Distributed estimation from relative measurements of heterogeneous and uncertain quality

This paper studies the problem of estimation from relative measurements in a graph, in which a vector indexed over the nodes has to be reconstructed from pairwise measurements of differences between its components associated to nodes connected by an edge. In order to model heterogeneity and uncertainty of the measurements, we assume them to be affected by additive noise distributed according to a Gaussian mixture. In this original setup, we formulate the problem of computing the Maximum-Likelihood (ML) estimates and we design two novel algorithms, based on Least Squares regression and Expectation-Maximization (EM). The first algorithm (LS- EM) is centralized and performs the estimation from relative measurements, the soft classification of the measurements, and the estimation of the noise parameters. The second algorithm (Distributed LS-EM) is distributed and performs estimation and soft classification of the measurements, but requires the knowledge of the noise parameters. We provide rigorous proofs of convergence of both algorithms and we present numerical experiments to evaluate and compare their performance with classical solutions. The experiments show the robustness of the proposed methods against different kinds of noise and, for the Distributed LS-EM, against errors in the knowledge of noise parameters.Comment: Submitted to IEEE transaction

Chapter 13 - Sharing strategies: carsharing, shared micromobility (bikesharing and scooter sharing), transportation network companies, microtransit, and other innovative mobility modes

Shared mobility—the shared use of a vehicle, bicycle, or other mode—is an innovative transportation strategy that enables users to gain short-term access to transportation modes on an “as-needed” basis. It includes various forms of carsharing, bikesharing, scooter sharing, ridesharing (carpooling and vanpooling), transportation network companies (TNCs), and microtransit. Included in this ecosystem are smartphone “apps” that aggregate and optimize these mobility options, as well as “courier network services” that provide last mile package and food delivery. This chapter describes different models that have emerged in shared mobility and reviews research that has quantified the environmental, social, and transportation-related impacts of these services

A Fast Potential and Self-Gravity Solver for Non-Axisymmetric Disks

Disk self-gravity could play an important role in the dynamic evolution of interaction between disks and embedded protoplanets. We have developed a fast and accurate solver to calculate the disk potential and disk self-gravity forces for disk systems on a uniform polar grid. Our method follows closely the method given by Chan et al. (2006), in which an FFT in the azimuthal direction is performed and a direct integral approach in the frequency domain in the radial direction is implemented on a uniform polar grid. This method can be very effective for disks with vertical structures that depend only on the disk radius, achieving the same computational efficiency as for zero-thickness disks. We describe how to parallelize the solver efficiently on distributed parallel computers. We propose a mode-cutoff procedure to reduce the parallel communication cost and achieve nearly linear scalability for a large number of processors. For comparison, we have also developed a particle-based fast tree-code to calculate the self-gravity of the disk system with vertical structure. The numerical results show that our direct integral method is at least two order of magnitudes faster than our optimized tree-code approach.Comment: 8 figures, accepted to ApJ

IDENTIFICATION OF ACTIVITIES INVOLVED IN CAG/CTG REPEAT INSTABILITY

CAG/CTG repeat instability is associated with at least 14 neurological disorders, including Huntington’s disease and Myotonic dystrophy type 1. In vitro and in vivo studies have showed that CAG/CTG repeats form a stable hairpin that is believed to be the intermediate for repeat expansion and contraction. Addition of extra DNA is essential for repeat expansion, so DNA synthesis is one of the keys for repeat expansion. In vivo studies reveal that 3’ CTG slippage with subsequent hairpin formation (henceforth called the 3’ CTG slippage hairpin) occurs during DNA synthesis. It is proposed that hairpin tolerance machinery is activated because prolonged stalling of DNA polymerase triggers severe DNA damage. As a means toward studying the hairpin-mediated expansion, we created a special hairpin substrate, mimicking the 3’ CTG slippage hairpin, to determine which polymerase promotes hairpin bypass. Our studies reveal polymerase β (pol β) is involved in the initial hairpin synthesis while polymerase δ (pol δ) is responsible for the resumption of DNA synthesis beyond the hairpin (extension step). Surprisingly, we also found that the pol δ can remove the short CTG hairpin by excision of the hairpin with its 3’ to 5’ exonuclease activity. Besides repairing the hairpin directly, resolving the hairpin is an alternative pathway to maintain CAG/CTG repeat stability. With limited understanding of which human helicase is responsible for resolving CAG/CTG hairpins, we conducted a screening approach to identify the human helicase involved. Werner Syndrome Protein (WRN) induces the hairpin repair activity when (CTG)35 hairpin is formed on the template strand. Primer extension assay reveals that WRN stimulates pol δ synthesis on (CAG)35/(CTG)35 template and such induction was still found in the presence of accessory factors. Helicase assay confirms that WRN unwinds CTG hairpin structures. Our studies provide a better understanding of how polymerases and helicases play a role in CAG/CTG repeat instability. Considering CAG/CTG repeat instability associated disorders are still incurable, our studies can provide several potential therapeutic targets for treating and/or preventing CAG/CTG repeat associated disorders

Public Bikesharing in North America During a Period of Rapid Expansion: Understanding Business Models, Industry Trends & User Impacts, MTI Report 12-29

Public bikesharing—the shared use of a bicycle fleet—is an innovative transportation strategy that has recently emerged in major cities around the world, including North America. Information technology (IT)-based bikesharing systems typically position bicycles throughout an urban environment, among a network of docking stations, for immediate access. Trips can be one-way, round-trip, or both, depending on the operator. Bikesharing can serve as a first-and-last mile connector to other modes, as well as for both short and long distance destinations. In 2012, 22 IT-based public bikesharing systems were operating in the United States, with a total of 884,442 users and 7,549 bicycles. Four IT-based programs in Canada had a total of 197,419 users and 6,115 bicycles. Two IT-based programs in Mexico had a total of 71,611 users and 3,680 bicycles. (Membership numbers reflect the total number of short- and long-term users.) This study evaluates public bikesharing in North America, reviewing the change in travel behavior exhibited by members of different programs in the context of their business models and operational environment. This Phase II research builds on data collected during our Phase I research conducted in 2012. During the 2012 research (Phase I), researchers conducted 14 expert interviews with industry experts and public officials in the United States and Canada, as well as 19 interviews with the manager and/or key staff of IT-based bikesharing organizations. For more information on the Phase I research, please see the Shaheen et al., 2012 report Public Bikesharing in North America: Early Operator and User Understanding. For this Phase II study, an additional 23 interviews were conducted with IT-based bikesharing organizations in the United States, Canada, and Mexico in Spring 2013. Notable developments during this period include the ongoing expansion of public bikesharing in North America, including the recent launches of multiple large bikesharing programs in the United States (i.e., Citi Bike in New York City, Divvy in Chicago, and Bay Area Bike Share in the San Francisco Bay Area). In addition to expert interviews, the authors conducted two kinds of surveys with bikesharing users. One was the online member survey. This survey was sent to all people for whom the operator had an email address.The population of this survey was mainly annual members of the bikesharing system, and the members took the survey via a URL link sent to them from the operator. The second survey was an on-street survey. This survey was designed for anyone, including casual users (i.e., those who are not members of the system and use it on a short-term basis), to take “on-street” via a smartphone. The member survey was deployed in five cities: Montreal, Toronto, Salt Lake City, Minneapolis-Saint Paul, and Mexico City. The on-street survey was implemented in three cities: Boston, Salt Lake City, and San Antonio

Predicting intensive care outcome: comparing three outcome prediction models, APACHE II, SAPS II, and MPM II

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The making of a new working class? A study of collective actions of migrant workers in South China

In this study, we argue that the specific process of the proletarianization of Chinese migrant workers contributes to the recent rise of labour protests. Most of the collective actions involve workers' conflict with management at the point of production, while simultaneously entailing labour organizing in dormitories and communities. The type of living space, including workers' dormitories and migrant communities, facilitates collective actions organized not only on bases of locality, ethnicity, gender and peer alliance in a single workplace, but also on attempts to nurture workers' solidarity in a broader sense of a labour oppositional force moving beyond exclusive networks and ties, sometimes even involving cross-factory strike tactics. These collective actions are mostly interest-based, accompanied by a strong anti-foreign capital sentiment and a discourse of workers' rights. By providing detailed cases of workers' strikes in 2004 and 2007, we suggest that the making of a new working class is increasingly conscious of and participating in interest-based or class-oriented labour protests

Understanding And Measuring Information Security Culture

The purpose of the current paper was to develop a measurement of information security culture. Our literature analysis indicated a lack of clear conceptualization and distinction between factors that constitute information security culture and factors that influence information security culture. A sequential mixed method consisting of a qualitative phase to explore the conceptualisation of information security culture, and a quantitative phase to validate the model is adopted for this research. Eight interviews with information security experts in eight different Saudi organisations were conducted, revealing that security culture can be constituted as reflection of security awareness and security ownership. Additionally, the qualitative interviews have revealed that factors that influence security culture are top management involvement, policy enforcement, and training. These factors were confirmed formed the basis for our initial information security culture model, which was operationalised and tested in different Saudi Arabian organisations. Using data from two hundred and fifty-four valid responses, we demonstrated the validity and reliability of the information security culture model. We were further able to demonstrate the validity of the model in a nomological net, as well as provide some preliminary findings on the factors that influence information security culture

Associations of pubertal stage and body mass index with cardiometabolic risk in Hong Kong Chinese children: A cross-sectional study

Background: Puberty is associated with a clustering of cardiometabolic risk factors (CMRFs) during adolescence that are manifested in later life. Although anthropometric variables such as body mass index (BMI) can predict cardiometabolic risk in children and adolescents, it is not clear whether there is an interaction between pubertal stage and BMI associated with cardiometabolic risk in this age group. This paper examines the association of pubertal stage and BMI with CMRFs in Hong Kong Chinese children. Methods: A cross-sectional school-based study was conducted among 1985 (95.1%) students aged 6 to 18 years. Fasting lipid profile and plasma glucose, blood pressure, body weight, body height and waist circumference were measured. A self-reported pubertal stage questionnaire was used to assess pubertal stage of participants. Two cardiometabolic risk scores, alpha and beta, were constructed to quantify cardiometabolic risk. Cardiometabolic risk score alpha refers to the sum of z-scores of sex-specific, age-adjusted waist circumference, height-adjusted systolic and diastolic blood pressure, fasting plasma glucose, triglyceride and low-density lipoprotein cholesterol, and minus z-score of sex-specific age-adjusted high-density lipoprotein cholesterol. Cardiometabolic risk score beta includes all components of risk score alpha except waist circumference. Results: The interaction of BMI z-score (ZBMI) and pubertal stage demonstrated a significant increase in variance explained in cardiometabolic risk score alpha in boys (0.5%, p = 0.024) and girls (0.7%, p = 0.006) and in cardiometabolic risk score beta in boys (0.8%, p = 0.030) but not in girls (0.5%, p = 0.051). Conclusions: Pubertal stage has an interaction effect on the association of cardiometabolic risk by BMI in boys and may have a similar but lesser effect in girls.published_or_final_versio