Investigation Of Nanoscale Dielectric Polarization And Refractive Indices Of BaTiO3 Surfaces And Ultrathin Films

The surface and interface effects on the dielectric polarization and refractive indices of BaTiO3 single crystals and BaTiO3 ultrathin films on SrTiO3 single crystal substrates are investigated theoretically by using a microscopic model based on the orbital approximation in correlation with the dipole-dipole interaction. The spontaneous polarization of BaTiO3 single crystals is drastically reduced near the c-surface. For BaTiO3/SrTiO3 films, the spontaneous polarization is reduced in the film as its thickness decreases. However, an electronic polarization appears within the SrTiO3 substrate in the neighborhood of the interface. This polarization, which vanishes far away from the interface into the SrTiO3 bulk, is induced by the polarization of the BaTiO3 film. Furthermore, we find the refractive index either for BaTiO3 single crystals or for BaTiO3 films and SrTiO3 substrates to be strongly reduced for light polarized perpendicular to the surface.The surface and interface effects on the dielectric polarization and refractive indices of BaTiO3 single crystals and BaTiO3 ultrathin films on SrTiO3 single crystal substrates are investigated theoretically by using a microscopic model based on the orbital approximation in correlation with the dipole-dipole interaction. The spontaneous polarization of BaTiO3 single crystals is drastically reduced near the c-surface. For BaTiO3/SrTiO3 films, the spontaneous polarization is reduced in the film as its thickness decreases. However, an electronic polarization appears within the SrTiO3 substrate in the neighborhood of the interface. This polarization, which vanishes far away from the interface into the SrTiO3 bulk, is induced by the polarization of the BaTiO3 film. Furthermore, we find the refractive index either for BaTiO3 single crystals or for BaTiO3 films and SrTiO3 substrates to be strongly reduced for light polarized perpendicular to the surface

Hypergravity affects cell traction forces of fibroblasts

Biological and Soft Matter Physic

Anisotropic fractal magnetic domain pattern in bulk Mn1.4PtSn

The tetragonal compound Mn1.4PtSn with D2d symmetry recently attracted attention as the first known material that hosts magnetic antiskyrmions, which differ from the skyrmions known so far by their internal structure. The latter have been found in a number of magnets with the chiral crystal structure. In previous works, the existence of antiskyrmions in Mn1.4PtSn was unambiguously demonstrated in real space by means of Lorentz transmission electron microscopy on thin-plate samples (∼100 nm thick). In the present study, we used small-angle neutron scattering and magnetic force microscopy to perform reciprocal- and real-space imaging of the magnetic texture of bulk Mn1.4PtSn single crystals at different temperatures and in applied magnetic field. We found that the magnetic texture in the bulk differs significantly from that of thin-plate samples. Instead of spin helices or an antiskyrmion lattice, we observe an anisotropic fractal magnetic pattern of closure domains in zero field above the spin-reorientation transition temperature, which transforms into a set of bubble domains in high field. Below the spin-reorientation transition temperature the strong in-plane anisotropy as well as the fractal self-affinity in zero field is gradually lost, while the formation of bubble domains in high field remains robust. The results of our study highlight the importance of dipole-dipole interactions in thin-plate samples for the stabilization of antiskyrmions and identify criteria which should guide the search for potential (anti)skyrmion host materials. Moreover, they provide consistent interpretations of the previously reported magnetotransport anomalies of the bulk crystals. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by the Max Planck Society

Loss of viability during freeze-thaw of intact and adherent human embryonic stem cells with conventional slow-cooling protocols is predominantly due to apoptosis rather than cellular necrosis

10.1007/s11373-005-9051-9Journal of Biomedical Science133433-44

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWASs for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally diverse individuals (European, African, Asian, and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole-genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n = 109,122 individuals. We identified 59 sentinel variants (p < 5 × 10−9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated that the independent signals colocalized with cell-type-specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated that our TL polygenic trait scores (PTSs) were associated with an increased risk of cancer-related phenotypes

Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by HLA-DRB1*04 subtypes

Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1*04 subtypes best accounted for the association, strongest with HLA-DRB1*04:04 and HLA-DRB1*04:07, and intermediary with HLA-DRB1*04:01 and HLA-DRB1*04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1*04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1*04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues

Nanoscale domain switching and 3-dimensional mapping of ferroelectric domains by scanning force microscopy

Nanoscale switching of ferroelectric domains in Barium-titanate and Tri-Glycine Sulphate bulk single crystals is demonstrated at room temperature by scanning force microscopy. Oppositely polarised domains are created by choosing an adequate polarity for the dc voltage applied to the conductive tip : a positive bias at the tip results in the polarisation pointing into the crystal, and vice versa. Direct writing of lines measuring as small as 500 nm is demonstrated. Any structure written by this method is imaged with voltage modulated scanning force microscopy. Applying an ac voltage to the conductive tip reveals the electnc field at the sample surface originating from both in-plane and out-of-plane polarised domains in ferroic samples. With this method domain walls are resolved down to 80 nm