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Paru dans « Construction Canada » 34(5), sept-oct. 1992, p. 29, 32-33, Originally published in « Construction Canada » 34(5), Sept-Oct. 1992, p. 29, 32-33

Originally published in « Construction Canada » 34(5), Sept-Oct. 1992, p. 29, 32-33, Paru dans « Construction Canada » 34(5), sept-oct. 1992, p. 29, 32-33

The 31st Meeting of the Society of Invertebrate Pathology, Sapporo, Japan, August, 1998

Biotechnology of Bacillus thuringiensis..., Chiang Mai, Thailand, November, 1996

National audience

The Gram-positive bacterium Bacillus thuringiensis is the most extensively used environment-friendly bioinsecticide worldwide. It produces a variety of crystalline proteins which are specifically lethal to different insect species. Following solubilization in the midgut lumen of susceptible insect larvae and binding to specific receptors located on the surface of the luminal membrane of midgut epithelial cells, the toxins insert into the membrane and form pores that abolish transmembrane ionic gradients which are vital for cellular functions. The three-dimensional structures of four B. thuringiensis Cry toxins have been elucidated. They share a similar three-domain structure in which domain I, composed of amphipathic α-helices, plays a crucial role in pore formation. The other two domains are composed of β-sheets and are responsible for receptor binding and toxin specificity. The mechanism by which these toxins insert into the cell membrane remains one of the most challenging biophysical questions regarding their mode of action. It involves extensive conformational changes in the toxin molecule and assembly of an oligomeric structure composed of a yet undetermined number of toxin subunits. A better understanding of these events is gradually emerging from the analysis of the functional properties of genetically engineered mutant toxins using a variety of biophysical techniques.

Proceedings, International Conference on Corrosion and Rehabilitation of Reinforced Concrete Structures: 08 December 1998, Orlando, Florida

Currently, municipal engineers often choose the type of sewer pipe based on initial cost alone, but this publication can help users consider the life-cycle cost, by providing valuable information on the performance and durability of four types of gravity sewer pipes. Pipe products and their materials and design are reviewed, and bedding and backfill types and installation procedures are examined. Resistance of the various pipes to fire, abrasion, and chemical and biological attack are discussed. The information is tied together with a summary that highlights the best type of pipe to use for each situation.

The output of sacrificial current by two metallized coatings was monitored under well-defined conditions. Experiments were conducted at two relative humidities (RH). The performance oj a zinc-aluminum alloy (78:22) was equal or slightly superior to that of pure zinc-coated anodes. However, there was a steady decline in current density output with time, which was attributed to oxidation products forming at the sacrificial anode/concrete interface.

Steel reinforcement corrosion in chloride contaminated concrete is a costly problem that can be mitigated by cathodic protection. A variety of anode systems are currently available for the cathodic protection of reinforcedconcrete. One of the most effective anode systems is made of a noble metal oxide coated titanium mesh. The titanium mesh is first mechanically fastened on the concrete and subsequently encapsulated with a shotcrete or concrete overlay. This system is performing extremely well on horizontal surfaces. However, delamination of the encapsulating shotcrete overlay has occasionally been observed on vertical surfaces such as piers, columns, andwalls. The present research project was initiated to address this problem. The performance of three different cementitious overlays (two proprietary and one designed in-house) were investigated under impressed currentover a period of 31 months. Samples were polarized outdoors or indoors under constant relative humidity. Numerous performance parameters were monitored on the samples that were energized at three different current densities. The worst performance was obtained with the Thorotop HCR overlay for which high circuit resistance and appreciable increases in the driving voltage were observed. The best overlay for cathodic protection was designed to have maximum adhesion using silica fume and minimum resistivity by the addition of carbon fibers.

CORROSION 97: 01 March 1997, New Orleans

4ième Colloque sur la Progression de la Recherche Québé coise sur les ouvrages d'art: 28 April 1997, Québec, Qué, Canada

4ième Colloque sur la Progression de la Recherche Québé coise sur les ouvrages d'art: 28 April 1997, Québec, Qué., Canada

Removing salt-contaminated concrete, patching, and applying waterproofing membranes are treatments used to rehabilitate corrosion-damaged infrastructure. There are concerns about the effectiveness of only using such an approach to mitigate reinforcement corrosion when the concrete is salt-contaminated. Sacrificial cathodic protection (ep) using metallized zinc coatings is regarded as a possible rehabilitationalternative.

Aussi disponible en français: L'étude des conduites souterraines permettra d'en repérer les points faibles

Aussi disponible en français: La réparation du béton endommagé par la corrosion: une nouvelle approche

Proceedings of the 14th Structures Congress : Building an International Community of Structural Engineers: 15 April 1996, Chicago, Illinois, U.S.A.

1995 Conference on Corrosion and Infrastructure: 28 November 1995, Baltimore, Maryland, U.S.A.

Reprinted in NRCC-38966, Durable Parking Structures: 20 March 1995, Calgary, Alberta, Canada

Pipeline corrosion frequently persists underneath disbanded coatings on pipelines that appear to be well protected cathodically. Application of higher cathodic potentials for improved protection may produce hydrogen gas (H2) bubbles that block current flow underneath a disbanded coating. A project was undertaken to determine whether an increase in applied potential results in higher polarization levels on the crevice should increase. Steady-state cathodic protection experiments were performed at three applied potentials in an electrochemical cell simulating the crevice steel under a disbanded coating. The recorded profiles showed that higher levels of protection underneath a disbanded coating could be achieved by applying higher cathodic potentials. Penetration of the cathodic currents underneath a disbanded coating also was more difficult in higher resistivity solutions.

This work was designed to observe how changes in the testing procedure affect results. Factors such as temperature, AC impedance, initial DC current, charge passed, and chloride ion profiles were monitored during polarization of four different concretes. It was found that simple measurement of initial current or resistivity gave the same ranking as conventional tests for the four concretes and can replace the rapid chloride test with a considerable time saving.

The publication is stored in the NRC Archives., Series: Paper (National Research Council of Canada. Institute for Research in Construction); no. IRC-P-3556

Using metallized zinc as the anode in cathodic protection requires special attention to adherence., Aussi disponible en francais: Des chercheurs dé couverent des techniques qui améliorent la protection cathodique