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The design of a parameter-dependent controller to reject periodic mould level fluctuations at a thin slab caster is presented. These fluctuations can be related to bulging of the solidified steel shell between the supporting rolls. They deteriorate the steel quality and prohibit high speed casting. A state of the art controller has been designed to suppress these casting speed dependent fluctuations and is based on a H∞-optimal controller design technique. The controller has been implemented at caster of the Corus Direct Sheet Plant in IJmuiden. Measurement results show a significant reduction of these periodic mould level fluctuations.

For a large number of DSC calibration substances the vapour pressure at room temperature or at transition temperature (whichever is the highest) is given. It is important to know the vapour pressure of substances, because a DSC measurement on a substance with a high vapour pressure requires encapsulation of the substance in a hermetically sealed crucible to prevent evaporation. Because the calibration procedure must be performed using the same type of sample pan as will be used during the actual measurements, the presented information allows one to decide which calibration substances and/or what type of sample pan should be used for calibration.

A number of compounds is investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibrations. A third compound, namely 4,4’-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Other compounds like NaNO3, In, Hg and Pb, show a slight supercooling. Nevertheless they can be used for heat calibration. The use of large samples of NaNO3and In gives the possibility to construct the equilibrium onset temperatures of the cooling peaks, so these two compounds are also appropriate for temperature calibration on cooling.

A number of compounds are investigated for DSC calibration during cooling. Adamantane and Zn show fast reversible transitions and can be applied both for temperature and for heat calibration. A third compound, namely 4,4′-azoxyanisole, has a liquid crystal to isotropic liquid transition at 409 K. This compound can be used for temperature calibration. Heat calibration with this compound is more problematic because of the small heat effect and the construction of the baseline. Two other compounds, namely Hg and Pb, show a slight undercooling. Nevertheless they can be used for heat calibration, and possibly also for temperature calibration during cooling.

Recently, we showed that complement resistance is an important virulence factor of Moraxella (Branhamella) catarrhalis. Our study used a serum bactericidal assay to determine complement resistance in M. catarrhalis. Although the serum bactericidal assay is considered the "gold standard" for determining complement resistance, it is laborious and time-consuming and therefore not well suited for large-scale studies. Using a large number (n = 324) of M. catarrhalis isolates obtained from the sputa of patients with lower respiratory tract infections (n = 200) and young carriers (n = 124), we assessed the value of a simple "culture-and-spot" test as an alternative to the serum bactericidal assay. For both groups of isolates, the degree of concordance between the two tests used was very significant (P < 0.0001). The agreement between the two assays was estimated to be "excellent beyond chance" (as determined by Cohen's kappa test). The culture-and-spot assay is a valuable alternative to the serum bactericidal assay, not only for screening purposes as shown here but also for studying the mechanism of complement resistance in M. catarrhalis at the molecular level.

An electronic surveillance network for monitoring antibiotic resistance in The Netherlands has been in operation since 1989. Seven public health laboratories participate and the system covers about 25% of all bacteriological determinations in The Netherlands. This paper reports the results of staphylococci isolated in the period 1989-1995. About 0.3% of the Staphylococcus aureus isolates in the study period were resistant to methicillin. This low percentage may be due to the restrictive use of antibiotics and to strict isolation measures aimed at eradicating methicillin-resistant S. aureus. Low frequencies of resistance among methicillin-resistant S. aureus were found for vancomycin (0%), chloramphenicol (11%), cotrimoxazole (11%), mupirocin (3% low-level resistance) and fusidic acid (7%). Twenty-one percent of the coagulase-negative staphylococci were resistant to methicillin. Low frequencies of resistance among these methicillin-resistant coagulase-negative staphylococci were those to vancomycin (0.4%), nitrofurantoin (2%), doxycycline (20%) and amikacin (20%). Coagulase-negative staphylococci from cerebrospinal fluid, blood and skin were less often resistant to quinolones than isolates from respiratory tract, faeces and urine. A significant increase in resistance of coagulase-negative staphylococci to methicillin, erythromycin, gentamicin and ciprofloxacin was observed in the investigated period but the resistance to doxycycline and co-trimoxazole decreased in the last few years. To confirm the determination of methicillin resistance and coagulase production, a PCR method was developed which detects both the mecA and the coagulase gene. The results of the PCR method correlated well with the methicillin MIC as determined by an agar-dilution method.

The mechanism of resistance to human complement-mediated killing in Moraxella catarrhalis was studied by comparing different complement-sensitive and complement-resistant M. catarrhalis strains in a functional bystander hemolysis assay and an enzyme-linked immunosorbent assay (ELISA) for soluble terminal complement complexes. Complement-resistant stains appeared to activate complement to the same extent as, or even slightly better than, complement-sensitive strains. This indicates that complement-resistant strains do not inhibit classical or alternative pathway activation but interfere with complement at the level of membrane attack complex formation. A clear difference in dose-response curves for resistant and sensitive strains was observed both in the bystander hemolysis assay and in the ELISA. Complement-resistant strains showed optimum curves, whereas complement-sensitive strains gave almost linear curves. We conclude that resistant strains bind and/or inactivate one of the terminal complement components or intermediates involved in membrane attack complex formation. Trypsin, known to abolish complement resistance, changed the optimum dose-response curve of a resistant strain to a linear one, which strongly suggests that complement resistance is mediated by an M. catarrhalis-associated protein. This protein acts directly or through the binding of a terminal complement inhibitor present in serum.

Two compounds are described with interesting properties for use in DSC. The first compound is adamantane (C10H16), with a reversible solid-solid transition at 208.62 K [1], suitable for DSC calibration at this low temperature [2]. The second compound is 4,4'-azoxyanisole (C14H14N2O3), with a liquid crystal range between 390 and 407 K [3]. This compound shows two transitions on heating, with a large heat effect at 390 K and a small heat effect at 407 K. For this reason, this substance is well suitable for testing the sensitivity and the resolution of DSC instruments [4]. For both compounds not only the heating, but also the cooling behaviour is investigated.

To assess the risk of Strongyloides stercoralistransmission from two patients with disseminated strongyloidiasis to medical staff who had been in close contact with the patients, blood and stool specimens were obtained from medical staff two to three months after close contact with the patients. Antibodies to S. stercoraliswere determined in blood. Stool specimens were tested for parasites with three different procedures.

HIGH levels of mercury may occur in the tissues of seals, dolphins and porpoises1–4. In the Netherlands from 225 to 765 p.p.m. (wet weight) in liver and from 9.9 to 31 p.p.m. in brain have been detected in adult specimens of the common seal (Phoca vitulina) which were found dead4. Brain concentrations were of the same order as those in the brain tissue of animals of various species poisoned experimentally by methyl-mercury compounds5. As most of the mercury in marine fish is present as methylmercury5, the high levels in seal brain suggest that these animals are affected by the toxic action of methylmercury compounds. Analyses of the methylmercury levels according to Westöö6in the livers of six seals shot in the German part of the Wadden Sea and two adults found dead showed that only 2 to 14% of the total mercury was methylmercury. Similarly, of the 10 and 15 p.p.m. total mercury in the brain of the latter two seals, only 2.2 and 13% respectively could be recovered as methylmercury. Neutron activation analysis of the tissue precipitate remaining after benzene extraction of the acidified homogenates obtained in the methylmercury analysis has shown that on average more than 90 % of the mercury remains attached to the tissue components. In humans and in experimental animals poisoned by methylmercury compounds most or probably all mercury is in the form of methylmercury (refs 7 and 8 and S. Skerfving, report by the Department of Environmental Hygiene, Karolinska Institute, Stockholm). Thus the mechanism of binding of mercury to the tissues of seals may be different.