Comparison of metal-based nanoparticles and nanowires: Solubility, reactivity, bioavailability and cellular toxicity

While the toxicity of metal-based nanoparticles (NP) has been investigated in an increasing number of studies, little is known about metal-based fibrous materials, so-called nanowires (NWs). Within the present study, the physico-chemical properties of particulate and fibrous nanomaterials based on Cu, CuO, Ni, and Ag as well as TiO$_{2}$ and CeO$_{2}$ NP were characterized and compared with respect to abiotic metal ion release in different physiologically relevant media as well as acellular reactivity. While none of the materials was soluble at neutral pH in artificial alveolar fluid (AAF), Cu, CuO, and Ni-based materials displayed distinct dissolution under the acidic conditions found in artificial lysosomal fluids (ALF and PSF). Subsequently, four different cell lines were applied to compare cytotoxicity as well as intracellular metal ion release in the cytoplasm and nucleus. Both cytotoxicity and bioavailability reflected the acellular dissolution rates in physiological lysosomal media (pH 4.5); only Ag-based materials showed no or very low acellular solubility, but pronounced intracellular bioavailability and cytotoxicity, leading to particularly high concentrations in the nucleus. In conclusion, in spite of some quantitative differences, the intracellular bioavailability as well as toxicity is mostly driven by the respective metal and is less modulated by the shape of the respective NP or NW

Superconductivity in the SU(N) Anderson Lattice at U=\infty

We present a mean-field study of superconductivity in a generalized N-channel cubic Anderson lattice at U=\infty taking into account the effect of a nearest-neighbor attraction J. The condition U=\infty is implemented within the slave-boson formalism considering the slave bosons to be condensed. We consider the $f$-level occupancy ranging from the mixed valence regime to the Kondo limit and study the dependence of the critical temperature on the various model parameters for each of three possible Cooper pairing symmetries (extended s, d-wave and p-wave pairing) and find interesting crossovers. It is found that the d- and p- wave order parameters have, in general, very similar critical temperatures. The extended s-wave pairing seems to be relatively more stable for electronic densities per channel close to one and for large values of the superconducting interaction J.Comment: Seven Figures; one appendix. Accepted for publication in Phys. Rev.

Point-contact spectra of the heavy-fermion superconductors U Be

We have measured the current-voltage characteristics of point contacts between UBe13 or UPt3 and the normal metals W or Pt (metallic point contacts) or GaAs (Schottky-barrier tunneling contact) in the temperature range between 50 mK and 1 K. In the metal-point-contact characteristics (dVdI vs V) there appear zero-bias minima of width 2 below Tc. The ratio 2 kBTc is close to the BCS value. The tunneling spectra of UPt3 exhibit weak additional structure below Tc. A value 2 has been estimated, which is a factor of 2 larger than that for the metal point contacts. © 1987 The American Physical Society

Environmental effects of ozone depletion, UV radiation and interactions with climate change : UNEP Environmental Effects Assessment Panel, update 2017

Peer reviewe

Dynamics of the magnetization in the heavy fermion system CeCu6

We have studied CeCu6 by inelastic neutron scattering. We found both quasielastic and also inelastic transitions, which we interpret as residual crystal field transitions. The quasielastic linewidth is a strongly nonlinear function of temperature, with approximately ΓQE=5.0 meV at 300 K, with a crossover ΓQE=kT at about 13 K and with a residual value of ΓQE=(0)=0.50 meV for T=0 K. Below 5 K the quasielastic intensity IQE decreases linearly with temperature. χstαIQE/T is in good agreement with direct measurements of the static susceptibility. The data are fully consistent with a nonordering groundstate of CeCu6. © 1986 Springer-Verlag

Dynamics of the magnetization in the heavy fermion system CeCu6

We have studied CeCu6 by inelastic neutron scattering. We found both quasielastic and also inelastic transitions, which we interpret as residual crystal field transitions. The quasielastic linewidth is a strongly nonlinear function of temperature, with approximately ΓQE=5.0 meV at 300 K, with a crossover ΓQE=kT at about 13 K and with a residual value of ΓQE=(0)=0.50 meV for T=0 K. Below 5 K the quasielastic intensity IQE decreases linearly with temperature. χstαIQE/T is in good agreement with direct measurements of the static susceptibility. The data are fully consistent with a nonordering groundstate of CeCu6. © 1986 Springer-Verlag

Automatic assessment of the nasality in children's speech

In der aktuellen Forschung bei Sprechstörungen hat es sich gezeigt, dass automatische Klassifikationssysteme zur Bewertung der Nasalität anwendbar sind. Bisher wurde dies aber immer nur für gehaltene Vokale oder Teile von Wörtern gezeigt. Um komplette Wörter oder Sätze zu untersuchen, waren bisher immer teure, apparative Methoden - beispielsweise ein Nasometer - notwendig. Unser Ansatz kommt mit einem Standard-PC und einem Mikrophon aus. Um unseren Ansatz zu verifizieren, wurden Daten eines Sprach-Tests von 13 Kindern von einer erfahrenen Logopädin untersucht. Diese klassifizierte jedes Zielwort eines standardisierten Tests zur Überprüfung von phonetischen Störungen als normal oder hypernasal. Anhand der spektralen Eigenschaften der gesprochenen Wörter wurde für das Spracherkennungssystem ein Klassifikationssystem trainiert, das automatisch hypernasalierte Wörter erkennen kann. Die Funktionsweise des Systems und die Genauigkeit der Klassifikation werden vorgestellt. Eine Erweiterung der Methode auf andere Lautbildungsstörungen wird derzeit untersucht