Top-down design of magnonic crystals from bottom-up magnetic nanoparticles through protein arrays.

We show that chemical fixation enables top-down micro-machining of large periodic 3D arrays of protein-encapsulated magnetic nanoparticles (NPs) without loss of order. We machined 3D micro-cubes containing a superlattice of NPs by means of focused ion beam etching, integrated an individual micro-cube to a thin-film coplanar waveguide and measured the resonant microwave response. Our work represents a major step towards well-defined magnonic metamaterials created from the self-assembly of magnetic nanoparticles.

Universal helimagnon and skyrmion excitations in metallic, semiconducting and insulating chiral magnets.

Nearly seven decades of research on microwave excitations of magnetic materials have led to a wide range of applications in electronics. The recent discovery of topological spin solitons in chiral magnets, so-called skyrmions, promises high-frequency devices that exploit the exceptional emergent electrodynamics of these compounds. Therefore, an accurate and unified quantitative account of their resonant response is key. Here, we report all-electrical spectroscopy of the collective spin excitations in the metallic, semiconducting and insulating chiral magnets MnSi, Fe1-xCoxSi and Cu2OSeO3, respectively, using broadband coplanar waveguides. By taking into account dipolar interactions, we achieve a precise quantitative modelling across the entire magnetic phase diagrams using two material-specific parameters that quantify the chiral and the critical field energy. The universal behaviour sets the stage for purpose-designed applications based on the resonant response of chiral magnets with tailored electric conductivity and an unprecedented freedom for an integration with electronics.

Long-term cytocompatibility of various endodontic sealers using a new root canal model.

It was the purpose of our study to determine the cytotoxicity of several types of root canal sealers in vitro over the period of 1 yr by using a new test model. Roots of extracted human teeth were filled with N2, Apexit, Roekoseal, AH Plus, Ketac Endo, Endomethasone, and one gutta-percha point. In addition, roots filled with laterally condensed gutta-percha/N2. Teeth filled with one gutta-percha point only were controls. All specimens were consecutively extracted with distilled water for a total period of 1 yr. Extracts were investigated for cytotoxicity by using immortalized 3T3 fibroblasts and primary human periodontal ligament fibroblasts. Results were statistically analyzed with Dunnett's t tests (p < 0.05). Pronounced cytotoxic effects were only caused by N2-extracts in both cell cultures (p < 0.05). Furthermore, statistically significant cytotoxic alterations were also induced by 10-week eluates of Endomethasone (p < 0.05). All other investigated materials did not significantly alter cell metabolism.

The cellular compatibility of five endodontic sealers during the setting period.

The purpose of this study was to evaluate the cellular compatibility of five endodontic sealers in the first 24 h after mixing. Specimens of N2, Endomethasone, Apexit, AH Plus, and Ketac Endo were extracted with cell culture medium 0, 1, 5, and 24 h after mixing. Eluates were tested for cytotoxicity with immortal 3T3 cells and primary human periodontal ligament fibroblasts using XTT-assays. Data were analyzed for statistically significant differences by means of Dunnett's t tests (p < 0.05). All extracts of N2 completely inhibited cell metabolism (p < 0.05). Similar effects were provoked by the first three eluates of Endomethasone, but the 24-h extract irritated cells significantly less (p < 0.05). Severe cytotoxicity was also observed with all Ketac Endo extracts (p < 0.05). A significant inhibition of mitochondrial activity was induced by the first (3T3) or the first and second eluate (periodontal ligament fibroblasts) of AH Plus (p < 0.05). The subsequent eluates of this sealer and all extracts of Apexit did not reveal any cytotoxic potency.

Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope.

Various authors have investigated the frequency of second canals (MB2) in the mesiobuccal roots of maxillary molars, predominantly first molars. Further, it has been reported that the percentage of MB2 canals that are treated during routine endodontic therapy is much lower than the number of second canals identified in vitro. It was the purpose of this study to investigate whether the use of an operating microscope may improve the diagnosis of MB2 canals in mesiobuccal roots of maxillary molars. The canal orifices of 100 maxillary first and second molars (50 of each) were initially inspected by Examiner 1 using individually-adapted x2 magnifying loupes. Subsequently, all teeth were examined by a second investigator using an operating microscope (OPM) with x8 magnification. Finally, the mesiobuccal roots of all teeth were separated. Then, the sections were analysed histologically and by SEM. The histological investigation revealed a total number of 63 MB2 canals, 39 in first, and 24 in second molars. Only 26 (41.3%) of those canals were identified using magnifying loupes, whereas 59 (93.7%) were found by means of an operating microscope.

Omnidirectional spin-wave nanograting coupler.

Magnonics as an emerging nanotechnology offers functionalities beyond current semiconductor technology. Spin waves used in cellular nonlinear networks are expected to speed up technologically, demanding tasks such as image processing and speech recognition at low power consumption. However, efficient coupling to microelectronics poses a vital challenge. Previously developed techniques for spin-wave excitation (for example, by using parametric pumping in a cavity) may not allow for the relevant downscaling or provide only individual point-like sources. Here we demonstrate that a grating coupler of periodically nanostructured magnets provokes multidirectional emission of short-wavelength spin waves with giantly enhanced amplitude compared with a bare microwave antenna. Exploring the dependence on ferromagnetic materials, lattice constants and the applied magnetic field, we find the magnonic grating coupler to be more versatile compared with gratings in photonics and plasmonics. Our results allow one to convert, in particular, straight microwave antennas into omnidirectional emitters for short-wavelength spin waves, which are key to cellular nonlinear networks and integrated magnonics.

Preoptic rather than mediobasal hypothalamic amino acid neurotransmitter release regulates GnRH secretion during the estrogen-induced LH surge in the ovariectomized rat.

Inhibitory and excitatory amino acid neurotransmitters have been suggested to participate in the feedback actions of estradiol (E2) on LH secretion. In the rat estrogen-receptive neurons have been demonstrated in the preoptic/anterior hypothalamic area (POA) and mediobasal hypothalamus/median eminence (MBH) and many of these neurons utilize gamma-aminobutyric acid (GABA) as neurotransmitter. The actions of excitatory amino acids (EAA) differ in ovariectomized (ovx) and ovx E2-substituted rats indicating that EAAs also participate in the positive feedback action of E2 on LH release. However, little information is available as to whether in vivo these transmitters exert their effects in the POA, where most of the GnRH perikarya are located, or in the MBH, i.e. at the nerve terminals. Therefore we conducted push pull cannula perfusions to compare the release rates of GABA, aspartate (ASP) and glutamate (GLU) in the MBH and POA. A subcutaneous implant of a silastic tube containing E2 resulted in LH surges in the afternoon of all treated animals. Prior to and during this LH surge the MBH release rates of neither GABA nor ASP nor GLU were significantly altered. In contrast, a conspicuous drop in preoptic GABA release occurred prior to and during the time of estrogen-induced LH surges and this was accompanied by enhanced preoptic secretion of ASP and GLU. In conclusion, we present the first data about amino acid release in the MBH during the E2-induced LH surge. Since only in the POA the LH surge is associated with changes in amino acid release, it appears that both inhibitory and excitatory amino acids act at the level of the GnRH cell bodies and/or dendrites and not on GnRH nerve terminals to mediate the feedback mechanism of E2 on LH release.