Variation In Network Size Research Articles

Climate warming restructures seasonal dynamics of grassland soil microbial communities.

Soil microbial community's responses to climate warming alter the global carbon cycle. In temperate ecosystems, soil microbial communities function along seasonal cycles. However, little is known about how the responses of soil microbial communities to warming vary when the season changes. In this study, we investigated the seasonal dynamics of soil bacterial community under experimental warming in a temperate tall-grass prairie ecosystem. Our results showed that warming significantly (p = 0.001) shifted community structure, such that the differences of microbial communities between warming and control plots increased nonlinearly (R 2 = 0.578, p = 0.021) from spring to winter. Also, warming significantly (p < 0.050) increased microbial network complexity and robustness, especially during the colder seasons, despite large variations in network size and complexity in different seasons. In addition, the relative importance of stochastic processes in shaping the microbial community decreased by warming in fall and winter but not in spring and summer. Our study indicates that climate warming restructures the seasonal dynamics of soil microbial community in a temperate ecosystem. Such seasonality of microbial responses to warming may enlarge over time and could have significant impacts on theterrestrial carbon cycle.

Personality Traits Predict Social Network Size in Older Adults.

Humans live in unusually large groups, where relationships are thought to be maintained through complex socio-communicative abilities. The size and quality of social networks are associated with health and well-being outcomes throughout life. However, how some individuals manage to form larger social networks is not well understood. If socio-communicative traits evolved to form and maintain relationships, personality traits should be associated with variation in network size. Here, using the English Longitudinal Study of Ageing (ELSA), we investigate the impact of extraversion, agreeableness, and verbal communication on network size (N = 5,202) and network size change over time (N = 1,511) in later life for kin and friend networks. Higher levels of extraversion and agreeableness were associated with greater social network sizes but did not predict network size change over 14 years. The findings are discussed considering the evolutionary hypothesis that communicative and affiliative traits may have evolved to support the maintenance of social networks.

Network size variation of geographical aided routing protocols in MANET

&lt;p&gt;&lt;span&gt;In position-based or geo-casting ad hoc networking applications, the data packets flooded in a limited area of the expected region toward the destination node. In such networks, a multi-hop routing is to followed when the position of the destination node is residing off-range the wireless transmission of the source node. Scientific literature references in this concept have been conducted depended on the diversity of quantitative metrics-tests regarding the size of the assigned networks so that this space is intended to be the variation in the density of the moving nodes (the number of nodes per unit of measurement). In this work, we studied the impact of the change in the size (area) of the ad hoc network with the concept of variation in the network's area while remaining the total number of nodes as a constant volume. In this paper, three of the position-based routing protocols have evaluated in terms of a network size variation. These routing protocols are: locations aided routing LAR, the distance routing effect algorithm for mobility DREAM, and the greedy perimeter stateless routing GPSR. With each simulation test, a quantitative metrics evaluation determined the most efficient protocol and the most efficient accessibility with the network environment changes in terms of actual workspace. &lt;/span&gt;&lt;/p&gt;

Relationships Stretched Thin: Social Support Mobilization in Poverty

Research on how the poor “make ends meet” typically shows that they are able to do so by relying on dense support networks of family and close friends. Recent research suggests, however, that these networks play a limited role. This article examines the role of informal networks in how sixty-one households in Barcelona, Spain, cope with poverty. We use a mixed-methods design that combines structured network delineation with semistructured interviews about the processes of support mobilization. Findings show a great variation in network size and resource capacity among households and in the kinds of ties that offer support. Social support was regarded as essential among members of poor households, but mobilized networks were often insufficient for covering even the most basic needs, and prolonged network mobilization could cause strain and long-term conflict. This analysis suggests that support networks may help people to cope with income volatility while simultaneously increasing the potential for social exclusion and isolation.

Cattle movements in Northern Ireland form a robust network: implications for disease management

The movements of undetected infected animals can facilitate long-distance pathogen spread, making control and eradication difficult by (re)infecting disease-free populations. Characterising movement patterns is essential in understanding pathogen spread and how potential interventions, particularly animal movement restrictions, could help as a control mechanism. In Northern Ireland (NI), cattle movements are important contributors to a significant portion of agricultural trade. They can be disrupted due to statutory interventions, for example, during bovine tuberculosis (bTB) control. Identifying populations at risk of becoming infected would allow for improved resource allocation. This could be through targeting herds with an above-average risk of becoming infected or spreading (amplifying) infection, and restricting their movement to manage future outbreaks.In this study, cattle movements were investigated using social network analysis (SNA) at the monthly temporal scale across NI during 2010-2015. Targeted and random herd restrictions were compared and their impact on the structure and connectivity of the networks’ was assessed (e.g. connected component subgraphs). This work was contextualised in relation to bTB, the most persistent infectious disease currently impacting agriculture in NI, where reduced connectivity would represent potential reduced vulnerability from infection introduction.There was seasonal variation in network size and level of connectivity with spring and autumn being the largest and most connected due to common farming practices in NI. Across the study period, there was limited inter-annual variation in global network metrics. On average there were 6.28 movements between each pair of nodes each month, low reciprocity (mean of 0.155) and the networks were moderately accessible with an average path length of 4.28. Movements were not confined to within each disease management area but frequently occurred between these areas (mean assortativity of -0.0731) and herds with high degree interacted with herds of low degree (mean assortativity of -0.351). The Giant Weakly Connected Component (GWCC) spanned most of the networks (between 75% and 100% of nodes); however the Giant Strongly Connected Component (GSCC) included, at most, 23% of the network. There was heterogeneous contributions across NI with little participation in the GSCC from some disease management areas, and the GSCC was comprised predominantly of ‘beef breeders’, ‘beef rearers’, and ‘other/mixed’ type herds. Targeted restrictions were more effective at fragmenting the network than randomly restricting movements when 25% of nodes or more were removed. Cattle networks in NI are extremely interconnected and robust to movement restrictions, suggesting potential vulnerability to movement-facilitated pathogen spread, such as bTB.

The Development of Social Capital Through International Students’ Involvement in Campus Organizations

&#x0D; &#x0D; &#x0D; This study examines campus organization involvement as a mechanism for social capital development. Researchers used analysis of variance (ANOVA) to examine variations in network size, strength, and composition for international students involved in different types of campus organizations. The researchers also examined the relationship of campus organization involvement to international students’ sense of attachment to the university. Students who participated in major-based organizations or leadership programs had larger, less dense, more diverse networks that lead to social networks which are particularly advantageous to social mobility. Students who participated in campus organizations related to their own cultural heritage had networks built of friends from all cultures, creating a greater sense of belonging and attachment to the university. Implications of social capital for practice and future research are discussed.&#x0D; &#x0D; &#x0D;

A survey and comparative analysis of the various routing protocols of Internet of Things

PurposeThe purpose of this paper is to provide insight into various swarm intelligence-based routing protocols for Internet of Things (IoT), which are currently available for the Mobile Ad-hoc networks (MANETs) and wireless sensor networks (WSNs). There are several issues which are limiting the growth of IoT. These include privacy, security, reliability, link failures, routing, heterogeneity, etc. The routing issues of MANETs and WSNs impose almost the same requirements for IoT routing mechanism. The recent work of worldwide researchers is focused on this area.Design/methodology/approachThe paper provides the literature review for various standard routing protocols. The different comparative analysis of the routing protocols is done. The paper surveys various routing protocols available for the seamless connectivity of things in IoT. Various features, advantages and challenges of the said protocols are discussed. The protocols are based on the principles of swarm intelligence. Swarm intelligence is applied to achieve optimality and efficiency in solving the complex, multi-hop and dynamic requirements of the wireless networks. The application of the ant colony optimization technique tries to provide answers to many routing issues.FindingsUsing the swarm intelligence and ant colony optimization principles, it has been seen that the protocols’ efficiency definitely increases and also provides more scope for the development of more robust, reliable and efficient routing protocols for the IoT.Research limitations/implicationsThe existing protocols do not solve all reliability issues and efficient routing is still not achieved completely. As of now no techniques or protocols are efficient enough to cover all the issues and provide the solution. There is a need to develop new protocols for the communication which will cater to all these needs. Efficient and scalable routing protocols adaptable to different scenarios and network size variation capable to find optimal routes are required.Practical implicationsThe various routing protocols are discussed and there is also an introduction to new parameters which can strengthen the protocols. This can lead to encouragement of readers, as well as researchers, to analyze and develop new routing algorithms.Social implicationsThe paper provides better understanding of the various routing protocols and provides better comparative analysis for the use of swarm-based research methodology in the development of routing algorithms exclusively for the IoT.Originality/valueThis is a review paper which discusses the various routing protocols available for MANETs and WSNs and provides the groundwork for the development of new intelligent routing protocols for IoT.

Beyond interviewer effects in the standardized measurement of ego-centric networks

The effects which interviewers exert on the collection of ego-centric networks have recently come into the focus of methodological considerations. Studies consistently show that the size of networks varies depending on the interviewer. We would like to expand on this research strand by pointing to different aspects which have so far gone unremarked in the discussion. First, size is mainly analysed as a network measure which is influenced during data collection, while other common measures such as network density or composition have not received sufficient consideration. Second, large-scale surveys using face-to-face interviews usually allocate interviewers to a single sampling point. Differences between sampling points (locality effects) are attributed to interviewer effects. Hence, we disentangle the effects of the locality and interviewer. Third, the discussion on interviewer effects often follows an “actor-oriented” consideration of how data collection situations are structured by interviewers. Expanding this approach from a relational perspective, we consider the relationship between the interviewers and respondents and whether this relationship influences the collection of network data. To test our hypotheses about the influence of interviewers, the locality and the interviewer-respondent relationship on different network measures, we use data from the 2010 German General Social Survey (n=2827 respondents, n=220 interviewers). The multilevel analyses show that the relationship between the interviewer and the respondent is not very relevant. Furthermore, the analyses show that interviewers have an influence on the network size but not on measures of their composition. However, evidence on the prevalence of locality or interviewer effects is mixed. Finally, homophilous interviewer-respondent relationships have very little effect on network characteristics. We find evidence of training and fatigue effects on network size. However, much of the variation in network size caused by the interviewer still remains unexplained. We draw conclusions on how to organize interview situations in surveys.

Temporal changes in the structure of a plant-frugivore network are influenced by bird migration and fruit availability.

Background. Ecological communities are dynamic collections whose composition and structure change over time, making up complex interspecific interaction networks. Mutualistic plant–animal networks can be approached through complex network analysis; these networks are characterized by a nested structure consisting of a core of generalist species, which endows the network with stability and robustness against disturbance. Those mutualistic network structures can vary as a consequence of seasonal fluctuations and food availability, as well as the arrival of new species into the system that might disorder the mutualistic network structure (e.g., a decrease in nested pattern). However, there is no assessment on how the arrival of migratory species into seasonal tropical systems can modify such patterns. Emergent and fine structural temporal patterns are adressed here for the first time for plant-frugivorous bird networks in a highly seasonal tropical environment.Methods. In a plant-frugivorous bird community, we analyzed the temporal turnover of bird species comprising the network core and periphery of ten temporal interaction networks resulting from different bird migration periods. Additionally, we evaluated how fruit abundance and richness, as well as the arrival of migratory birds into the system, explained the temporal changes in network parameters such as network size, connectance, nestedness, specialization, interaction strength asymmetry and niche overlap. The analysis included data from 10 quantitative plant-frugivorous bird networks registered from November 2013 to November 2014.Results. We registered a total of 319 interactions between 42 plant species and 44 frugivorous bird species; only ten bird species were part of the network core. We witnessed a noteworthy turnover of the species comprising the network periphery during migration periods, as opposed to the network core, which did not show significant temporal changes in species composition. Our results revealed that migration and fruit richness explain the temporal variations in network size, connectance, nestedness and interaction strength asymmetry. On the other hand, fruit abundance only explained connectance and nestedness.Discussion. By means of a fine-resolution temporal analysis, we evidenced for the first time how temporal changes in the interaction network structure respond to the arrival of migratory species into the system and to fruit availability. Additionally, few migratory bird species are important links for structuring networks, while most of them were peripheral species. We showed the relevance of studying bird–plant interactions at fine temporal scales, considering changing scenarios of species composition with a quantitative network approach.

Naming Game with Multiple Hearers

A new model called Naming Game with Multiple Hearers (NGMH) is proposed in this paper. A naming game over a population of individuals aims to reach consensus on the name of an object through pair-wise local interactions among all the individuals. The proposed NGMH model describes the learning process of a new word, in a population with one speaker and multiple hearers, at each interaction towards convergence. The characteristics of NGMH are examined on three types of network topologies, namely ER random-graph network, WS small-world network, and BA scale-free network. Comparative analysis on the convergence time is performed, revealing that the topology with a larger average (node) degree can reach consensus faster than the others over the same population. It is found that, for a homogeneous network, the average degree is the limiting value of the number of hearers, which reduces the individual ability of learning new words, consequently decreasing the convergence time; for a scale-free network, this limiting value is the deviation of the average degree. It is also found that a network with a larger clustering coefficient takes longer time to converge; especially a small-word network with smallest rewiring possibility takes longest time to reach convergence. As more new nodes are being added to scale-free networks with different degree distributions, their convergence time appears to be robust against the network-size variation. Most new findings reported in this paper are different from that of the single-speaker/single-hearer naming games documented in the literature.

Design Constraints on a Synthetic Metabolism

A metabolism is a complex network of chemical reactions that converts sources of energy and chemical elements into biomass and other molecules. To design a metabolism from scratch and to implement it in a synthetic genome is almost within technological reach. Ideally, a synthetic metabolism should be able to synthesize a desired spectrum of molecules at a high rate, from multiple different nutrients, while using few chemical reactions, and producing little or no waste. Not all of these properties are achievable simultaneously. We here use a recently developed technique to create random metabolic networks with pre-specified properties to quantify trade-offs between these and other properties. We find that for every additional molecule to be synthesized a network needs on average three additional reactions. For every additional carbon source to be utilized, it needs on average two additional reactions. Networks able to synthesize 20 biomass molecules from each of 20 alternative sole carbon sources need to have at least 260 reactions. This number increases to 518 reactions for networks that can synthesize more than 60 molecules from each of 80 carbon sources. The maximally achievable rate of biosynthesis decreases by approximately 5 percent for every additional molecule to be synthesized. Biochemically related molecules can be synthesized at higher rates, because their synthesis produces less waste. Overall, the variables we study can explain 87 percent of variation in network size and 84 percent of the variation in synthesis rate. The constraints we identify prescribe broad boundary conditions that can help to guide synthetic metabolism design.

Exploring variation in active network size: Constraints and ego characteristics

Studies of active personal networks have primarily focused on providing reliable estimates of the size of the network. In this study, we examine how compositional properties of the network and ego characteristics are related to variation in network size. There was a negative relationship between mean emotional closeness and network size, for both related and unrelated networks. Further, there was a distinct upper bound on total network size. These results suggest that there are constraints both on the absolute number of individuals that ego can maintain in the network, and also on the emotional intensity of the relationships that ego can maintain with those individuals.

Adaptive Content Delivery System with Multicasting and Buffering for Heterogeneous Networks

Multicasting is a remarkable technology that can effectively provide point-to-multipoint communications. The multicast communication can substantially decrease traffic in a network and thus save network resources and transmission costs. If multicasting is applied to a content delivery system, however, the transmission speed must be set to the lowest one among the available capacities of links on the multicast tree for all client terminals to receive the contents simultaneously. This type of problem is especially serious for heterogeneous networks. This paper studies effective content delivery systems for non-real-time point-to-multipoint services over heterogeneous environments and proposes an adaptive delivery system to select multicasting and store-and-forward transferring data streams. The results obtained by computer simulation show that our proposed system can reduce delivery time and that it is scalable to large networks and robust against variations in network size as well as environmental heterogeneities.

GEOGRAPHIC PATTERNS IN PLANT–POLLINATOR MUTUALISTIC NETWORKS

Recent reviews of plant-pollinator mutualistic networks showed that gen- eralization is a common pattern in this type of interaction. Here we examine the ecological correlates of generalization patterns in plant-pollinator networks, especially how interaction patterns covary with latitude, elevation, and insularity. We review the few published anal- yses of whole networks and include unpublished material, analyzing 29 complete plant- pollinator networks that encompass arctic, alpine, temperate, Mediterranean, and subtrop- ical-tropical areas. The number of interactions observed (I) was a linear function of network size (M) the maximum number of interactions: ln I 5 0.575 1 0.61 ln M; R 2 5 0.946. The connectance (C), the fraction of observed interactions relative to the total possible, decreased exponentially with species richness, the sum of animal and plant species in each community (A 1 P): C 5 13.83 exp(20.003(A 1 P)). After controlling for species richness, the residual connectance was significantly lower in highland (.1500 m elevation) than in lowland networks and differed marginally among biogeographic regions, with both alpine and trop- ical networks showing a trend for lower residual connectance. The two Mediterranean networks showed the highest residual connectance. After correcting for variation in network size, plant species were shown to be more generalized at higher latitude and lowland habitats, but showed increased specialization on islands. Oceanic island networks showed an im- poverishment of potential animal pollinators (lower ratio of animal to plant species, A : P, compared to mainland networks) associated with this trend of increased specialization. Plants, but not their flower-visiting animals, supported the often-repeated statements about higher specificity in the tropics than at higher latitudes. The pattern of interaction build- up as diversity increases in pollination networks does not differ appreciably from other

Geographic Patterns in Plant-Pollinator Mutualistic Networks

Recent reviews of plant-pollinator mutualistic networks showed that gen- eralization is a common pattern in this type of interaction. Here we examine the ecological correlates of generalization patterns in plant-pollinator networks, especially how interaction patterns covary with latitude, elevation, and insularity. We review the few published anal- yses of whole networks and include unpublished material, analyzing 29 complete plant- pollinator networks that encompass arctic, alpine, temperate, Mediterranean, and subtrop- ical-tropical areas. The number of interactions observed (I) was a linear function of network size (M) the maximum number of interactions: ln I 5 0.575 1 0.61 ln M; R 2 5 0.946. The connectance (C), the fraction of observed interactions relative to the total possible, decreased exponentially with species richness, the sum of animal and plant species in each community (A 1 P): C 5 13.83 exp(20.003(A 1 P)). After controlling for species richness, the residual connectance was significantly lower in highland (.1500 m elevation) than in lowland networks and differed marginally among biogeographic regions, with both alpine and trop- ical networks showing a trend for lower residual connectance. The two Mediterranean networks showed the highest residual connectance. After correcting for variation in network size, plant species were shown to be more generalized at higher latitude and lowland habitats, but showed increased specialization on islands. Oceanic island networks showed an im- poverishment of potential animal pollinators (lower ratio of animal to plant species, A : P, compared to mainland networks) associated with this trend of increased specialization. Plants, but not their flower-visiting animals, supported the often-repeated statements about higher specificity in the tropics than at higher latitudes. The pattern of interaction build- up as diversity increases in pollination networks does not differ appreciably from other

A theoretical study of random segregation of minicircles in trypanosomatids

The kinetoplast (k) DNA network of trypanosomatids is made up of approximately 50 maxicircles and the order of 10(4) minicircles. It has been proposed, based on various observations and experiments, that the minicircles are randomly segregated between daughter cells when the parent cell divides. In this paper, this random segregation hypothesis is theoretically tested in a population dynamics model to see if it can account for the observed phenomena. The hypothesis is shown to successfully explain, in Leishmania tarentolae, the observation that there are a few major and many minor minicircle classes, the fluctuations of minicircle class copy numbers over time, the loss of non-essential minicircle classes, the long survival times of a few of these classes and that these classes are likely to be the major classes within the population. Implications of the model are examined for trypanosomatids in general, leading to several predictions. The model predicts variation in network size within a population, variation in the average network size and large-scale changes in class copy number over long time-scales, an evolutionary pressure towards larger network sizes, the selective advantage of non-random over random segregation, very strong selection for the amplified class in Crithidia fasciculata if its minicircles undergo random segregation and that Trypanosoma brucei may use sexual reproduction to maintain its viability.

Static interconnection network extensibility based on marginal performance/cost analysis

The paper examines the trade-off between cost and performance of a hypercube based computer interconnection network founded on a detailed cost analysis model. A cost function is proposed which considers the economies of scale of bandwidth available through optical fibre communication and the nonincremental increase in node complexity resulting from variations in network size. When considering topology choice, an important consideration is expansion. Any comparison of expansion should be done through marginal analysis: weighing the additional benefits (performance) against the additional cost resulting from expansion. To demonstrate this technique, four interconnection networks are considered: boolean n-cube, nearest neighbour mesh hypercube, generalised hypercube, and spanning multiaccess channel hypercube. Systems with equalised performance are studied, investigating the variations in cost. This permits the investigation of the trade-off of performance/cost between high capacity communication channels and increased number of channels and degree.