cell, provide a potential method to monitor the partitioning of antibiotics into a cell membrane, and lastly detail the mechano-electrical response of a relevant, disease-causing bacteria