Psychosocial correlates of juvenile delinquency

The present thesis is a detailed and in depth examination of the reasons of re-offending, perceived by young offenders in custody, drawn from the largest Young Offenders' Institution in Scotland. Mainly materialistic and affective reasons were provided, in line with previous research, yet the issue of drugs abuse emerged as salient. The thesis focused on the immediate and more proximally related factors of re-offending, predicting young offenders' decisions to re-offend in the future. One hundred and fifty two young offenders were randomly selected and participated in a structured interview. The interview assessed several background characteristics, their perceptions of the costs and benefits of their future offending, their perceived normative influences in their future offending and their perceptions of desisting from future offending by controlling several criminogenic factors in the future. In addition, the participants completed two self-reported measures: the Parental Bonding Instrument(PBI)- and the Moral Disengagement Scale(MDS). Intentions of re-offending in the future were predicted by perceived control and attitudes towards future offending. Background factors, related and predictive of recidivism and chronic offending, failed to contribute to the prediction of variation of intentions, over and above the contribution of perceptions of control and attitudes of re-offending. The results suggest that attitudes towards offending and perceptions of control over offending provide a parsimonious framework of assessing and predicting young offenders' intentions of reoffending in the future. Moreover, the detailed examination of the control and behavioural beliefs underlying the two constructs, perceived control to desist from offending and attitudes towards offending, can guide to the specific needs that are perceived as criminogenic by the young offenders and potentially inform the content and the direction of any intervention programs within the correctional settings of young offenders aiming at reducing levels of recidivism. Two dimensions of child-rearing practices, parental care and protection, were examined in relation to normative data, background characteristics and cognitive representations of future offending, and it was found that the relation between perceptions of parenting and intentions of re-offending were mediated by attitudes towards offending in the future. In addition, the associations of moral disengagement, as a failure of self-regulation of morality with past recidivism rates and age of initiation of offending were examined, and were found, contrary to expectations, mainly unrelated. However, the overall score of Moral Disengagement of the young offenders was significantly higher in comparison to normative data. The results suggest that Moral Disengagement could be a factor differentiating young people involved in criminal activity and processed by the legal system from young people who are not involved in criminal activity and/or are unaffected by official monitoring. Moral Disengagement, however, might not be related with frequency of offending within groups of young people in the correctional institutions. Moral disengagement was also found mainly unrelated with background characteristics of the young offenders, suggesting that self-regulation of morality is relatively independent from influences from the social environment. Finally, the relations of Moral Disengagement and cognitive representations of offending in the future were discussed in terms of self-regulation of hierarchically organised feedback loops

Computational study of the interaction between a newtonian fluid and a cellular biological medium in a straight vessel

In this work, we solve numerically the governing equations for quasi-steady Newtonian flow past and through a cellular biological medium, which is attached to the surface of a straight vessel. The flow past the cellular biological medium is described by the Navier-Stokes equations. For the modeling of momentum transfer within the cellular biological medium, we consider that the cellular biological medium constitutes a biphasic fluid-solid mixture with poroelastic behaviour. The system of governing equations is solved numerically with the mixed finite element method. The computational domain is discretized using an unstructured, variable density triangular element mesh. From the numerical solution we obtain the spatial distributions of: (i) the fluid velocity and pressure, and (ii) the displacement and stresses of the solid matrix within the cellular biological medium. Also, the components of the overall hydrodynamic force exerted by the flowing fluid on the cellular biological medium are calculated. A parametric analysis is performed with regard to the Reynolds and Darcy numbers that characterize the flow past and through the cellular biological medium

Hierarchical hybrid simulation of biofilm growth dynamics in 3D porous media

Recently, we developed the first hierarchical, hybrid simulator for the prediction of the pattern of evolution and the rate of growth of heterogeneous biofilms within the pore space of porous media [Kapellos et al., Adv. Water Resour. (2007) 30:1648-1667]. A n improved version of our simulator is presented in this work. A continuum-based approach for fluid flow and solute transport is combined with individual-based approaches for biofilm growth, detachment, and migration in the pore space. The Navier-Stokes-Brinkman equations are solved numerically with a marker-and-cell finite difference scheme to determine the velocity and pressure fields in the pore space. Momentum transport in the biofilms is described in the context of biphasic poroelasticity and a Galerkin finite element method is used to determine the solid stress field. Shear-induced biofilm detachment is taken into account explicitly and a Lagrangian-type simulation is used to determine the trajectories of detached fragments. Nutrient transport in the pore space is described by the convectiondiffusion- reaction equation, which is solved numerically with an operator-splitting finite difference scheme. Further, a novel, physically-constrained cellular-automaton model is used for biofilm proliferation. As an example application, the simulator is used to investigate the impact of biofilm formation on the fate and transport of suspended particles in a network of three-dimensional pores

Microbial Competition in Bioreactors

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Liquid velocity in a high-solids-loading three-phase external-loop airlift reactor

BACKGROUND: Airlift reactors are of interest for many different processes, especially for three-phase systems. In this study the behavior of a high-loading three-phase external-loop airlift reactor was examined. In particular, the effect of parameters such as airflow rate (riser superficial gas velocities between 0.003 and 0.017 m s-1), solids loading (up to 50%, v/v) on liquid circulation velocity in the air-water-alginate beads system as a crucial hydrodynamic parameter was studied. RESULTS: It was observed that increase of the airflow rate resulted in increase of the liquid velocity in the system. The same result but less pronounced was observed by introducing small amounts of solid particles up to 7.5% v/v. However, further introduction of solids caused decrease of the liquid velocity. Laminar regime for the liquid circulation was observed for low gas velocities. Minimum gas velocities for recirculation initiation in the reactor were determined for all solid loadings and linear dependence on the solid content was found. Gas holdups for the three-phase system were larger than for the two-phase system in all experiments. A simple model for predicting the liquid circulation velocity in the three-phase system with high solid loading of low-density particles was developed. This model is based on the viscosity of integrated medium (solid + liquid) which is a new aspect to analyze this phenomenon. CONCLUSIONS: The developed model shows very good agreement with the experimental results for all solid loadings. It also includes the influence of reactor geometry on the liquid circulation velocity thus enabling optimization

Dependence of slip velocity on operating parameters of air-lift bioreactors

In this study we analyzed the quality of local mixing in external loop air-lift bioreactors for two hydrodynamic regimes in terms of slip velocity. In particular. the effects of design and operating parameters (e.g., reactor geometry, superficial gas velocity and flow regime) on the slip velocity were determined. Several correlations found in the literature based on theoretical models of fluid flow and several semi-empirical and empirical correlations were examined and the applicability of all the proposed correlations was tested on available experimental data. The most accurate correlations for the prediction of the slip velocity in each bioreactor operating regime were identified. New correlations for homogeneous and heterogeneous flow regimes were developed. These correlations are among the most accurate and have increasing accuracy with increase of superficial gas velocity. They also give insight into how the change in geometry properties or gas flow will alter the slip velocity. This is very important in the design and optimization of air-lift bioreactors

Constructed wetlands in the treatment of agro-industrial wastewater: A review

Due to their simplicity and low operation cost, constructed wetlands are becoming more prevalent in wastewater treatment all over the world. Their range of applications is no longer limited to municipal wastewater but has expanded to the treatment of heavily polluted wastewaters such as agro-industrial effluents. This paper provides a comprehensive literature review of the application of constructed wetlands in treating a variety of agro-industrial wastewaters, and discusses pollutant surface loads and the role of constructed wetland type, prior-treatment stages and plant species in pollutant removal efficiency. Results indicate that constructed wetlands can tolerate high pollutant loads and toxic substances without losing their removal ability, thus these systems are very effective bio-reactors even in hostile environments. Additionally, the review outlines issues that could improve pollutant treatment efficiency and proposes design and operation suggestions such as suitable vegetation, porous media and constructed wetland plain view. Finally, a decision tree for designing constructed wetlands treating agro-industrial wastewaters provides an initial design tool for scientists and engineers