Mott transitions in the multi-orbital systems

We investigate the Mott transitions in the two-orbital Hubbard model with different bandwidths. By combining dynamical mean field theory with the exact diagonalization, we discuss the stability of itinerant quasi-particle states in each band. We demonstrate that separate Mott transitions occur at different Coulomb interaction strengths in general, which merge to a single transition only under special conditions. In particular, it is clarified that the $xy$ and pair-hopping components of the Hund coupling play a key role to control the nature of the Mott transitions.Comment: 2 pages, 1 figure, submitted to SCES200

The Role of Prevalidation in the Development, Validation and Acceptance of Alternative Methods

Experience has shown that the outcome of large and expensive validation studies on alternative methods can be compromised if their managers do not insist that optimised test protocols and proof of their performance are submitted before the start of the formal validation study. One way for the sponsors of validation studies to confirm both the likely relevance of a method for its stated purpose and its readiness for validation would be to require a prevalidation study before formal validation was contemplated. This process would involve the developers (or other proponents of the method) and selected indipendent laboratories in protocol refinement (Phase I) and protocol transfer (Phase II). The optimised protocol would then be assessed in a protocol performance phase (Phase III), which would involve the testing of a relevant set of coded test materials and an evolution of a proposed prediction model. In certain circumstances, a successful outcome of Phase III might be sufficient for promotion of the regulatory acceptance of the method. Normally, however, the method would proceed to a formal validation study. The European Centre for the Validation of Alternative Methods, a recognised validation authority, now proposes to introduce this prevalidation scheme into its validation strategy.JRC.(EI)-Environment Institut

The Validation of Toxicological Prediction Models.

An alternative method consists of two parts: the test system itself, and a prediction model for converting in vitro endpoints into predictions of in vivo toxicity. It is shown that there are certain circumstances in which a new prediction model can be introduced without the necessity to generate new test systems data.JRC.(EI)-Environment Institut

An Evaluation of the Proposed OECD Testing Strategy for Skin Corrosion.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra

A Study on UV Filter Chemicals from Annex VII of European Union Directive 76/768/EEC, in the In Vitro 3T3 NRU Phototoxicity Test.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra

Catch-up validation study of an in vitro skin irritation test method based on an open source reconstructed epidermis (phase I)

We have developed a new in vitro skin irritation test based on an open source reconstructed epidermis (OS-REp) with openly accessible protocols for tissue production and test performance. Due to structural, mechanistic and procedural similarity, a blinded catch-up validation study for skin irritation according to OECD Performance Standards (PS) was conducted in three laboratories to promote regulatory acceptance, with OS-REp models produced at a single production site only. While overall sensitivity and predictive capacity met the PS requirements, overall specificity was only 57%. A thorough analysis of the test results led to the assumption that some of the false-positive classifications could have been evoked by volatile skin-irritating chemicals tested in the same culture plate as the non-irritants falsely predicted as irritants. With GC/MS and biological approaches the cross-contamination effect was confirmed and the experimental set-up adapted accordingly. Retesting of the affected chemicals with the improved experimental set-up and otherwise identical protocol resulted in correct classifications as non-irritants. Taking these re-test results into account, 93% overall sensitivity, 70% specificity and 82% accuracy was achieved, which is in accordance with the OECD PS. A sufficient reliability of the method was indicated by a within-laboratory-reproducibility of 85–95% and a between-laboratory-reproducibility of 90%

Follow-up to the ECVAM Prevalidation Study on in vitro Tests for Acute Skin Irritation. ECVAM Skin Irritation Task Force Report 2.

Abstract not availableJRC.I-Institute for Health and Consumer Protection (Ispra