Toward optimal control of flat plate photobioreactors: the greenhouse analogy?

Abstract: The cultivation of algae in photo-bioreactors shows similarities to crop cultivation in greenhouses, especially when the reactors are driven by sun light. Advanced methodologies for dynamic optimization and optimal control for greenhouses are known from earlier research. The aim here is to extend these methodologies to microalgae cultivated in a flat plate photo-bioreactor. A one-state space model for the algal biomass in the reactor is presented. The growth rate vs. light curve is parameterized on the basis of experimental evidence. Spatial distribution of light and growth rate between the plates is also considered. The control variable is the dilution rate. Dynamic optimal control trajectories are presented for various choices of goal function and external solar irradiation trajectories over a horizon of 3 days. It was found that the algae present in the reactor at final time represent a value for the future. Numerical and theoretical results suggest that the control is bang-(singular-)bang, with a strong dependence on the weather. The optimal biomass also depends on the available light, and achieving it to reach a new optimal steady cycle after a prolonged change in weather may take several days. A preliminary theoretical analysis suggests a control law that maximizes the effective growth rate. The analysis shows that like in the greenhouse case, the co-state of the algal biomass plays a pivot role in developing on-line controllers

An Animal-Assisted Intervention Study in the Nursing Home: Lessons Learned

AAI studies in the nursing home pose a specific set of challenges. In this article the practical and ethical issues encountered during a Dutch psychogeriatric nursing home AAI study are addressed with the aim of sharing our experiences for future researchers as well as AAI practitioners in general. In our study we compared three groups of clients with dementia who participated in group sessions of either visiting dog teams, visiting FurReal Friend robot animals, or visiting students (control group) and monitored the effect on social interaction and neuropsychiatric symptoms through video analysis and questionnaires. We encountered the following four categories of challenges during our study. Participant-related challenges include the legal implications of working with vulnerable patients, the practical implications of a progressive neurodegenerative disease with accompanying memory loss and behavioral problems, and the ethical implications of the use of robot animals for people with diminished cognitive functions. A very important challenge involves the selection of the participating dogs and ensuring animal welfare during the study. We partnered with a local university of applied sciences to help us successfully address these issues. The nursing home setting poses several practical challenges due to its inherent organizational structure, the high workload of nursing home staff, and an often suboptimal environment for a controlled randomized trial, especially when comparing nonpharmacological interventions. Balancing the desire for scientifically sound procedures with the practical limitations of a nursing home setting is often difficult and requires specific considerations

In vitro and in vivo evaluation of [I-123]-VEGF(165) as a potential tumor marker

peer reviewedOne of the research challenges in oncology is to develop new biochemical methods for noninvasive tumor therapy evaluation to determine,whether the chemotherapeutics is effective. Vascular endothelial growth factor (VEGF) was labeled with radioiodine and evaluated in vitro as well as in vivo, using A2058, a melanoma cell line overexpressing VEGFR-1 and -2. Saturation binding analysis with [I-125]-VEGF resulted in a K-d of 0.1 nM. Internalization assays indicate the preserved ligand induced internalization and metabolization of the tracer. Biodistribution studies with [I-123]-VEGF in wild type and A2058 tumor-bearing athymic mice showed low background activity and a tumor to reference tissue ratio of maximum 6.12. These results suggest that [I-123]-VEGF is a potentially suitable tracer for tumor therapy evaluation. (c) 2005 Elsevier Inc. All rights reserved

Influence of ionic and non-ionic radiographic contrast media on leukocyte adhesion molecules.

BACKGROUND: Many papers have focused on the importance of granulocytes in the process of reperfusion and ischemia. Most of the clinical studies measured several parameters of this process during and after coronary angiography, without taking into account the effect of the radiographic contrast media (RCM) used during this procedure. MATERIALS AND METHODS: We performed a randomized patient study (n = 37) to evaluate the effect of ionic and non-ionic RCM on granulocyte adhesion during coronary angiography. We also evaluated the influence of the ionicity and osmolarity of the different substances on granulocyte adhesion molecules in in vitro experiments. RESULTS: The osmolarity of patient serum samples increased from 302 +/- 1 to 309 +/- 1 mOsm/kg (p < 0.05) after infusion of RCM. The CD11b expression in the samples of the non-ionic RCM treated group increased from 221 +/- 21 MFI to 377 +/- 30 MFI (p < 0.05) measured as the absolute mean fluorescence intensity (MFI), yet did not alter significantly in the ionic RCM group. In contrast, the in vitro experiments showed a reduction of the CD11b expression from 360 +/- 70 MFI to 149 +/- 30 MFI (p < 0.05) in the ionic RCM group. CONCLUSIONS: The upregulation of adhesion molecules was significantly reduced in vivo with ionic RCM, while ionic substances caused opposite effects in vitro. This effect should be taken into account when performing leukocyte functional analysis of samples taken during angiography

Scalable context-dependent analysis of emergency egress models

Pervasive environments offer an increasing number of services to a large number of people moving within these environments, including timely information about where to go and when, and contextual information about the surrounding environment. This information may be conveyed to people through public displays or direct to a person's mobile phone. People using these services interact with the system but they are also meeting other people and performing other activities as relevant opportunities arise. The design of such systems and the analysis of collective dynamic behaviour of people within them is a challenging problem. We present results on a novel usage of a scalable analysis technique in this context. We show the validity of an approach based on stochastic process-algebraic models by focussing on a representative example, i.e. emergency egress. The chosen case study has the advantage that detailed data is available from studies employing alternative analysis methods, making cross-methodology comparison possible. We also illustrate how realistic, context-dependent human behaviour, often observed in emergency egress, can naturally be embedded in the models, and how the effect of such behaviour on evacuation can be analysed in an efficient and scalable way. The proposed approach encompasses both the agent modelling viewpoint, as system behaviour emerges from specific (discrete) agent interaction, and the population viewpoint, when classes of homogeneous individuals are considered for a (continuous)approximation of overall system behaviour

Effect of macrophage depletion on immune effector mechanisms during corneal allograft rejection in rats

PURPOSE. In rats, corneal allograft rejection is delayed for at least 100 days by clodronate liposomes. These liposomes selectively deplete macrophages. To investigate the immunologic basis for absence of graft rejection in treated rats, the effect of these liposomes on the generation of cytotoxic T lymphocytes (CTLs) and antibody production after orthotopic corneal allotransplantation was determined. METHODS. Transplantations of corneal buttons from PVG rats were performed in AO rats. After surgery, one group received clodronate liposomes subconjunctivally at five time points, and the other group remained untreated. On postoperative day (POD) 3, 7, 12, or 17, rats were killed, the presence of CTLs was investigated at three different anatomic locations, and antibodies against donor antigens were tested. RESULTS. NO significant differences were found between the groups tested 3 and 7 days after surgery. But on POD 12 (the time of onset of rejection in the untreated group) and on POD 17, the CTL activities detected in the submandibular lymph nodes (P less than or equal to 0.008) and the spleen (P less than or equal to 0.009) were significantly less in the treated groups compared with the untreated groups. in the untreated groups complement-independent antibodies were present only on POD 17, whereas no antibodies were found in the treated rats. CONCLUSIONS. Local treatment with clodronate liposomes was shown to downregulate local and systemic CTL responses and to prevent the generation of antibodies. Local depletion of macrophages in the initiation phase of the immune response appears to lead to a less vigorous attack on the grafted tissue and therefore to promote graft survival