Performance Evaluation of Deflection Routing in Optical IP Packet-Switched Networks

In previous papers [5,6], an optical switch architecture was proposed to handle variable-length packets such as IP datagrams, based on an AWG device to route packets and equipped with a fiber delay-line stage as optical input buffer. Unfortunately, extensive simulations of optical networks built with switches of this type showed that considerable buffering capability would be required in order to achieve acceptable performance. In this work, therefore, we studied the effectiveness of packet deflection as a mean for solving packet contentions on outputs of optical switches. Optical transport networks were simulated, evaluating the performance of packet deflection routing, based on a traffic model adherent to real IP traffic measurements. Full-mesh and wheel network topologies have been considered, comparing results to assess deflection effectiveness. Our simulation results show that deflection routing leads to satisfying performance even using buffers with limited size. Furthermore, the average delivery delay does not suffer heavy penalty from packet deflection, even under heavy traffic conditions.     

Traffic dynamics of the leaf-cutting ant, Atta cephalotes

Colonies of Atta cephalotes (Myrmicinae: Formicidae) construct cleared paths between their nest and the vegetation sources at which they harvest leaf tissue. Here, we employ ideas from traffic engineering to study streams of laden and unladen ants on these paths. The relationship between average traffic speed and the concentration of workers on the road surface follows a relationship similar to what is expected by analogy to fluid dynamics. Although the traffic is composed of eusocial organisms with a common interest in group success, the coarse-grained behavior of Atta traffic displays little more coordination than a moving fluid. The relationship between speed and concentration implies that maximum flow rates (which are likely to be closely tied to colony-level rates of resource acquisition) occur at a relatively high concentration that keeps individual speeds well below their "free flow" maximum. We predict that this optimal concentration will characterize peak traffic throughout a trail network, and we propose a simple behavioral mechanism that would allow trails to be cleared to the correct width to provide the optimal concentration. Collisions (including encounters for antennation) are common in leaf-cutting ant traffic because traffic is not segregated into unidirectional streams. Nonetheless, we find a counterintuitive suggestion that flow rates (with concentration differences statistically removed) are higher when traffic is near a 50:50 mix of outbound and returning ants than when it contains majority flows in a single direction. Mixed-direction traffic may help disperse laden ants with reduced agility, thereby preventing inhomogeneities in the traffic stream that could clog the trail.     

QoS Support by the HiperLAN/2 MAC Protocol: A Performance Evaluation

HiperLAN/2 (HIgh PErformance Radio Local Area Network) is a new standard from ETSI (European Telecommunications Standards Institute) for high-speed wireless LANs, interconnecting portable devices to each other and to broadband core networks, based on different networking technologies such as IP, ATM, IEEE 1394, and others. This paper introduces the basic features of the HiperLAN/2 MAC protocol. It presents performance evaluation results, specifically related to the mechanisms provided by HiperLAN/2 to manage bandwidth resource requests and granting. These results are assessed in terms of their flexibility and efficiency in supporting delay sensitive traffic, such as voice and Web data traffic, which are expected to be transported by broadband wireless LANs.     

Cerebellar complex spikes multiplex complementary behavioral information

Purkinje cell (PC) discharge, the only output of cerebellar cortex, involves 2 types of action potentials, high-frequency simple spikes (SSs) and low-frequency complex spikes (CSs). While there is consensus that SSs convey information needed to optimize movement kinematics, the function of CSs, determined by the PC’s climbing fiber input, remains controversial. While initially thought to be specialized in reporting information on motor error for the subsequent amendment of behavior, CSs seem to contribute to other aspects of motor behavior as well. When faced with the bewildering diversity of findings and views unraveled by highly specific tasks, one may wonder if there is just one true function with all the other attributions wrong? Or is the diversity of findings a reflection of distinct pools of PCs, each processing specific streams of information conveyed by climbing fibers? With these questions in mind, we recorded CSs from the monkey oculomotor vermis deploying a repetitive saccade task that entailed sizable motor errors as well as small amplitude saccades, correcting them. We demonstrate that, in addition to carrying error-related information, CSs carry information on the metrics of both primary and small corrective saccades in a time-specific manner, with changes in CS firing probability coupled with changes in CS duration. Furthermore, we also found CS activity that seemed to predict the upcoming events. Hence PCs receive a multiplexed climbing fiber input that merges complementary streams of information on the behavior, separable by the recipient PC because they are staggered in time.

Purkinje cell (PC) discharge, the only output of cerebellar cortex, involves both high-frequency simple spikes and low-frequency complex spikes; the function of the latter, determined by a PC’s climbing fibre input, remains controversial. This study shows that PCs receive a multiplexed climbing fibre input that merges complementary streams of information relevant for behaviour.     

Mid-infrared spectroscopy-based antibody aggregate quantification in cell culture fluids

Therapeutic antibody purification involves several steps which potentially induce antibody aggregation. Currently, aggregate monitoring mainly employs chromatographic, SDS-PAGE and light scattering techniques. In this study, the feasibility of mid-infrared spectroscopy (MIR) for the quantification of soluble antibody aggregates was investigated. Several multivariate models were evaluated to quantify antibody aggregation in chromatography elution streams and in clarified CHO cell culture supernatants (a surrogate for bioreactor output). A general model was established that is applicable for aggregate quantification directly from different cell culture solutions. Real-process samples and process-sample mimics were used to verify the general aggregate quantification model using two different antibodies. Results showed good prediction ability down to 1% aggregate content. Together with recently published results using MIR for host cell protein and target protein quantification, the results presented here indicate that MIR could provide multi-parameter process information from a single, fast, cost-effective and straightforward measurement. In conclusion, our study demonstrates that MIR is suitable for aggregate quantification in therapeutic antibody purification processes.     

The Group Migration of Dictyostelium Cells Is Regulated by Extracellular Chemoattractant Degradation

Starvation of Dictyostelium induces a developmental program in which cells form an aggregate that eventually differentiates into a multicellular structure. The aggregate formation is mediated by directional migration of individual cells that quickly transition to group migration in which cells align in a head-to-tail manner to form streams. Cyclic AMP acts as a chemoattractant and its production, secretion, and degradation are highly regulated. A key protein is the extracellular phosphodiesterase PdsA. In this study we examine the role and localization of PdsA during chemotaxis and streaming. We find that pdsA⁻ cells respond chemotactically to a narrower range of chemoattractant concentrations compared with wild-type (WT) cells. Moreover, unlike WT cells, pdsA⁻ cells do not form streams at low cell densities and form unusual thick and transient streams at high cell densities. We find that the intracellular pool of PdsA is localized to the endoplasmic reticulum, which may provide a compartment for storage and secretion of PdsA. Because we find that cAMP synthesis is normal in cells lacking PdsA, we conclude that signal degradation regulates the external cAMP gradient field generation and that the group migration behavior of these cells is compromised even though their signaling machinery is intact.     

Mixture models, robustness, and the weighted likelihood methodology

Problems associated with the analysis of data from a mixture of distributions include the presence of outliers in the sample, the fact that a component may not be well represented in the data, and the problem of biases that occur when the model is slightly misspecified. We study the performance of weighted likelihood in this context. The method produces estimates with low bias and mean squared error, and it is useful in that it unearths data substructures in the form of multiple roots. This in turn indicates multiple potential mixture model fits due to the presence of more components than originally specified in the model. To compute the weighted likelihood estimates, we use as starting values the method of moment estimates computed on bootstrap subsamples drawn from the data. We address a number of important practical issues involving bootstrap sample size selection, the role of starting values, and the behavior of the roots. The algorithm used to compute the weighted likelihood estimates is competitive with EM, and it is similar to EM when the components are not well separated. Moreover, we propose a new statistical stopping rule for the termination of the algorithm. An example and a small simulation study illustrate the above points.     

Multiplexing of ChIP-Seq Samples in an Optimized Experimental Condition Has Minimal Impact on Peak Detection

Multiplexing samples in sequencing experiments is a common approach to maximize information yield while minimizing cost. In most cases the number of samples that are multiplexed is determined by financial consideration or experimental convenience, with limited understanding on the effects on the experimental results. Here we set to examine the impact of multiplexing ChIP-seq experiments on the ability to identify a specific epigenetic modification. We performed peak detection analyses to determine the effects of multiplexing. These include false discovery rates, size, position and statistical significance of peak detection, and changes in gene annotation. We found that, for histone marker H3K4me3, one can multiplex up to 8 samples (7 IP + 1 input) at ~21 million single-end reads each and still detect over 90% of all peaks found when using a full lane for sample (~181 million reads). Furthermore, there are no variations introduced by indexing or lane batch effects and importantly there is no significant reduction in the number of genes with neighboring H3K4me3 peaks. We conclude that, for a well characterized antibody and, therefore, model IP condition, multiplexing 8 samples per lane is sufficient to capture most of the biological signal.     

MS3 eliminates ratio distortion in isobaric multiplexed quantitative proteomics

Quantitative mass spectrometry-based proteomics is highly versatile but not easily multiplexed. Isobaric labeling strategies allow mass spectrometry-based multiplexed proteome quantification; however, ratio distortion owing to protein quantification interference is a common effect. We present a two-proteome model (mixture of human and yeast proteins) in a sixplex isobaric labeling system to fully document the interference effect, and we report that applying triple-stage mass spectrometry (MS3) almost completely eliminates interference.     

The effects of small dispersal rates on extinction times in structured metapopulation models

Habitat destruction is a critical factor that affects persistence in several taxa, including Pacific salmon. Salmon are noted for their ability to home to their natal streams for reproduction. Since straying (i.e., spawners reproducing in nonnatal streams) is typically low in salmon, its effects have not been appreciated. In this article, we develop both a general analytical model and a simple simulation model describing structured metapopulations to study how weak connections between subpopulations affect the ability of a species to tolerate habitat destruction and/or declines in habitat quality. Our goals are to develop general principles and to relate these principles to salmon population dynamics. The analytical model describes the dynamics of two density-dependent subpopulations, connected by dispersal, whose growth rates fluctuate in response to environmental and demographic stochasticity. We find that, for moderate levels of environmental variability, small dispersal rates can significantly increase mean extinction times. This effect declines with increasing habitat quality, increasing temporal correlation, and increasing spatial correlation, but it is still significant for realistic parameter values. The simulation model shows there is a threshold rate of dispersal that minimizes extinction probabilities. These results cannot be seen in classical metapopulation models and provide new insights into the rescue effect.     

A strategy for scheduling reduce task based on intermediate data locality of the MapReduce

In this paper, researching on task scheduling is a way from the perspective of resource allocation and management to improve performance of Hadoop system. In order to save the network bandwidth resources in Hadoop cluster environment and improve the performance of Hadoop system, a ReduceTask scheduling strategy that based on data-locality is improved. In MapReduce stage, there are two main data streams in cluster network, they are slow task migration and remote copies of data. The two overlapping burst data transfer can easily become bottlenecks of the cluster network. To reduce the amount of remote copies of data, combining with data-locality, we establish a minimum network resource consumption model (MNRC). MNRC is used to calculate the network resources consumption of ReduceTask. Based on this model, we design a delay priority scheduling policy for the ReduceTask which is based on the cost of network resource consumption. Finally, MNRC is verified by simulation experiments. Evaluation results show that MNRC outperforms the saving cluster network resource by an average of 7.5% in heterogeneous.     

Modeling stochastic Ca2+ release from a cluster of IP3-sensitive receptors

We focused our attention on Ca(2+) release from the endoplasmic reticulum through a cluster of inositol(1,4,5)-trisphosphate (IP(3)) receptor channels. The random opening and closing of these receptors introduce stochastic effects that have been observed experimentally. Here, we present a stochastic version of Othmer-Tang model (OTM) for IP(3) receptor clusters. We address the average behavior of the channels in response to IP(3) stimuli. In our stochastic simulation we found that the fraction of open channels versus [IP(3)] follows a Hill curve, whose associate Hill coefficient increases when intracellular Ca(2+) level increase. This finding suggests that feedback from cytosolic Ca(2+) plays a key role in the channel response to IP(3). We also study several aspects of the stochastic properties of Ca(2+) release and we compare with experimental observations.     

A hierarchical aggregate data model with spatially correlated disease rates

The aggregate data study design (Prentice and Sheppard, 1995, Biometrika 82, 113-125) estimates individual-level exposure effects by regressing population-based disease rates on covariate data from survey samples in each population group. In this work, we further develop the aggregate data model to allow for residual spatial correlation among disease rates across populations. Geographical variation that is not explained by model predictors and has a spatial component often arises in studies of rare chronic diseases, such as breast cancer. We combine the aggregate and Bayesian disease-mapping models to provide an intuitive approach to the modeling of spatial effects while drawing correct inference regarding the exposure effect. Based on the results of simulation studies, we suggest guidelines for use of the proposed model.     

Role of streams in myxobacteria aggregate formation

Cell contact, movement and directionality are important factors in biological development (morphogenesis), and myxobacteria are a model system for studying cell-cell interaction and cell organization preceding differentiation. When starved, thousands of myxobacteria cells align, stream and form aggregates which later develop into round, non-motile spores. Canonically, cell aggregation has been attributed to attractive chemotaxis, a long range interaction, but there is growing evidence that myxobacteria organization depends on contact-mediated cell-cell communication. We present a discrete stochastic model based on contact-mediated signaling that suggests an explanation for the initialization of early aggregates, aggregation dynamics and final aggregate distribution. Our model qualitatively reproduces the unique structures of myxobacteria aggregates and detailed stages which occur during myxobacteria aggregation: first, aggregates initialize in random positions and cells join aggregates by random walk; second, cells redistribute by moving within transient streams connecting aggregates. Streams play a critical role in final aggregate size distribution by redistributing cells among fewer, larger aggregates. The mechanism by which streams redistribute cells depends on aggregate sizes and is enhanced by noise. Our model predicts that with increased internal noise, more streams would form and streams would last longer. Simulation results suggest a series of new experiments.     

Can China achieve its 2020 carbon intensity target? A scenario analysis based on system dynamics approach

Since Chinese government put a target to decrease carbon intensity 40–45% in 2020 than that of 2005, a series of emission mitigation measures has been implemented. Against this backdrop, we established a system dynamics model to investigate the energy consumption, CO₂ emission and mitigation options in China. The results show that the carbon intensity will reduce by 22.68%, 26.84%, 43.77%, and 46.65% in BaU (Business as usual), NEP (New energy policy), CTP (Carbon tax policy) and IP (Integrated policy) scenarios in 2020 compared with 2005. Obviously, Chinese government can accomplish the target under CTP and IP scenarios. Moreover, the “inflection point” in CTP and IP scenarios reveals the decision-making process between tax burden and emission reduction behavior. A brief analysis of interactive effect is accomplished by equilibrium theory and simulation results. It shows that the interactive effect of two policies, which act on the same object with same action direction, is weaker than the aggregation of two separated effects, whereas it is larger than any individual effect. In a nutshell, these findings are helpful for policymakers to optimize their policy decision-making to cut CO₂ emissions.     

Some simulation results for the neutral allele model, with interpretations

Our aim in this paper is to describe a number of results arising from a simulation study of a particular “neutral mutations” model. This simulation was carried out because the stochastic process under consideration does not appear to yield theoretical answers to several questions of biological interest; however, wherever possible, we have attempted to supplement our simulation results with partial theoretical support. Our main concern is to consider the behavior of gene frequencies and of tests of the neutral mutations model based on these gene frequencies in various circumstances, in particular where the population is geographically subdivided and also where full identification of alleles is not possible. We conclude that the effect of geographical subdivision, unless extremely strong, is quite minor, while that of non-identification is moderate.     

道路交通事故所致骨折特点、致伤机制及其与交通方式关系的研究

研究道路交通事故所致骨折的流行病学特点、骨折的特征及致伤机制;探讨交通方式与骨折的关系及其法医学意义,为预防、控制道路交通事故、交通伤骨折的急救及法医学的鉴定提供重要的依据.本文对2004年昆明市道路交通事故所致骨折518例临床法医鉴定及199例法医病理检验鉴定资料进行系统性分析研究.2005年及2006年.全国与云南省的交通事故数量下降趋势明显.交通事故所致骨折有以下特点:(1)多处、多发性骨折常见;(2)骨折部位呈"离心性分布";(3)暴力传导性骨折明显;(4)骨折刨伤严重,粉碎性及开放性骨折多见,多数需手术治疗;(5)下肢骨折常见,胫腓骨是下肢骨折最常见的部位;(6)四肢多发骨折常发生同侧肢体,摩托车、电动车、自行车驾驶员及乘员和行人发生四肢骨折时以同侧肢体多见,机动车驾驶员及机动车乘员以异侧肢体多见.骨折损伤方式以碰撞为主,其次是摔跌.     

The architecture of a middleware layer for controlling the quality of multimedia sessions

Collaborative multimedia systems demand overall session quality control beyond the level of Quality of Service (QoS) as pertaining to individual streams in isolation of others. To this end, we have recently introduced the concept of Quality of Session (QoSess) control. At every instant in time, the quality of the session depends on the actual QoS offered by the system to each of the application streams, as well as on the relative priorities of these streams according to the application semantics. In this paper, we present the architecture of a middleware layer for controlling the quality of a session. In addition, we describe the inter-stream bandwidth adaptation mechanisms, which are used by the QoSess layer to dynamically control the bandwidth shares of the streams belonging to a session. This revised version was published online in July 2006 with corrections to the Cover Date.     

Aggregate statistical measures and metapopulation dynamics

There are two main types of metapopulation models. Spatially implicit models are analytically tractable but neglect spatial heterogeneities. Spatially explicit models are more realistic but too complex. In this paper, I build a bridge between both approximations. I derive a new metapopulation model using a well-known technique in population genetics. Spatial heterogeneities are captured by an aggregate statistical measure of spatial correlation. When this correlation is zero, i.e., space is homogeneous, the model becomes the well-known Levins' model. As spatial correlation increases, equilibrium patch occupancy decreases from what would be expected under the spatially homogeneous assumption. I proceed by testing how well spatial complexities from a spatially explicit simulation can be encapsulated by such an aggregate statistical measure.     

Development of a Multiplexed Bead-Based Suspension Array for the Detection and Discrimination of Pospiviroid Plant Pathogens

Efficient and reliable diagnostic tools for the routine indexing and certification of clean propagating material are essential for the management of pospiviroid diseases in horticultural crops. This study describes the development of a true multiplexed diagnostic method for the detection and identification of all nine currently recognized pospiviroid species in one assay using Luminex bead-based suspension array technology. In addition, a new data-driven, statistical method is presented for establishing thresholds for positivity for individual assays within multiplexed arrays. When applied to the multiplexed array data generated in this study, the new method was shown to have better control of false positives and false negative results than two other commonly used approaches for setting thresholds. The 11-plex Luminex MagPlex-TAG pospiviroid array described here has a unique hierarchical assay design, incorporating a near-universal assay in addition to nine species-specific assays, and a co-amplified plant internal control assay for quality assurance purposes. All assays of the multiplexed array were shown to be 100% specific, sensitive and reproducible. The multiplexed array described herein is robust, easy to use, displays unambiguous results and has strong potential for use in routine pospiviroid indexing to improve disease management strategies.