Electrolytic conductivity is an important measuring quantity for the control and monitoring of processes in aqueous media, which are important in various areas of industry. In the metrological hierarchy the primary measuring methods are superior to all others, i. e. secondary measuring methods (e. g. with standard measuring cells) and measurements with commercial conductivity meters with 2- and 4-pole measuring cells are subordinate to them.ZMK & ANALYTIK GmbH developed a primary measuring device for electrolytic conductivity. The temperature control was realized by performing the measurements in a liquid bath.The following article contains the statement of the measurement uncertainty budget for the primary measurement method. The combined measurement uncertainty is composed of several contributions. As important contributions, the resistance measurement, the measurement of the temperature as well as the displacement of the measuring electrodes by a defined displacement path were considered in the measurement uncertainty, which in turn are composed of individual contributions. The individual measurement uncertainty contributions of the electrical measurements (resistances), the measurements of the temperature, the dimensional measurements as well as other contributions are presented in detail. The correlation of individual contributions among each other is taken into account.

Zusammenfassung Die elektrolytische Leitfähigkeit ist eine wichtige Messgröße zur Kontrolle und Überwachung von Prozessen in wässrigen Medien, die in unterschiedlichen Bereichen der Industrie von Bedeutung sind. In der metrologischen Hierarchie sind die primären Messverfahren allen anderen übergeordnet, d. h. ihnen nachgeordnet sind sekundäre Messverfahren (z. B. mit Standardmesszellen) sowie Messungen mit kommerziellen Leitfähigkeitsmessgeräten mit 2- und 4-Polmesszellen. Die ZMK & ANALYTIK GmbH entwickelte eine Primärmesseinrichtung für die elektrolytische Leitfähigkeit. Die Temperierung wurde durch Durchführung der Messungen in einem Flüssigkeitsbad realisiert. Der folgende Artikel beinhaltet die Aufstellung der Messunsicherheitsbilanz für das primäre Messverfahren. Die kombinierte Messunsicherheit setzt sich aus mehreren Beiträgen zusammen. Als wichtige Beiträge wurden die Widerstandsmessung, die Messung der Temperatur sowie die Verschiebung der Messelektroden um einen definierten Verschiebeweg in der Messunsicherheit berücksichtigt, die sich wiederum aus Einzelbeiträgen zusammensetzen. Die einzelnen Messunsicherheitsbeiträge der elektrischen Messungen (Widerstände), der Messungen der Temperatur, den dimensionellen Messungen sowie weitere Beiträge werden detailliert dargestellt. Die Korrelation einzelner Beiträge untereinander wird berücksichtigt.

For primary pH measurements, a platinum hydrogen electrode and a silver chloride electrode are immersed in the same solution in a cell without transference (Harned cell). The platinum electrode is covered with dispersed platinum (platinum black) to increase the surface area. To determine the influence of specific deposition conditions (current density, duration, and composition of the electrolyte) on the properties of platinum black, the surface area, and the electrode performance, platinized platinum electrodes were investigated systematically using scanning electron microscopy and optical microscopy. Confocal laser scanning microscopy was applied to obtain quantitative information about roughness parameters. After assessment of the surface structures, improved conditions for the fabrication of platinized platinum electrodes were derived. It was found that all investigated electrochemically coated platinum electrodes obtained comparable values of standard potential of Ag/AgCl-electrodes within the measurement uncertainty. The platinum layer obtained by sputtering was significantly less distinct and less homogenous than the layer of platinum obtained by electrochemical deposition. The examinatio of shiny (uncoated) platinum electrodes evidenced a significant difference between multiple-used and freshly prepared platinum electrodes. Thus, uncoated platinum electrodes are not suitable for the Harned cell measurement either. Thus, to obtain reliable and reproducible results in pH measurements using the primary method, an electrochemical coating of the platinum electrodes under defined conditions is required.

This work presents a new differential potentiometric cell for the standardization of pH buffer solutions and its evaluation, by means of a bilateral interlaboratory comparison, in relation to a traditional Baucke cell. The results obtained with the two cells were exactly the same for three of the pH buffer solutions analyzed (1.68, 4.01, and 6.86) and similar to each other for the remaining buffer solution (9.18). The new cell showed an average measurement time of only 21minutes, in comparison with one to three hours for other cells described in the literature (including the Baucke cell).

The pH value is an important quantity used to characterize aqueous solutions including biological media. There are only few fields of application for spectroscopic pH measurements. pH is usually measured electrochemically by potentiometry. The cell voltage of a pH measuring chain with glass electrode is measured by means of an appropriate pH measuring device. To be able to assess whether the result of a pH measurement meets all requirements a statement of the measurement uncertainty is mandatory. In the following the metrological traceability chain for pH is described. The paper will focus on important uncertainty contributions to be taken into account by the user. This especially includes technical product parameters.

pH and electrolytic conductivity are important metrological quantities for several areas of industry. To get reliable results it is necessary to calibrate measuring instruments and devices regularly. For this purpose certified reference solutions are needed. DKD-K-06901 is a manufacturer of certified reference solutions and offers calibration services in the field of analytical chemistry. There are three accredited calibration procedures for the determination of pH used by ZKM - ANALYTIK - GmbH. A new calibration procedure for electrolytic conductivity was established by experts in DKD-K-06901 as the result of a development project in cooperation with National Metrology Institutes. The validation of all procedures is guaranteed by the participation in national and international comparison measurements. Furthermore DKD-K-06901 is actively involved in the work of technical and standardisation committees for developments of analytical quantities.

International efforts concentrate on the traceability of electrolytic conductivity at the field level having small associated measurement uncertainties. Although the measurement of conductivity at ...

Measurements of pH are performed on a large scale at laboratory level, and in industry. To meet the quality-control requirements and other technical specifications there is a need for traceability in measurement results. The prerequisite for the international acceptance of analytical data is reliability. To measure means to compare. Comparability entails use of recognised references to which the standard buffer solutions used for calibration of pH meter-electrode assemblies can be traced. The new recommendation on the measurement of pH recently published as a provisional document by the International Union on Pure and Applied Chemistry (IUPAC) enables traceability for measured pH values to a conventional reference frame which is recognised world-wide. The primary method for pH will be described. If analytical data are to be accepted internationally it is necessary to demonstrate the equivalence of the national traceability structures, including national measurement standards. For the first time key comparisons for pH have been performed by the Consultative Committee for Amount of Substance (CCQM, set up by the International Bureau of Weights and Measures, BIPM) to assess the equivalence of the national measurement procedures used to determine the pH of primary standard buffer solutions. The results of the first key comparison on pH CCQM-K9, and other international initiatives to improve the consistency of the results of measurement for pH, are reported.

In spring of 1995 a field experiment was started on a loess-derived Chernozem, managed by deep (22 cm) and shallow (12 cm) inversion tillage by spade plough, to test the effect of stepwise mechanical loading on the structure of a silty clay soil (30% clay) and its recovery during subsequent years. Beside an unwheeled control tillage systems were compacted track by track at a water content near field capacity using the following loading treatments: light (2 X 2.5 t; number of wheel passes times wheel load); medium (2 X 5 t) and high (6 X 5 t). Soil physical investigations. density distribution, and spatial visualizations of macropores based on computed tomography (CT) and scanning electron microscopy of aggregate surfaces indicate that increasing loading leads to a progressive homogenization of soil structure. Different stages of this process include the compression of aerated macropores or interaggregate pore space, respectively, by light loading and the deformation of aggregates to a coherent soil mass by high loading. Accordingly, the intraaggregate structure is characterized by an increase of parallel arrangement of clay particles, causing an extension of the range of normal shrinkage by elimination of structural shrinkage and displacement of residual shrinkage to lower moisture contents. Soil homogenization caused by kneading and supported by positive pore water pressure is the dominant harmful process of structure deterioration of the silty clay, when compacted with high loads at high soil water content.As a consequence of 12 cm shallow tillage over years the lower part of the topsoil has been preconsolidated. Therefore, the deformation resistance is slightly higher compared to 22cm deep tillage.The stronger the deformation and homogenization of soil structure by loading, the stronger is the contraction of the soil matrix associated with a reheterogenization during three years after loading. Cracking by shrinkage induces a reaggregation of structure, having been obtained before by medium and high loading. Thereby the density of the soil matrix between cracks increases.As a consequence of this heterogenization by densification and cracking aggregates are preferentially remoistened via crack walls, inducing a partial but not a complete reswelling as shown by CT-images. Therefore the spatial position of the crack pattern does not change. On the other hand, at the end of investigation period, the light loaded treatment was not longer different to the unloaded control.Reaggregation by wetting and drying cycles is a key process in silty clays in initiating a restoration of the degraded structure. The formation of biopores is less significant. However, the mechanism of "structure repair" by physical processes does not lead to a reproduction of unloaded structure.

Influenza and related pneumonia continue to cause significant amounts of morbidity and mortality despite the availability of effective vaccines. Two comparable counties in Massachusetts served as project areas of a national trial to see if reimbursement for immunizing Medicare-B eligible recipients against influenza would increase the use of the vaccine and reduce the costs attributed to related morbidity. Providers of health and social services to elders were recruited to participate in one county. A variety of professional and public education campaigns and media were used to promote influenza immunizations. Laboratory-based surveillance was instituted in both counties to assess the extent of circulating virus in each. Vaccine was made available to medical providers in both counties. While the amount of vaccine used in the comparison county increased by 6% from pre-project time (16,000 to 17,000 doses administered), vaccine use increased 219% in the intervention county (21,250 to 46,494 doses administered). In a post-project survey of participating physicians, 88% of 238 respondents reported administering less than 100 doses of influenza vaccine per year prior to the project. By the end of the project, only 32% administered less than 100 in the previous year. This project demonstrated the need for educating both the provider and the public in order to successfully promote immunizations. It was not clear, however, if reimbursement was a more important factor for promoting influenza immunizations than was universal distribution of free vaccine.

Frequently the use of morphological observation of soil structure to assess effects of tillage operations has been restricted by the extreme slowness of sample preparation. A method for rapid analysis of structure with the help of X-ray radiographs is described. The method is based on differences in attenuation of transmitted X-rays by soil pores and the adjoining soil mass. After digitizing X-ray pictures of unimpregnated soil cores using a video scanner and digitizer we found a close relationship between the average bulk density of soil within a core and the mean greylevel value of the digital image when sample thickness, origin and organic matter content of soil material, energy of radiation and sensitivness of X-ray film are the same. Application of a universal image processing system (DIAS) for the quantification of image parameters by procedures of binarization, skeletonization and direction coding demonstrated that radiographs are useful for analyzing spatial distribution, shape and orientation of soil structure elements. Results are illustrated by examples of soil tillage experiments,

Recently a new virus has been described which infects woodchucks, Marmota monax. This virus, named woodchuck hepatitis virus (WHV) is closely related to human hepatitis virus (HBV). The virions have the same principal antigenic system involving surface and core determinants and a serological relationship has been found. WHV has also a DNA polymerase associated with the core. It has previously been reported that trisodium phosphonoformate (PFA) but not phosphonoacetic acid (PAA) inhibits DNA polymerase associated with HBV. This investigation shows the same type of inhibition pattern by PFA and PAA on WHV DNA polymerase.

Droperidol-fentanyl sedation for cardiac catheterization was evaluated in 106 consecutive children ≥ two years of age. The dose of 0.025 c.c. per kilogram of body weight (maximum 1 c.c.) produced adequate sedation in all but two patients without producing significant hypoventilation or heart rate changes. In patients without left heart volume overload or myocardial disease, left ventricular volume studies and pressurevelocity indices of contractile state were normal. Side effects were rarely encountered and easily controlled or reversed with diphenhydramine. Although we recommend this combination for cardiac catheterization sedation, we would not recommend exceeding our dosage schedule.