About the existing discrepancy in the determinations of theAvogadro constant

The values for the Avogadro constant N_A, derived from lattice spacing, density, and molar mass of silicon single crystals at several metrological institutes, show significant differences. To illuminate this discrepancy, comparison measurements of lattice spacing and density were performed. Positron annihilation measurements were used to estimate the vacancy concentration in Si samples. All crystals lead to nearly the same lattice spacing after correction for the influence of carbon and oxygen impurities. It is proved that the discrepancy in the determinations of the Avogadro constant cannot be explained by vacancies or interstitials. Also indications for macroscopic bubbles or cavities could not be found     

Congenital ball-and-socket anomaly of the ankle

We present the clinical and radiographic appearance of 11 patients with a ball-and-socket ankle joint with an average follow-up of 13.7 years. Ten patients demonstrated parallel symptoms of the femur-fibula-ulna syndrome (FFU) associated with a mean leg-length discrepancy of 4.3 cm (range, 2-20). In six patients, an annual follow-up of talar development was possible. Radiographically the patients showed an additional tarsal coalition at a mean age of 4.8 years (range, 3.2-5.9). This earlier fusion could be detected by an arthrographic examination. All patients had no clinical complaints except a slight reduction of hindfoot mobility. The ball-and-socket ankle joint is presumably not congenital itself but secondary to congenital conditions in the peritalar region.     

The Avogadro constant: determining the number of atoms in a single-crystal ²⁸Si sphere

The Avogadro constant, the number of entities in an amount of substance of one mole, links the atomic and the macroscopic properties of matter. Since the molar Planck constant--the product of the Planck constant and the Avogadro constant--is very well known via the measurement of the Rydberg constant, the Avogadro constant is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a new definition of the kilogram in terms of a fundamental constant. Here, we describe a new and unique approach to determine the Avogadro constant from the number of atoms in 1 kg single-crystal spheres that are highly enriched with the (28)Si isotope. This approach has enabled us to apply isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, N(A)=6.022 140 82(18)×10(23) mol(-1), is now the most accurate input datum for a new definition of the kilogram.     

Measuring delirium severity in older general hospital inpatients without dementia. The Delirium Severity Scale

The authors evaluated the validity, reliability, and sensitivity to change of the Delirium Severity Scale (DSS), a 10-minute assessment consisting of Forward Digit Span and Similarities. Twenty-two older inpatients with delirium but not dementia and 15 control patients were administered the DSS during hospitalization. Scores were significantly inversely correlated with experts' quantitative ratings of severity at all three time-points examined. The DSS showed significant improvement over time (P < 0.001) and significant correlation with improvement in expert ratings (P = 0.026). The DSS shows promise as a valid and reliable measure sensitive to changing symptom severity.     

Deducing calibration and measurement capabilities from key comparisons

The Mutual Recognition Arrangement does not explain how the calibration and measurement capabilities of an institute should be deduced from the results of a key comparison. A way is proposed that uses the uncertainty budget of the measuring method and first identifies the main uncertainty contributions. Then, the results of the key comparison are used to support the main parts of the uncertainty budget of a participant. The uncertainty for a wide range of measurement conditions can then be calculated with this approved uncertainty budget. Additionally, the typical uncertainty budget of the method can help to choose the samples or measurement conditions for the comparison that allow checking the main uncertainty contributions independently. The ideas are illustrated by an example from density comparisons.     

Phenols and metals in sugar-cane spirits. Quantitative analysis and effect on radical formation and radical scavenging

A fluorescence-based analytical method for quantification of phenolic compounds in sugar cane spirits (and other distilled alcoholic beverages) was developed. Sample preparation involved reverse-phase solid phase extraction and separation by gradient reversed-phase HPLC with fluorescence detection. Twenty-one Brazilian sugar cane spirits (aged and non-aged cachaça) were analyzed and phenol, guaiacol, o-cresol, p-/m-cresol, 3, 5-xylenol, 4-ethylphenol, 4-ethylguaiacol, 2-ethylphenol, eugenol, (+)-catechin, (-)-epicatechin, and scopoletin quantified. The detection limit was between 0.01 mg l^-1 (eugenol and scopoletin) and 0.1 mg l^-1 [(+)-catechin and (-)-epicatechin]. Kaempferol and quercetin were quantified in the same spirits, together with copper and iron, using HPLC (spectrophotometric detection) and atomic absorption spectroscopy, respectively. Large variations between various spirits were noted: total phenols were between 1.5 and 70 mg l^-1, flavonoids were from below detection to 3.5 mg l^-1, Cu was between 0.04 and 7.0 mg l^-1; and Fe between 0.01 and 0.78 mg l^-1. The tendency of radical formation in the spirits was determined by electron spin resonance spectroscopy using N-t-butyl-!-phenylnitrone spin trapping, and radical scavenging capacity was determined spectrophometrically using the stable 2,2-diphenyl-1-picrylhydrazyl radical as probe. Radical formation depends mainly on the Cu content, while the radical scavenging and antioxidative capacity mainly depends on the flavonoid content. (+)-Catechin and (-)-epicatechin are most important for the antioxidative capacity as confirmed in a model experiment, where oxidation was induced by iron catalysis.     

Density Determination of a Small Isotopically Enriched Silicon Single Crystal

For a new determination of the Avogadro constant using small crystals of isotopically enriched silicon, the density of a sample was determined at Physikalisch-Technische Bundesanstalt. The sample has a mass of 58 g and a ²⁸Si enrichment of about 99.98%. Its density was compared by the pressure-of-flotation method to the density of a large hollow transfer standard that was manufactured from natural silicon, to have the same density. The flotation measurement yielded a relative density difference of 0.64(10) 10^-6. The density of the transfer standard was then measured by hydrostatic weighing, which is traceable to a primary density standard. Thus, the density of the small ²⁸Si sample was determined to be 2320.08031(40) kg/m ³, i.e., with a relative standard uncertainty of 0.17 10^-6