Materials: carbon nanotubes in an ancient Damascus sabre.

The steel of Damascus blades, which were first encountered by the Crusaders when fighting against Muslims, had features not found in European steels--a characteristic wavy banding pattern known as damask, extraordinary mechanical properties, and an exceptionally sharp cutting edge. Here we use high-resolution transmission electron microscopy to examine a sample of Damascus sabre steel from the seventeenth century and find that it contains carbon nanotubes as well as cementite nanowires. This microstructure may offer insight into the beautiful banding pattern of the ultrahigh-carbon steel created from an ancient recipe that was lost long ago.

Software based digital signal processing and spectrum deconvolution in X-ray spectroscopy.

Approaches for software based digital signal processing and numerical deconvolution of measured signals which overcome limitations of state-of-the-art systems are described. The basic technical equipment for digital signal processing consists of an energy resolving detector with a preamplifier followed by a fast sampling analogue-to-digital converter (ADC). The main idea is the numerical decomposition of the measured signal into contributions caused by single photon absorption using standard pulses. The latter can be obtained by measurements under definite conditions. The maximum pulse rate is then limited only by the ratio of sampling time to the time between two pulses which should be attributed to single events. Thus pulse overlaps do not require pulse rejection. At sampling rates of 10(8) samples per second theoretically a comparable photon rate can be detected at throughputs of 100%. Beyond that it is outlined that in a comparable manner a numerical deconvolution of measured energy spectra (statistic distribution functions of single events) into combinations of standard spectra, which can likewise be determined by measurement, offers outstanding possibilities, too. On the one hand the energy resolution attainable for individual events for a given detector can be improved drastically by the statistical treatment of spectra. On the other hand an energy resolving work principle becomes possible for certain detectors, which do not permit this conventionally due to their poor signal to noise ratio.

Quantification of house dust mite allergens in ambient air.

The house dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae are important sources of indoor allergens. In sensitized patients, house dust mites induce and exacerbate diseases like asthma bronchiale, rhinitis, and conjunctivitis. The most significant exposure of persons occurs overnight in bed and to a lesser extent, during the daytime while performing activities like vacuum cleaning or bed making. In general, house dust mite antigens are quantified in samples of reservoir dust of carpets or beds. Yet, assessing allergens in ambient air would better represent human exposures because inhalation is the main route of uptake, and a close correlation between levels of floor and air antigens has not yet been proved. Unfortunately, because of extremely low airborne particle concentrations, analyses are difficult to perform and depend on sophisticated sampling strategies, as well as on sensitive immunometric detection assays. Using monoclonal immunoassays, house dust mite antigens, quantified in undisturbed conditions in ambient air, are found at pg/m3 levels. The disturbance of reservoir dust by vacuum cleaning or bed making increases the airborne allergen levels up to ng/m3 concentrations. In this review, we discuss the current knowledge regarding the analysis of airborne house dust mites in both undisturbed and disturbed ambient air. The advantages and disadvantages of different sampling strategies are outlined.

Micronucleus formation in human lymphocytes and in the metabolically competent human hepatoma cell line Hep-G2: results with 15 naturally occurring substances.

To examine the concordance of two metabolizing systems for use in genotoxocity testing with the micronucleus test, 15 naturally occurring substances (arecoline, the plant extract aristolochic acid, beta-asarone, benzyl acetate, coumarin, emodine, isatidine dihydrate, monocrotaline, psoralen, reserpine, retrorsine, safrole, sanguinarine chloride, tannin and thiourea) were tested for their genotoxicity in the cytokinesis-block micronucleus test in vitro with human lymphocytes and in the presence and the absence of an exogenous metabolizing system from rat liver S9-mix and the metabolically competent human hepatoma cell line Hep-G2. Arecoline, the plant extract aristolochic acid, psoralen and tannin caused a significant increase in the number of micronuclei in human lymphocytes in the presence and the absence of an exogenous metabolising system from rat liver S9-mix and the metabolically competent human hepatoma cell line Hep-G2. A significant increase in the number of micronuclei with beta-asarone, coumarin, monocrotaline and retrorsine could be detected in the presence of S9-mix and the cell line Hep-G2. Benzyl acetate, emodine, isatidine dihydrate, reserpine, safrole, sanguinarine chloride and thiourea did not reveal any micronucleus inducing activity in either human lymphocytes or in Hep-G2. In addition to the other Hep-G2 results in the literature, this human hepatoma cell line could have a useful potential in the in vitro micronucleus test.

DAFS experiments with non-centrosymmetric single crystals.

Diffraction anomalous fine structure (DAFS) experiments were applied to an epitaxially grown (Ga,In)P layer on a [001] GaAs substrate as a single-crystalline model substance. The requirements for the reliable measurement of reflection intensities as a function of photon energy, as well as the quantitative DAFS analysis resulting in the complex-valued fine-structure function of the scattering factor, are described. In the case of single crystals, effort had to be put into performing the DAFS measurements in order to hold the position of the Bragg reflection exactly during the energy scan. Using the zinc-blende-type structure as an example, it is shown for the first time that, similar to single-crystal structure analysis, the lack of inversion symmetry has a significant impact on the DAFS signal, so that DAFS may contribute to structure analysis as well.