Universality of collapsing two-dimensional self-avoiding trails

Results of a numerically exact transfer matrix calculation for the model of Interacting Self-Avoiding Trails are presented. The results lead to the conclusion that, at the collapse transition, Self-Avoiding Trails are in the same universality class as the O(n=0) model of Blote and Nienhuis (or vertex-interacting self-avoiding walk), which has thermal exponent $\nu=12/23$, contrary to previous conjectures.Comment: Final version, accepted for publication in Journal of Physics A; 9 pages; 3 figure

Fibres as shear reinforcement in RC beams: an overview on assessment of material properties and design approaches

It is recognized that understanding at a material level is needed in the development of rational, physical-mechanical, models for predicting the behaviour of fibre reinforced concrete at service and strength limit conditions. To this end, understanding the post-cracking mechanisms of the fibres, and their symbiotic relationship with the cementitious matrix that surrounds them, is required for the development of realistic modelling approaches that accurately represent empirical observations. Several experimental test setups and inverse analysis procedures have been proposed to derive the fundamental stress-crack width (–w) law, but a consensus still does not exists on the best strategy for its determination. In structures governed by shear, fibre reinforcement increases the stiffness and shear stress transfer across a crack, but a methodology to capture the contribution of fibres in this regards is challenging. To overcome this, a clear strategy is needed in deriving relationships that simulate fibre reinforcement mechanisms in the mobilized fracture modes and, also, develop design approaches capable of capturing the relevant contributions of the fibres. This study firstly reviews current inverse analysis models used to describe the tensile (Model I fracture) relationship for FRC and, secondly, discusses a newly proposed model, referred to as the integrated shear model (ISM). The ISM is developed from mesoscale observations from gamma- and X-ray imaging on FRC elements under Modes I and II fracture conditions. The resulting model is compared to test data reported in the literature and a good correlation is observed.The authors wish to acknowledge the grant SFRH/BSAB/114302/2016 provided by FCT and the Australian Research Council grant DP150104107, as well as the support provided by the UNSW for the research activities carried out under the status of Visiting Professorial Fellow for the first author. The support of the FCT through the project PTDC/ECM EST/2635/2014 is also acknowledged

Old Dogs Can Learn to Like New Tricks: One Instructor\u27s Change in Attitude to Online Instruction from 2009-2017

This qualitative case study examined a veteran instructor\u27s change in attitude about university online instruction. After a short review of the literature and explanation of the project, researchers conducted a content analysis of an instructor\u27s annual self-reports about his online teaching of a graduate course in the social sciences. The self-reports were written between 2009 and 2017. The researchers also examined students\u27 end-of-semester evaluation scores about the course and instructor. Results suggest that the teacher began online teaching with a mixed attitude. After four years of teachin ghte online course (delivered once each spring) the instructor reported more about content issues and less about online delivery. In the final the period (2016-17) the researchers found that the instructor was invested fully in online delivery. Although the study is not generalizable, its results suggest that instructors who stay with an online system over an extended period of time may gain more confidence in the efficacy on online delivery. The findings complement previous findings in the literature about faculty attitudes toward technology use in instruction

An integrated approach for predicting the shear capacity of fibre reinforced concrete beams

This paper describes the development of an integrated design approach for determining shear capacity of flexurally reinforced steel fibre reinforced concrete members. The approach considers fibre distribution profile, fibre pull-out resistance and the modified compression field theory integrated using a comprehensive strategy. To assess the performance of the developed model, a database consisting of 122 steel fibre reinforced and prestressed concrete beams failing in shear was assembled from available literature. The model predictions were shown to correlate well with the test data. The performance of the analytical model was also compared to predictions attained by the two approaches recommended by the fib Model Code 2010, one based on an empirical equation and the other on the modified compression field theory approach. The predictive performance of the proposed approach was also assessed by using the Demerit Points Classification (DPC), being the prediction as better as lower is the total penalty points provided by the classification. The model developed in this paper demonstrated a superior performance to those of the Model Code, with a higher predictive performance in terms of safety and reliability.The authors wish to acknowledge the grant SFRH/BSAB/114302/2016 provided by FCT and the Australian Research Council grant DP150104107, as well as the support provided by the UNSW Sydney for the research activities carried out under the status of Visiting Professorial Fellow for the first author. The support of the FCT through the project PTDC/ECM-EST/2635/2014 is also acknowledged.info:eu-repo/semantics/publishedVersio

Stability and Control Characteristics at a Mach Number of 1.97 of an Airplane Configuration Having Two Types of Variable-sweep Wings

Wind tunnel tests of stability and control of variable sweep wing aircraft at Mach 1.9

From Physical to Cyber: Escalating Protection for Personalized Auto Insurance

Nowadays, auto insurance companies set personalized insurance rate based on data gathered directly from their customers' cars. In this paper, we show such a personalized insurance mechanism -- wildly adopted by many auto insurance companies -- is vulnerable to exploit. In particular, we demonstrate that an adversary can leverage off-the-shelf hardware to manipulate the data to the device that collects drivers' habits for insurance rate customization and obtain a fraudulent insurance discount. In response to this type of attack, we also propose a defense mechanism that escalates the protection for insurers' data collection. The main idea of this mechanism is to augment the insurer's data collection device with the ability to gather unforgeable data acquired from the physical world, and then leverage these data to identify manipulated data points. Our defense mechanism leveraged a statistical model built on unmanipulated data and is robust to manipulation methods that are not foreseen previously. We have implemented this defense mechanism as a proof-of-concept prototype and tested its effectiveness in the real world. Our evaluation shows that our defense mechanism exhibits a false positive rate of 0.032 and a false negative rate of 0.013.Comment: Appeared in Sensys 201

Examining c-di-GMP and possible quorum sensing regulation in Pseudomonas fluorescens SBW25:links between intra and inter-cellular regulation benefits community cooperative activities such as biofilm formation

Bacterial success in colonizing complex environments requires individual response to micro-scale conditions as well as community-level cooperation to produce large-scale structures such as biofilms. Connecting individual and community responses could be achieved by linking the intracellular sensory and regulatory systems mediated by bis-(3′-5′)-cyclic dimeric guanosine monophosphate (c-di-GMP) and other compounds of individuals with intercellular quorum sensing (QS) regulation controlling populations. There is growing evidence to suggest that biofilm formation by many pseudomonads is regulated by both intra and intercellular systems, though in the case of the model Pseudomonas fluorescens SBW25 Wrinkly Spreader in which mutations increasing c-di-GMP levels result in the production of a robust cellulose-based air-liquid interface biofilm, no evidence for the involvement of QS regulation has been reported. However, our recent review of the P. fluorescens SBW25 genome has identified a potential QS regulatory pathway and other QS–associated genes linked to c-di-GMP homeostasis, and QS signal molecules have also been identified in culture supernatants. These findings suggest a possible link between c-di-GMP and QS regulation in P. fluorescens SBW25 which might allow a more sophisticated and responsive control of cellulose production and biofilm formation when colonising the soil and plant-associated environments P. fluorescens SBW25 normally inhabits.Анализ ц-ди-ГМФ и возможного чувства кворума у Pseudomonas fluorescens SBW 25: связь между внутри и межклеточной регуляцией способствует кооперативному поведению в сообществе и формированию биоплёнкиУспешность бактериальной колонизации сложных экониш требует индивидуального ответа на изменения условий на микроуровне равно как и кооперации на уровне сообщества для продукции таких крупно масштабных структур как биоплёнки. Координация индивидуальных ответ ов и ответов сообщества может быть достигнута путем связывания внутриклеточных сенсорных и регуляторных систем, опосредуемых бис-(3',5')-циклическим димерным гуанозинмонофосфатом (ц-ди-ГМФ) и другими соединениями индивидуумов с межклеточной регуляцией - чувством кворума (ЧК), контролирующем популяци ю. Накапливается всё больше доказательств того, что формирование биопленки многими псевдомонадами регулируется как внутри клеточными, так и меж клеточными регуляторными системами, хотя в случае модельной Pseudomonas fluorescens SBW25 Wrinkly Spreader, у которой мутации, повышающ ие уровни ц-ди-ГМФ, приводят к созданию прочной целлюлозной биоплёнки на границе раздела фаз воздух-жидкость, не было обнаружено ни ка кого свидетельства вовлечения кворум-зависимой регуляции. Однако наш недавний обзор генома P. fluorescens SBW25 выявил потенциальный ЧК-зависимый регуляторный пу ть и другие ЧК-зависимые гены, связанные с гомеостазом ц-ди-ГМФ, а молекулы ЧК-сигналинга были идентифицированы в культуре. Эти данные свидетельствуют о возможной связи между ц-ди-ГМФ-регуляцией и ЧК у P. fluorescens SBW25, что позволяет более сложный и гибкий контроль над продукцией целлюлозы и образовани ем биопленки при колонизации почв и экониш, aссоциированных с растениям и, - естественными средами обитания P. fluorescens SBW25

Surface critical behaviour of the Interacting Self-Avoiding Trail on the square lattice

The surface critical behaviour of the interacting self-avoiding trail is examined using transfer matrix methods coupled with finite-size scaling. Particular attention is paid to the critical exponents at the ordinary and special points along the collapse transition line. The phase diagram is also presented.Comment: Journal of Physics A (accepted

Sheared bioconvection in a horizontal tube

The recent interest in using microorganisms for biofuels is motivation enough to study bioconvection and cell dispersion in tubes subject to imposed flow. To optimize light and nutrient uptake, many microorganisms swim in directions biased by environmental cues (e.g. phototaxis in algae and chemotaxis in bacteria). Such taxes inevitably lead to accumulations of cells, which, as many microorganisms have a density different to the fluid, can induce hydrodynamic instabilites. The large-scale fluid flow and spectacular patterns that arise are termed bioconvection. However, the extent to which bioconvection is affected or suppressed by an imposed fluid flow, and how bioconvection influences the mean flow profile and cell transport are open questions. This experimental study is the first to address these issues by quantifying the patterns due to suspensions of the gravitactic and gyrotactic green biflagellate alga Chlamydomonas in horizontal tubes subject to an imposed flow. With no flow, the dependence of the dominant pattern wavelength at pattern onset on cell concentration is established for three different tube diameters. For small imposed flows, the vertical plumes of cells are observed merely to bow in the direction of flow. For sufficiently high flow rates, the plumes progressively fragment into piecewise linear diagonal plumes, unexpectedly inclined at constant angles and translating at fixed speeds. The pattern wavelength generally grows with flow rate, with transitions at critical rates that depend on concentration. Even at high imposed flow rates, bioconvection is not wholly suppressed and perturbs the flow field.Comment: 19 pages, 9 figures, published version available at http://iopscience.iop.org/1478-3975/7/4/04600