A Statistical Model for Early Detection of DDoS Attacks on Random Targets in SDN

Wireless Personal Communications - Software Defined Networks (SDNs) have accelerated and simplified the management, configuration and error detection in today’s networking systems. However,...     

Ozone formation potential of organic compounds in the Eastern United States: a comparison of episodes, inventories, and domains

Direct sensitivity analysis is applied for 3-D assessment of ozone reactivity (or ozone formation potential) in the Eastern United States. A detailed chemical mechanism (SAPRC-99) is implemented in a multiscale air quality model to calculate the reactivity of 32 explicit and 9 lumped compounds. Simulations are carried out for two different episodes and two different emission scenarios. While absolute reactivities of VOCs show a great deal of spatial variability, relative reactivities (normalized to the reactivity of a base mixture) produce a significantly more homogeneous field. Three types of domain-wide relative reactivity metrics are formed for 1-h and 8-h averaging intervals. In general, ozone reactivity metrics (with the exception of those based on daily peak ozone) are fairly robust and consistent between different episodes or emission scenarios. The 3-D metrics also show fairly similar rankings for VOC reactivity when compared to the box model scales. However, the 3-D metrics have a noticeably narrower range for species reactivities, as they result in lower reactivity for some of the more reactive, radical-producing VOCs (especially aldehydes). As expected, episodes and emission scenarios with less radical availability have higher absolute reactivities for all species and higher relative reactivities for the more radical-producing species. Finally, comparing the results with those from a different domain (central California) shows that relative reactivity metrics are comparable over these two significantly different domains.     

Seasonal Influence on Vapor-and Particle-Phase Polycyclic Aromatic Hydrocarbon Concentrations in School Communities Located in Southern California

Ambient concentrations of 15 vapor-and particle-phase (PM _2.5 ) polycyclic aromatic hydrocarbons (PAHs), listed by the US EPA as priority pollutants, were measured between July 2002 and November 2003 in six Southern California communities participating in a multi-year chronic respiratory health study of schoolchildren. The communities were geographically distributed over two hundred kilometers, extending from Long Beach in coastal Los Angeles, to high mountain areas to the north and west of the Los Angeles basin, and south into Eastern San Diego County. Seasonal and spatial variation in the atmospheric concentrations of PAHs is of interest because this class of compounds includes potent mutagens, carcinogens, and species capable of generating reactive oxygen species (ROS) that may lead to oxidative stress. Naphthalene accounted for 95% of the total PAH mass; annual averages ranged from 89 to 142 ng m ^{? 3} . Benzo[ghi]perylene (BGP) and the pro-carcinogen benzo[a]pyrene (BAP), present almost exclusively in the particle-phase, ranged respectively from 38 to 231 pg m ^?3 and 75 and 111 pg m ^{? 3} , with the highest values observed in Long Beach, a community with a high volume of seaport-related activities, and Lancaster, a commuter dormitory community. A considerable increase in the particle-phase PAH concentration, relative to the vapor-phase, was observed as ambient temperature decreased. Cold/hot season ratios for PAHs in PM _2.5 averaged 5.7, reaching 54 at Long Beach. The presented data underscore the importance of seasonal variations on atmospheric PAH concentrations. These observations are relevant to future interpretation and analysis of community-scale human health effects research.     

The adjoint of CMAQ

An adjoint model for the internationally used Community Multiscale Air Quality (CMAQ) modeling platform of the U.S. EPA is developed. The adjoint version for CMAQ (CMAQ-ADJ) provides the user community with forward (decoupled direct method or DDM) and backward (adjoint) sensitivity analysis capabilities. Current implementation is for gas-phase processes. Discrete adjoints are implemented for all processes with the exception of horizontal advection, for which, because of inherent discontinuities in the advection scheme, the continuous approach is superior. The adjoint of chemistry is constructed by interfacing CMAQ with the kinetic pre-processor, which provides for increased flexibility in the choice of chemical solver and facilitates the implementation of new chemical mechanisms. The adjoint implementation is evaluated both on a process-by-process basis and for the full model. In general, adjoint results show good agreement with brute-force and DDM sensitivities. As expected for a continuous adjoint implementation in a nonlinear scheme, the agreement is not perfect for horizontal transport. Sensitivities of various air quality, public health, and environmental metrics with respect to emissions are calculated using the adjoint method. In order to show applicability to regional climate studies, as an example, the sensitivities of these metrics with respect to local temperatures are calculated.     

Thiol-functionalised mesoporous silica-coated magnetite nanoparticles for high efficiency removal and recovery of Hg from water

The preparation and testing of thiol-functionalised silica-coated magnetite nanoparticles (TF-SCMNPs) is described. The characteristics of these particles are assessed at different stages in the production process using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and a magnetometer. The particles were found to be almost spherical with a uniform mesoporous structure with a pore size of ∼2.1 nm. The particles were strongly responsive to an external magnetic field making separation from solution possible in less than 1 min. The adsorption characteristics of the particles were quantified in a series of isotherm experiments using Hg(II) solution concentrations between 40 and 1000 μg l⁻¹ at adsorbent concentrations of 4 and 8 mg l⁻¹. The adsorption capacity was higher than for other commonly used adsorbents with 90% of Hg(II) removed during the first 5 min and equilibrium in less than 15 min. Both the Langmuir and Freundlich isotherm models were applied to the isotherm data and the maximum adsorption capacity was achieved when the ratio of adsorbent to adsorbate was low. Both temperature and pH had an effect on adsorption but when the TF-SCMNPs were used for removal of Hg(II) from tap water and bottled water, which contained other ions, there appeared to be no interference. Hg(II) could be successfully desorbed using thiourea in a 3 M HCl solution; this did not result in the destruction of the nanoparticles and they could subsequently be reused without loss of their activity in repetitive adsorption tests.     

Rock characterisation facility (RCF) shaft sinking — numerical computations using FLAC

Using FLAC and FLAC^3D, numerical computations were carried out to simulate a comprehensive pump test at Sellafield and to predict the hydro-mechanical consequences sinking of a shaft at that site might bring about. Transient discharge into the borehole could not be reproduced; however, the reproduction of the post-transient flow was good. Shaft sinking was modelled with FLAC^3D. The mechanical as well as the hydrogeological effects of the planned shaft on its rock surrounding, both near and far field, were typical and did not point to any difficulties that might be encountered had the shaft been constructed. By using new failure criterion, it was possible to capture the excavation damage zone by the simulations. It could not be captured by more established failure criteria such as Mohr–Coulomb or Hoek and Brown. Considering the assumptions made to set up the simulations, no coupling between the mechanical and the fluid flow computations was deemed necessary.     

Propolis emulgel: a natural remedy for burn and wound

Objectives: To develop an alternative medicine, propolis, in emulgel formulation for burn and wound treatment.

Methods: The effect of two independent variables: emulsifying agent concentration and oil concentration on the cumulative amount of propolis release (dependent variable) from liquid paraffin and isopropyl palmitate emulgels was investigated. Eight formulations were prepared and evaluated for physical appearance, pH, propolis content, viscosity, and in vitro propolis release. The release results were fitted into different kinetic equations and analyzed using contour plot, interaction surface plot and one-way ANOVA. The selected emulgel formulation was investigated for its wound and burn healing activity in rats.

Results: All the prepared emulgels showed acceptable physical properties concerning color, homogeneity, consistency, and pH value. The concentration of emulsifying agent had more pronounced effect on propolis release than oil concentration. Formulations F1–F6 showed “anomalous” drug release, while Formulations F7 and F8 showed zero-order kinetic.

Conclusion: The formulation F7 with 5% isopropyl palmitate, 5% emulsifier mixture, 1% hydroxyl propyl methyl cellulose, 1% oleic acid, and 10% propylene glycol is a promising formula for better management of wound and burn.     

Memory for activities: Adult age differences and intentionality.

24 17–24 yr olds and 24 56–76 yr olds were tested for memory of activities on a series of tasks (e.g., letter cancellation and anagrams) that varied along the rote–cognitive dimension. Half the Ss in each age group were forewarned of the subsequent memory test (intentional learning); the remaining Ss were not forewarned (incidental learning). An overall age difference, favoring young Ss, was found. However, the magnitude of the age difference varied across activities, being slight for cognitively demanding tasks and pronounced for less-demanding activities. Memory was unaffected by the forewarning variable for both age groups. Results are interpreted in terms of an age deficit in the retrieval of memory traces established by activities, with cognitively demanding activities yielding more distinctive and therefore more retrievable traces than less-demanding activities for older adults. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A Stochastic Approximation Approach for Foresighted Task Scheduling in Cloud Computing

Wireless Personal Communications - With the increasing and elastic demand for cloud resources, finding an optimal task scheduling mechanism become a challenge for cloud service providers. Due to...     

Real-time detection of traffic anomalies in wireless mesh networks

Anomaly detection is emerging as a necessary component as wireless networks gain popularity. Anomaly detection has been addressed broadly in wired networks and powerful methods have been developed for correct detection of a variety of known attacks and other anomalies. In this paper, we propose a real-time anomaly detection and identification scheme for wireless mesh networks (WMN) using components from previous methods developed for wired networks. Experiments over a WMN testbed show the effectiveness of the proposed scheme in isolating different types of anomalies, such as Denial-of-service attacks, port scan attacks, etc. Our scheme uses Chi-square statistics and it is based on similar ideas as the scheme presented by Lakhina et al. although it has lower computational complexity. The original method by Lakhina et al. was developed for wired networks and used Principal Component Analysis (PCA) for reducing the dimensions of observed data and Hotelling’s t ² statistics to distinguish between normal and abnormal traffic conditions. However, in our studies we found that dimension reduction is the most computationally intensive process of the scheme. In this paper we propose an alternative way of reducing dimensions using flow variances in a Chi-square test. Experimental results show that the Chi-square test performs similarly well to the PCA-based method at merely a fraction of the computations. Moreover, we propose an automatic identification scheme to pin-point the cause of the detected anomaly and its contribution in terms of additional or lack of traffic. Our results and comparison with other statistical tools show that the Chi-square test and the PCA-based method with identification scheme make powerful tools for real-time detection of various anomalies in an interference prone wireless networking environment.