Guaranteed greedy routing in overlay networks

Greedy routing can be used in mobile ad-hoc networks as geographic routing protocol. This paper proposes to use greedy routing also in overlay networks by positioning overlay nodes into a multi-dimensional Euclidean space. Greedy routing can only be applied when a routing decision makes progress towards the final destination. Our proposed overlay network is built such that there will be always progress at each forwarding node. This is achieved by constructing at each node a so-called nearest neighbor convex set (NNCS). NNCSs can be used for various applications such as multicast routing, service discovery and Quality-of-Service routing. NNCS has been compared with Pastry, another topology-aware overlay network. NNCS has superior relative path stretches indicating the optimality of a path.

A new methodological approach for studying intergenerational mobility with an application to Swiss data

Despite the widespread interest in the topic and a vast international literature, very little is known about the development of intergenerational mobility in Switzerland. Based on a new harmonized database for Switzerland (comprising various surveys such as different waves of the ISSP, EVS, and the ESS), we provide a systematic account of changes in the link between social origin and destination over time (covering birth cohorts from around 1935 to 1980). We analyze effects of parental education and class on own educational achievement and social class for both men and women, using a refined variant of the methodological approach proposed by Jann and Combet (2012). The approach is based on the concept of proportional reduction of error (PRE) and features a number of advantages over more traditional approaches. For example, it provides smooth estimates of changes in social mobility that have a clear interpretation and it can easily incorporate control variables and multiple dimensions of parental characteristics. To evaluate the validity of our approach, we employ the oft-used log-multiplicative layer effect (a.k.a Unidiff) model (Xie 1992, Erikson and Goldthorpe 1992) as a benchmark. Results indicate that our approach performs well and produces qualitatively similar findings as Xie's model. For both men and women, effects of social origin initially decreased, but then, towards the end of the observation period, increased again. This u-shaped pattern, which can be observed with respect to both education and class, appears to be more pronounced for women than for men.

Intergenerational Mobility in Switzerland. A Comparison of Methodological Approaches

Despite the widespread interest in the topic and a vast international literature, only little is known about the development of intergenerational mobility in Switzerland. Based on a new harmonized database for Switzerland (comprising various surveys such as different waves of the ISSP, EVS, or the ESS), we provide a systematic account of changes in the link between social origin and destination over time (covering birth cohorts from 1940 through 1980). We analyze effects of parental education and class on own educational achievement and social class for both men and women, using a refined variant of the methodological approach proposed by Jann and Combet (2012). The approach is based on the concept of proportional reduction of error (PRE) and features a number of advantages over more traditional approaches. For example, it provides smooth estimates of changes in social mobility that have a clear interpretation and it can easily incorporate control variables and multiple dimensions of parental characteristics. To evaluate the validity of our approach, we employ the oft-used log-multiplicative layer effect model (Xie 1992) as a benchmark. Results indicate that our approach performs well and produces qualitatively similar findings as Xie’s model. For men, effects of social origin have been stable over the observed period. For women, however, social mobility significantly decreased among younger cohorts, mostly due to expanding female education and labor force participation. Jann, Ben, Benita Combet (2012). Zur Entwicklung der intergenerationalen Mobilität in der Schweiz (On the Development of Intergenerational Mobility in Switzerland). Swiss Journal of Sociology 38(2): 177-199. Xie, Yu (1992). The Log-Multiplicative Layer Effect Model for Comparing Mobility Tables. American Sociological Review 57(3): 380-395.

Tel Aviv - Mumbai - Tel Aviv: Same-Sex couples seeking parenthood in India

In Israel religious belonging remains a central category of citizenship. Laws concerning reproductive technologies such as the surrogacy law from 1996 are strongly informed by Orthodox rabbis’ kinship concepts (Kahn 2000, Shalev 1998, Weisberg 2005). A set of regulations secures that heterosexual Jewish couples bring into being children who are unequivocally Jewish themselves. The Israeli surrogacy law can therefore be understood as part of a policy seeking to reproduce the boundaries of the Jewish-Israeli collective. Same-sex couples do not fit this narrow definition of family and have no access to surrogacy in Israel. Yet gay couples maintain that parenthood is a universal civil right and bypass their exclusion through surrogacy arrangements abroad. The proposed paper follows these couples to Mumbai, which has become a popular destination for surrogacy in recent years. After their children’s birth the couples spend three to five weeks in India. In this time they not only take on their new tasks as fathers. They are also occupied with the bureaucracy of disconnecting the children from India and turning them into Israeli citizens. The paper elaborates on the bureaucratic processes and the hurdles same-sex couples encounter when seeking recognition of their parenthood and citizenship for their children. It unveils the intricacies and ramifications of Israel’s contradicting surrogacy policy of enforcing narrow definitions of family inside the country and simultaneously outsourcing problematic cases.

Post-immigration education of adult immigrants in Switzerland

In 2000, 20 per cent of the Swiss resident population was constituted by foreigners (Fibbi and Wanner 2009). As in other European countries, the migrant population in Switzerland can broadly be differentiated into three groups: 1) Migrant groups from less-developed regions with substantially lower educational attainments and an increased risk for unemployment than in the reference population, 2) Migrant groups that are rather more successful, although still somewhat behind the majority population, 3) Migrant groups who even outperform the majority population in terms of educational and employment success (Heath et al. 2008). Given these inequalities – in particular in the first migrant group – participation in further education in the country of destination might contribute to better integrate migrants in the Swiss society in general and the labour market in particular. On the basis of the pooled SAKE data set (1991-2000), patterns of participation in further education of adult migrants are analysed. As the results show, many migrant groups differ from the Swiss reference population regarding participation in further education. While inequalities are often explained by educational attainments and occupational status, in some cases they hold even if controlled for the determinants explaining participation in further education in general. Regarding migrant-specific determinants, type of residence permit proved to be an important indicator explaining the disadvantages in access to further education encountered by migrants originating from Former Yugoslavia.

Context-Aware Adaptive Opportunistic Routing in Mobile Ad-hoc and Sensor Networks

Mobile ad-hoc networks (MANETs) and wireless sensor networks (WSNs) have been attracting increasing attention for decades due to their broad civilian and military applications. Basically, a MANET or WSN is a network of nodes connected by wireless communication links. Due to the limited transmission range of the radio, many pairs of nodes in MANETs or WSNs may not be able to communicate directly, hence they need other intermediate nodes to forward packets for them. Routing in such types of networks is an important issue and it poses great challenges due to the dynamic nature of MANETs or WSNs. On the one hand, the open-air nature of wireless environments brings many difficulties when an efficient routing solution is required. The wireless channel is unreliable due to fading and interferences, which makes it impossible to maintain a quality path from a source node to a destination node. Additionally, node mobility aggravates network dynamics, which causes frequent topology changes and brings significant overheads for maintaining and recalculating paths. Furthermore, mobile devices and sensors are usually constrained by battery capacity, computing and communication resources, which impose limitations on the functionalities of routing protocols. On the other hand, the wireless medium possesses inherent unique characteristics, which can be exploited to enhance transmission reliability and routing performance. Opportunistic routing (OR) is one promising technique that takes advantage of the spatial diversity and broadcast nature of the wireless medium to improve packet forwarding reliability in multihop wireless communication. OR combats the unreliable wireless links by involving multiple neighboring nodes (forwarding candidates) to choose packet forwarders. In opportunistic routing, a source node does not require an end-to-end path to transmit packets. The packet forwarding decision is made hop-by-hop in a fully distributed fashion. Motivated by the deficiencies of existing opportunistic routing protocols in dynamic environments such as mobile ad-hoc networks or wireless sensor networks, this thesis proposes a novel context-aware adaptive opportunistic routing scheme. Our proposal selects packet forwarders by simultaneously exploiting multiple types of cross-layer context information of nodes and environments. Our approach significantly outperforms other routing protocols that rely solely on a single metric. The adaptivity feature of our proposal enables network nodes to adjust their behaviors at run-time according to network conditions. To accommodate the strict energy constraints in WSNs, this thesis integrates adaptive duty-cycling mechanism to opportunistic routing for wireless sensor nodes. Our approach dynamically adjusts the sleeping intervals of sensor nodes according to the monitored traffic load and the estimated energy consumption rate. Through the integration of duty cycling of sensor nodes and opportunistic routing, our protocol is able to provide a satisfactory balance between good routing performance and energy efficiency for WSNs.

Cross-Layer Optimizations for Multimedia Distribution over Wireless Multimedia Sensor Networks and Flying Ad-Hoc Networks with Quality of Experience Support

The proliferation of multimedia content and the demand for new audio or video services have fostered the development of a new era based on multimedia information, which allowed the evolution of Wireless Multimedia Sensor Networks (WMSNs) and also Flying Ad-Hoc Networks (FANETs). In this way, live multimedia services require real-time video transmissions with a low frame loss rate, tolerable end-to-end delay, and jitter to support video dissemination with Quality of Experience (QoE) support. Hence, a key principle in a QoE-aware approach is the transmission of high priority frames (protect them) with a minimum packet loss ratio, as well as network overhead. Moreover, multimedia content must be transmitted from a given source to the destination via intermediate nodes with high reliability in a large scale scenario. The routing service must cope with dynamic topologies caused by node failure or mobility, as well as wireless channel changes, in order to continue to operate despite dynamic topologies during multimedia transmission. Finally, understanding user satisfaction on watching a video sequence is becoming a key requirement for delivery of multimedia content with QoE support. With this goal in mind, solutions involving multimedia transmissions must take into account the video characteristics to improve video quality delivery. The main research contributions of this thesis are driven by the research question how to provide multimedia distribution with high energy-efficiency, reliability, robustness, scalability, and QoE support over wireless ad hoc networks. The thesis addresses several problem domains with contributions on different layers of the communication stack. At the application layer, we introduce a QoE-aware packet redundancy mechanism to reduce the impact of the unreliable and lossy nature of wireless environment to disseminate live multimedia content. At the network layer, we introduce two routing protocols, namely video-aware Multi-hop and multi-path hierarchical routing protocol for Efficient VIdeo transmission for static WMSN scenarios (MEVI), and cross-layer link quality and geographical-aware beaconless OR protocol for multimedia FANET scenarios (XLinGO). Both protocols enable multimedia dissemination with energy-efficiency, reliability and QoE support. This is achieved by combining multiple cross-layer metrics for routing decision in order to establish reliable routes.

High colonization rates of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli in Swiss Travellers to South Asia- a prospective observational multicentre cohort study looking at epidemiology, microbiology and risk factors.

BACKGROUND International travel contributes to the worldwide spread of multidrug resistant Gram-negative bacteria. Rates of travel-related faecal colonization with extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae vary for different destinations. Especially travellers returning from the Indian subcontinent show high colonization rates. So far, nothing is known about region-specific risk factors for becoming colonized. METHODS An observational prospective multicentre cohort study investigated travellers to South Asia. Before and after travelling, rectal swabs were screened for third-generation cephalosporin- and carbapenem-resistant Enterobacteriaceae. Participants completed questionnaires to identify risk factors for becoming colonized. Covariates were assessed univariately, followed by a multivariate regression. RESULTS Hundred and seventy persons were enrolled, the largest data set on travellers to the Indian subcontinent so far. The acquired colonization rate with ESBL-producing Escherichia coli overall was 69.4% (95% CI 62.1-75.9%), being highest in travellers returning from India (86.8%; 95% CI 78.5-95.0%) and lowest in travellers returning from Sri Lanka (34.7%; 95% CI 22.9-48.7%). Associated risk factors were travel destination, length of stay, visiting friends and relatives, and eating ice cream and pastry. CONCLUSIONS High colonization rates with ESBL-producing Enterobacteriaceae were found in travellers returning from South Asia. Though risk factors were identified, a more common source, i.e. environmental, appears to better explain the high colonization rates.

The positive effects of protean career attitude for self-initiated expatriates: Cultural adjustment as a mediator

Purpose – The authors sought to explain why and how protean career attitude might influence self‐initiated expatriates' (SIEs) experiences positively. A mediation model of cultural adjustment was proposed and empirically evaluated. Design/methodology/approach – Data from 132 SIEs in Germany containing measures of protean career attitude, cultural adjustment, career satisfaction, life satisfaction, and intention to stay in the host country were analysed using path analysis with a bootstrap method. Findings – Empirical results provide support for the authors' proposed model: the positive relations between protean career attitude and the three expatriation outcomes (career satisfaction, life satisfaction and intention to stay in the host country) were mediated by positive cross‐cultural adjustment of SIEs. Research limitations/implications – All data were cross‐sectional from a single source. The sample size was small and included a large portion of Chinese participants. The study should be replicated with samples in other destination countries, and longitudinal research is suggested. Practical implications – By fostering both a protean career attitude in skilled SIE employees and their cultural adjustment, corporations and receiving countries could be able to retain this international workforce better in times of talent shortage. Originality/value – This study contributes to the scarce research on the conceptual relatedness of protean career attitude and SIEs, as well as to acknowledging the cultural diversity of the SIE population.