3,623 research outputs found

    Adversarial Attacks on Remote User Authentication Using Behavioural Mouse Dynamics

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    Mouse dynamics is a potential means of authenticating users. Typically, the authentication process is based on classical machine learning techniques, but recently, deep learning techniques have been introduced for this purpose. Although prior research has demonstrated how machine learning and deep learning algorithms can be bypassed by carefully crafted adversarial samples, there has been very little research performed on the topic of behavioural biometrics in the adversarial domain. In an attempt to address this gap, we built a set of attacks, which are applications of several generative approaches, to construct adversarial mouse trajectories that bypass authentication models. These generated mouse sequences will serve as the adversarial samples in the context of our experiments. We also present an analysis of the attack approaches we explored, explaining their limitations. In contrast to previous work, we consider the attacks in a more realistic and challenging setting in which an attacker has access to recorded user data but does not have access to the authentication model or its outputs. We explore three different attack strategies: 1) statistics-based, 2) imitation-based, and 3) surrogate-based; we show that they are able to evade the functionality of the authentication models, thereby impacting their robustness adversely. We show that imitation-based attacks often perform better than surrogate-based attacks, unless, however, the attacker can guess the architecture of the authentication model. In such cases, we propose a potential detection mechanism against surrogate-based attacks.Comment: Accepted in 2019 International Joint Conference on Neural Networks (IJCNN). Update of DO

    The political cost of corruption: scandals, campaign finance, and reelection in the Brazilian chamber of deputies

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    Políticos notoriamente envolvidos em escândalos de corrupção logram reelegerse apesar da opinião pública em geral condenar a corrupção. Nesse artigo nos debruçamos sobre esse paradoxo examinando o efeito de escândalos de corrupção no comportamento de membros da Câmara dos Deputados. Em particular, focamos em suas estratégias de financiamento de campanha e escolhas de carreira. Para explorar esses temas utilizamos um banco de dados original que contém informações sobre todos os deputados e deputadas federais de 1995 a 2010. Embora muitos parlamentares acusados de corrupção sejam penalizados nas urnas, mostramos que gastos de campanha elevados atenuam o efeito negativo de escândalos. Nossos resultados são robustos para várias especificações e controlando por explicações alternativas. Este artigo apresenta uma discussão original das estratégias utilizadas por políticos corruptos para se manterem no poder. Mostramos que se tornam imunes às consequências eleitorais de escândalos se gastarem acima de patamares específicos. Esses achados são muito relevantes para discussões normativas em termos de reforma política que visam fortalecer accountability eleitoral no Brazil.While corruption is widely disapproved of, some corrupt politicians continue to win elections. We tackle this paradox by examining the effects of malfeasance scandals in politicians' behavior. In particular, we focus on their campaign finance strategies and career choices. We explore these issues empirically with an original dataset that includes all lower-house members of Congress (MCs) in Brazil from 1995 to 2010. Although tainted incumbents tend to be penalized electorally, we show that campaign spending attenuates this effect. These results are robust, controlling for a host of potential confounders and biases. Hence, we offer a first exploration of incumbents' strategies to avoid the electoral cost of their publicized wrongdoings. Above a certain threshold of funding, Brazilian members of Congress become impervious to negative exposure, regardless of the severity of their ethical and/or criminal violations. These results carry important normative consequences in terms of regulating campaign financing as a means of improving accountability

    Health-related Quality Of Life And Self-reported Long-term Conditions: A Population-based Survey

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    Conselho Nacional de Desenvolvimento CientĂ­fico e TecnolĂłgico (CNPq)To estimate and compare the effect of self-reported long-term health conditions and sociodemographic factors on perceived health-related quality of life (HRQoL). Methods: A population-based survey of adults (18 to 65 years) living in Brasilia, Brazil, was conducted in 2012. Descriptive and multivariate analyses using a Tobit model were performed with data on sociodemographic variables, self-reported conditions, and the European Quality of Life-5 Dimensions (EQ-5D) health states, providing utility scores (preferred health state) between 0 and 1 for HRQoL estimates. Results: The mean utility of 1,820 adults interviewed (mean age: 38.4612.6 years) was 0.883 (95% confidence interval [95% CI] 0.874-0.892), with 76.2% in the highest utility range (0.8 to 1.0). EQ-5D dimensions with moderate problems were pain/discomfort (33.8%) and anxiety/depression (20.5%). Serious problems were reported by only 0.3% of the sample in the mobility and self-care domain and by 3.1% in the pain/discomfort domain. Multivariate analysis revealed reduced HRQoL in individuals with depression, diabetes, and hypertension. Living in satellite towns (outside the city core), belonging to a lower economic class, or not being formally employed were also associated with decreased HRQoL. Beta coefficients for these impacts ranged from -0.033 (not formally employed) to -0.141 (depression), reflecting the strongest impact. Conclusion: Of the long-term health conditions studied, depression had the greatest impact on HRQoL. Social class, employment status, and place of residence also affected HRQoL.3916268Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) [564831/2010-7]Conselho Nacional de Desenvolvimento CientĂ­fico e TecnolĂłgico (CNPq

    Dynamic formation of oriented patches in chondrocyte cell cultures

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    Growth factors have a significant impact not only on the growth dynamics but also on the phenotype of chondrocytes (Barbero etal. in J. Cell. Phys. 204:830-838, 2005). In particular, as chondrocytes approach confluence, the cells tend to align and form coherent patches. Starting from a mathematical model for fibroblast populations at equilibrium (Mogilner etal. in Physica D 89:346-367, 1996), a dynamic continuum model with logistic growth is developed. Both linear stability analysis and numerical solutions of the time-dependent nonlinear integro-partial differential equation are used to identify the key parameters that lead to pattern formation in the model. The numerical results are compared quantitatively to experimental data by extracting statistical information on orientation, density and patch size through Gabor filter

    Transmission of viruses via our microbiomes.

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    BackgroundBacteria inhabiting the human body have important roles in a number of physiological processes and are known to be shared amongst genetically-related individuals. Far less is known about viruses inhabiting the human body, but their ecology suggests they may be shared between close contacts.ResultsHere, we report the ecology of viruses in the guts and mouths of a cohort and demonstrate that substantial numbers of gut and oral viruses were shared amongst genetically unrelated, cohabitating individuals. Most of these viruses were bacteriophages, and each individual had distinct oral and gut viral ecology from their housemates despite the fact that some of their bacteriophages were shared. The distribution of bacteriophages over time within households indicated that they were frequently transmitted between the microbiomes of household contacts.ConclusionsBecause bacteriophages may shape human oral and gut bacterial ecology, their transmission to household contacts suggests they could have substantial roles in shaping the microbiota within a household

    Examining the inertial subrange with nanoscale cross-wire measurements of turbulent pipe flow at high Reynolds number near the centreline [post-print]

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    Highly resolved, two-component velocity measurements were made near the centreline of turbulent pipe flow for Reynolds numbers in the range . These unique data were obtained with a nanoscale cross-wire probe and used to examine the inertial subrange scaling of the longitudinal and transverse velocity components. Classical dissipation rate estimates were made using both the integration of one-dimensional dissipation spectra for each velocity component and the third-order moment of the longitudinal structure function. Although the second-order moments and one-dimensional spectra for each component showed behaviour consistent with local isotropy, clear inertial range similarity and behaviour were not exhibited in the third-order structure functions at these Reynolds numbers. When corrected for the effects of radial inhomogeneities at the centreline following the generalized expression of Danaila et al. (J. Fluid Mech., vol. 430, 2001, pp. 87-109), re-derived for the pipe flow domain, the third-order moments of the longitudinal structure function exhibited a clearer plateau per the classical Kolmogorov \u27four-fifths law\u27. Similar corrections described by Danaila et al. (J. Fluid Mech., vol. 430, 2001, pp. 87-109) applied to the analogous equation for the mixed structure functions (i.e. the \u27four-thirds law\u27) also yielded improvement over all ranges of scale, improving with increasing Reynolds number. The rate at which the \u27four-fifths\u27 law and \u27four-thirds\u27 law were approached by the third-order structure functions was found to be more gradual than decaying isotropic turbulence for the same Reynolds numbers

    The use of Kolmogorov-Smirnov test in event-by-event analysis

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    We propose to use the Kolmogorov-Smirnov test to uncover non-statistical differences between events created in heavy ion collisions within the same centrality class. The advantage of the method over other approaches which are currently in use, is that it is sensitive to any difference between the events and is not restricted to simple moments of the distribution of hadrons. The particular application examined here is the identification of the fireball decay due to spinodal fragmentation and/or sudden rise of the bulk viscosity.Comment: 4 pages, 2 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee v2 one typo corrected and references update

    Ten Years after 9/11: The Changing Terrorist Threat

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