Ultrathin Amorphous Silica Membrane Enhances Proton Transfer across Solid-to-Solid Interfaces of Stacked Metal Oxide Nanolayers while Blocking Oxygen

A large jump of proton transfer rates across solid-to-solid interfaces by inserting an ultrathin amorphous silica layer into stacked metal oxide nanolayers is discovered using electrochemical impedance spectroscopy and Fourier-transform infrared reflection absorption spectroscopy (FT-IRRAS). The triple stacked nanolayers of Co3O4, SiO2, and TiO2 prepared by atomic layer deposition (ALD) enable a proton flux of 2400 ± 60 s−1 nm−2 (pH 4, room temperature), while a single TiO2 (5 nm) layer exhibits a threefold lower flux of 830 s−1 nm−2. Based on FT-IRRAS measurements, this remarkable enhancement is proposed to originate from the sandwiched silica layer forming interfacial SiOTi and SiOCo linkages to TiO2 and Co3O4 nanolayers, respectively, with the O bridges providing fast H+ hopping pathways across the solid-to-solid interfaces. Together with the complete O2 impermeability of a 2 nm ALD-grown SiO2 layer, the high flux for proton transport across multi-stack metal oxide layers opens up the integration of incompatible catalytic environments to form functional nanoscale assemblies such as artificial photosystems for CO2 reduction by H2O

Bridging the ensemble Kalman and particle filters

In many applications of Monte Carlo nonlinear filtering, the propagation step is computationally expensive, and hence the sample size is limited. With small sample sizes, the update step becomes crucial. Particle filtering suffers from the well-known problem of sample degeneracy. Ensemble Kalman filtering avoids this, at the expense of treating non-Gaussian features of the forecast distribution incorrectly. Here we introduce a procedure that makes a continuous transition indexed by γ∈[0,1] between the ensemble and the particle filter update. We propose automatic choices of the parameter γ such that the update stays as close as possible to the particle filter update subject to avoiding degeneracy. In various examples, we show that this procedure leads to updates that are able to handle non-Gaussian features of the forecast sample even in high-dimensional situation

Emergence of a Teicoplanin-Resistant Small Colony Variant of Staphylococcus epidermidis During Vancomycin Therapy

Small colony variants of Staphylococcus aureus can cause persistent and recurrent infections. There are only a few reports of small colony variants of coagulase-negative staphylococci. Herein a case of infection with a teicoplanin-resistant small colony variant of Staphylococcus epidermidis is presented. The small colony variant was isolated from blood cultures of a patient with acute leukaemia and therapy-induced neutropenia who was treated with vancomycin for catheter-associated bloodstream infection. Despite removal of the catheter and adequate antibiotic therapy, the infection did not clear and the patient died 20days after continuous antibiotic therap

Chiral Symmetry Restoration at Finite Temperature in the Linear Sigma--Model

The temperature behaviour of meson condensates $$and$$ is calculated in the $SU(3)\times SU(3)$-linear sigma model. The couplings of the Lagrangian are fitted to the physical $\pi,K,\eta,\eta'$ masses, the pion decay constant and a $O^+(I=0)$ scalar mass of $m_\sigma=1.5$ GeV. The quartic terms of the mesonic interaction are converted to a quadratic term with the help of a Hubbard-Stratonovich transformation. Effective mass terms are generated this way, which are treated self-consistently to leading order of a $1/N$-expansion. We calculate the light $$ and strange $<\bar s s>$-quark condensates using PCAC relations between the meson masses and condensates. For a cut-off value of 1.5 GeV we find a first-order chiral transition at a critical temperature $T_c\sim 161$ MeV. At this temperature the spontaneously broken subgroup $SU(2)\times SU(2)$ is restored. Entropy density, energy density and pressure are calculated for temperatures up to and slightly above the critical temperature. To our surprise we find some indications for a reduced contribution from strange mesons for $T\geq T_c$.Comment: 17 pages, HD--TVP--93--15. (3 figures - available on request

The non-destructive study of museums objects by means of neutrons imaging methods and results of investigations

Based on experience from many kinds of investigations with neutron imaging methods (radiography, tomography, time-dependent studies) and in comparison to conventional X-ray methods, the authors discuss the potential of future improved studies for cultural-heritage purposes. Whereas the focus of the paper is on the imaging aspect, other established techniques as neutron activation analysis (NAA), prompt gamma activation analysis (PGAA), neutron-induced autoradiography and neutron scattering are mentioned too. Although a great potential for studies similar to those described in the paper exists, a considerable effort is needed to define the best-suited methods for the dedicated cultural historical request. A real barrier between the experts at large research facilities (as, e.g., neutron sources are) and the partners from the museums side has to be overcome in order to solve the problems. A joint European approach will help in this respect

Fracturas de implantes de tibia. Consecuencias para los ensayos de los implantes

El objetivo de este trabajo es estudiar los modelos de fracturas de prótesis de tibia descritos en la literatura y, sobre la base de dichos conocimientos, desarrollar un ensayo para implantes en la cual se logren simular condiciones fisiológicas. El caso descrito con mayor frecuencia en la literatura es la migración de la parte medial de la prótesis, fenómeno que, a menudo, antecede a la fractura de la prótesis. La posición defectuosa resultante de dicha migración modifica el eje mecánico y provoca una sobrecarga en la parte medial de la prótesis. Se ha desarrollado un ensayo de implantes que simula el modelo de fallo in-vivo. Dos bases de material sintético de diferente dureza simulan la diferente densidad ósea medial y lateral, para permitir una migración del lado medial del platillo. En el ensayo dinámico el platillo tibial es sometido a una carga de un solo lado y el vástago de la prótesis se apuntala con un contrasoporte. Para simular el entorno fisiológico, todo el dispositivo se encuentra sumergido en una solución de Ringer a 37°. El implante de tibia es expuesto durante 10 millones de ciclos a una carga que corresponde al quíntuple del peso del cuerpo (4.000 N). El punto de aplicación de la fuerza fue tomado de datos de análisis del caminar (marcha en superficie plana, ascendente y descendente, subir escaleras). Con esta carga fisiológica se efectuaron los primeros ensayos. En éstas quedó demostrado que productos clínicamente exitosos podían superar el ensayo. Por el contrario, los productos con modelos de fracturas conocidos no la superaron. Los primeros resultados con estos productos demostraron también que el ensayo generaba muestras de fractura semejantes a las que se producen in vivo. Debido a la configuración fisiológica del dispositivo se somete el sistema completo es decir el platillo, el vástago de la prótesis y la unión - generalmente modular - entre ambos a ensayo. El "ensayo fisiológico de tibia " descrito ayuda a evaluar los diseños de tibia antes de que se autorice su venta. Nuevos implantes y modificaciones de diseño en implantes ya existentes son puestos a la venta después de cumplir con las exigencias del ensayo.Peer Reviewe