On the reduction of the CSP dichotomy conjecture to digraphs

It is well known that the constraint satisfaction problem over general relational structures can be reduced in polynomial time to digraphs. We present a simple variant of such a reduction and use it to show that the algebraic dichotomy conjecture is equivalent to its restriction to digraphs and that the polynomial reduction can be made in logspace. We also show that our reduction preserves the bounded width property, i.e., solvability by local consistency methods. We discuss further algorithmic properties that are preserved and related open problems.Comment: 34 pages. Article is to appear in CP2013. This version includes two appendices with proofs of claims omitted from the main articl

Designing Efficient Taxi Pickup Operations at Airports

This paper provides a practical procedure for designing efficient taxi pickup operations at airports. How to do this effectively is an open question. Solutions are not available, and practices vary. They reflect different approaches to and lack of research on the subject. The solutions are often unsatisfactory. At many airports, passengers routinely suffer long waits outdoors, exposed to the elements, after a tiring journey. Such disagreeable experiences are avoidable. Designing efficient taxi pickup operations at airports is problematic. The peculiarities of the process preclude easy solutions. First, the process involves queuing, so system performance is a nonlinear function of the loads. Second, it features unstable transient situations, since travelers typically arrive in bulk over short periods. Third, traffic is significantly differentiated and consists of a wide variety of groups implying different service characteristics. Standard results from queuing theory thus do not have a useful application to this problem. The design process uses simulation that is based on detailed observation of local practices. It involves four steps: (a) detailed local measurements of the arrival of both travelers and taxis, and the service rates provided by taxis in different queuing positions; (b) creation and validation of a simulation model sufficiently detailed to account for these realities; (c) exploration of design alternatives to estimate the characteristics of the service they would provide; and (d) selection of a preferred design that properly balances efforts to minimize average and extreme wait times. The paper demonstrates the procedure through application to Lisbon International Airport, Portugal.SIMUL8 Corporatio

An Airport Experience Framework from a Tourism Perspective

This study, by integrating the perspectives of sociological, psychological, and service marketing and management, all of which affect the passenger experience, proposes a theoretical framework for the creation of the airport experience in relation to tourism. This research responds to the current phenomenon in which airports are offering other types of experiences within the airport terminal, expanding the role of an airport from being a utility for transportation into a place where various and different values can be offered. This research explores the current airport experience and adds to research on airport experience by clarifying ten key components necessary for airport passenger experience propositions based on existing research, the current industry phenomena, and the empirical study. The paper also underlines those components that can enhance passenger experience in relation to tourism and highlights the role that airports contribute to a destination

Multi-omic detection of <i>Mycobacterium leprae</i> in archaeological human dental calculus

Mineralized dental plaque (calculus) has proven to be an excellent source of ancient biomolecules. Here we present a Mycobacterium leprae genome (6.6-fold), the causative agent of leprosy, recovered via shotgun sequencing of sixteenth-century human dental calculus from an individual from Trondheim, Norway. When phylogenetically placed, this genome falls in branch 3I among the diversity of other contemporary ancient strains from Northern Europe. Moreover, ancient mycobacterial peptides were retrieved via mass spectrometry-based proteomics, further validating the presence of the pathogen. Mycobacterium leprae can readily be detected in the oral cavity and associated mucosal membranes, which likely contributed to it being incorporated into this individual's dental calculus. This individual showed some possible, but not definitive, evidence of skeletal lesions associated with early-stage leprosy. This study is the first known example of successful multi-omics retrieval of M. leprae from archaeological dental calculus. Furthermore, we offer new insights into dental calculus as an alternative sample source to bones or teeth for detecting and molecularly characterizing M. leprae in individuals from the archaeological record.publishedVersio

Second surgery for progressive glioblastoma: a multi‐centre questionnaire and cohort‐based review of clinical decision‐making and patient outcomes in current practice

PURPOSE: Glioblastoma prognosis is poor. Treatment options are limited at progression. Surgery may benefit, but no quality guidelines exist to inform patient selection. We sought to describe variations in surgical management at progression, highlight where further evidence is needed, and build towards a consensus strategy. METHODS: Current practice in selection of patients with progressive GBM for second surgery was surveyed online amongst specialists in the UK and Europe. We complemented this with an assessment of practice in a retrospective cohort study from six United Kingdom neurosurgical units. We used descriptive statistics to analyse the data. RESULTS: 234 questionnaire responses were received. Maintaining or improving patient quality of life was key to decision making, with variation as to whether patient age, performance status or intended extent of resection was relevant. MGMT methylation status was not important. Half considered no minimum time after first surgery. 288 patients were reported in the cohort analysis. Median time to second surgery from first surgery 390 days. Median overall survival 815 days, with no association between time to second surgery and time to death (p = 0.874). CONCLUSIONS: This is the most wide-ranging examination of contemporaneous practice in management of GBM progression. Without evidence-based guidelines, the variation is unsurprising. We propose consensus guidelines for consideration, to reduce heterogeneity in decision making, support data collection and analysis of factors influencing outcomes, and to inform clinical trials to establish whether second surgery improves patient outcomes, or simply selects to patients already performing well