Antiferromagnetic Correlations in Strongly Valence Fluctuating CeIrSn.

CeIrSn with a quasikagome Ce lattice in the hexagonal basal plane is a strongly valence fluctuating compound, as we confirm by hard x-ray photoelectron spectroscopy and inelastic neutron scattering, with a high Kondo temperature of T_{K}∼480 K. We report a negative in-plane thermal expansion α/T below 2 K, which passes through a broad minimum near 0.75 K. Volume and a-axis magnetostriction for B∥a are markedly negative at low fields and change sign before a sharp metamagnetic anomaly at 6 T. These behaviors are unexpected for Ce-based intermediate valence systems, which should feature positive expansivity. Rather they point towards antiferromagnetic correlations at very low temperatures. This is supported by muon spin relaxation measurements down to 0.1 K, which provide microscopic evidence for a broad distribution of internal magnetic fields. Comparison with isostructural CeRhSn suggests that these antiferromagnetic correlations emerging at T≪T_{K} result from geometrical frustration.

4f Crystal Field Ground State of the Strongly Correlated Topological Insulator SmB_{6}.

We investigated the crystal-electric field ground state of the 4f manifold in the strongly correlated topological insulator SmB_{6} using core-level nonresonant inelastic x-ray scattering. The directional dependence of the scattering function that arises from higher multipole transitions establishes unambiguously that the Γ_{8} quartet state of the Sm f^{5} J=5/2 configuration governs the ground-state symmetry and, hence, the topological properties of SmB_{6}. Our findings contradict the results of density functional calculations reported so far.

Determining the in-plane orientation of the ground-state orbital of CeCu2Si2.

We have successfully determined the hitherto unknown sign of the B(4)(4) Stevens crystal-field parameter of the tetragonal heavy-fermion compound CeCu(2)Si(2) using vector q-dependent nonresonant inelastic x-ray scattering experiments at the cerium N(4,5) edge. The observed difference between the two different directions, q∥[100] and q∥[110], is due to the anisotropy of the crystal-field ground state in the (001) plane and is observable only because of the utilization of higher than dipole transitions possible in nonresonant inelastic x-ray scattering. This approach allows us to go beyond the specific limitations of dc magnetic susceptibility, inelastic neutron scattering, and soft x-ray spectroscopy, and provides us with a reliable information about the orbital state of the 4f electrons relevant for the quantitative modeling of the quasiparticles and their interactions in heavy-fermion systems.

Magnetic field induced orbital polarization in cubic YbInNi4: determining the quartet ground state using x-ray linear dichroism.

We have been able to induce a linear dichroic signal in the Yb M(5) x-ray absorption white line of cubic YbInNi(4) by the application of a magnetic field. The nonzero integrated intensity of the magnetic field induced dichroic spectrum indicates a net noncubic 4f orbital polarization. A quantitative analysis of the temperature and field strength dependence establishes that the crystal-field ground state is a Γ(8) quartet. The results demonstrate the potential of magnetic field induced linear dichroism as a new powerful approach for the investigation of the degeneracy and orbital degrees of freedom of cubic heavy-fermion and Kondo systems.

Comparative analysis of biofilm models to determine the efficacy of antimicrobials.

Biofilms are one of the greatest challenges in today's treatment of chronic wounds. While antimicrobials kill platonic bacteria within seconds, they are rarely able to harm biofilms. In order to identify effective substances for antibacterial therapy, cost-efficient, standardized and reproducible models that aim to mimic the clinical situation are required. In this study, two 3D biofilm models based on human plasma with immune cells (lhBIOM) or based on sheep blood (sbBIOM) containing S. aureus or P. aeruginosa, are compared with the human biofilm model hpBIOM regarding their microscopic structure (scanning electron microscopy; SEM) and their bacterial resistance to octenidine hydrochloride (OCT) and a sodium hypochlorite (NaOCl) wound-irrigation solution. The three analyzed biofilm models show little to no reaction to treatment with the hypochlorous solution while planktonic S. aureus and P. aeruginosa cells are reduced within minutes. After 48 h, octenidine hydrochloride manages to erode the biofilm matrix and significantly reduce the bacterial load. The determined effects are qualitatively reflected by SEM. Our results show that both ethically acceptable human and sheep blood based biofilm models can be used as a standard for in vitro testing of new antimicrobial substances. Due to their composition, both fulfill the criteria of a reality-reflecting model and therefore should be used in the approval for new antimicrobial agents.

Side effects of frequently used oral antidiabetics on wound healing in vitro.

Lifestyle diseases such as diabetes and arteriosclerosis are rising in the increasingly aging society, and the number of patients with daily intake of glucose-lowering medication has also increased. Interestingly, knowledge about oral antidiabetics with regard to wound healing is scarce. Therefore, the aim of this study was to identify possible (side) effects of the most frequently prescribed oral antidiabetics on skin cells and wound healing. Four oral antidiabetics of different substance classes (i.e., metformin, glibenclamide, sitagliptin, repaglinide) were investigated with regard to the promotion of cell metabolism and migration of human skin fibroblasts and keratinocytes by XTT and scratch assays. In addition, histological and immunohistochemical analyses were performed in a 3D wound model to address the impact of the antidiabetics on regeneration processes, such as cell migration, fibroblast activity, epidermal thickness, and cell apoptosis. In comparison to systemic application, metformin displayed the most adverse effects in vitro in nearly all analyses, interestingly at serum equivalent concentrations. In contrast, sitagliptin and glibenclamide had a slight but insignificant effect on fibroblasts compared with keratinocytes. Repaglinide tended to have a negative influence on keratinocyte metabolism. Interestingly, antidiabetics generally induced a significantly enhanced rate of apoptosis in fibroblasts, with the exception of repaglinide.Antidiabetics influenced key players in wound healing, namely, keratinocytes and fibroblasts. Particularly, metformin impaired human skin cells. These findings should be kept in mind in further studies because of their putative relevance in patients suffering from chronic wounds that do not respond to various wound therapies.

Automatic cell segmentation in strongly agglomerated cell networks for different cell types.

This paper presents a method of separating cells that are connected to each other forming clusters. The difference to many other publications covering similar topics is that the cell types we are dealing with form clusters of highly varying morphology. An advantage of our method is that it can be universally used for different cell types. The segmentation method is based on a growth simulation starting from the nuclei areas. To start the evaluation, the cells need to be made visible with a histological stain, in our case with the May-Grünwald solution. After the staining process has been completed, the nuclei areas can be distinguished from the other cell areas by a histogram backprojection algorithm. The presented method can, in addition to histological stained cells, also be applied to fluorescent-stained cells.

Possible anisotropic s--f hybridization in a cubic heavy-fermion compound: CeIn1Sn2.

Polarized neutron scattering measurements on a single crystal of composition CeIn1Sn2 show a broad, single-ion, spectral response centered on a characteristic energy of approximately 9+/-1 meV at the zone boundary point (0 0 1.5). The zone center spectral response is closely similar in form but has a slightly reduced amplitude, smaller by some 20%. Constant-omega scans show that these intensity modulations, of amplitude approximately 10%, resembling intersite antiferromagnetic correlations, are superimposed on a mean variation that follows the Ce3+, 4f;{1}, single-ion form factor, and are tentatively attributed to q-dependent hybridization of the localized 4f state with the conduction electrons.

Determining the crystal-field ground state in rare earth heavy fermion materials using soft-x-ray absorption spectroscopy.

We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth heavy fermion systems, complementing neutron scattering. Using realistic and universal parameters, we provide a theoretical mapping between the polarization dependence of Ce M(4,5) spectra and the charge distribution of the Ce 4f states. The experimental resolution can be orders of magnitude larger than the 4f crystal-field splitting itself. To demonstrate the experimental feasibility of the method, we investigated CePd2Si2, thereby settling an existing disagreement about its crystal-field ground state.