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Numerical simulations performed to complement experimental studies of a biaxial test show that stress and strain are both structured at the mesoscopic scale. Certain features can be explained by a calculation from linear elasticity.

We present an experimental investigation of the formation of shear bands in a granular sample submitted to a biaxial test. Our principal result is the direct observation of the bifurcation at the origin of the localization process in the material. At the bifurcation, the shear band is spatially extended: we observe a breaking of symmetry without any sudden localization of the deformation in a narrow band. Our work thus allows to clearly distinguish different phenomena: bifurcation which is a ponctual event which occurs before the peak, localization which is a process that covers a range of deformation of several percents during which the peak occurs and finally stationary shear bands which are well-defined permanent structures that can be observed at the end of the localization process, after the peak.

We propose PCAM, a Probabilistic Cyber-Alert Management framework, that enables chief information security officers to better manage cyber-alerts. Workers in Cyber Security Operation Centers usually work in 8- or 12-hour shifts. Before a shift, PCAM analyzes data about all past alerts and true alerts during the shift time-frame to schedule a given set of analysts in accordance with workplace constraints so that the expected number of “uncovered” true alerts (i.e., true alerts not shown to an analyst) is minimized. PCAM achieves this by formulating the problem as a bi-level non-linear optimization problem and then shows how to linearize and solve this complex problem. We have tested PCAM extensively. Using statistics derived from 44 days of real-world alert data, we are able to minimize the expected number of true alerts that are not manually examined by a team consisting of junior, senior, and principal analysts. We are also able to identify the optimal mix of junior, senior, and principal analysts needed during both day and night shifts given a budget, outperforming some reasonable baselines. We tested PCAM’s proposed schedule (from statistics on 44 days) on a further 6 days of data, using an off-the-shelf false alarm classifier to predict which alerts are real and which ones are false. Moreover, we show experimentally that PCAM is robust to various kinds of errors in the statistics used. [ABSTRACT FROM AUTHOR]

This study evaluated the partitioning of polychlorinated biphenyls (PCBs) during long-term, passive, land biotreatment of PCB-impacted industrial lagoon sediments. Over six years under field conditions, two land treatment units (LTUs) experienced 40% total PCB reductions from initial concentrations of 8-l0 mg/kg. A third LTU with 113 mg/kg initial total PCBs showed little reduction over five years. In each unit throughout the study, oil concentrations declined at a rate greater than that for PCBs. Measured aqueous equilibrium concentrations for the PCB-impacted sediments were typically an order of magnitude or more smaller than values estimated using correlations based on total organic matter partitioning. Measured aqueous PCB concentrations agreed with predictions based on equilibration with a PCB-containing oil phase, best modeled by Raoult's law. It was postulated that, as a consequence of PCB oil-phase partitioning, biotreatment would lead to higher PCB concentrations in the oily matter and thus increased PCB partitioning to the aqueous phase if the degradation of oily matter proceeded faster compared to PCBs. Such was the case in this study, wherein low-level aqueous phase PCB concentrations of tetrachloro PCBs increased several fold over the years as oily matter was degraded. The contribution of oil to PCB partitioning needs to be incorporated in the assessment of risk and treatability goals for land biotreatment of contaminated sediments from industrial sites. DOI: 10.1061/(ASCE)0733-9372(2005)131:2(278) CE Database subject headings: Oil; PCB; Biological treatment; Sediment; Soil treatment.

The hydraulic characteristics of horizontally installed sorbent wick sampling devices were evaluated through wick tracer studies and laboratory soil column experiments to assess the influence of horizontal wick length and sampler interface design on sampling pore water in unsaturated soils. The nominal sampler design consisted of a cylindrical porous metal interface packed with granular-activated carbon encapsulating the end of a fiberglass wick that extended 100 cm horizontally from the interface before dropping 100 cm vertically to a collection vessel. The maximum sampling rate of horizontally installed wick systems declines exponentially with increasing horizontal wick length, while the vertical length influences the range of soil-water pressures that may be sampled. The nominal design sampled pore water from clay loam laboratory columns at 8 to 14 mL [h.sup.-1] under steady-state infiltration conditions and 2 to 5 mL [h.sup.-1] under draining conditions across a -10 to -45 cm [H.sub.2]O soil-water pressure range. Sampling rates in medium-grained sand under similar flow conditions were less than that of the clay loam due to reduced water content and reduced interface/soil contact area. An analysis of observed sampling velocities versus calculated soil water contents and hydraulic conductivities indicated that the design performs best when the soil water content is greater than 0.15 and unsaturated hydraulic conductivity is greater than 0.2 cm [h.sup.-1]. A hydraulic model was developed that estimates the sampling velocity of the nominal design based on sampler interface pressure, which was linearly correlated with soil pressure. DOI: 10.1061/(ASCE)0733-9372(2005) 131:1 (11) CE Database subject headings: Activated carbon; In situ tests; Soil treatment; PCB; Organic compounds; Sampling: Soil water: Vadose zone.

Experiments investigated the chemical capture and quantitative recovery of chlorinated hydrophobic organic compounds (HOCs) sampled from the pore-water of unsaturated soils with a new in situ sorbent wicking device. The sampling device is comprised of an annular porous stainless-steel interface encasing granular-activated carbon and a fiberglass wick. Laboratory column studies using Ottawa sand spiked with tri- and tetrachlorobenzenes evaluated the accuracy of the sampling device in assessing average pore-water concentrations. The findings from these experiments showed that the sorbent-wick sampler provided reliable and repeatable estimates of the pore-water concentrations of the chlorobenzenes in the unsaturated soil columns at pore-water concentrations as low as several parts per billion. Field trials were conducted in a land biotreatment unit containing industrial soil/sludge materials to assess the availability of trace levels of aqueous-phase polychlorinated biphenyls (PCBs). The land treatment unit had undergone 5 years of intrinsic remediation and the test results indicated that the samplers were able to replicate the aqueous-phase PCB homolog pattern measured in ex situ aqueous extraction tests. Orthosubstituted PCBs were dominant in sorbent-wick samples and aqueous extracts: these PCBs appear relatively recalcitrant in land biotreatment units. The sorbent-wicking device offers the ability to obtain time-averaged mass and volumetric flux rates of HOCs in land treatment units. DOI: 10.1061/(ASCE)0733-9372(2005) 131:1(21) CE Database subject headings: Activated carbons; In situ tests; Soil treatment; PCB; Organic compounds: Sampling: Soil water: Vadose zone.

Two species of the clawed frog family, Xenopus laevis and X. tropicalis , are widely used as tools to investigate both normal and disease-state biochemistry, genetics, cell biology, and developmental biology. To support both frog specialist and non-specialist scientists needing access to these models for their research, a number of centralized resources exist around the world. These include centers that hold live and frozen stocks of transgenic, inbred and mutant animals and centers that hold molecular resources. This infrastructure is supported by a model organism database. Here, we describe much of this infrastructure and encourage the community to make the best use of it and to guide the resource centers in developing new lines and libraries. [ABSTRACT FROM AUTHOR]

As a prelude to his keynote speech at the forthcoming Health Libraries Group conference, Sean McNamara, Head of CILIP Scotland, provides an insight into the work being undertaken with health librarians in Scotland and considers how CILIP Scotland might support the health information sector in the coming years. [ABSTRACT FROM AUTHOR]

We have performed a simulation study of three-dimensional cohesionless granular flows down an inclined chute. We find that the oscillations observed in [L. E. Silbert, Phys. Rev. Lett. 94, 098002 (2005)] near the angle of repose are harmonic vibrations of the lowest normal mode. Their frequencies depend on the contact stiffness as well as on the depth of the flow. Could these oscillations account for the phenomena of "booming sand"? We estimate an effective contact stiffness from the Hertz law, but this leads to frequencies that are several times higher than observed. However, the Hertz law also predicts interpenetrations of a few nanometers, indicating that the oscillations frequencies are governed by the surface stiffness, which can be much lower than the bulk one. This is in agreement with previous studies ascribing the ability to sing to the presence of a soft coating on the grain surface. [ABSTRACT FROM AUTHOR]

Abstract: We report two-dimensional simulations of strongly vibrated granular materials without gravity. The coefficient of restitution depends on the impact velocity between particles by taking into account both the viscoelastic and plastic deformations of particles, occurring at low and high velocities respectively. Use of this model of restitution coefficient leads to new unexpected behaviors. When the number of particles N is large, a loose cluster appears near the fixed wall, opposite the vibrating wall. The pressure exerted on the walls becomes independent of N, and linear in the vibration velocity V, quite as the granular temperature. The collision frequency at the vibrating wall becomes independent of both N and V, whereas at the fixed wall, it is linear in both N and V. These behaviors arise because the velocity-dependent restitution coefficient introduces a new time scale related to the collision velocity near the cross over from viscoelastic to plastic deformation. [Copyright &y& Elsevier]

An interview with several oral health researchers in Canada is presented. Corey Felix comments on his relationship with his mentor doctor Richard Price who has helped him advance his dental and research career. The importance of promoting summer undergraduate research programs as an effective way to attract and retain new recruits was emphasized by doctor Michael Glogauer. Doctor Gilles Lavigne cites the role that the Quebec health agency has played in doing his research.

The article presents a panel discussion of the relationship between oral health and systemic health in Canada. Doctor Howard Tenenbaum cites the important factors to consider when reflecting on the oral health-systemic health connection. According to doctor Deborah Matthews, the most significant systemic condition that have been linked to periodontal conditions is diabetes. Doctor George Sándor comments on the responsibility of dental associations.

An interview with doctor Richard Ellen, a professor in the faculty of dentistry at the University of Toronto in Ontario, is presented. He comments on the changes in the funding for health research since the Medical Research Council was replaced by the Canadian Institutes of Health Research (CIHR). He cites the impact of the 16% success rate of CIHR's grants competition on health research in Canada. He enumerates the areas of oral health research where Canadians are considered world leaders.

Abstract: This paper examines the use of Acacia as a nurse crop to overcome some of the ecological and economic impediments to reforestation of degraded areas dominated by grasses including Imperata cylindrica. The study site at Hai Van Pass in central Vietnam was initially reforested using Acacia auriculiformis. After 8 years these stands were thinned and under-planted with Hopea odorata, Dipterocarpus alatus, Parashorea chinensis, Tarrietia javanica, Parashorea stellata, Scaphium lychnophorum, Peltophorum dasyrhachis var. tonkinensis and other high-value native species. At the time of field assessment (early 2004), the Acacia trees were aged between 16 and 18 years and basal area ranged from 9 to 13m2 ha−1 after several thinnings. Acacias facilitated the establishment of native species, but after 6–7 years of growth, further thinning is needed to maintain growth rates. In addition to assisting the establishment of native species, the Acacia nurse crop should provide a revenue stream (NPV about US$ 180, or IRR 19%) sufficient to cover the establishment costs of the underplanted native species (about US$ 100). [Copyright &y& Elsevier]

Abstract: Plug conveying along a vertical tube has been investigated through simulation, using a discrete element simulation approach for the granulate particles and a pressure field approach for the gas. The result is compared with an experiment. The dynamics of a plug are described by porosity, velocity and force profiles. Their dependence on simulation parameters provides an overall picture of plug conveying. [Copyright &y& Elsevier]

This paper uses a fluid-mechanical model of a granular medium to calculate the hydrodynamic modes of a spatially uniform basic state. These modes are the granular analogs of the heat, sound, and shear modes of the standard fluid. Attention is focused on the possibility of an unstable mode that might result in the spontaneous development of inhomogeneities in density. Two cases are considered: the cooling medium which loses energy without replenishment, and the heated medium which reaches a steady state when an energy source balances the loss of energy through particle collisions. The spatially uniform state of the cooling granular medium is unstable. Two modes, analogous to the shear and heat conduction modes of a standard fluid, are unstable at long wavelengths. The growth of these modes is algebraic, rather than exponential, in time. The shear mode does not involve the formation of density inhomogeneities, but the heat mode does. At long wavelengths the heat mode can be visualized by imagining a converging velocity increasing the density of particles in a certain region. The increased collisional dissipation of granular thermal energy reduces the pressure, and prevents it from reversing the convergent velocities, so the condensation is not checked. The stability of the heated granular medium depends on the energy source. If the energy source selectively deposits energy in hot regions of a disturbance, the diffusion and collisional damping can be overwhelmed, and the disturbance grows exponentially. The standard fluid (completely elastic particles) can be recovered as a special case of the heated granular medium. In all cases, waves analogous to the sound and heat conduction modes are present. In some cases, a second type of sound wave is present at long wavelengths with the peculiar property of being damped more quickly for more elastic particles. [ABSTRACT FROM AUTHOR]

The dynamics of a one-dimensional granular medium has a finite time singularity if the number of particles in the medium is greater than a certain critical value. The singularity (‘‘inelastic collapse’’) occurs when a group of particles collides infinitely often in a finite time so that the separations and relative velocities vanish. To avoid the finite time singularity, a double limit in which the coefficient of restitution r approaches 1 and the number of particles N becomes large, but is always below the critical number needed to trigger collapse, is considered. Specifically, r→1 with N∼(1-r)-1. This procedure is called the ‘‘quasielastic’’ limit. Using a combination of direct simulation and kinetic theory, it is shown that a bimodal velocity distribution develops from random initial conditions. The bimodal distribution is the basis for a ‘‘two-stream’’ continuum model in which each stream represents one of the velocity modes. This two-stream model qualitatively explains some of the unusual phenomena seen in the simulations, such as the growth of large-scale instabilities in a medium that is excited with statistically homogeneous initial conditions. These instabilities can be either direct or oscillatory, depending on the domain size, and their finite-amplitude development results in the formation of clusters of particles. [ABSTRACT FROM AUTHOR]

The dynamics of a one-dimensional gas of inelastic point particles is investigated. To model inelastic collisions, it is supposed that the relative velocity of two colliding particles is reduced by a factor r, where 0

A blog related to Robert MacGregor, a dentist pursuing his career in dentistry is presented.

An interview with Doctor Philip Poon, chairman of the Government Relations and Public Advocacy Committee of the Canadian Dental Association (CDA), is presented. He relates that he accepted the role as chairman because CDA works with the federal government on issues that are important to him. He cites that bringing oral health issues on a par with general health is one of their main challenges.

We present a numerical implementation of an active inclusion in a granular material submitted to a biaxial test. We discuss the dependence of the response to this perturbation on two parameters: the intragranular friction coefficient on one hand, and the degree of the loading on the other hand. We compare the numerical results to theoretical predictions taking into account the change of volume of the inclusion as well as the anisotropy of the elastic matrix. [ABSTRACT FROM AUTHOR]

The article profiles Dr. Don Friedlander, president of the Canadian Dental Association (CDA). He practised dentistry while working on his undergraduate degree at McGill University in Montreal, Quebec. Friedlander served in executive positions in the Ottawa Dental Society (ODS), the Ontario Dental Association (ODA) Board of Governors and the CDA.

The article profiles Canadian Dental Association (CDA) president Dr. Deborah Stymiest. Dr. Stymiest was raised in Sydney Mines on Nova Scotia's Cape Breton Island. Dr. Stymiest study biology at Mount Allison University and received her dental degree from Dalhousie University in 1983. In 1997, she joined CDA's Board of Governors and her tenure at the Association includes serving as the Atlantic Canada representative in the Executive Council and operating on several committees and task forces.

The article focuses on dentist Allan Jeffries' active engagement to charitable events in Canada. Jeffries admits that he was partly motivated on philanthropic activities by relatives and friends who suffered and eventually died because of cancer. His most recent initiative includes the four-day Tour for Kids cycling event which was organized by the Coast to Coast Against Cancer Foundation in support to three oncology camps in Ontario.

The article profiles Darryl Smith, president of the Canadian Dental Association (CDA). It mentions that the significance of giving oral health care for individuals with dental needs has been reinforced by his experience as a rural practitioner. He finished his dental degree at the University of Alberta in Edmonton.

The elastic coupling between plastic events is generally invoked to interpret plastic properties and the failure of amorphous soft glassy materials. We report an experiment where the emergence of a selforganized plastic flow is observed well before the failure. For this we impose an homogeneous stress on a granular material, and measure local deformations for very small strain increments using a light scattering setup. We observe a nonhomogeneous strain that appears as transient bands of mesoscopic size and a welldefined orientation, which is different from the angle of the macroscopic frictional shear band that appears at the failure. The presence and the orientation of those microbands may be understood by considering how localized plastic reorganizations redistribute stresses in a surrounding continuous elastic medium. We characterize the length scale and persistence of the structure. The presence of plastic events and the mesostructure of the plastic flow are compared to numerical simulations. [ABSTRACT FROM AUTHOR]