Star-like Network Research Articles

MtDNA and nuclear data reveal patterns of low genetic differentiation for the isopods <i>Stenosoma lancifer and Stenosoma acuminatum</i>, with low dispersal ability along the northeast Atlantic coast

Evidence for a general lack of genetic differentiation of intertidal invertebrate assemblages in the North Atlantic, based on mtDNA sequence variation, has been interpreted as resulting from recent colonization following the Last Glacial Maximum. In the present study, the phylogeographic patterns of one nuclear and one mtDNA gene fragments of two isopods, Stenosoma lancifer (Miers, 1881) and Stenosoma acuminatum Leach, 1814, from the northeast Atlantic were investigated. These organisms have direct development, which makes them poor dispersers, and are therefore expected to maintain signatures of past historical events in their genomes. Lack of genetic structure, significant deviations from neutrality and star-like haplotype networks have been observed for both mtDNA and nuclear markers of S. lancifer , as well as for the mtDNA of S. acuminatum . No sequence variation was observed for the nuclear gene fragment of S. acuminatum . These results suggest a scenario of recent colonization and demographic expansion and/or high population connectivity driven by ocean currents and sporadic long-distance dispersal through rafting.

Synchronization of Continuous Dynamical Networks With Discrete-Time Communications

In this paper, synchronization of continuous dynamical networks with discrete-time communications is studied. Though the dynamical behavior of each node is continuous-time, the communications between every two different nodes are discrete-time, i.e., they are active only at some discrete time instants. Moreover, the communication intervals between every two communication instants can be uncertain and variable. By choosing a piecewise Lyapunov-Krasovskii functional to govern the characteristics of the discrete communication instants and by utilizing a convex combination technique, a synchronization criterion is derived in terms of linear matrix inequalities with an upper bound for the communication intervals obtained. The results extend and improve upon earlier work. Simulation results show the effectiveness of the proposed communication scheme. Some relationships between the allowable upper bound of communication intervals and the coupling strength of the network are illustrated through simulations on a fully connected network, a star-like network, and a nearest neighbor network.

Genetic population structure of the paper waspPolistes olivaceus(Hymenoptera: Vespidae) in Bangladesh

AbstractDispersal triggers gene flow, which in turn strongly affects the ensuing genetic population structure of a species. Using nuclear microsatellite loci and mitochondrial DNA (mtDNA), we estimated the genetic population structure of the waspPolistes olivaceusthroughout Bangladesh. The level of population differentiation using nuclear markers (FST) appeared to be much lower than that estimated using mtDNA haplotype sequences (ФST), even after correcting for effective population size differences between the two markers. These results suggest a philopatric tendency, in which gynes disperse less than males. We observed no isolation by distance among the study populations at either the nuclear or mtDNA level, suggesting nonequilibrium between gene flow and drift as a result of very frequent interpopulation movement. For the nuclear markers, an individual assignment test showed no genetically and geographically distinct groups. Instead, phylogenetic analyses as well as a minimum spanning network using mtDNA haplotypes consistently revealed two distinct lineages. The distribution of haplotypes indicated western populations with a single lineage and offered clear evidence for restricted gene flow across the Jamuna–Padma–Upper Meghna river system. Mismatch distributions exhibited a unimodal distribution, which along with a starlike haplotype network, suggested a population expansion in lineage I but not in lineage II. Overall, these results suggest that gene flow among populations ofP. olivaceuswas affected by both female philopatry and a major river system across Bangladesh.

Low but structured chloroplast diversity in Atherosperma moschatum (Atherospermataceae) suggests bottlenecks in response to the Pleistocene glacials

The cool temperate rainforests of Australia were much reduced in range during the cold and dry glacial periods, although genetic evidence indicates that two key rainforest species, Nothofagus cunninghamii and Tasmannia lanceolata, survived within multiple locations and underwent only local range expansions at the end of the Last Glacial. To better understand the glacial response of a co-occurring but wind-dispersed and less cold-tolerant rainforest tree species, Atherosperma moschatum, a chloroplast phylogeographic study was undertaken. A total of 3294 bp of chloroplast DNA sequence was obtained for 155 samples collected from across the species' range. The distribution of six haplotypes observed in A. moschatum was geographically structured with an inferred ancestral haplotype restricted to Tasmania, while three non-overlapping and endemic haplotypes were found on the mainland of south-eastern Australia. Last glacial refugia for A. moschatum are likely to have occurred in at least one location in western Tasmania and in Victoria and within at least two locations in the Great Dividing Range of New South Wales. Nucleotide diversity of A. moschatum was lower (π = 0·00021) than either N. cunninghamii (0·00101) or T. lanceolata (0·00073), and was amongst the lowest recorded for any tree species. This study provides evidence for past bottlenecks having impacted the chloroplast diversity of A. moschatum as a result of the species narrower climatic niche during glacials. This hypothesis is supported by the star-like haplotype network and similar estimated rates of chloroplast DNA substitution for A. moschatum and the two more cold tolerant and co-occurring species that have higher chloroplast diversity, N. cunninghamii and T. lanceolata.

Network-topology-adaptive quantum conference protocols

As an important application of the quantum network communication, quantum multiparty conference has made multiparty secret communication possible. Previous quantum multiparty conference schemes based on quantum data encryption are insensitive to network topology. However, the topology of the quantum network significantly affects the communication efficiency, e.g., parallel transmission in a channel with limited bandwidth. We have proposed two distinctive protocols, which work in two basic network topologies with efficiency higher than the existing ones. We first present a protocol which works in the reticulate network using Greeberger—Horne—Zeilinger states and entanglement swapping. Another protocol, based on quantum multicasting with quantum data compression, which can improve the efficiency of the network, works in the star-like network. The security of our protocols is guaranteed by quantum key distribution and one-time-pad encryption. In general, the two protocols can be applied to any quantum network where the topology can be equivalently transformed to one of the two structures we propose in our protocols.

The HADES DAQ System: Trigger and Readout Board Network

HADES is a di-electron spectrometer operating at GSI, Germany. Currently, the HADES data and trigger system is being upgraded. The main aim is to substantially increase the event rate capabilities by a factor of up to 20 to reach 100 kHz in light systems and 20 kHz in heavy ion reactions. The data rate will be about 400 MByte/s in peak. In this context, the complete readout system has been exchanged to use optical communication. In this contribution we present a general-purpose real-time network protocol that has been developed to meet the new requirements. These include strong timing constraints with latencies less than 5 μs for endpoint-to-endpoint communication through up to 10 intermediate hubs in a star-like network setup. In summary, this network connects over 500 FPGAs distributed over the whole HADES detector. Monitoring and slow control features as well as readout and trigger distribution were joined in a single network protocol. Hence, channel multiplexing with inherent arbitration by priority is implemented. Switching between channels takes less than 100 ns. For control and monitoring, a dedicated channel provides a data bus with a virtual address space spanning the whole network. The configuration is highly flexible and thus adaptable to different experimental setups and hardware.

Evaluation of Genetic Diversity and Population Structure of Panonychus citri (Acari: Tetranychidae) in China using Ribosomal Internal Transcribed Spacer 1 Sequences

Abstract The citrus red mite, Panonychus citri (McGregor) (Acari: Tetranychidae), has a world-wide distribution and is the most important citrus (Citrus spp.) pest in many countries, including Japan, Spain, and China. To characterize the population genetic structure of the citrus red mite, the genetic variation in 15 populations from three citrus-planting regions of China (citrus belt of upper and middle reaches of Yangtze River [UMYR], citrus base of Yungui Plateau [YGP], and citrus belt of South China [SC]) was investigated using the ribosomal internal transcribed spacer (ITS) 1 region. These populations were characterized by high genetic diversity. Neutrality tests, mismatch analysis, and star-like network strongly supported the population expansion. Analysis of molecular variance (AMOVA) showed that no significant population genetic structure existed among UMYR, YGP, and SC. However, a significant global φST and the genetic structure were found between (UMYR + YGP) and SC. Pairwise φST values between most populations were not significant, and a high gene flow was found among some geographically distant populations. The significant influence of host plants on the genetic structure of P. citri populations was found by the AMOVA for five host-related groups. In addition, the Mantel test revealed that geographical isolation was a factor responsible for the genetic differentiation. Therefore, our current observed population structure of P. citri can be contribute to several factors together, i.e., ongoing gene flow, the retention of ancestral polymorphisms, and natural selection (e.g., host plants, acaricides).

Genetic diversity and demographic history of Dosidicus gigas (Cephalopoda: Ommastrephidae) in the Humboldt Current System

During the late Pleistocene-Holocene, the Humboldt Current System (HCS, Peru-Chile) was subject to important oceanographic variations that may have affected the abundance and distri- bution of marine populations, as well as their genetic structure and diversity. The fast growth and short life span of jumbo squid Dosidicus gigas make this squid a valuable model organism for evalu- ating how environmental fluctuations affect the genetic diversity of marine populations. We sequenced a 657 bp fragment of the mtDNA cytochrome c oxidase I (COI) gene of 169 jumbo squids from 6 locations in the HCS. We measured and compared genetic diversity among localities and per- formed neutrality tests to detect deviation from mutation-drift equilibrium. We inferred the demo- graphic history of jumbo squids using Bayesian skyline analyses to estimate effective population size through time. A total of 23 haplotypes were found among the sequences. Haplotype and nucleotide diversity were low in all locations. D. gigas was characterized by an absence of population genetic structure and a star-like haplotype network. Neutrality test values were negative and statistically sig- nificant, and therefore consistent with a past population expansion. Similarly, Bayesian skyline analyses indicated a recent demographic expansion after the last glacial maximum. Our results suggest that D. gigas consists of a single, large population in the HCS, that may have experienced a dramatic demographic popu lation expansion consistent with the oceanographic changes associated with the last glacial- interglacial transition.

Key role of glycoprotein Ib/V/IX and von Willebrand factor in platelet activation-dependent fibrin formation at low shear flow

AbstractA microscopic method was developed to study the role of platelets in fibrin formation. Perfusion of adhered platelets with plasma under coagulating conditions at a low shear rate (250−1) resulted in the assembly of a star-like fibrin network at the platelet surface. The focal fibrin formation on platelets was preceded by rises in cytosolic Ca2+, morphologic changes, and phosphatidylserine exposure. Fibrin formation was slightly affected by αIIbβ3 blockage, but it was greatly delayed and reduced by the following: inhibition of thrombin or platelet activation; interference in the binding of von Willebrand factor (VWF) to glycoprotein Ib/V/IX (GpIb-V-IX); plasma or blood from patients with type 1 von Willebrand disease; and plasma from mice deficient in VWF or the extracellular domain of GpIbα. In this process, the GpIb-binding A1 domain of VWF was similarly effective as full-length VWF. Prestimulation of platelets enhanced the formation of fibrin, which was abrogated by blockage of phosphatidylserine. Together, these results show that, in the presence of thrombin and low shear flow, VWF-induced activation of GpIb-V-IX triggers platelet procoagulant activity and anchorage of a star-like fibrin network. This process can be relevant in hemostasis and the manifestation of von Willebrand disease.

Exact Boundary Controllability for Quasilinear Hyperbolic Systems on a Tree-Like Network and Its Applications

In this paper we establish the local exact boundary controllability on a star-like network under certain interface conditions. By means of this result, the local exact boundary controllability of unsteady flows with fewer controls is realized in a tree-like network of open canals with general topology.

Analysis of the finite source retrial queues with server breakdowns and repairs

This paper is concerned with the queueing analysis as well as reliability evaluation of an $M/G/1//K$ retrial queue with a finite number of sources in which the server is subject to breakdowns and repairs. The server has a exponentially distributed life time and a generally distributed repair time. Our analysis extends previous work on this topic and includes the analysis of the arriving customer's distribution, the busy period, the waiting time process and main reliability characteristics. This queueing system and its variants could be used to model magnetic disk memory systems, star-like local area networks and other communication systems with detected or undetected breakdowns.

Coordinated and uncoordinated optimization of networks

In this paper, we consider spatial networks that realize a balance between an infrastructure cost (the cost of wire needed to connect the network in space) and communication efficiency, measured by average shortest path length. A global optimization procedure yields network topologies in which this balance is optimized. These are compared with network topologies generated by a competitive process in which each node strives to optimize its own cost-communication balance. Three phases are observed in globally optimal configurations for different cost-communication trade offs: (i) regular small worlds, (ii) starlike networks, and (iii) trees with a center of interconnected hubs. In the latter regime, i.e., for very expensive wire, power laws in the link length distributions P(w)∝w(-α) are found, which can be explained by a hierarchical organization of the networks. In contrast, in the local optimization process the presence of sharp transitions between different network regimes depends on the dimension of the underlying space. Whereas for d=∞ sharp transitions between fully connected networks, regular small worlds, and highly cliquish periphery-core networks are found, for d=1 sharp transitions are absent and the power law behavior in the link length distribution persists over a much wider range of link cost parameters. The measured power law exponents are in agreement with the hypothesis that the locally optimized networks consist of multiple overlapping suboptimal hierarchical trees.

Temperature Detecting System of Beer Fermentation Based on DS18B20

This Paper introduces a temperature detection system in beer fermentation. A temperature monitoring system with characteristics of bus topology structure is composed of industrial computer, temperature detector, bus converter, transmission bus and especially 1-wire digital temperature sensor DS18B20. Four-core cable is used to form a tree-like or star-like network, in which 54 digital temperature sensors existing on 18 fermentation tanks can be connected. The quantity of junction wires between temperature sensor and computer will be reduced greatly. Temperature detector provides power supply for bus converter and DS18B20 through Four-core cable. Because bus converter has used hardware fault detecting technology, the fault temperature sensor can automatically detach from the main bus and will not affect normal working of other sensor in network. So to solve the problem of a certain sensor or branch's damage causing the paralysis of entire bus. The length of detecting temperature bus can reach more than 500 meters. These all make system maintenance and expansion easy. The experiments show that this system is characterized by high intelligence, high-precision, capability of making temperature test on multi-points and compensating function. The method has a good applicable value to the temperature test.

Monophyly of Opisthorchis viverrini populations in the lower Mekong Basin, using mitochondrial DNA nad1 gene as the marker

The liver fluke, Opisthorchis viverrini, causes serious public-health problems in the Lower Mekong Basin. This study aimed to clarify whether O. viverrini populations may be genetically divided into sub-specific taxa. We collected 6 populations of O. viverrini from different places in Cambodia, Lao PDR, and Thailand, along both sides of the Mekong River, and analyzed the population structure of these using the mitochondrial nad1 gene as a marker. The results of the DNA polymorphism measurements, by theta- w ( θw) and - π ( θπ) values, neutrality tests, and mismatch distribution, suggested that the population of O. viverrini has expanded under the influence of purifying selection and selective sweep. The analysis of molecular variance (AMOVA) test revealed no significant genetic differences among the O. viverrini populations on opposite sides of the Mekong River. O. viverrini haplotypes occurred in multiple populations, and no distinct geographical clade. The star-like haplotype network confirmed a demographic expansion of the O. viverrini population. Overall, the genetic data from these populations suggested that the postulated existence of an O. viverrini species complex should be rejected. The bio-geographical diversity of O. viverrini populations should be explored further, using other appropriate markers and a wider range of samples from geographically different areas.

Phylogeography of Plathymenia reticulata (Leguminosae) reveals patterns of recent range expansion towards northeastern Brazil and southern Cerrados in Eastern Tropical South America

Little is known about past vegetation dynamics in Eastern Tropical South America (ETSA). Here we describe patterns of chloroplast (cp) DNA variation in Plathymenia reticulata, a widespread tree in the ETSA Atlantic Forest and Cerrado biomes, but not found in the xeromorphic Caatinga. Forty one populations, comprising 220 individuals, were analysed by sequencing the trnS-trnG and trnL-trnL-trnF cpDNA regions. Combined, they resulted in 18 geographically structured haplotypes. The central region of the sampling area, comprising Minas Gerais and Goiás Brazilian states, is a centre of genetic diversity and probably the most longstanding area of the distribution range of the species. In contrast, populations from northeastern Brazil and the southern Cerrados showed very low diversity levels, almost exclusively with common haplotypes which are also found in the central region. Coupled with a long-branched star-like network, these patterns suggest a recent range expansion of P. reticulata to those regions from central region sources. The recent origin of the species (in the early Pleistocene) or the extinction of some populations due to drier and cooler climate during the last glacial maximum could have been responsible for that phylogeographic pattern. The populations from northeastern Brazil originated from two colonization routes, one eastern (Atlantic) and one western (inland). Due to its high diversity and complex landscape, the central region, especially central-north Minas Gerais (between 15 degrees -18 degrees S and 42 degrees -46 degrees W), should be given the highest priority for conservation.

Get to Know Your Network Topology

Get to Know Your Network Topology

Comparative phylogeography among hydrothermal vent species along the East Pacific Rise reveals vicariant processes and population expansion in the South

The use of sequence polymorphism from individual mitochondrial genes to infer past demography has recently proved controversial because of the recurrence of selective sweeps acting over genes and the need for unlinked multilocus data sets. However, comparative analyses using several species for one gene and/or multiple genes for one species can serve as a test for potential selective effects and clarify our understanding of historical demographic effects. This study compares nucleotide polymorphisms in mitochondrial cytochrome oxidase I across seven deep-sea hydrothermal vent species that live along the volcanically active East Pacific Rise. Approximate Bayesian Computation (ABC) method, developed to trace shared vicariant events across species pairs, indicates the occurrence of two across species divergence times, and suggests that the present geographical patterns of genetic differentiation may be explained by two periods of significant population isolation. The oldest period dates back 11.6 Ma and is associated with the vent limpet Lepetodrilus elevatus, while the most recent period of isolation is 1.3 Ma, which apparently affected all species examined and coincides with a transition zone across the equator. Moreover, significant negative Tajima's D and star-like networks were observed for all southern lineages, suggesting that these lineages experienced a concomitant demographic and geographical expansion about 100 000-300 000 generations ago. This expansion may have initiated from a wave of range expansions during the secondary colonization of new sites along the Southern East Pacific Rise (founder effects below the equator) or recurrent bottleneck events because of the increase of eruptive phases associated with the higher spreading rates of the ridge in this region.

On the Space-Time Variations of Rain Attenuation

Rain attenuation shows a considerable temporal and spatial variability. To simulate fade mitigation techniques such as route diversity, a space-time channel model which accounts for the spatial and temporal variation of rain attenuation is needed. In this paper we investigate the space-time correlation of rain attenuation utilizing 42 GHz star-like network measurements. By combining the spatial and temporal correlation properties of rain attenuation, a simulation model for generating multiple correlated rain attenuation time series based on the Maseng-Bakken model is developed. The model is validated by comparing the statistical and angular diversity properties of the model with those of measurements and theoretical diversity gain models. Furthermore, parameters for the Maseng-Bakken dynamic rain attenuation model were extracted from the star-like network measurements. In addition, using a systematic multivariable technique a model for the parameter betas which controls the dynamics of rain attenuation in the Maseng-Bakken model was developed. Moreover, using available rain attenuation measurements the advantage of route diversity with selection combining is investigated.

Evolutionary game in a structured population: Theory and application

In this paper, we investigate the evolution of cooperation on star-like networks under two different update rules: Helbing–Schlag proportional imitation update rule (rule-A) and its modified version (rule-B). The replicator equations are derived explicitly and the dynamics of the system is discussed theoretically and numerically.

Gravity model for spatial network based on optimal expected traffic

In this paper, we propose a spatial network model based on the optimal expected traffic. The model maximizes the total expected traffic of the network. By changing two parameters α and γ which represent the dependence of the network on the fitness and geographical constraints respectively, the model can vary its topology from heterogeneous star-like networks to homogeneous road-like networks. We use our model to simulate the Chinese city airline network and compare it with the real data. In the end of the paper, we discuss the relationship of the expected and the real traffic （namely the real weight on the network）.