3,028 research outputs found

    Transparency effect in the emergence of monopolies in social networks

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    Power law degree distribution was shown in many complex networks. However, in most real systems, deviation from power-law behavior is observed in social and economical networks and emergence of giant hubs is obvious in real network structures far from the tail of power law. We propose a model based on the information transparency (transparency means how much the information is obvious to others). This model can explain power structure in societies with non-transparency in information delivery. The emergence of ultra powerful nodes is explained as a direct result of censorship. Based on these assumptions, we define four distinct transparency regions: perfect non-transparent, low transparent, perfect transparent and exaggerated regions. We observe the emergence of some ultra powerful (very high degree) nodes in low transparent networks, in accordance with the economical and social systems. We show that the low transparent networks are more vulnerable to attacks and the controllability of low transparent networks is harder than the others. Also, the ultra powerful nodes in the low transparent networks have a smaller mean length and higher clustering coefficients than the other regions.Comment: 14 Pages, 3 figure

    A comparative study on the functional response of Wolbachia-infected and uninfected forms of the parasitoid wasp Trichogramma brassicae

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    Trichogramma species (Hymenoptera: Trichogrammatidae) are haplo-diploid egg parasitoids that are frequently used as biological control agents against lepidopteran pests. These wasps display two reproductive modes, including arrhenotoky (bisexuality) and thelytoky (unisexuality). Thelytokous forms are often associated with the presence of endosymbiotic Wolbachia bacteria. The use of thelytokous wasps has long been considered as a way to enhance the efficacy of biological control. The present study investigates the potential of a thelytokous Wolbachiainfected and an arrhenotokous uninfected Trichogramma brassicae Bezdenko strain as inundative biocontrol agents by evaluating their functional response towards different egg densities of the factitious host, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae). The results revealed a type II functional response for both strains in which parasitism efficiency decreases with host egg density because of an increasing host handling time. A model with an indicator variable was used to compare the parameters of Holling’s disc equation in different data sets. It was demonstrated that the two strains did not differ in host attack rate. However, the Wolbachia-infected strain did have an increased host handling time when compared to the bisexual strain. Some applied aspects of the findings are discusse

    Differential Phase Estimation with the SeaMARC II Bathymetric Sidescan Sonar System

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    A maximum-likelihood estimator is used to extract differential phase measurements from noisy seafloor echoes received at pairs of transducers mounted on either side of the SeaMARC II bathymetricsidescan sonar system. Carrier frequencies for each side are about 1 kHz apart, and echoes from a transmitted pulse 2 ms long are analyzed. For each side, phase difference sequences are derived from the full complex data consisting of base-banded and digitized quadrature components of the received echoes. With less bias and a lower variance, this method is shown to be more efficient than a uniform mean estimator. It also does not exhibit the angular or time ambiguities commonly found in the histogram method used in the SeaMARC II system. A figure for the estimation uncertainty of the phasedifference is presented, and results are obtained for both real and simulated data. Based on this error estimate and an empirical verification derived through coherent ping stacking, a single filter length of 100 ms is chosen for data processing application

    Time-Varying Lyapunov Control Laws with Enhanced Estimation of Distribution Algorithm for Low-Thrust Trajectory Design

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    Enhancements in evolutionary optimization techniques are rapidly growing in many aspects of engineering, specifically in astrodynamics and space trajectory optimization and design. In this chapter, the problem of optimal design of space trajectories is tackled via an enhanced optimization algorithm within the framework of Estimation of Distribution Algorithms (EDAs), incorporated with Lyapunov and Q-law feedback control methods. First, both a simple Lyapunov function and a Q-law are formulated in Classical Orbital Elements (COEs) to provide a closed-loop low-thrust trajectory profile. The weighting coefficients of these controllers are approximated with various degrees of Hermite interpolation splines. Following this model, the unknown time series of weighting coefficients are converted to unknown interpolation points. Considering the interpolation points as the decision variables, a black-box optimization problem is formed with transfer time and fuel mass as the objective functions. An enhanced EDA is proposed and utilized to find the optimal variation of weighting coefficients for minimum-time and minimum-fuel transfer trajectories. The proposed approach is applied in some trajectory optimization problems of Earth-orbiting satellites. Results show the efficiency and the effectiveness of the proposed approach in finding optimal transfer trajectories. A comparison between the Q-law and simple Lyapunov controller is done to show the potential of the potential of the EEDA in enabling the simple Lyapunov controller to recover the finer nuances explicitly given within the analytical expressions in the Q-law

    FTIR microspectroscopy reveals chemical changes in mice fetus following Phenobarbital administration

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    Phenobarbital is a phenobarbiturate used as a sedative, anticonvulsant or hypnotic with the doses prescribed and can cause teratogenic effects. The goal of this study was to examine an alternative method for the recognition of the mechanism or the bimolecular potential changes in mice fetus caused by Phenobarbital using FTIR micro spectroscopy. The mice were injected with Phenobarbital (120 mg/Kg) on gestation day 9. Fetuses were dissected on day 15 of gestation and morphological and histological studies on the fetus were carried out. Sections (10 μm) of normal and Phenobarbital treated fetus brains and livers were used for FTIR measurement in the wave number region of 400- 4000 cm. The results were shown by 2 derivatization of spectra and also subtracting from control spectra. In liver, the intensity at 1054 cm, 1155 cm, 1353 cm, 1453cm,1645 cm, 1622 cm, 2944 cm, 2913 cm and 2845 cm were shifted and increased. In the brain, the intensity at 879 cm, 911 cm, 955 cm, 1223 cm, 1256 cm, 1304 cm, 1360 cm, 1453 cm, 1529 cm, 1636 cm, 2845 cm, 2915 cm and 2950 cm were increased and shifted. The most important changes of the fetus brain tissue are on the β structure of proteins due to the amide I bands at 1636 cm, while extensive effects on the DNA structure were obvious for the Phenobarbital treated liver tissues. As a conclusion, FTIR spectroscopy might well be assumed as a potentially powerful teratogenic measurement instrument with a unique ability to identify the modified bimolecular structures. © 2015 by School of Pharmacy Shaheed Beheshti University of Medical Sciences and Health Services

    Generation of pcdna 3.1+-gh as a recombinant expression vector of ostrich growth hormone cdna in saccharomyces cerevisiae

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    Growth hormone is essential hormone for vertebrates like the ostrich (Struthio camelus) for growth stimulation, carbohydrate metabolism, protein assimilation etc. Growth hormone is secreted by the pituitary gland and expressed in many cells and tissues. The purpose of this study was generation of pcDNA 3.1+-GH recombinant expression vector in order to sub-clone ostrich growth hormone cDNA into Escherichia coli. In brief, total RNA was extracted from the pituitary gland tissue and cDNA sample was synthesised. The cDNA was amplified by PCR and revealed a 672 bp fragment on 2% agarose gel electrophoresis. Then, the ostrich growth hormone cDNA was extracted from the gel and was cloned into pCR8/GW/TOPO vector by T/A cloning technique to produce pCR8/GW/TOPO-GH. After obtaining the sequence of cDNA of the ostrich in Iran, it was submitted in GenBank (Accession number: JN559394). Finally, the GH cDNA was sub-cloned using pcDNA 3.1+ into Saccharomyces cerevisiae and pcDNA 3.1+-GH recombinant expression vector was generated. The results of present study were showed that ostrich growth hormone cDNA was successfully sub-cloned into Saccharomyces cerevisiae. Therefore, the pcDNA 3.1+-GH recombinant expression vector generated in this study could be useful to express the ostrich growth hormone in yeast cells as a simple and affordable way to produce this hormone at a large scale

    Malware Detection in Cloud Computing Infrastructures

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    Cloud services are prominent within the private, public and commercial domains. Many of these services are expected to be always on and have a critical nature; therefore, security and resilience are increasingly important aspects. In order to remain resilient, a cloud needs to possess the ability to react not only to known threats, but also to new challenges that target cloud infrastructures. In this paper we introduce and discuss an online cloud anomaly detection approach, comprising dedicated detection components of our cloud resilience architecture. More specifically, we exhibit the applicability of novelty detection under the one-class support Vector Machine (SVM) formulation at the hypervisor level, through the utilisation of features gathered at the system and network levels of a cloud node. We demonstrate that our scheme can reach a high detection accuracy of over 90% whilst detecting various types of malware and DoS attacks. Furthermore, we evaluate the merits of considering not only system-level data, but also network-level data depending on the attack type. Finally, the paper shows that our approach to detection using dedicated monitoring components per VM is particularly applicable to cloud scenarios and leads to a flexible detection system capable of detecting new malware strains with no prior knowledge of their functionality or their underlying instructions. Index Terms—Security, resilience, invasive software, multi-agent systems, network-level security and protection

    Wireless structural health monitoring (SHM) system for damage detection using ultrasonic guided waveform response

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    This paper presents an improved version of a wireless device embedded with a smart PZT sensor to detect flaws and structural defects on selected investigated structure. Smart PZT sensors were used as an actuator and sensor, coupled with two XBee's and one signal generator IC chip. Programme execution on transmitting and receiving the ultrasonic guided wave via the PZT sensor had been written in MATLAB. The developed source code is basically to receive serial data from one Xbee to another remote Xbee attached to the investigated structural system. The refined waveform response is utilised for prognosis of the true structural status. The 4-mm simulated holed into one of the aluminium structural plate is benchmarked with its pristine condition in validating the effectiveness of the developed SHM wireless module. Results showed that the wave is more even in non-defected area and disrupted in affected area. Ultrasonic waves increase continuously for non-destructive evaluation and structural health monitoring in various structural applications because the guided wave can propagate long distances and reach difficult-to-access regions; for inspecting porous and some non-porous materials ultrasonic waves attenuate fast and are very useful. Recent advances in ultrasonic wave application model and results are discussed in this paper
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