A survey of time series analysis through parametric models

The paper is a survey of recent works on time series analysis using parametric models. The main emphasis is on linear models, in particular the ARMA model. Usual me¬thods of parameter estimation, goodness of fit tests and the choice of model order are con¬sidered. Some extensions of the methods to related problems are briefly discussed     

Jochen Roose: Die Europäisierung von Umweltorganisationen. Die Umweltbewegung auf dem langen Weg nach Brüssel

KZfSS Kölner Zeitschrift für Soziologie und Sozialpsychologie -     

Staying safe and visible via message sharing in online social networks

As an imperative channel for fast information propagation, online social networks (OSNs) also have their defects. One of them is the information leakage, i.e., information could be spread via OSNs to the users whom we are not willing to share with. Thus the problem of constructing a circle of trust to share information with as many friends as possible without further spreading it to unwanted targets has become a challenging research topic but still remained open. Our work is the first attempt to study the Maximum Circle of Trust problem seeking to share the information with the maximum expected number of poster’s friends such that the information spread to the unwanted targets is brought to its knees. First, we consider a special and more practical case with the two-hop information propagation and a single unwanted target. In this case, we show that this problem is NP-hard, which denies the existence of an exact polynomial-time algorithm. We thus propose a Fully Polynomial-Time Approximation Scheme (FPTAS), which can not only adjust any allowable performance error bound but also run in polynomial time with both the input size and allowed error. FPTAS is the best approximation solution one can ever wish for an NP-hard problem. We next consider the number of unwanted targets is bounded and prove that there does not exist an FPTAS in this case. Instead, we design a Polynomial-Time Approximation Scheme (PTAS) in which the allowable error can also be controlled. When the number of unwanted targets are not bounded, we provide a randomized algorithm, along with the analytical theoretical bound and inapproximaibility result. Finally, we consider a general case with many hops information propagation and further show its #P-hardness and propose an effective Iterative Circle of Trust Detection (ICTD) algorithm based on a novel greedy function. An extensive experiment on various real-world OSNs has validated the effectiveness of our proposed approximation and ICTD algorithms. Such an extensive experiment also highlights several important observations on information leakage which help to sharpen the security of OSNs in the future.     

Traditional vs. Modern Food Systems? Insights from Vegetable Supply Chains to Ho Chi Minh City (Vietnam)

This article describes the development of vegetable marketing in Ho Chi Minh City (Vietnam), where modern distribution outlets are competing fiercely with traditional traders for wholesale and retail customers. Data from interviews with supply chain stakeholders and a survey of vegetable wholesalers have been used to compare the performance of modern and traditional chains, and the findings reveal the chains as segmented in their product focus, the modern sector focusing exclusively on quality. Modern marketing channels are generally more efficient than traditional ones but still account for only around 2% of vegetable distribution. The article argues that policy‐makers should not promote the ‘modernisation’ of food systems at the expense of traditional channels which meet important consumer needs.     

Developments in implicit leadership theory and cognitive science: Applications to improving measurement and understanding alternatives to hierarchical leadership

After reviewing key findings regarding leadership categorization theory, we develop new perspectives regarding the design of behavioral measures of leadership and the implications of shared leadership and complex adaptive leadership conceptualizations of leadership. In particular, by applying recent developments in cognitive science, we explain how an understanding of symbolic, connectionist, and embodied representations of knowledge can benefit behavioral measures of leadership. Additionally, we address some practical issues associated with the measurement of leadership and argue that ratings which tap episodic memory at the event level may be more meaningful than ratings based on semantic memory. Finally, we discuss how notions of shared leadership and of leaders as catalysts for complexity can create unique complications for leadership perceptions, coordinated behavior within a group, and the measurement of leadership.     

A Hybrid Geometric Phase II/III Clinical Trial Design based on Treatment Failure Time and Toxicity

The problem of comparing several experimental treatments to a standard arises frequently in medical research. Various multi-stage randomized phase II/III designs have been proposed that select one or more promising experimental treatments and compare them to the standard while controlling overall Type I and Type II error rates. This paper addresses phase II/III settings where the joint goals are to increase the average time to treatment failure and control the probability of toxicity while accounting for patient heterogeneity. We are motivated by the desire to construct a feasible design for a trial of four chemotherapy combinations for treating a family of rare pediatric brain tumors. We present a hybrid two-stage design based on two-dimensional treatment effect parameters. A targeted parameter set is constructed from elicited parameter pairs considered to be equally desirable. Bayesian regression models for failure time and the probability of toxicity as functions of treatment and prognostic covariates are used to define two-dimensional covariate-adjusted treatment effect parameter sets. Decisions at each stage of the trial are based on the ratio of posterior probabilities of the alternative and null covariate-adjusted parameter sets. Design parameters are chosen to minimize expected sample size subject to frequentist error constraints. The design is illustrated by application to the brain tumor trial.     

We're All in This Together: Context, Contacts, and Social Trust in Canada

How do conditions of diversity and inequality affect the sense of solidarity with each other that is manifested as social trust? This article brings together the literatures on racial heterogeneity, inter-group contact and relative deprivation to test and enrich the existing theoretical understanding of trust. It explores the effects of city and neighborhood contexts, individual experiences of inter-group relations, and their moderating effects on social trust. Findings suggest that the influence of a city's level of ethnic/racial diversity and income inequality is conditioned by inter-group social ties and experiences of discrimination. By considering the characteristics of neighborhoods, racial diversity of cities no longer has any significant association with trust in others. However, income inequality at the city level interacts with experiences of discrimination to undermine trust. Public policies aimed at improving social cohesion would benefit from considering the joint impact of economic and social policies that regulate resource distribution and hence shape inter-group relations.     

Nursing a Grievance? The Role of Healthcare Assistants in a Modernized National Health Service

The complex division of labour in health care has encouraged the analysis of occupational boundary disputes between separate professions. Less attention has been directed at the divisions in individual occupational groups but in a context of intensive health sector workforce reform there has been a growth in lower status occupations. This article extends debate about lower status occupations by exploring the manner in which nurses and healthcare assistants engage in boundary work to advance their occupational interests. The UK government's modernization agenda has encouraged a more prominent role for healthcare assistants and the findings confirm that this agenda has reinforced occupational boundary disputes between nurses and healthcare assistants. Tensions between nurses and healthcare assistants took particular forms influenced by gendered notions of caring work. The consequences of these boundary management strategies in terms of work undertaken, pay and status are also explored.