Helium droplet assisted synthesis of plasmonic Ag@ZnO core@shell nanoparticles

Plasmonic Ag@ZnO core@shell nanoparticles are formed by synthesis inside helium droplets with subsequent deposition and controlled oxidation. The particle size and shape can be controlled from spherical sub-10 nm particles to larger elongated structures. An advantage of the method is the complete absence of solvents, precursors, and other chemical agents. The obtained particle morphology and elemental composition have been analyzed by scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDS). The results reveal that the produced particles form a closed and homogeneous ZnO layer around a 2–3 nm Ag core with a uniform thickness of (1.33 ± 0.15) nm and (1.63 ± 0.31) nm for spherical and wire-like particles, respectively. The results are supported by ultraviolet photoelectron spectroscopy (UPS), which indicates a fully oxidized shell layer for the particles studied by STEM. The plasmonic properties of the produced spherical Ag@ZnO core@shell particles are investigated by two-photon photoelectron (2PPE) spectroscopy. Upon excitation of the localized surface plasmon resonance in Ag at around 3 eV, plasmonic enhancement leads to the liberation of electrons with high kinetic energy. This is observed for both Ag and Ag@ZnO particles, showing that even if a Ag cluster is covered by the ZnO layer, a plasmonic enhancement can be observed by photoelectron spectroscopy.

     

Cytotoxicity screening of 23 engineered nanomaterials using a test matrix of ten cell lines and three different assays

Background  

Engineered nanomaterials display unique properties that may have impact on human health, and thus require a reliable evaluation of their potential toxicity. Here, we performed a standardized in vitro screening of 23 engineered nanomaterials. We thoroughly characterized the physicochemical properties of the nanomaterials and adapted three classical in vitro toxicity assays to eliminate nanomaterial interference. Nanomaterial toxicity was assessed in ten representative cell lines.     

Sex influence on face recognition memory moderated by presentation duration and reencoding.

Objective: It has been suggested that women have a better face recognition memory than men. Here we analyzed whether this advantage depends on a better encoding or consolidation of information and if the advantage is visible during short-term memory (STM), only, or whether it also remains evident in long-term memory (LTM). Method: We tested short- and long-term face recognition memory in 36 nonclinical participants (19 women). We varied the duration of item presentation (1, 5, and 10 s), the time of testing (immediately after the study phase, 1 hr, and 24 hr later), and the possibility to reencode items (none, immediately after the study phase, after 1 hr). Results: Women showed better overall face recognition memory than men (ηp2 = .15, p     

On Taylor vortices and Ekman layers in flow-induced vibration of hard disk drives

This paper is about flow-induced vibration (FIV) of disks in hard disk drives (HDD) influenced by two classical flow structures in fluid dynamics, Taylor Couette vortices (TCV) and Ekman layers. FIV is computed with a fully coupled commercial aerodynamics/structural code. The emphasis is on FIV of disks and geometries under conditions typical for high speed, server HDDs. In typical server drives computational fluid dynamic (CFD) analysis predicts the occurrence of TCVs in the disk to shroud clearance. TCVs typically do not occur in mobile and desktop drives. The main controlling non-dimensional parameters are the Reynolds number, the Taylor number and the aspect ratio of the disk to shroud clearance. The existence of Ekman layers on the disk surfaces is persistent. The Ekman layers and their radial return flow interact in a complex manner with the flow in the disk to shroud clearance. The turbulent viscosity between shrouded disks results from “bursting” phenomena that are typical for the flow field near the disk rims and shroud. The details of a turbulent burst are presented together with its momentary disk excitation effect. The benchmark case used is a fully shrouded set of two disks with a disk to shroud clearance and a disk thickness to shroud aspect ratio such that TCVs occur in the disk to shroud clearance. The TCVs interact with the Ekman layers such that the outer TCVs are continuously destroyed and recreated. An example is presented of fully coupled FIV of a two-disk axi-symmetric benchmark case. The two co-rotating shrouded disks attract aerodynamically: they deflect statically inward. The results also show the dynamic disk deformation dominated by the disk (0,0) “umbrella” mode. In addition, there is random disk deflection caused by the turbulent bursting. At server drive conditions and a 70 mm diameter disk the peak to peak deflection is approximately 20% of the mean deflection. Three dimensional effects are also presented such as wavy TCVs. In another benchmark with a cavity the flow near unshrouded disk edges is shown. In that case the pressure fluctuations can be an order of magnitude greater than in shrouded regions.     

Kinetics of water adsorption in microporous aluminophosphate layers for regenerative heat exchangers

The performance of thick aluminophosphate molecular sieve layers for heat exchanger applications is evaluated. The aluminophosphate AlPO-18 (AEI structure type code) molecular sieve sorbent is coated on aluminium supports prior the sorption measurements. Two AlPO-18 samples with different morphological appearance, i.e. nano-sized crystals with monomodal size distribution and micron-sized crystals of varying sizes, are used to prepare layers with thickness in the range of 80–750 μm. As a binder component, polyvinyl alcohol (PVOH) was utilized in order to prepare mechanically stable layers, which are mechanically stable over numerous measuring cycles. The sorption measurements are conducted under canonical conditions at 40 °C. The AlPO-18 layers showed decreased mass flows with increasing the thickness. Additionally, the layers comprising nanosized crystals showed higher equilibrium loadings and faster kinetics compared to films based on micron-sized crystals. Following the kinetic studies of pressure, temperature and heat flow, it can be concluded that the heat transport is the rate limiting mechanism for thick aluminophosphate layers. Importantly, the diffusion limitation plays a role only for relatively thin microporous aluminophosphate layers (<200 μm). Below this thickness complete heat transfer is achieved within 2 min which allows fast heat exchanger cycles. Thus, the application of microporous aluminophosphate layers for heat transformation and storage applications is considered possible.     

Sensitivity of slanted fibre Bragg gratings to external refractiveindex higher than that of silica

The influence of external refractive index higher than that of silica on the transmission spectra properties of slanted fibre Bragg grating in investigated. An analytical method is presented for their potential use as refractometer for refractive index ranges beyond 1.45