Jožef Stefan Institute

About: Jožef Stefan Institute is a facility organization based out in Ljubljana, Slovenia. It is known for research contribution in the topics: Liquid crystal & Dielectric. The organization has 3828 authors who have published 12614 publications receiving 291025 citations.

Confocal μ-XRF depth analysis of paint layers

Abstract: Focused narrow-band beam of the synchrotron radiation was used for in-depth analysis of historic and modern paint layers. The fluorescent radiation induced by 21 keV impact radiation was detected by a Si(Li) detector equipped with a polycapillary X-ray lens in con-focal geometry. Scanning of the sample was performed by a motorized x–y–z stage. Space resolution of 30 μm was achieved. The procedure of evaluation of concentrations was based on the independent parameter method and included absorption of radiation in the outer layers and secondary fluorescence enhancement induced by hard X-rays of the same and neighboring layers.

The synthesis and microwave dielectric properties of Mg3B2O6 and Mg2B2O5 ceramics

Abstract: Single-phase Mg3B2O6 and Mg2B2O5 ceramics were synthesized and then structurally and dielectrically characterized. The highest Qxf value of 230,900 GHz was obtained for a Mg3B2O6 ceramic with a density of 97% and 1000-μm grains. Considerably lower Qxf values (10,000–32,000 GHz) were determined for the Mg2B2O5 ceramic. Mg3B2O6 and Mg2B2O5 exhibited permittivities (ɛ) of 7.2 and 6.2–7.0, respectively. Both ceramics showed negative temperature coefficients of resonant frequency (τf) of −18 to −45 ppm/°C.

3D Cultures of Parkinson's Disease-Specific Dopaminergic Neurons for High Content Phenotyping and Drug Testing

Abstract: Parkinson's disease (PD)-specific neurons, grown in standard 2D cultures, typically only display weak endophenotypes. The cultivation of PD patient-specific neurons, derived from induced pluripotent stem cells carrying the LRRK2-G2019S mutation, is optimized in 3D microfluidics. The automated image analysis algorithms are implemented to enable pharmacophenomics in disease-relevant conditions. In contrast to 2D cultures, this 3D approach reveals robust endophenotypes. High-content imaging data show decreased dopaminergic differentiation and branching complexity, altered mitochondrial morphology, and increased cell death in LRRK2-G2019S neurons compared to isogenic lines without using stressor agents. Treatment with the LRRK2 inhibitor 2 (Inh2) rescues LRRK2-G2019S-dependent dopaminergic phenotypes. Strikingly, a holistic analysis of all studied features shows that the genetic background of the PD patients, and not the LRRK2-G2019S mutation, constitutes the strongest contribution to the phenotypes. These data support the use of advanced in vitro models for future patient stratification and personalized drug development.

The thermal decomposition of K0.5Bi0.5TiO3 ceramics

Abstract: The high-temperature behaviour of K0.5Bi0.5TiO3, prepared using a conventional solid-state reaction method, was investigated using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy and Knudsen effusion combined with mass spectrometry. The results revealed the formation of an off-stoichiometric matrix phase with an excess of bismuth and a deficit of potassium compared to the stoichiometric K0.5Bi0.5TiO3 during the solid-state reaction. During the thermal treatment potassium and bismuth vapours were detected over the solid sample and related to the thermal decomposition of the matrix phase. The losses of the potassium and bismuth components shifted the nominal composition to a three-phase region, and as a result, K2Ti6O13 and a new Bi-rich ternary phase were formed in the system, the latter being formed after prolonged sintering. Differential thermal analyses and heating-microscope analyses showed a narrow sintering-temperature range limited by the melting of the sample above 1040 °C.