SMT-based Model Checking for Recursive Programs

We present an SMT-based symbolic model checking algorithm for safety verification of recursive programs. The algorithm is modular and analyzes procedures individually. Unlike other SMT-based approaches, it maintains both "over-" and "under-approximations" of procedure summaries. Under-approximations are used to analyze procedure calls without inlining. Over-approximations are used to block infeasible counterexamples and detect convergence to a proof. We show that for programs and properties over a decidable theory, the algorithm is guaranteed to find a counterexample, if one exists. However, efficiency depends on an oracle for quantifier elimination (QE). For Boolean Programs, the algorithm is a polynomial decision procedure, matching the worst-case bounds of the best BDD-based algorithms. For Linear Arithmetic (integers and rationals), we give an efficient instantiation of the algorithm by applying QE "lazily". We use existing interpolation techniques to over-approximate QE and introduce "Model Based Projection" to under-approximate QE. Empirical evaluation on SV-COMP benchmarks shows that our algorithm improves significantly on the state-of-the-art.Comment: originally published as part of the proceedings of CAV 2014; fixed typos, better wording at some place

Canonical Wnt signaling negatively modulates regulatory T cell function

Foxp3 is crucial for both the development and function of regulatory T (Treg) cells; however, the posttranslational mechanisms regulating Foxp3 transcriptional output remain poorly defined. Here, we demonstrate that Tcell factor 1 (TCF1) and Foxp3 associates in Treg cells and that active Wnt signaling disrupts Foxp3 transcriptional activity. A global chromatin immunoprecipitation sequencing comparison in Treg cells revealed considerable overlap between Foxp3 and Wnt target genes. The activation of Wnt signaling reduced Treg-mediated suppression both invitro and invivo, whereas disruption of Wnt signaling in Treg cells enhanced their suppressive capacity. The activation of effector Tcells increased Wnt3a production, and Wnt3a levels were found to be greatly increased in mononuclear cells isolated from synovial fluid versus peripheral blood of arthritis patients. We propose a model in which Wnt produced under inflammatory conditions represses Treg cell function, allowing a productive immune response, but, if uncontrolled, could lead to the development of autoimmunity

A study on the relationship between fat, oil and grease (FOG) deposits in sewer systems and FOG disposal patterns

Fat, oil and grease (FOG) deposits are one of the leading causes of sewer system blockages, thereby increasing the risks of undesired and polluting flooding and sewer overflows. FOG accumulates throughout the entire sewer network; e.g., in public sewer pipes and lateral house connections it reduces the available discharge capacity, and in pump sumps it increases the risk of pump failures. Previous studies primarily focused on FOG deposits occurring in parts of sewer systems downstream of Food Service Establishments (FSE). It is thought, however, that domestic FOG disposal is also an important contributor to FOG deposits, and therefore warrants further investigation. Consequently, the objective of this research was to investigate the relationship between domestic FOG disposal patterns and the occurrence of FOG deposits in sewer systems. By considering both the household scale and the scale of catchments, it was possible to study the influence of individual and population disposal patterns. The first part of this study focused on the influence of individual disposal patterns; samples of FOG deposits were collected from clogged building drainage systems and questionnaires were conducted to reveal information about the household’s cooking and disposal habits. Only three out of the eleven households showed a link between the cooking fats and oils used and the FOG deposits collected, as their fatty acid profiles displayed similarities. The second part of this study focused on the influence of population disposal patterns on the occurrence of FOG deposits, by studying the severe accumulation of FOG at pumping stations in relation to catchment demographics and sewer system characteristics. Generalized linear mixed model (GLMM) procedures were used to model the probability of the presence or absence of FOG in pump sumps. The model revealed that severe accumulation of FOG in pump sumps was negatively correlated to the average income of inhabitants attached to the catchment, suggesting that individuals within an income-group shared FOG disposal patterns. Furthermore, FSE density and kinetic energy of wastewater per unit of volume per day were found to be important factors correlated with the occurrence of FOG deposits. The results provide important insights into factors that may influence the accumulation of FOG. Further research is required to obtain insights in how particular diets, cleaning habits and FOG disposal patterns may influence the accumulation of FOG.Civil Engineering and GeosciencesWater ManagementUrban Drainag

The end of the sectoral approach? Understanding the role of integration in urban water management

Urban areas are highly dependent on their urban water systems, which provide essential services such as access to clean drinking water, public health protection, and flood control. Global developments increasingly threaten the provision of these services: changing weather patterns, ongoing urbanization processes, and depleting natural resources lead to environmental and public health issues, and increase the risk of urban flooding.While traditional urban water systems (i.e., centralized water supply systems, sewer networks, and large-scale wastewater treatment facilities) have significantly contributed to global public health and protected cities from flooding, they are ill-equipped in the face of emerging global developments. For example, traditional systems have a limited ability to cope with extreme climate conditions, have a high net energy consumption, and lead to the deterioration of the environmental quality....Sanitary Engineerin

Towards the integrated management of urban water systems: Conceptualizing integration and its uncertainties

Climate change and urbanization, as well as growing environmental and economic concerns, highlight the limitations of traditional wastewater practices and thereby challenge the management of urban water systems. Both in theory and in practice, it has been widely acknowledged that the challenges of the twenty-first century require solutions that address problems in a more integrated way. Although the demand for integration is obvious, implementation has proved challenging because of the complexity and uncertainty involved. In addition, the urban water literature contains a wide diversity of approaches to integration, each contribution having its own understanding of the term, as well as how to deal with the complexity that comes with it. In this article, we take a first step in supporting both decision-making and decision-makers in urban water systems integration. First, we work towards a more comprehensive perspective on integration in urban water management; one that uses and structures the variety of existing approaches. In so doing, we introduce a typology of urban water systems integration that distinguishes between geographical, physical, informational, and project-based forms. Second, we explore the implications that such integrated solutions bring for decision-makers. They will be faced with additional uncertainty arising (1) at the interfaces of previously unconnected systems and (2) from the social and institutional changes that systems integration requires. Finally, we draft three decision-making challenges that come with integration and provide some possibilities for dealing with them.</p

The role of integration for future urban water systems: Identifying Dutch urban water practitioners' perspectives using Q methodology

Urban water systems are under increased pressure from ongoing developments like climate change, population growth and urbanization. While it is clear that current urban water challenges need a more integrated approach, practitioners disagree on what such an integrated approach means exactly. Integration could therefore be described as a wicked problem, with practitioners having different understandings of integration, as well as the opportunities and challenges they should focus on; e.g., climate adaptation, resource recovery or collective replacement. This lack of consensus challenges decision-making, and thus the implementation of integration. To foster urban water systems integration, this study uses Q methodology to explore the different perspectives that Dutch urban water practitioners have on integration for future urban water systems. Our analysis reveals four salient perspectives: perspective 1 sees coordination as a means to make the system future-proof, perspective 2 focuses on climate adaptation, perspective 3 aims for recovery, and perspective 4 is all about efficiency and being in control. While all perspectives acknowledge that traditional urban water practices need to change, they differ on which sustainability challenges are considered most important and what means should be used. Practitioners need to understand these differences to deal effectively with the wicked nature of integration.Sanitary Engineerin

Female fertility after colorectal surgery for familial adenomatous polyposis: a nationwide cross-sectional study

Background: Information on postoperative fertility problems in female patients with familial adenomatous polyposis (FAP) is scarce. Previous studies in FAP or colitis patients almost uniformly describe a reduction in fertility after ileal pouch-anal anastomosis, compared with ileorectal anastomosis. Objective: To describe fertility problems in female FAP patients after colectomy and to investigate the relationship between self-reported fertility problems and the type of operation and other surgery-related factors (eg, comorbid conditions). Methods: A questionnaire addressing surgery, fertility problems, and desire to have children was sent to a nationwide sample of FAP patients. Medical data were verified in the FAP-registry of the Netherlands Foundation for the Detection of Hereditary Tumors. Differences between women with and without fertility problems were investigated. Results: Of 138 patients, 23 (17%) reported current or past fertility problems. The prevalence of fertility problems was similar among those who had undergone ileorectal anastomosis, ileal pouch-anal anastomosis, and proctocolectomy with ileostomy. None of the other surgery-related factors, nor desmoid tumors or cancer were associated significantly with the development of fertility problems. Patients reporting fertility problems were significantly younger at diagnosis of FAP (mean, 20 vs. 27 years, P < 0.05) and at the time of the first surgical procedure (mean, 22 vs. 28 years, P < 0.05). Conclusions: The risk of developing postoperative fertility problems is not associated significantly with the type of surgery, indication for surgery, complications, or other comorbid conditions. Postoperative fertility problems are more common among women who had their first surgical procedure at a younger age