Magnetic Properties of Nickel–Zinc Ferrite Toroids Prepared from Nanoparticles

Toroids comprised of silica-coated 10 nm diameter nickel–zinc (Ni–Fe) ferrite nanoparticles (Ni_0.5Zn_0.5Fe₂O₄) have been fabricated by careful control of both the coating process and subsequent densification by viscous sintering. A narrow processing window is identified between a maximum temperature at which the nanoparticles coarsen, losing their super-paramagnetic properties, and a lower temperature required for viscous flow densification. Key to the successful fabrication was drying and cold isostatic pressing of the silica-coated nanoparticles; other routes invariably led to cracking during either drying or sintering. The super-paramagnetic blocking temperature, the coercive field, and remanent magnetization could all be controlled over a wide range by varying the thickness of the silica coating from 1 to 15 nm. The dipole–dipole coupling distance is estimated to be 4 nm. The high-frequency (1–500 MHz) properties were sensitive to the sintering temperature as well as the thickness of the silica coating. Toroids sintered at 1000°C or less exhibited no high-frequency magnetic losses and their permeability decreased with increasing temperature, suggesting that the permeability was controlled by thermally activated magnetization relaxation.     

An integrated multichannel waveform generator for large-scale spatio-temporal stimulation of neural tissue

We present an ASIC designed for electrical stimulation of neural tissue using multielectrode arrays. The ASIC is foreseen for applications in systems that require simultaneous stimulation and recording of signals from various types of neural tissue, both in vitro and in vivo. The developed ASIC comprises 64 independent stimulation channels, which are capable to generate arbitrarily defined bipolar current or voltage waveforms, controlled in real time with time resolution of 12.5 μs and amplitude resolution of 7 bits. The amplitude range of output signal can be scaled over a very wide range, which ensures compatibility with various electrode arrays of different size and geometry. Each channel is also equipped with a stimulation artifact suppressor controlled in real time, which reduces the dead time of the system after each stimulation pulse.     

The profile of volatile compounds and polyphenols in wines produced from dessert varieties of apples

The aim of this study was to determine the influence of apple variety (Šampion, Idared and Gloster) on the polyphenol profile, volatile composition and sensory characteristics of apple wines. Apples were harvested from the orchard in Garlica Murowana (Poland) and the experiments were conducted on a laboratory scale. Statistically significant differences were detected in the chemical composition of the analyzed wines. The highest antioxidant activity was found in Šampion wines, which was associated with a relatively high concentration of chlorogenic acid and procyanidins. These samples also contained high amounts of acetaldehyde, ethyl acetate and methanol. Idared wines showed a similar polyphenol profile, but they had lower antioxidant capacity and were characterized by a high level of butanol and acetic acid. Gloster wines were distinguished from other samples by a lower concentration of polyphenols and higher concentration of fusel alcohols. During sensory evaluation, wines produced from Idared apples scored the highest value for overall quality.     

Accelerated development of CuSbS2 thin film photovoltaic device prototypes

Development of alternative thin film photovoltaic technologies is an important research topic because of the potential of low‐cost, high‐efficiency solar cells to produce terawatt levels of clean power. However, this development of unexplored yet promising absorbers can be hindered by complications that arise during solar cell fabrication. Here, a high‐throughput combinatorial method is applied to accelerate development of photovoltaic devices, in this case, using the novel CuSbS₂ absorber via a newly developed three‐stage self‐regulated growth process to control absorber purity and orientation. Photovoltaic performance of the absorber, using the typical substrate CuIn_xGa_{1 − x}Se₂ (CIGS) device architecture, is explored as a function of absorber quality and thickness using a variety of back contacts. This study yields CuSbS₂ device prototypes with ~1% conversion efficiency, suggesting that the optimal CuSbS₂ device fabrication parameters and contact selection criteria are quite different than for CIGS, despite the similarity of these two absorbers. The CuSbS₂ device efficiency is at present limited by low short‐circuit current because of bulk recombination related to defects, and a small open‐circuit voltage because of a theoretically predicted cliff‐type conduction band offset between CuSbS₂ and CdS. Overall, these results illustrate both the potential and limits of combinatorial methods to accelerate the development of thin film photovoltaic devices using novel absorbers. Copyright © 2016 John Wiley & Sons, Ltd.     

如何选用正确的干燥设备,以适应工艺需求

<正>在干燥工序中,选用哪种干燥设备?如何正确使用干燥设备来取得最佳的干燥效果?这是干燥设备选型过程中最常见的问题。1去湿干燥     

Phenolic acids and related compounds as antioxidants for edible oils

A series of hydroxy aromatic acids, esters and lactones have been evaluated as antioxidants for lard at 120°C at 0·025%, 0·05% and 0·1% concentrations. Most of the compounds studied are direct biochemical precursors of chalcones and these, in turn, of various flavonoids commonly occurring in plant material.Antioxidant efficiency has been shown to be very dependent on the number of phenolic hydroxyl groups in the molecule and also to be promoted by steric hindrance. Cinnamic acids are more effective than corresponding benzoic acids, and phenylacetic and phenylpropionic acids are even more effective. 3,4-Dihydroxy chalcone is more effective than the analogous caffeic acid. In general, the presence of a carbonyl group in the molecule appears to be necessary in this series for a high level of antioxidant activity.     

Activation of dispersed PtSn/C nanoparticles by tungsten oxide matrix towards more efficient oxidation of ethanol

A novel electrocatalytic system for oxidation of ethanol, in which carbon-supported PtSn nanoparticles were modified with ultra-thin films/deposits of tungsten oxide, was proposed, fabricated and characterized here using electrochemical as well as spectroscopic (X-ray diffraction) and microscopic (transmission electron) techniques. The enhancement effect was evident from comparative diagnostic electrochemical experiments utilizing WO₃-modified and bare (unmodified) PtSn nanoparticles in acid medium (0.5 mol dm⁻³ H₂SO₄) at room temperature in the presence of ethanol. It is noteworthy that, the chronoamperometric electrocatalytic currents measured at potentials as low as 0.3 V (vs. RHE) were significantly larger for WO₃-modified PtSn/C relative to bare PtSn/C. In another diagnostic “stripping” experiment, it was found that oxidation of CO-adsorbate occurred in the presence of WO₃ at potentials almost 100 mV lower in comparison to the unmodified system. The overall activation effect may have origin in interactions of tungsten oxide with tin (from PtSn alloy nanoparticles) leading to stabilization of the catalytic tin oxo species. WO₃ may also provide large population of reactive oxo groups at the Pt/Sn-based electrocatalytic interface.