On min–max r-gatherings

AbstractWe consider a min–max version of the previously studied r-gathering problem with unit-demands. The problem we consider is a metric facility-location problem, in which each open facility must serve at least r customers, and the maximum of all the facility- and connection-costs should be minimized (rather than their sum). This problem is motivated by scenarios in which r customers are required for a facility to be worth opening, and the costs represent the time until the facility/connection will be available (i.e., we want to have the complete solution ready as soon as possible).We present a 3-approximation algorithm for this problem, and prove that it cannot be approximated better (assuming P≠NP). Next we consider this problem with the additional natural requirement that each customer will be assigned to a nearest open facility, and present a 9-approximation algorithm. We further consider previously introduced special cases and variants, and obtain improved algorithmic and hardness results

Fundamental structures of dynamic social networks

Social systems are in a constant state of flux with dynamics spanning from minute-by-minute changes to patterns present on the timescale of years. Accurate models of social dynamics are important for understanding spreading of influence or diseases, formation of friendships, and the productivity of teams. While there has been much progress on understanding complex networks over the past decade, little is known about the regularities governing the micro-dynamics of social networks. Here we explore the dynamic social network of a densely-connected population of approximately 1000 individuals and their interactions in the network of real-world person-to-person proximity measured via Bluetooth, as well as their telecommunication networks, online social media contacts, geo-location, and demographic data. These high-resolution data allow us to observe social groups directly, rendering community detection unnecessary. Starting from 5-minute time slices we uncover dynamic social structures expressed on multiple timescales. On the hourly timescale, we find that gatherings are fluid, with members coming and going, but organized via a stable core of individuals. Each core represents a social context. Cores exhibit a pattern of recurring meetings across weeks and months, each with varying degrees of regularity. Taken together, these findings provide a powerful simplification of the social network, where cores represent fundamental structures expressed with strong temporal and spatial regularity. Using this framework, we explore the complex interplay between social and geospatial behavior, documenting how the formation of cores are preceded by coordination behavior in the communication networks, and demonstrating that social behavior can be predicted with high precision.Comment: Main Manuscript: 16 pages, 4 figures. Supplementary Information: 39 pages, 34 figure

Dietary Behaviors Among Patients with Type 2 Diabetes Mellitus in YOGYAKARTA, Indonesia

Purpose: To describe dietary behaviors and examine relationships between selected factors and dietary behaviors among type 2 diabetes mellitus (T2DM) patients in Yogyakarta, Indonesia.Method: Seventy T2DM patients from a hospital in Yogyakarta who met the inclusion criteria were recruited. Patient\u27s dietary behaviors were measured by the Dietary Behaviors Questionnaire developed for this study with adequate reliability. The questionnaire comprised of four dimensions: recognizing the amount of calorie needs, selecting healthy diet, arranging a meal plan, and managing dietary behaviors challenges. Higher scores indicate better dietary behaviors.Result: More than half of the patients were women (54.3%) with an average age of 56.8 years and diabetes duration of 9.7 years. The results revealed a moderate level of the total score of dietary behaviors. Considering each dimension, the results showed a moderate level of recognizing the amount of calorie needs, selecting healthy diet, and managing dietary behaviors challenges. The patients reported a high level of arranging meal plans. Pearson\u27s correlation was used to examine the relationships between selected factors and dietary behaviors. There was a positive significant relationship between the knowledge regarding diabetic diet and the total dietary behaviors scores (r = .36, p< .01). There were positive significant relationships between the knowledge regarding diabetic diet and the dimensions of recognizing the amount of calorie needs (r = .27, p< .05), selecting healthy diet (r = .35, p< .01), and managing dietary behaviors challenges (r = .28, p< .05). In contrast, the findings indicated no significant relationship between knowledge regarding diabetic diet and arranging a meal plan dimension. Furthermore, there was no significant relationship between the diabetes duration and dietary behaviors.Conclusion: Dietary behaviors among T2DM patients in Yogyakarta were at a moderate level. Knowledge regarding diabetic diet is essential. Further study regarding intervention in increasing patients\u27 knowledge is needed to achieve better dietary behaviors

The 60es turnaround as a test on the causal relationship between sociability and happiness

The nexus between relational life and life satisfaction is riddled with endogeneity problems. By investigating the causal relationship going from the first to the second variable we consider that retirement is a shock which increases the time investable in (outside job) relational life. As a consequence we instrument investment in relational goods with the aggregate exogenous age-retirement pattern. With such approach we document that investment in relational life has a positive and significant effect on life satisfaction. Consequences of our findings in terms of retirement effects and age-happiness pattern are also discussed.life satisfaction, relational goods, social capital

Entrepreneurship and Cultural Creativity

We investigate the relationship between cultural creativity and entrepreneurship in two respects: first, cultural and personal creativity as a characteristic of self-employed individuals; second, self-employment in professions that can be classified as belonging to the 'Creative Class' as compared to the non-creative class. The analysis is based on micro-data for individuals of the German Socio Economic Panel (SOEP). We find, indeed, some significant links between entrepreneurship and cultural creativity that deserve further investigation.Entrepreneurship, new business formation, cultural creativity, creative class

Fast and Robust Archetypal Analysis for Representation Learning

We revisit a pioneer unsupervised learning technique called archetypal analysis, which is related to successful data analysis methods such as sparse coding and non-negative matrix factorization. Since it was proposed, archetypal analysis did not gain a lot of popularity even though it produces more interpretable models than other alternatives. Because no efficient implementation has ever been made publicly available, its application to important scientific problems may have been severely limited. Our goal is to bring back into favour archetypal analysis. We propose a fast optimization scheme using an active-set strategy, and provide an efficient open-source implementation interfaced with Matlab, R, and Python. Then, we demonstrate the usefulness of archetypal analysis for computer vision tasks, such as codebook learning, signal classification, and large image collection visualization