Ferdinand Hardinghaus

Cytotoxicity screening of 23 engineered nanomaterials using a test matrix of ten cell lines and three different assays

BackgroundEngineered nanomaterials display unique properties that may have impact on human health, and thus require a reliable evaluation of their potential toxicity. Here, we performed a standardized in vitro screening of 23 engineered nanomaterials. We thoroughly characterized the physicochemical properties of the nanomaterials and adapted three classical in vitro toxicity assays to eliminate nanomaterial interference. Nanomaterial toxicity was assessed in ten representative cell lines.ResultsSix nanomaterials induced oxidative cell stress while only a single nanomaterial reduced cellular metabolic activity and none of the particles affected cell viability. Results from heterogeneous and chemically identical particles suggested that surface chemistry, surface coating and chemical composition are likely determinants of nanomaterial toxicity. Individual cell lines differed significantly in their response, dependent on the particle type and the toxicity endpoint measured.ConclusionIn vitro toxicity of the analyzed engineered nanomaterials cannot be attributed to a defined physicochemical property. Therefore, the accurate identification of nanomaterial cytotoxicity requires a matrix based on a set of sensitive cell lines and in vitro assays measuring different cytotoxicity endpoints.

Zn doping of YBa2Cu3O7 in melt textured materials: peak effect and high trapped fields

Abstract The previously introduced modified melt crystallization process (MMCP) has been applied to prepare single grain YBCO bulk material with Zn partially substituting for Cu. Hole doping was controlled by an appropriate oxidizing treatment of the as-grown bulk. A field induced pinning was indicated by a well pronounced peak of the critical current density jc in the jc vs. H relationship for the maximal oxidized (overdoped) material containing Zn, whereas pure overdoped YBCO shows no peak effect. The peak effect for Zn-doped YBCO appearing for T=77 K at a relatively high field of about 3 T can be attributed to pair breaking by locally induced magnetic moments due to in plane Zn for Cu substitution. Besides high quality of the bulk YBCO, the peak effect is the reason for the trapped field as large as 1.12 T at 77 K in the cylinder of only 25 mm in diameter.

YBCO — monoliths with trapped fields more than 14 T and peak effect

Abstract This paper reports on the trapped fields of 14.3 and 11.4 T measured in the gap between two YBCO cylinders and on top of a single YBCO cylinder, respectively. The magnetic flux has been trapped at 17 and 22 K, respectively. The composite material consists of a YBCO-matrix with Ag inclusions and was reinforced by a bandage of steel. A modified melt crystallisation process was applied to grow the bulk superconductors which takes into account the features in the phase diagram due to the additional silver component. On the other hand, the trapped fields at 77 K benefit from the newly proposed chemical doping by Zn on Cu plane sites which results in a well pronounced peak effect near 3 T. This peak in relatively high fields is thought to result from pair breaking by induced magnetic moments due to in plane substitution of Cu by Zn. Thus, more than 1.1 T has efficiently been trapped in a cylindrical sample of only 25 mm in diameter.

Large YBCO — Monoliths with Peak Effect and High Trapped Fields

The present paper reports on the trapped fields of 9.0 and 11.4 T (on top of a single YBCO cylinder) which have been trapped at 42.5 and 17 K, respectively. The composite material consists of a YBCO-matrix with Ag inclusions and was reinforced by a bandage from steel. A modified melt crystallisation process was applied to grow the superconducting bulk. On the other hand, the trapped fields at 77 K benefit from the newly proposed chemical doping by Zn on Cu plane sites which results in a well pronounced peak effect between 1 and 3 T. Thus, more than 1.1 T has efficiently been trapped in a cylindrical sample of only 25 mm in diameter.

Control of the Birefringence Dispersion of an Optical Polymer by Doping with an Inorganic Crystal

The birefringence dispersion of a polymer film was controlled by doping with an inorganic birefringent crystal. Nanosized crystals of strontium carbonate (SrCO3) with a needlelike shape of average length of 192 nm were oriented during the preparation of the film by solvent casting, and the contributions of the SrCO3 crystals to the birefringence and to the birefringence dispersion of the composite film were analyzed. A SrCO3-doped polymer film with reverse birefringence dispersion was fabricated, and the birefringence dispersion of this film was shown to be successfully controlled by the presence of the crystals.