Complexity of fuzzy answer set programming under Łukasiewicz semantics

Fuzzy answer set programming (FASP) is a generalization of answer set programming (ASP) in which propositions are allowed to be graded. Little is known about the computational complexity of FASP and almost no techniques are available to compute the answer sets of a FASP program. In this paper, we analyze the computational complexity of FASP under Łukasiewicz semantics. In particular we show that the complexity of the main reasoning tasks is located at the first level of the polynomial hierarchy, even for disjunctive FASP programs for which reasoning is classically located at the second level. Moreover, we show a reduction from reasoning with such FASP programs to bilevel linear programming, thus opening the door to practical applications. For definite FASP programs we can show P-membership. Surprisingly, when allowing disjunctions to occur in the body of rules – a syntactic generalization which does not affect the expressivity of ASP in the classical case – the picture changes drastically. In particular, reasoning tasks are then located at the second level of the polynomial hierarchy, while for simple FASP programs, we can only show that the unique answer set can be found in pseudo-polynomial time. Moreover, the connection to an existing open problem about integer equations suggests that the problem of fully characterizing the complexity of FASP in this more general setting is not likely to have an easy solution

The Role of Time Preferences in the Intergenerational Transfer of Smoking

Peer reviewedPublisher PD

Exploring a Non-Minimal Sterile Neutrino Model Involving Decay at IceCube and Beyond

We study the phenomenology of neutrino decay together with neutrino oscillations in the context of eV-scale sterile neutrinos. We review the formalism of visible neutrino decay in which one of the decay products is a neutrino that potentially can be observed. We apply the formalism developed for decay to the recent sterile neutrino search performed by IceCube with TeV neutrinos. We show that for $\nu_4$ lifetime $\tau_4/m_4 \lesssim 10^{-16} {\rm eV^{-1}s}$, the interpretation of the high-energy IceCube analysis can be significantly changed.Comment: 12 pages, 7 figures. Find code at: https://github.com/arguelles/nuSQUIDSDeca

Who succeeds at university?: factors predicting academic achievement of first-year Dutch students

Literature distinguishes three complexes of factors that affect university achievement. Firstly, factors related to characteristics of the education system and study financing. Secondly, Factors related to how institutions organise their education. Finally, these concern student characteristics. The effects on achievement were examined. Dutch first-year university students filled in a self-report questionnaire on motivation and deep information processing. Further, student ratings provided information on quality of courses. Finally, information on quantity of courses, in terms of number of contact hours was obtained through study guides. Multilevel analyses showed that ability, motivation, quality of assessment and the numbers of self-study hours, active hours and passive hours, affected achievement

Young, online and connected : the impact of everyday Internet use of Dutch adolescents on social cohesion

Adolescents spend a significant part of their day online on different activities. Many of them use the Internet to connect with social networks and for entertainment. The negative consequences of adolescents’ internet use seem to dominate both popular and, to a lesser extent, academic discourse. Using large-scale, nationally representative data, this dissertation provides insight into the balance between the positive and negative outcomes by investigating how adolescents’ everyday internet use is related to social cohesion. Adolescents use the internet as a tool to maintain social relationships in the current networked society. Concerns about adolescents distancing themselves from others and society because of their online behaviours appear an exaggeration; the studies have instead shown that adolescents are involved in a variety of social and societal activities online. In other words, adolescents are not only connected to the internet, but they use it to be better connected tot heir social networks and society

Barrett Esophagus: Improving Surveillance Strategies

The aim of surveillance in patients with a Barrett esophagus (BE) is to detect progression of dysplasia at an early and therefore likely curable stage. The interval of endoscopic surveillance in patients with BE is currently based on the histopathological stage (i.e. grade of dysplasia). This approach is however known to have several pitfalls. First, only patients with intestinal metaplasia (IM) in the columnar-lined segment of the esophagus (CLE) have so far been regarded to have a premalignant condition and are enrolled in an endoscopic surveillance program, in contrast to patients with only cardiac-type mucosa (CM) in their biopsies. However, as IM and CM can be both present in the CLE and are endoscopically indiscernible, sampling error can occur, and exclusion of patients with only CM from endoscopic follow-up might therefore be incorrect. In addition, it has been suggested that IM in CLE may develop over time, and a follow-up endoscopy in the course of time may than detect IM. Secondly, in line with the risk of neoplastic progression, the presence or absence of dysplasia in IM determines the frequency of endoscopic surveillance, but the interpretation of dysplasia is subject to considerable interobserver variability, leading to both superfl uous follow-up endoscopies in some patients and insuffi cient control of others. Therefore, it is relevant to perform risk stratifi cation to defi ne which subgroup of patients with CLE with or without IM should undergo endoscopic follow-up, and at which frequency. The aim of the work described in this thesis was to assess the currently used criteria for performing endoscopic surveillance in patients with CLE, and to evaluate which clinical characteristics and biomarkers could contribute to risk stratifi cation in patients with CLE, in order to refi ne surveillance strategies in these patients

Complexity of fuzzy answer set programming under Łukasiewicz semantics: first results

Fuzzy answer set programming (FASP) has recently been proposed as a generalization of answer set programming in which propositions are allowed to be graded. Little is known about its computational complexity. In this paper we present some results and reveal a connection to an open problem about integer equations, suggesting that characterizing the complexity of FASP may not be straightforward