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Learning models from data with measurement error: Tackling underreporting

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arXiv 2019年

作者： Adams, Roy Ji, Yuelong Wang, Xiaobin Saria, Suchi Department of Computer Science Johns Hopkins University Center on the Life Origins of Disease Department of Population Family and Reporductive Health Johns Hopkins University Bloomberg School of Public Health Department of Applied Math and Statistics Johns Hopkins University Bayesian Health.

Measurement error in observational datasets can lead to systematic bias in inferences based on these datasets. As studies based on observational data are increasingly used to inform decisions with real-world impact, it is critical that we develop a robust set of techniques for analyzing and adjusting for these biases. In this paper we present a method for estimating the distribution of an outcome given a binary exposure that is subject to underreporting. Our method is based on a missing data view of the measurement error problem, where the true exposure is treated as a latent variable that is marginalized out of a joint model. We prove three different conditions under which the outcome distribution can still be identified from data containing only error-prone observations of the exposure. We demonstrate this method on synthetic data and analyze its sensitivity to near violations of the identifiability conditions. Finally, we use this method to estimate the effects of maternal smoking and opioid use during pregnancy on childhood obesity, two import problems from public health. Using the proposed method, we estimate these effects using only subject-reported drug use data and substantially refine the range of estimates generated by a sensitivity analysis-based approach. Further, the estimates produced by our method are consistent with existing literature on both the effects of maternal smoking and the rate at which subjects underreport smoking. Copyright © 2019, The Authors. All rights reserved.

关键词： Measurement errors

Privacy-Preserving Linear Regression for Brain-computer Interface Applications

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Privacy-Preserving Linear Regression for Brain-Computer Inte...

2018 IEEE International Conference on Big Data, Big Data 2018

作者： Agarwal, Anisha Dowsley, Rafael McKinney, Nicholas D. Wu, Dongrui Lin, Chin-Teng Cock, Martine De Nascimento, Anderson School of Engineering and Technology University of Washington Tacoma United States Dept. of Computer Science Aarhus University Aarhus Denmark School of Automation Huazhong University of Science and Technology Wuhan China School of Software University of Technology Sydney Australia Dept. of Applied Math. Comp. Sc. and Statistics Ghent University Belgium

ISBN: (纸本)9781538650356

Many machine learning (ML) applications rely on large amounts of personal data for training and inference. Among the most intimate exploited data sources is electroencephalogram (EEG) data. The emergence of consumer-grade, low-cost brain-computer interfaces (BCIs) and corresponding software development kits1 is bringing the use of BCI within reach of application developers. The access that BCI applications have to neural signals rightly raises privacy concerns. Application developers can easily gain knowledge beyond the professed scope from unprotected EEG signals, including passwords, ATM PINs, and other personal data [1]. The challenge we address is how to engage in meaningful ML with EEG data while protecting the privacy of users. © 2018 IEEE.

关键词： Electroencephalography

Antimicrobial activity of Acorus calamus L. rhizome extract and its total flavonoid and phenolic contents

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AIP Conference Proceedings 2019年第1期2155卷

作者： Wiwik Susanah Rita I. Made Dira Swantara Gusti Ayu Primandani Utami 1Chemistry Department Faculty of Math. And Natural Science Udayana University Bali Indonesia 2Magister of Applied Chemistry Department Faculty of Math. And Natural Science Udayana University Bali Indonesia

Acorus calamus L. rhizome has potential activity as an antimicrobial agent. This study aims to evaluate the antimicrobial activity of the rhizome extracts and its total flavonoid and phenolic contents. Extraction was carried out by using ethanol at room temperature followed by fractionation into n-hexane, ethyl acetate, and n-butanol. Antimicrobial activity towards Escherichia coli, Staphylococcus aureus, and Candida albicans were evaluated by agar diffusion method. Total flavonoid and phenolic contents were determined by UV-Vis Spectrophotometer using the standard of quercetin and gallic acid, respectively. The A. calamus rhizome ethyl acetate fraction strongly inhibited Escherichia coli, Staphylococcus aureus and Candida albicans, followed by n-butanol and n-hexane fractions, respectively. There was no inhibition of water fraction towards all the microbes. Total flavonoid contents of ethyl acetate, butanol, n-hexane, and water fractions were successively 2978.34, 399.07, 142, 23, and 14.80 mg QE/100g, while total phenolic contents of those fractions were 1820.51, 329.71, 237.81, and 74.36 mg GAE/100g, respectively. The results show that there is a positive correlation between antimicrobial activity and its total flavonoid and phenolic contents.

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Algebraic approach to promise constraint satisfaction

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arXiv 2018年

作者： Barto, Libor Bulín, Jakub Krokhin, Andrei Opršal, Jakub Department of Algebra Fac. Math. & Phys. Charles University Prague Czech Republic Department of Computer Science Durham University United Kingdom

The complexity and approximability of the constraint satisfaction problem (CSP) has been actively studied over the last 20 years. A new version of the CSP, the promise CSP (PCSP) has recently been proposed, motivated by open questions about the approximability of variants of satisfiability and graph colouring. The PCSP significantly extends the standard decision CSP. The complexity of CSPs with a fixed constraint language on a finite domain has recently been fully classified, greatly guided by the algebraic approach, which uses polymorphisms ' high-dimensional symmetries of solution spaces ' to analyse the complexity of problems. The corresponding classification for PCSPs is wide open and includes some long-standing open questions, such as the complexity of approximate graph colouring, as special cases. The basic algebraic approach to PCSP was initiated by Brakensiek and Guruswami, and in this paper we significantly extend it and lift it from concrete properties of polymorphisms to their abstract properties. We introduce a new class of problems that can be viewed as algebraic versions of the (Gap) Label Cover problem, and show that every PCSP with a fixed constraint language is equivalent to a problem of this form. This allows us to identify a "measure of symmetry" that is well suited for comparing and relating the complexity of different PCSPs via the algebraic approach. We demonstrate how our theory can be applied by giving both general and specific hardness/tractability results. Among other things, we improve the state-of-the-art in approximate graph colouring by showing that, for any k ≥ 3, it is NP-hard to find a (2k − 1)-colouring of a given k-colourable graph. Copyright © 2018, The Authors. All rights reserved.

关键词： Constraint satisfaction problems

A simple method to find all solutions to the functional equation of the smoothing transform

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arXiv 2019年

作者： Alsmeyer, Gerold Mallein, Bastien Inst. Math. Stochastics Department of Mathematics and Computer Science University of Münster Orléans-Ring 10 MünsterD-48149 Germany LAGA UMR 7539 Université Paris 13 - Sorbonne Paris Cité Université Paris 8 99 avenue Jean-Baptiste Clément Villetaneuse93430 France

Given a nonincreasing null sequence T = (Tj )j≽1 of nonnegative random variables satisfying some classical integrability assumptions and (Equation presented) for some α > 0, we characterize the solutions of the well-known functional equation (Equation presented), related to the so-called smoothing transform and its min-type variant. In order to do so within the class of nonnegative and nonincreasing functions, we provide a new three-step method whose merits are that (1) it simplifies earlier approaches in some relevant aspects, (2) it works under weaker, close to optimal conditions in the so-called boundary case when (Equation presented), (3) it can be expected to work as well in more general setups like random environment. At the end of this article, we also give a one-to-one correspondence between those solutions that are Laplace transforms and thus correspond to the fixed points of the smoothing transform and certain fractal random measures. The latter are defined on the boundary of a weighted tree related to an associated branching random *** Codes 39B22, 60E05, 60J85, 60G42 Copyright © 2019, The Authors. All rights reserved.

关键词： Stochastic systems

Election Score Can Be Harder Than Winner

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arXiv 2018年

作者： Fitzsimmons, Zack Hemaspaandra, Edith Dept. of Math. and Computer Science College of Holy Cross WorcesterMA01610 United States Department of Computer Science Rochester Institute of Technology RochesterNY14623 United States

Election systems based on scores generally determine the winner by computing the score of each candidate and the winner is the candidate with the best score. It would be natural to expect that computing the winner of an election is at least as hard as computing the score of a candidate. We show that this is not always the case. In particular, we show that for Young elections for dichotomous preferences the winner problem is easy, while determining the score of a candidate is hard. This complexity behavior has not been seen before and is unusual. The easiness of the winner problem for dichotomous Young crucially uses the fact that dichotomous preferences guarantee the transitivity of the majority relation. In addition to dichotomous preferences we also look at single-peaked preferences, the most well-studied domain restriction that guarantees the transitivity of the majority relation. We show that for the three major hard election systems and their natural variants, dichotomous Young is the only case where winner is easy and score is hard. This also solves an open question from Peters (2018), by providing a polynomial-time algorithm for Dodgson score for single-peaked electorates. Copyright © 2018, The Authors. All rights reserved.

关键词： Polynomial approximation

The master stability function for synchronization in simplicial complexes

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arXiv 2020年

作者： Gambuzza, L.V. Di Patti, F. Gallo, L. Lepri, S. Romance, M. Criado, R. Frasca, Mattia Latora, V. Boccaletti, S. Department of Electrical Electronics and Computer Science Engineering University of Catania Catania95125 Italy CNR-Institute of Complex Systems Via Madonna del Piano Sesto Fiorentino Florence50019 Italy Department of Physics and Astronomy University of Catania Catania95125 Italy Department of Applied Math. and Data Complex Networks and Cybersecurity Research Institute University Rey Juan Carlos C/Tulipn s/n Mstoles Madrid28933 Spain Department of Physics and Astronomy University of Catania INFN Catania95125 Italy School of Mathematical Sciences Queen Mary University of London LondonE1 4NS United Kingdom The Alan Turing Institute The British Library LondonNW1 2DB United Kingdom Unmanned Systems Research Institute Northwestern Polytechnical University Xi'an710072 China Moscow Institute of Physics and Technology Dolgoprudny Moscow Region141701 Russia

All interesting and fascinating collective properties of a complex system arise from the intricate way in which its components interact. Various systems in physics, biology, social sciences and engineering have been successfully modelled as networks of coupled dynamical systems, where the graph links describe pairwise interactions. This is, however, too strong a limitation, as recent studies have revealed that higher-order many-body interactions are present in social groups, ecosystems and in the human brain, and they actually affect the emergent dynamics of all these systems. Here, we introduce a general framework that allows to study coupled dynamical systems accounting for the precise microscopic structure of their interactions at any possible order. We consider the most general ensemble of identical dynamical systems, organized on the nodes of a simplicial complex, and interacting through synchronization-non-invasive coupling function. The simplicial complex can be of any dimension, meaning that it can account, at the same time, for pairwise interactions, three-body interactions and so on. In such a broad context, we show that complete synchronization, a circumstance where all the dynamical units arrange their evolution in unison, exists as an invariant solution, and we give the necessary condition for it to be observed as a stable state in terms of a Master Stability Function. This generalizes the existing results valid for pairwise interactions (i.e. graphs) to the case of complex systems with the most general possible architecture. Moreover, we show how the approach can be simplified for specific, yet frequently occurring, instances, and we verify all our theoretical predictions in synthetic and real-world systems. Given the completely general character of the method proposed, our results contribute to the theory of dynamical systems with many-body interactions and can find applications in an extremely wide range of practical cases. Copyright © 2020, The Auth

关键词： Dynamical systems

Knot mosaic tabulation

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Involve 2018年第1期11卷 13-26页

作者： Lee, Hwa Jeong Ludwig, Lewis D. Paat, Joseph Peiffer, Amanda School of Undergraduate Studies College of Transdisciplinary Studies Daegu Gyeongbuk Institute of Science and Technology Daegu 42988 South Korea Department of Mathematics and Computer Science Denison University 100 West College Granville 43023 OH United States Department of Applied Mathematics and Statistics Johns Hopkins 211-E Whitehead Hall 3400 N. Charles St. Baltimore 21218-2682 MD United States Department of Math and Computer Science Denison University Granville 43020 OH United States

In 2008, Lomonaco and Kauffman introduced a knot mosaic system to define a quantum knot system. A quantum knot is used to describe a physical quantum system such as the topology or status of vortexing that occurs in liquid helium II for example. Kuriya and Shehab proved that knot mosaic type is a complete invariant of tame knots. In this article, we consider the mosaic number of a knot, which is a natural and fundamental knot invariant defined in the knot mosaic system. We determine the mosaic number for all eight-crossing or fewer prime knots. This work is written at an introductory level to encourage other undergraduates to understand and explore this topic. No prior knowledge of knot theory is assumed or required. © 2018, math.matical sciences Publishers. All rights reserved.

关键词： crossing number knot mosaic knots mosaic number

Building Sense Tagged Corpus Using Wikipedia for Supervised Word Sense Disambiguation

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Procedia computer science 2018年 123卷 403-412页

作者： Abdulgabbar Saif Nazlia Omar Ummi Zakiah Zainodin Mohd Juziaddin Ab Aziz Computer-Math Department Faculty of Applied Sciences Thamar University Yemen Center for Artificial Intelligence Technology Faculty of Information Science & Technology Universiti Kebangsaan Malaysia Malaysia

Building of sense-tagged data is a main challenge for supervised techniques that achieved promising results in word sense disambiguation. The manual building of sense-tagged data is a labor and a time-consuming task because each ambiguous word has to be labeled in collected contexts by linguistic experts. Therefore, this paper proposes a knowledge-based method for building the Arabic sense-tagged corpus from Wikipedia. The method starts with mapping Arabic WordNet and Wikipedia to select the Wikipedia article for the corresponding sense in WordNet. In this mapping step, the cross-lingual method is used to measure the similarity between features of a Wikipedia article and a WordNet sense separately. Then, the incoming-links of Wikipedia articles are exploited to extract instances for the sense of each ambiguous word in WordNet. For handling the lack of instances of some articles in Wikipedia, the multiword-based technique is proposed to increase a number of instances for each concept. Experimental results show that the cross-lingual method outperforms monolingual method that is based on Arabic features only. The sense-tagged corpus is created for 50 ambiguous words yielding 148 senses with 30,961 instances.

关键词： Word Sense Disambiguation Wikipedia Arabic WordNet Alignment Text Processing Similarity Measures