Nonequilibrium Phase Transitions in Directed Small-World Networks

Many social, biological, and economic systems can be approached by complex networks of interacting units. The behaviour of several models on small-world networks has recently been studied. These models are expected to capture the essential features of the complex processes taking place on real networks like disease spreading, formation of public opinion, distribution of wealth, etc. In many of these systems relations are directed, in the sense that links only act in one direction (outwards or inwards). We investigate the effect of directed links on the behaviour of a simple spin-like model evolving on a small-world network. We show that directed networks may lead to a highly nontrivial phase diagram including first and second-order phase transitions out of equilibrium.Comment: 4 pages, RevTeX format, 4 postscript figs, uses eps

The HV1 proton channel of Lingulodinium polyedrum localizes to the bioluminescent scintillon

In 1972, J. Woodland Hastings and colleagues predicted the existence of a proton selective channel that opens in response to depolarizing voltage (HV1) across the vacuole membrane of bioluminescent dinoflagellates and conducts protons into specialized luminescence compartments (scintillons), thus causing the pH drop that triggers the light flash. RNA-Seq data from several luminescent dinoflagellate species provided candidate HV1 genes. When expressed in mammalian cells, the predicted HV1 from Lingulodinium polyedrum displays the hallmark properties of bona fide proton channels, including time-dependent opening with depolarization, perfect proton selectivity, and characteristic pH dependent gating. RT-PCR and Western blotting confirm expression of HV1 in L. polyedrum and isolated scintillons. Fluorescence confocal microscopy of L. polyedrum cells stained with antibodies to luminescence proteins luciferase (LCF), luciferin binding protein (LBP) and to HV1 (LpHV1) reveal structures consistent with HV1’s proposed function in bioluminescence. Isolated scintillons immunostained with antibody to LpHV1 displayed LpHV1 expression, showing that LpHV1 is present in this organelle. In addition, proteomics analysis demonstrated that isolated scintillon preparations contain peptides that map to LpHV1, including a portion of the epitope used to raise the antibody. These results indicate that LpHV1 is the voltage gated proton channel that triggers bioluminescence in L. polyedrum

Anytime coalition structure generation on synergy graphs

We consider the coalition structure generation (CSG) problem on synergy graphs, which arises in many practical applications where communication constraints, social or trust relationships must be taken into account when forming coalitions. We propose a novel representation of this problem based on the concept of edge contraction, and an innovative branch and bound approach (CFSS), which is particularly efficient when applied to a general class of characteristic functions. This new model provides a non-redundant partition of the search space, hence allowing an effective parallelisation. We evaluate CFSS on two benchmark functions, the edge sum with coordination cost and the collective energy purchasing functions, comparing its performance with the best algorithm for CSG on synergy graphs: DyCE. The latter approach is centralised and cannot be efficiently parallelised due to the exponential memory requirements in the number of agents, which limits its scalability (while CFSS memory requirements are only polynomial). Our results show that, when the graphs are very sparse, CFSS is 4 orders of magnitude faster than DyCE. Moreover, CFSS is the first approach to provide anytime approximate solutions with quality guarantees for very large systems (i.e., with more than 2700 agents

NR-SLAM: Non-Rigid Monocular SLAM

In this paper we present NR-SLAM, a novel non-rigid monocular SLAM system founded on the combination of a Dynamic Deformation Graph with a Visco-Elastic deformation model. The former enables our system to represent the dynamics of the deforming environment as the camera explores, while the later allows us to model general deformations in a simple way. The presented system is able to automatically initialize and extend a map modeled by a sparse point cloud in deforming environments, that is refined with a sliding-window Deformable Bundle Adjustment. This map serves as base for the estimation of the camera motion and deformation and enables us to represent arbitrary surface topologies, overcoming the limitations of previous methods. To assess the performance of our system in challenging deforming scenarios, we evaluate it in several representative medical datasets. In our experiments, NR-SLAM outperforms previous deformable SLAM systems, achieving millimeter reconstruction accuracy and bringing automated medical intervention closer. For the benefit of the community, we make the source code public.Comment: 12 pages, 7 figures, submited to the IEEE Transactions on Robotics (T-RO

Trust-Based Mechanisms for Robust and Efficient Task Allocation in the Presence of Execution Uncertainty

Vickrey-Clarke-Groves (VCG) mechanisms are often used to allocate tasks to selfish and rational agents. VCG mechanisms are incentive-compatible, direct mechanisms that are efficient (i.e. maximise social utility) and individually rational (i.e. agents prefer to join rather than opt out). However, an important assumption of these mechanisms is that the agents will always successfully complete their allocated tasks. Clearly, this assumption is unrealistic in many real-world applications where agents can, and often do, fail in their endeavours. Moreover, whether an agent is deemed to have failed may be perceived differently by different agents. Such subjective perceptions about an agent’s probability of succeeding at a given task are often captured and reasoned about using the notion of trust. Given this background, in this paper, we investigate the design of novel mechanisms that take into account the trust between agents when allocating tasks. Specifically, we develop a new class of mechanisms, called trust-based mechanisms, that can take into account multiple subjective measures of the probability of an agent succeeding at a given task and produce allocations that maximise social utility, whilst ensuring that no agent obtains a negative utility. We then show that such mechanisms pose a challenging new combinatorial optimisation problem (that is NP-complete), devise a novel representation for solving the problem, and develop an effective integer programming solution (that can solve instances with about 2×105 possible allocations in 40 seconds).

Dental Treatment under General Anesthesia in Healthy and Medically Compromised/Developmentally Disabled Children: A Comparative Study

Aim: To compare the type, number of procedures and working time of dental treatment provided under dental general anesthesia (DGA) in healthy and medically compromised/developmentally disabled children (MCDD children). Design: This cross-sectional prospective study involved 80 children divided into two groups of 40 children each. Group 1 consisted of healthy and Group 2 consisted of MCDD children. Results: Healthy children needed more working time than MCDD children, the means being 161±7.9 and 84±5.7 minutes, respectively (P= 0.0001). Operative dentistry and endodontic treatments showed a significant statistical difference (P= 0.0001). The means of procedures were 17±5.0 for healthy children and 11±4.8 for MCDD children (P= 0.0001). Conclusions: Healthy children needed more extensive dental treatment than MCDD children under DGA. The information from this sample of Mexican children could be used as reference for determining trends both within a facility as well as in comparing facilities in cross-population studies

Introducing Polyautoimmunity: Secondary Autoimmune Diseases No Longer Exist

Similar pathophysiological mechanisms within autoimmune diseases have stimulated searches for common genetic roots. Polyautoimmunity is defined as the presence of more than one autoimmune disease in a single patient. When three or more autoimmune diseases coexist, this condition is called multiple autoimmune syndrome (MAS). We analyzed the presence of polyautoimmunity in 1,083 patients belonging to four autoimmune disease cohorts. Polyautoimmunity was observed in 373 patients (34.4%). Autoimmune thyroid disease (AITD) and Sjögren's syndrome (SS) were the most frequent diseases encountered. Factors significantly associated with polyautoimmunity were female gender and familial autoimmunity. Through a systematic literature review, an updated search was done for all MAS cases (January 2006–September 2011). There were 142 articles retrieved corresponding to 226 cases. Next, we performed a clustering analysis in which AITD followed by systemic lupus erythematosus and SS were the most hierarchical diseases encountered. Our results indicate that coexistence of autoimmune diseases is not uncommon and follows a grouping pattern. Polyautoimmunity is the term proposed for this association of disorders, which encompasses the concept of a common origin for these diseases

A Qualitative Study Investigating How First-Year Engineering Students\u27 Value Beliefs Influence their Choice of Selecting an Engineering Major

First year engineering (FYE) programs are gaining popularity across universities in the United States. In addition to providing general engineering knowledge and skills to undergraduate freshmen, FYE programs also provide students with diverse opportunities to help them select the engineering discipline they will further pursue. The 2014 cohort of the FYE program of a large Midwestern university was the sample used for a two-phased study. The aim of the study was to understand how students make informed decisions of which engineering major to pursue and to help FYE administration to improve the resources they provide students. The first phase of the study focused on understanding the sources of information students used to make their decision. A preliminary analysis of student surveys indicated that the most important activity they are performing to select a major is “Self-Led Exploration” (SLE) of engineering disciplines. This paper focuses on the second part of the study, which aims to qualitatively answer the research question: How do students’ value beliefs influence their decision of which engineering major to pursue? Answers to open ended questions from FYE surveys also served to inform this second study. Moreover, a brief examination of both the interviews and the surveys suggested a possible overlapping between the sources students used to inform their decision and the reasons why they selected a particular major. From that overlap, a secondary research question emerged: What is the relation between students’ value beliefs of the engineering disciplines and the type of sources they use to inform their decision of a major? To analyze our transcripts we used Eccle’s expectancy-value theory. We hypothesize that students’ value beliefs, how well a task aligns with their personal values, goals, and needs, influences their career choice and the type of resources they use to inform themselves