River, reservoir and lake sediment contamination by heavy metals downstream from urban areas of Switzerland

This paper quantifies sediment contamination by heavy metals in four reservoirs and one lake located downstream from major urban areas in Switzerland. The waterbodies include the Wettingen Reservoir (located on the Limmat River downstream from Zürich), the Klingnau Reservoir (on the lower Aare River), the Wohlen Reservoir (downstream from Berne), the Verbois Reservoir (downstream from Geneva) and Vidy Bay (Lake Geneva, city of Lausanne). For all sediment cores and contaminants, a trend is observed from high contaminant values in the lower part of the cores, decreasing to lower concentrations in the upper part of the cores. However, for each site and each element, specific features are recognized. Applying the criteria of the Swiss ordinance on soil protection, all sediment cores must be classified as contaminated by one or more contaminants and at variable levels. From these data, it is concluded that: reservoirs and lakes located downstream from major urban centres in Switzerland have accumulated significant volumes of contaminated sediments in the past, representing the largest, but not the most intensely, contaminated sites on a national scale; the main environmental risk is remobilization of the contaminants and their return to the food chain, particularly by infiltration into the groundwater; and although the processes of remobilization are identified, the conditions of occurrence and the amplitude of the processes are still poorly known. Different options of reservoir and lake sediment management also are discussed and further research topics defined.     

An experimental study on iterative methods to compute transient solutions of large Markov models

In this article, we report results of an experimental study on six iterative methods to compute the transient probabilities of large Markov models: full matrix exponentiation, forward Euler method, explicit Runge-Kutta methods of order 2 and 4 and Adams-Bashforth multi-steps methods of order 2 and 4. We suggest a simple but efficient implementation of these algorithms. We discuss how to tune their few parameters. We present experimental results that contradict the literature.     

Lattice Reduction: A Toolbox for the Cryptanalyst

In recent years, methods based on lattice reduction have been used repeatedly for the cryptanalytic attack of various systems. Even if they do not rest on highly sophisticated theories, these methods may look a bit intricate to practically oriented cryptographers, both from the mathematical and the algorithmic point of view. The aim of this paper is to explain what can be achieved by lattice reduction algorithms, even without understanding the actual mechanisms involved. Two examples are given. One is the attack devised by the second author against Knuth's truncated linear congruential generator. This attack was announced a few years ago and appears here for the first time in complete detail. Received 19 May 1994 and revised 31 December 1997     

Pharmacokinetics and Tissue Uptake of Doxorubicin Associated With Erythroctte-nembrane:erithroctte-Ghosts vs Erythrocyte-Vesicles

This study examined the usefuless of erythrocyte-membrane as a biodegradable carrier for intravenous injection of doxorubicin (DOX). Two different preparations of erythrocyte-membrane were used, erythrocyte-ghosts and erythrocyte-vesicles. Ghosts were prepared from red blood cells by hemolysis and repetitive washing until complete removal of hemoglobin. Erythrocyte-vesicles were prepared by ultrasonication of the ghosts suspension by a sonic dismembrator. The membrane products were then incubated with DOX before the injection. In CD rats, the disposition of DOX solution (DOX in normal saline) and erythrocyte-vesicles-DOX followed a two-compartment open model, whereas the ghosts-DOX exhibited a three-compartment characteristics. The area under the curve of the amount in the heart vs time for ghosts-DOX was approximately the same as for the solution. However, the amount of DOX in the heart after erythrocyte-vesicles-DOX injection was below the sensitivity of the detection. The fraction of DOX excreted unchanged in the urine was 0.54 for ghosts-DOX, 0.22 for DOX solution and 0.06 for erythrocyte-vesicles-DOX. The uptake of the drug by the spleen was increased after the administration of erythrocyte-vesicles-DOX. The observed and the calculated data address the usefulness of these delivery systems for DOX.     

The role of telecommunications in economic development

Annals of Telecommunications - Les télécommunications ont connu un développement soutenu depuis plus de vingt ans. La diffusion des services a toujours été sensible à...     

An approximate nonlinear design procedure for partially prestressed concrete beams

The theoretical basis and the main results of an approximate nonlinear design procedure which attempts to predict the behavior at ultimate of prestressed and partially prestressed concrete members is presented. Difficulties encountered in simulating the actual behavior of concrete and steel are discussed; particular emphasis is put on comparing the various available stress-strain relationships for prestressing steels, and observed variability in their actual properties. Recommended equations and corresponding coefficients are given. Typical results showing the influence on ultimate behavior of major variables such as the type and amount of prestressing steel, the amount of nonprestressed tensile and compressive reinforcement, and the ultimate concrete compressive strain are presented and compared with code derived results. They help point out where the code recommendations, if used, may lead to an unsafe design and what modifications may be needed to make them more representative of observed trends.     

The use of various buffers in the preparation of human lymphocytes for SEM observation

A study is presented of various buffers utilized in the preparation of human lymphocytes for scanning electron microscopy. Of nineteen different buffers tested, Hanks' balanced salt solution +0·04 mol sucrose appeared most adequate for satisfactory preservation of lymphocyte surface architecture.