Linearizing Control Based on Adaptive Observer for Anaerobic Continuous Sulphate Reducing Bioreactors with Unknown Kinetics

Anaerobic reactors are a typical example of processes that exhibit non-linear behavior and, also time varying parameters; hence their operation is known to be difficult to model and control. In contrast to modeling approaches, in practice linear controllers are widely employed for industrial processes because of their easy implementation and manipulation by plant operators; nevertheless linear approaches are not robust when the operating conditions change suddenly and/or strong disturbances are present. In order to introduce robust controllers to these processes, this paper addresses the tracking problem for the substrate (sulphate) control in a class of continuous bioreactors. An experimentally corroborated bioreactor model serves as benchmark problem for advanced non-linear analysis and control techniques; taking into account system non-linearities, stability and performance objectives over large operating regions. It is considered that, as it is common in practice, the rate of substrate consumption exhibits uncertainty. Results show that the proposed controller exhibits better dynamic performance than a classical Proportional-Integral control tuned using the methodology suggested by Internal Model Control

Relational Goods and Endurance of Voluntary Associational Participation: The Mapuche Indigenous Case in Santiago de Chile.

In this article, I analyse the reasons for sustaining membership in voluntary ethnic associations of Mapuche people living in Santiago de Chile. By following a relational goods approach, I suggest that the constructed nature of ethnicity leads the Mapuche to create and join ethnic associations in an urban milieu. This study reveals that the main motivations for sustaining an active associational engagement in Santiago are based on three accounts: identity recovery struggle, leaving an identity legacy and bonding with their ethnic peers; all of these identified as relational goods. This investigation is based on an eight-month ethnographic fieldwork conducted in Santiago.This work was supported by the University of Cambridge Sociology Graduate Education Committee (GEC) Fieldwork Funding; Newnham College, University of Cambridge Fieldwork Grant; and under the Programme Becas de Doctorado con Acuerdo Bilateral en el Extranjero Becas Chile-Cambridge (Grant Fondecyt: N° 84140015)

Uptake of genetic testing and long-term tumor surveillance in von Hippel-Lindau disease

<p>Abstract</p> <p>Background</p> <p>von Hippel-Lindau (VHL) disease is a hereditary cancer syndrome caused by germline mutations in the <it>VHL </it>gene. Patients have significant morbidity and mortality secondary to vascular tumors. Disease management is centered on tumor surveillance that allows early detection and treatment. Presymptomatic genetic testing is therefore recommended, including in at-risk children.</p> <p>Methods</p> <p>We tested 17 families (n = 109 individuals) for <it>VHL </it>mutations including 43 children under the age of 18. Personalized genetic counseling was provided pre and post-test and the individuals undergoing presymptomatic testing filled out questionnaires gathering socio-demographic, psychological and psychiatric data. Mutation analysis was performed by direct sequencing of the <it>VHL </it>gene. Mutation-carriers were screened for VHL disease-related tumors and were offered follow-up annual examinations.</p> <p>Results</p> <p>Mutations were identified in 36 patients, 17 of whom were asymptomatic. In the initial screening, we identified at least one tumor in five of 17 previously asymptomatic individuals. At the end of five years, only 38.9% of the mutation-carriers continued participating in our tumor surveillance program. During this time, 14 mutation carriers developed a total of 32 new tumors, three of whom died of complications. Gender, education, income, marital status and religiosity were not found to be associated with adherence to the surveillance protocol. Follow-up adherence was also independent of pre-test depression, severity of disease, or number of affected family members. The only statistically significant predictor of adherence was being symptomatic at the time of testing (OR = 5; 95% CI 1.2 - 20.3; p = 0.02). Pre-test anxiety was more commonly observed in patients that discontinued follow-up (64.7% vs. 35.3%; p = 0.01).</p> <p>Conclusions</p> <p>The high initial uptake rate of genetic testing for VHL disease, including in minors, allowed the discontinuation of unnecessary screening procedures in non mutation-carriers. However, mutation-carriers showed poor adherence to long-term tumor surveillance. Therefore, many of them did not obtain the full benefit of early detection and treatment, which is central to the reduction of morbidity and mortality in VHL disease. Studies designed to improve adherence to vigilance protocols will be necessary to improve treatment and quality of life in patients with hereditary cancer syndromes.</p

Spatial and seasonal patterns of salinity in a large and shallow tropical estuary of the western caribbean

Salinity profiles and meteorological data were analyzed during February, May, and September 2006 in Chetumal Bay, a large, shallow estuary of the Western Caribbean. Local meteorological conditions revealed three seasons: (1) a dry season (March-May); (2) a wet season (June-October); and (3) the nortes season, with northerly wind events (October-February). During the nortes and wet seasons, salinity ranged between 13 and 16 psu, and salinity was highest in the dry season, ranging between 18 and 22 psu over most of the area; a strong stratification and a significant contribution of salty water characterized this season. Strong horizontal gradients were observed near Rio Hondo during the three seasons. Deep and narrow peculiar bathymetric features called the pozas showed a strong stratification and a relatively high salinity. The northern part of Chetumal Bay and probably the entire system are far from being homogeneous. © Coastal and Estuarine Research Federation 2009

Role of dislocation elastic field on impurity segregation in Fe-based alloys

International audienceAbstract Dislocation engineering in crystalline materials is essential when designing materials for a large range of applications. Segregation of additional elements at dislocations is frequently used to modify the influence of dislocations on material properties. Thus, the influence of the dislocation elastic field on impurity segregation is of major interest, as its understanding should lead to engineering solutions that improve the material properties. We report the experimental study of the elastic field influence on atomic segregation in the core and in the area surrounding edge dislocations in Fe-based alloys. Each element is found either to segregate in the edge dislocation core or to form atmospheres. The elastic field has a strong effect on the segregation atmosphere, but no effect on the dislocation core segregation. The theory is in good agreement with experiments, and should support dislocation engineering

Thermal ageing effect on solute segregation and precipitation in the heat-affected-zone of dissimilar metal welds for nuclear power plants

Solute segregation in the carbon-depleted (CDZ) heat-affected zone of dissimilar metal welds (DMW) designed for nuclear power plant EPRTM reactors has been investigated by atom probe tomography (APT) and related to the mechanical properties (toughness test). The analysis of grain boundaries (GBs) by APT allowed the quantification of the P segregation and other solute elements, in all the analyzed samples, before and after long-term ageing heat treatments. The post-weld stress-relief heat treatment applied to the samples before the ageing heat treatments leads to important GBs segregation levels. Following thermal ageing treatments allow a relative increase of GB segregation. P segregation increases with the various thermal ageing conditions. The experimental data were used to model P segregation in high-angle GBs. The simulations show that P segregation is kinetically limited by bulk diffusion, explaining the observed P segregation increase with temperature. P segregation in GBs in the CDZ of the DMW should remain low compared to the expected equilibrium segregation level during the entire reactor service. In addition to solute segregation in extended defects, APT measurements revealed the presence of Cu-rich clusters in GBs, dislocations, and grains in all the aged samples. These clusters were not observed in the sample before ageing