Concentrations and spatial variations of cyclodienes and other organochlorines in herring and perch from the Baltic Sea

Naive T lymphocytes specific for a given primary antigen occur in low frequencies and require the relevant antigen to be presented by specialist antigen presenting cells (APC), i.e., dendritic cells (DC). For these reasons, the in vitro induction of primary T lymphocyte responses remains a significant technical challenge. We have attempted to improve current strategies for generating in vitro responses by optimising (i) isolation and concomitant activation of DC from peripheral blood, (ii) uptake, processing and presentation of antigen by DC and (iii) antigen driven T lymphocyte proliferation. We established that RPMI 1640 media supplemented with 10% autologous serum resulted in the best yield of CMRF-44+, CD14-, CD19- DC after enrichment over a Nycodenz gradient. Optimal presentation of whole protein and peptide antigen was achieved by addition after the purification of the APC, i.e., at the start of the T lymphocyte proliferation assay. RPMI 1640 supplemented with 10% autologous serum or plasma supported the best antigen driven specific T lymphocyte responses. Using these optimised conditions, we compared the efficacy of PBMC and purified blood DC for priming T lymphocyte responses to the chronic myeloid leukaemia (CML) specific bcr-abl (b3a2) peptide. Peptide specific T lymphocyte responses were generated with both purified DC and whole PBMC, suggesting that T lymphocyte precursor frequency was the limiting factor in these experiments. These results will aid in the generation of human T lymphocyte lines to primary antigens, for in vitro and therapeutic applications.     

First principles study of three-component SrTiO<Subscript>3</Subscript>/BaTiO<Subscript>3</Subscript>/PbTiO<Subscript>3</Subscript> ferroelectric superlattices

The geometrical, chemical and ferroelectric properties of a new nanoscale short-period three-component SrTiO₃/BaTiO₃/PbTiO₃ perovskite superlattice are investigated using a first principles density functional approach. The study focuses on varying the thickness of each component in the superlattice and determining the resulting lattice distortion and total polarization. Thicknesses of up to three unit cells in a single component are considered and the in-plane lattice constants normal to the [001] stacking direction are fixed to the bulk SrTiO₃ values to simulate a rigid substrate. It is found that the PbTiO₃ layers play a key role in strain and polarization enhancement. By increasing the amount of PbTiO₃ in the superlattices the strain in the other components increases significantly resulting in an enhanced total polarization of the superlattice relative to bulk BaTiO₃. Increasing the number of BaTiO₃ layers also improves the overall polarization. All the SrTiO₃ layers in each superlattice are found to be highly polarized. Many of the calculated features are similar to those found previously by others for the SrTiO₃/BaTiO₃/CaTiO₃ superlattice, although in the present study significantly greater enhancement factors and polarization values are found. The predicted enhancement of the polarization is mostly attributed to lattice strain due to mismatch of the in-plane lattice constant of the three-component materials.     

Mixed Valence Perovskite Cs2Au2I6: A Potential Material for Thin‐Film Pb‐Free Photovoltaic Cells with Ultrahigh Efficiency

New light is shed on the previously known perovskite material, Cs₂Au₂I₆, as a potential active material for high‐efficiency thin‐film Pb‐free photovoltaic cells. First‐principles calculations demonstrate that Cs₂Au₂I₆ has an optimal band gap that is close to the Shockley–Queisser value. The band gap size is governed by intermediate band formation. Charge disproportionation on Au makes Cs₂Au₂I₆ a double‐perovskite material, although it is stoichiometrically a single perovskite. In contrast to most previously discussed double perovskites, Cs₂Au₂I₆ has a direct‐band‐gap feature, and optical simulation predicts that a very thin layer of active material is sufficient to achieve a high photoconversion efficiency using a polycrystalline film layer. The already confirmed synthesizability of this material, coupled with the state‐of‐the‐art multiscale simulations connecting from the material to the device, strongly suggests that Cs₂Au₂I₆ will serve as the active material in highly efficient, nontoxic, and thin‐film perovskite solar cells in the very near future.     

Modified four-point bending specimen for determining the interface fracture energy for thin, brittle layers

A well-known four-point bending test has been modified such that the critical energy release rate for delaminating cracks propagating at the interface of a thin, brittle layer bonded to a substrate can be measured. The energy release rate required for crack delaminating at those interfaces is obtained by attaching a stiffening layer to the layer system. Another advantage of this modification is that segmentation of the layer and plastic deformation of the substrate during bending are avoided. The interface fracture energy of a plasma sprayed ZrO₂-ceramic layer on a flame sprayed high alloyed steel substrate has been measured. This revised version was published online in August 2006 with corrections to the Cover Date.     

"DNA traffic lights": concept of wavelength-shifting DNA probes and application in an aptasensor

Add it and see it: The concept of "DNA traffic lights" for wavelength-shifting DNA probes has a great potential in the application of biosensors, for example, in DNA aptamers. A visual color change in the DNA aptasensor fluorescence from green to red occurs after specific target binding.