On the Generalised Colouring Numbers of Graphs that Exclude a Fixed Minor

The generalised colouring numbers $\mathrm{col}_r(G)$ and $\mathrm{wcol}_r(G)$ were introduced by Kierstead and Yang as a generalisation of the usual colouring number, and have since then found important theoretical and algorithmic applications. In this paper, we dramatically improve upon the known upper bounds for generalised colouring numbers for graphs excluding a fixed minor, from the exponential bounds of Grohe et al. to a linear bound for the $r$-colouring number $\mathrm{col}_r$ and a polynomial bound for the weak $r$-colouring number $\mathrm{wcol}_r$. In particular, we show that if $G$ excludes $K_t$ as a minor, for some fixed $t\ge4$, then $\mathrm{col}_r(G)\le\binom{t-1}{2}\,(2r+1)$ and $\mathrm{wcol}_r(G)\le\binom{r+t-2}{t-2}\cdot(t-3)(2r+1)\in\mathcal{O}(r^{\,t-1})$. In the case of graphs $G$ of bounded genus $g$, we improve the bounds to $\mathrm{col}_r(G)\le(2g+3)(2r+1)$ (and even $\mathrm{col}_r(G)\le5r+1$ if $g=0$, i.e. if $G$ is planar) and $\mathrm{wcol}_r(G)\le\Bigl(2g+\binom{r+2}{2}\Bigr)\,(2r+1)$.Comment: 21 pages, to appear in European Journal of Combinatoric

Chromatic numbers of exact distance graphs

For any graph G = (V;E) and positive integer p, the exact distance-p graph G[\p] is the graph with vertex set V , which has an edge between vertices x and y if and only if x and y have distance p in G. For odd p, Nešetřil and Ossona de Mendez proved that for any fixed graph class with bounded expansion, the chromatic number of G[\p] is bounded by an absolute constant. Using the notion of generalised colouring numbers, we give a much simpler proof for the result of Nešetřil and Ossona de Mendez, which at the same time gives significantly better bounds. In particular, we show that for any graph G and odd positive integer p, the chromatic number of G[\p] is bounded by the weak (2

"Maybe it becomes a buddy, but do not call it a robot" - Seamless cooperation between companion robotics and smart homes

This paper describes the findings arising from ongoing qualitative usability evaluation studies on mobile companion robotics in smart home environments from two research projects focused on socio-technical innovation to support independent living (CompanionAble and Mobiserv). Key findings are described, and it is stated that the robotic companion, the smart home environment, and external services need to be seamlessly integrated to create a truly supportive and trusted system. The idea of robot personas is introduced, and based on our empirical observations, it is argued that the robot persona, rather than the physical embodiment, is the most important determinant of the degree of users' acceptance in terms of users' perceived trustability and responsiveness of the robot and therefore their sense of enhanced usability and satisfaction with such personal assistive systems. © 2011 Springer-Verlag

Real-world K-Anonymity applications:The KGEN approach and its evaluation in fraudulent transactions

K-Anonymity is a property for the measurement, management, and governance of the data anonymization. Many implementations of k-anonymity have been described in state of the art, but most of them are not practically usable over a large number of attributes in a “Big” dataset, i.e., a dataset drawing from Big Data. To address this significant shortcoming, we introduce and evaluate KGEN, an approach to K-anonymity featuring meta-heuristics, specifically, Genetic Algorithms to compute a permutation of the dataset which is both K-anonymized and still usable for further processing, e.g., for private-by-design analytics. KGEN promotes such a meta-heuristic approach since it can solve the problem by finding a pseudo-optimal solution in a reasonable time over a considerable load of input. KGEN allows the data manager to guarantee a high anonymity level while preserving the usability and preventing loss of information entropy over the data. Differently from other approaches that provide optimal global solutions compatible with smaller datasets, KGEN works properly also over Big datasets while still providing a good-enough K-anonymized but still processable dataset. Evaluation results show how our approach can still work efficiently on a real world dataset, provided by Dutch Tax Authority, with 47 attributes (i.e., the columns of the dataset to be anonymized) and over 1.5K+ observations (i.e., the rows of that dataset), as well as on a dataset with 97 attributes and over 3942 observations.</p

Model-checking for successor-invariant first-order formulas on graph classes of bounded expansion

A successor-invariant first-order formula is a formula that has access to an auxiliary successor relation on a structure's universe, but the model relation is independent of the particular interpretation of this relation. It is well known that successor-invariant formulas are more expressive on finite structures than plain first-order formulas without a successor relation. This naturally raises the question whether this increase in expressive power comes at an extra cost to solve the model-checking problem, that is, the problem to decide whether a given structure together with some (and hence every) successor relation is a model of a given formula. It was shown earlier that adding successor-invariance to first-order logic essentially comes at no extra cost for the model-checking problem on classes of finite structures whose underlying Gaifman graph is planar [1], excludes a fixed minor [2] or a fixed topological minor [3], [4]. In this work we show that the model-checking problem for successor-invariant formulas is fixed-parameter tractable on any class of finite structures whose underlying Gaifman graphs form a class of bounded expansion. Our result generalises all earlier results and comes close to the best tractability results on nowhere dense classes of graphs currently known for plain first-order logic

On the generalised colouring numbers of graphs that exclude a fixed minor

The generalised colouring numbers colr(G) and wcolr(G) were introduced by Kierstead and Yang as a generalisation of the usual colouring number, and have since then found important theoretical and algorithmic applications. In this paper, we dramatically improve upon the known upper bounds for generalised colouring numbers for graphs excluding a fixed minor, from the exponential bounds of Grohe et al. to a linear bound for the r-colouring number colr and a polynomial bound for the weak r-colouring number wcolr. In particular, we show that if G excludes Kt as a minor, for some fixed t≥4, then colr(G)≤(t−12)(2r+1) and wcolr(G)≤(r+t−2t−2)⋅(t−3)(2r+1)∈O(rt−1). In the case of graphs G of bounded genus g, we improve the bounds to colr(G)≤(2g+3)(2r+1) (and even colr(G)≤5r+1 if g=0, i.e. if G is planar) and wcolr(G)≤(2g+(r+22))(2r+1)

Internet-of-Things Architectures for Secure Cyber-Physical Spaces: the VISOR Experience Report

Internet of things (IoT) technologies are becoming a more and more widespread part of civilian life in common urban spaces, which are rapidly turning into cyber-physical spaces. Simultaneously, the fear of terrorism and crime in such public spaces is ever-increasing. Due to the resulting increased demand for security, video-based IoT surveillance systems have become an important area for research. Considering the large number of devices involved in the illicit recognition task, we conducted a field study in a Dutch Easter music festival in a national interest project called VISOR to select the most appropriate device configuration in terms of performance and results. We iteratively architected solutions for the security of cyber-physical spaces using IoT devices. We tested the performance of multiple federated devices encompassing drones, closed-circuit television, smart phone cameras, and smart glasses to detect real-case scenarios of potentially malicious activities such as mosh-pits and pick-pocketing. Our results pave the way to select optimal IoT architecture configurations -- i.e., a mix of CCTV, drones, smart glasses, and camera phones in our case -- to make safer cyber-physical spaces' a reality

Influence of Chronic Exposure to Treated Sewage Effluent on the Distribution of White Blood Cell Populations in Rainbow Trout (Oncorhynchus mykiss) Spleen

Impairment of immune function in aquatic animals has been proposed as a possible consequence of low-level contamination of surface waters with anthropogenic substances such as through the discharge of wastewater into rivers, lakes, and oceans. The study at hand investigated the effects of chronic (32 weeks) exposure to sewage treatment plant (STP) effluent on the prevalence and distribution of different leucocyte populations in spleen samples of rainbow trout (Oncorhynchus mykiss). To simulate an infection, fish were injected intraperitoneally (ip) with inactivated Aeromonas salmonicida salmonicida, 6 weeks prior to the termination of the experiment. Immunohistological analysis revealed a marked decrease in thrombocyte numbers, an increase of monocytes, altered distribution of B-cells, and higher surface immunoglobulin expression, as well as activation of MHC class II expression in the spleen after exposure to 15% (v/v) effluent. The most prominent finding of the present study, however, was the occurrence of intraplasmatic deposits or inclusions with strong autofluorescence in spleen sections from effluent-exposed trout. In addition to effluent effects, injection of trout with A. salmonicida stimulated infiltration of monocytes, increased staining intensity on thrombocytes, and enhanced MHC class I expression in larger leucocytes surrounding melanomacrophage centres. In general, the current study demonstrates a marked, potentially adverse effect of STP effluent on spleen leucocytes and on the integrity of spleen tissue. The observed response suggests a constant unspecific stimulation of different leucocyte populations and is reminiscent of chronic inflammatio

Frontal alpha asymmetry in response to stressor moderates the relation between parenting hassles and child externalizing problems

Inequitable urban environments are associated with toxic stress and altered neural social stress processing that threatens the development of self-regulation. Some children in these environments struggle with early onset externalizing problems that are associated with a variety of negative long-term outcomes. While previous research has linked parenting daily hassles to child externalizing problems, the role of frontal alpha asymmetry (FAA) as a potential modifier of this relationship has scarcely been explored. The present study examined mother-child dyads, most of whom were living in low socioeconomic status households in an urban environment and self-identified as members of racial minority groups. Analyses focused on frustration task electroencephalography (EEG) data from 67 children (mean age = 59.0 months, SD = 2.6). Mothers reported the frequency of their daily parenting hassles and their child’s externalizing problems. Frustration task FAA moderated the relationship between parenting daily hassles and child externalizing problems, but resting FAA did not. More specifically, children with left frontal asymmetry had more externalizing problems as their mothers perceived more hassles in their parenting role, but parenting hassles and externalizing problems were not associated among children with right frontal asymmetry. These findings lend support to the motivational direction hypothesis and capability model of FAA. More generally, this study reveals how individual differences in lateralization of cortical activity in response to a stressor may confer differential susceptibility to child behavioral problems with approach motivation (i.e., left frontal asymmetry) predicting externalizing problems under conditions of parental stress