Vibrating Reed Study of Superconducting Cuprates Fabricated by Superfast Melt Quenching in a Solar Furnace

In this study, the potential possibilities of the precision of the vibrating reed method for the evaluation of the Тс of superconducting precursors in an HTSC Bi-Pb-Sr-Cu-O system were investigated. A special technology for obtaining these samples by using solar energy for melting and following superfast melt quenching was applied to increase their internal inhomogeneity, allowing to receive high-quality textural ceramic samples of Bi1,7Pb0,3Sr2Can-1CunOy (n=2-30) showing critical temperatures of superconducting precursor transitions above bulk Тс. To determine critical temperatures of superconducting precursors above bulk Тс for the first time, the original vibrating reed method of studying these multiphase samples in an applied magnetic field was used. It was shown that this method has sensitivity to superconducting diamagnetism making possible to reveal new superconducting precursor phases above bulk Tc.

Multiphysics Modeling for Detailed Analysis of Multi-Layer Lithium-Ion Pouch Cells

Multiphysics modeling permits a detailed investigation of complex physical interactions and heterogeneous performance in multiple electro-active layers of a large-format Li-ion cell. For this purpose, a novel 3D multiphysics model with high computational efficiency was developed to investigate detailed multiphysics heterogeneity in different layers of a large-format pouch cell at various discharge rates. This model has spatial distribution and temporal evolution of local electric current density, solid lithium concentration and temperature distributions in different electro-active layers, based on a real pouch cell geometry. Other than previous models, we resolve the discharge processes at various discharge C-rates, analyzing internal inhomogeneity based on multiple electro-active layers of a large-format pouch cell. The results reveal that the strong inhomogeneity in multiple layers at a high C-rate is caused by the large heat generation and poor heat dissipation in the direction through the cell thickness. The thermal inhomogeneity also strongly interacts with the local electrochemical and electric performance in the investigated cell.

STM STUDIES OF ISOLATED Mn12-Ph SINGLE-MOLECULE MAGNETS

We have studied Mn12O12(C6H5COO)16(H2O)4 (Mn12-Ph) single-molecule magnets on highly ordered pyrolytic graphite (HOPG) using low-temperature scanning tunneling microscopy (LT-STM) experiments. We report Mn12-Ph in isolation, resembling single molecules with metallic core atoms and organic outer ligands. The local tunneling current observed within the molecular structure shows a strong bias voltage dependency, which is distinct from that of the HOPG surface. Furthermore, evidence of internal inhomogeneity in the local density of states has been observed with high spatial resolution, and this inhomogeneity appears to be due to localized metallic behavior. These results facilitate magneto-metric studies of single-molecule magnets in isolation. As compared to bulk crystal studies, our experiments allow the specific investigation of atomic sites in the molecule.

Morphology of crosslinked poly(ε-caprolactone) microparticles

ABSTRACTIn order to explore the feasibility for preparing defined crosslinked particulate structures, oligo(ε-caprolactone) [oCL] derived microparticles (MPs) were crosslinked in non-molten, non-dissolved, i.e. solid state in aqueous suspension by applying a controlled regime with well-defined polymer network precursors either with or without photoinitiator. The MPs (diameter ∼ 40 μm) were prepared by an oil-in-water emulsion process from linear 2oCL or 4-arm star-shaped 4oCL with methacrylate end groups. Crosslinking was initiated by UV-laser irradiation (308 nm) at room temperature. Conversion of methacrylate was monitored by ATR-FTIR spectroscopy and crosslinking was confirmed by a lack of MP dissolution in dichloromethane. In a quantitative evaluation of swelling by dynamic light scattering, higher swelling ratios were detected for particles synthesized with photoinitiator. Wrinkled particle surfaces and distorted particle shapes were observed by light microscopy in the solvent-swollen state and by scanning electron microscopy after deswelling. This work indicated some limitations due to internal inhomogeneity of the MP, but particle crosslinking in solid state was generally possible and may be further improved by higher chain mobility during crosslinking.

Structural comparisons of the native and reactive-centre-cleaved forms of α1-antitrypsin by neutron- and X-ray-scattering in solution

alpha 1-Antitrypsin is the best-characterized member of the serpin (serine-proteinase inhibitor) superfamily. Its solution structure was studied by high-flux neutron-scattering and synchrotron X-ray-scattering. Neutron data show that its absorption coefficient A1% 280,1cm is 5.4. The neutron radius of gyration RG at infinite contrast for native alpha 1-antitrypsin is 2.61 nm, characteristic of a moderately elongated structure, and its cross-sectional RG is 1.34 nm. The internal inhomogeneity of scattering densities within alpha 1-antitrypsin is high at 29 x 10(-5). The X-ray RG is 2.91 nm, in good agreement with the neutron RG of 2.82 nm in 1H2O. This RG is unchanged in reactive-centre-cleaved alpha 1-antitrypsin. These parameters are also unchanged at pH 8 in sodium/potassium phosphate buffers up to 0.6 M. The neutron and X-ray curves for native alpha 1-antitrypsin were compared with Debye simulation based on the crystal structure of reactive-centre-cleaved (papain) alpha 1-antitrypsin. After allowance for residues not visible in the crystallographic electron-density map, and rejoining the proteolysed site between Met-358 and Ser-359 by means of a relatively minor conformational re-arrangement, good agreement to a structural resolution of 4 nm is obtained with the neutron data in two contrasts and with the X-ray data. The structures of the native and cleaved forms of alpha 1-antitrypsin are thus similar within the resolution of solution scattering. This places an upper limit on the magnitude of the presumed conformational changes that occur in alpha 1-antitrypsin on reactive-centre cleavage, as indicated in earlier spectroscopic investigations of the Met-358-Ser-359 peptide-bond cleavage. Methods for scattering-curve simulations from crystal structures are critically assessed. The RG data lead to dimensions of 7.8 nm x 4.9 nm x 2.2 nm for native alpha 1-antitrypsin. The high internal inhomogeneity and the asymmetric shorter semi-axes of 4.9 nm and 2.2 nm suggest that the three oligosaccharide chains of alpha 1-antitrypsin are essentially freely extended into solvent in physiological conditions. This conclusion is also supported by the Debye simulations, and by modelling based on hydrodynamic parameters.