Tools to monitor corrosion of cement-containing water mains.

Approximately 40,000 km of the drinking water network in The Netherlands consists of asbestos cement water pipes. The number of fractures in these pipes has increased greatly in recent years. This is due to corrosion of the asbestos cement (AC) which affects the condition of the pipe. Every time a fracture occurs, the question is raised of whether the pipe in question has to be replaced or repaired. A relatively simple destructive technique and non-destructive tests are used on a large scale to assess the condition of the AC pipes in use. Not only is corrosion detrimental to the pipes themselves, it also influences the water quality. Corrosion of the inner walls of cement-containing pipes involves the leaching of hydroxides. This causes pH changes resulting in scaling in water mains and domestic installations. Monitoring techniques have been developed to determine the effects of leaching on water quality. The large-scale use of the relatively simple techniques at water companies increases insight into the condition of the drinking water network, the life expectancy of the pipes and the effects of corrosion on the water quality. Applying these techniques enables those involved to make decisions on pipe replacement and to provide solutions for reducing the effects of leaching.

maintenance and rehabilitation strategy for water supply systems in The Netherlands

El articulo trata sobre el desafio que implica el mantenimiento y la rehabilitacion de los sistemas de suministro de agua y, especificamente, sobre el modelo desarrollado por Holanda dentro de su programa de investigacion en la industria del agua. El modelo para el mantenimiento del sistema de suministro de agua identifica los elementos necesarios para un mantenimiento racional, y las relaciones entre dichos elementos; y puede emplearse para tomar decisiones respecto a la rehabilitacion, y para preveer necesidades de rehabilitacion futuras

Maintenance and rehabilitation strategy for water supply systems in The Netherlands

El articulo trata sobre el desafio que implica el mantenimiento y la rehabilitacion de los sistemas de suministro de agua y, especificamente, sobre el modelo desarrollado por Holanda dentro de su programa de investigacion en la industria del agua. El modelo para el mantenimiento del sistema de suministro de agua identifica los elementos necesarios para un mantenimiento racional, y las relaciones entre dichos elementos; y puede emplearse para tomar decisiones respecto a la rehabilitacion, y para preveer necesidades de rehabilitacion futuras

Effects of ?-latrotoxin, lanthanides and elevated potassium concentration on acetylcholine release and free intracellular calcium levels in rat cerebral cortex synaptosomes.

At peripheral cholinergic nerve terminals, lanthanum (La(3+)) increases acetylcholine (ACh) release and supports transmitter release induced by ?-latrotoxin (?-LTx). The present experiments investigate these interactions at central cholinergic nerve terminals by measuring the effects of La(3+) and gadolinium (Gd(3+)), another element of the lathanide (Ln(3+)) series, on ACh release and free intracellular calcium concentrations ([Ca(2+)](i)) in rat cortical synaptosomal preparations. Ln(3+) had no measurable effect on basal synaptosomal ACh release, ACh contents or [Ca(2+)](i). Release of ACh induced by ?-LTx was inhibited by the presence of Ln(3+), as were ACh release responses to elevated K(+). The rise in [Ca(2+)](i) induced by ?-LTx was inhibited by Ln(3+) at concentrations similar to those that inhibited ACh release. Addition of Ln(3+) subsequent to an ?-LTx-evoked increase in [Ca(2+)](i) resulted in an immediate (within 4 s) cessation of calcium entry. Gd(3+) binding studies using the radioisotope (153)Gd(3+) revealed that Gd(3+) bound extremely rapidly to synaptosomes and that under the experimental conditions used to measure either ?-LTx- or K(+)-induced ACh release, little or no free Gd(3+) was likely to exist in the medium. We conclude that at central cholinergic neurons 1-Ln(3+) do not affect basal ACh release and 2-Ln(3+) are effective inhibitors for ?-LTx-induced ACh release and changes in [Ca(2+)](i).

Purification and characterization of Saccharomyces cerevisiae mitochondrial elongation factor Tu.

Yeast mitochondrial elongation factor Tu (EF-Tu) was purified 200-fold from a mitochondrial extract of Saccharomyces cerevisiae to yield a single polypeptide of Mr = approximately 47,000. The factor was detected by complementation with Escherichia coli elongation factor G and ribosomes in an in vitro phenylalanine polymerization reaction. Mitochondrial EF-Tu, like E. coli EF-Tu, catalyzes the binding of aminoacyl-tRNA to ribosomes and possesses an intrinsic GTP hydrolyzing activity which can be activated either by kirromycin or by ribosomes. Kinetic and binding analyses of the interactions of mitochondrial EF-Tu with guanine nucleotides yielded affinity constants for GTP and GDP of approximately 5 and 25 microM, respectively. The corresponding affinity constants for the E. coli factor are approximately 0.3 and 0.003 microM, respectively. In keeping with these observations, we found that purified mitochondrial EF-Tu, unlike E. coli EF-Tu, does not contain endogenously bound nucleotide and is not stabilized by GDP. In addition, we have been unable to detect a functional counterpart to E. coli EF-Ts in extracts of yeast mitochondria and E. coli EF-Ts did not detectably stimulate amino acid polymerization with mitochondrial EF-Tu or enhance the binding of guanine nucleotides to the factor. We conclude that while yeast mitochondrial EF-Tu is functionally analogous to and interchangeable with E. coli EF-Tu, its affinity for guanine nucleotides and interaction with EF-Ts are quite different from those of E. coli EF-Tu.

Anion-exchange chromatography of proteins on AG MP-1 using high-performance liquid chromatography equipment.

That the macroporous anion-exchange resin AG MP-1 can be used with HPLC equipment and common aqueous buffers for the chromatography of proteins is shown. The utility of this system is illustrated by the partial purification and complete resolution of the three protein synthesis elongation factors from each other, starting with a crude extract of Escherichia coli. The factors were purified 10- to 30-fold in a yield of 50 to 90% with a single 60-min chromatographic program of increasing NaCl concentration. Other proteins from various biological sources were purified with similar results. Thus, it appears that AG MP-1 is useful, at least in some applications, for the rapid, reproducible, and economical purification of proteins using HPLC equipment.