Prevalence of internet addiction in the general population: results from a German population-based survey

Despite a growing number of publications, there is still no generally agreed-upon definition and assessment procedure for Internet addiction, and there is a lack of representative data on its prevalence in the general population. Based on a reliable and valid scale of Internet addiction, the purpose of this study was to determine the proportion of the general population of Internet addiction with psychometric evidence and to identify associated psychosocial and health consequences. Out of a representative survey of the German population (N=2512) the leisure time Internet users (n=1382) were queried by standardised questionnaires on Internet addiction, depression, anxiety (HADS) and depersonalisation (CDS-2). According to strict criteria of the Assessment of Internet and Computer Game Addiction (AICA-S), 2.1% of the sample was characterised as addicted by meeting criteria of craving, withdrawal symptoms, tolerance, etc. These reported daily Internet use, excessive online times. The majority reported additional adverse psychosocial and health consequences. Risk factors were male gender and social factors (unmarried, unemployment, students, low income). Online gambling, social networks, gaming chats and pornography were preferentially used by Internet addicts. Assessment of Internet addiction requires a multifaceted approach; the AICA-S is an instrument suitable for further epidemiological study.     

Multiscale Visualization and Exploration of Large Bipartite Graphs

A bipartite graph is a powerful abstraction for modeling relationships between two collections. Visualizations of bipartite graphs allow users to understand the mutual relationships between the elements in the two collections, e.g., by identifying clusters of similarly connected elements. However, commonly‐used visual representations do not scale for the analysis of large bipartite graphs containing tens of millions of vertices, often resorting to an a‐priori clustering of the sets. To address this issue, we present the Who's‐Active‐On‐What‐Visualization (WAOW‐Vis) that allows for multiscale exploration of a bipartite social‐network without imposing an a‐priori clustering. To this end, we propose to treat a bipartite graph as a high‐dimensional space and we create the WAOW‐Vis adapting the multiscale dimensionality‐reduction technique HSNE. The application of HSNE for bipartite graph requires several modifications that form the contributions of this work. Given the nature of the problem, a set‐based similarity is proposed. For efficient and scalable computations, we use compressed bitmaps to represent sets and we present a novel space partitioning tree to efficiently compute similarities; the Sets Intersection Tree. Finally, we validate WAOW‐Vis on several datasets connecting Twitter‐users and ‐streams in different domains: news, computer science and politics. We show how WAOW‐Vis is particularly effective in identifying hierarchies of communities among social‐media users.     

Efficient climate policies under technology and climate uncertainty

This article explores efficient climate policies in terms of investment streams into fossil and renewable energy technologies. The investment decisions maximise social welfare while observing a probabilistic guardrail for global mean temperature rise under uncertain technology and climate parameters. Such a guardrail constitutes a chance constraint, and the resulting optimisation problem is an instance of chance constrained programming, not stochastic programming as often employed. Our analysis of a model of economic growth and endogenous technological change, MIND, suggests that stringent mitigation strategies cannot guarantee a very high probability of limiting warming to 2 °C since preindustrial time under current uncertainty about climate sensitivity and climate response time scale. Achieving the 2 °C temperature target with a probability P? of 75% requires drastic carbon dioxide emission cuts. This holds true even though we have assumed an aggressive mitigation policy on other greenhouse gases from, e.g., the agricultural sector. The emission cuts are deeper than estimated from a deterministic calculation with climate sensitivity fixed at the P? quantile of its marginal probability distribution (3.6 °C). We show that earlier and cumulatively larger investments into the renewable sector are triggered by including uncertainty in the technology and climate response time scale parameters. This comes at an additional GWP loss of 0.3%, resulting in a total loss of 0.8% GWP for observing the chance constraint. We obtained those results with a new numerical scheme to implement constrained welfare optimisation under uncertainty as a chance constrained programming problem in standard optimisation software such as GAMS. The scheme is able to incorporate multivariate non-factorial probability measures such as given by the joint distribution of climate sensitivity and response time. We demonstrate the scheme for the case of a four-dimensional parameter space capturing uncertainty about climate and technology.     

Failure of fibrous anisotropic materials under combined loading

A failure criterion for anisotropic materials under combined stress is developed and demonstrated. The generality and accuracy of the present theory are illustrated by examination through the use of material systems under various loading conditions. Calculated results are compared with the experimental data throughout four quadrants. It agrees with observation quite well at high values of shear stress, where the Tsai–Hill theory becomes too conservative. The present criterion is also compared with other criteria. The comparison shows that this criterion has a good agreement with the experimental data even when the shear stress component is greater than the shear strength.     

Functional Adhesive Surfaces with “Gecko” Effect: The Concept of Contact Splitting

Nature has developed reversibly adhesive surfaces whose stickiness has attracted much research attention over the last decade. The central lesson from nature is that “patterned” or “fibrillar” surfaces can produce higher adhesion forces to flat and rough substrates than smooth surfaces. This paper critically examines the principles behind fibrillar adhesion from a contact mechanics perspective, where much progress has been made in recent years. The benefits derived from “contact splitting” into fibrils are separated into extrinsic/intrinsic contributions from fibril deformation, adaptability to rough surfaces, size effects due to surface‐to‐volume ratio, uniformity of stress distribution, and defect‐controlled adhesion. Another section covers essential considerations for reliable and reproducible adhesion testing, where better standardization is still required. It is argued that, in view of the large number of parameters, a thorough understanding of adhesion effects is required to enable the fabrication of reliable adhesive surfaces based on biological examples.     

Cobalt(II)‐Catalyzed Electrophilic Alkynylation of 1,3‐Dicarbonyl Compounds To Form Polysubstituted Furans via π–π Activation

Polysubstituted furans were obtained with excellent yields via the electrophilic alkynylation of 1,3‐dicarbonyl compoundsws with phenyl‐ or ester‐substituted brominated alkynes. The reaction is catalyzed by the inexpensive and readily available catalyst, cobalt(II) chloride, and has a wide substrate scope. The C(sp) C(sp³) coupling occurs under mild conditions with short reaction times and does not require an inert atmosphere or ligands. It is proposed that the reaction proceeds through a chelation complex of cobalt(II) with the deprotonated 1,3‐dicarbonyl compound.

     

2‐Aminopyridines as an α‐Bromination Shuttle in a Transition Metal‐Free One‐Pot Synthesis of Imidazo[1,2‐a]pyridines

A wide range of imidazo[1,2‐a]pyridines are accessible from cheap and readily available 2‐aminopyridines and 1,3‐dicarbonyl compounds using a unique CBrCl₃/2‐aminopyridine system for bromination at the α‐carbon. 2‐Aminopyridine is not only the substrate but also acts as a bromination shuttle, transferring the bromine atom from CBrCl₃ to the α‐carbon of the 1,3‐dicarbonyl. The reaction mechanism involves a series of reversible steps, including an addition reaction with cyclic transition state, to form a bromo‐hemiaminal intermediate. Isolated yields of up to 97% were obtained under mild conditions and at short reaction times in this transition metal‐free, one‐pot synthesis.

     

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