Platinum migration out of zeolites onto iron oxide: an alternative to H spillover

TPR shows that the reduction of Fe₂O₃ to Fe₃O₄ is strongly enhanced in mixtures with platinumcontaining mordenite. However, no hydrogen spillover takes place from Pt⁰ particles along the walls of the zeolite pores. Only migration of platinum out of the zeolite onto the Fe₂O₃ leads to enhanced reduction of Fe₂O₃. TEM and EDX prove unambiguously that Pt clusters decorate Fe₂O₃ particles after an oxidative pretreatment of intimate mixtures, followed by reduction. Two paths exist for this migration of oxidized platinum: as Pt²⁺ ions and as PtO or PtO₂ clusters. The rate for both transport mechanisms increases with temperature. Pretreatment with H₂O vapor results in hydrated ions which have higher mobility and lead to more homogeneous distribution of the platinum over iron oxide particles. Reduction in wet hydrogen is slower than in dry hydrogen; no reduction to Fe ⁰ occurs in wet hydrogen.     

Factors that influence the release of metals from stainless steels exposed to physiological media

Release rates of chromium, nickel and iron from grade 304 stainless steel with three different surface finishes, BA, 2B and 2D, have been determined after exposure to artificial lysosomal fluid. Metal release rates are discussed in relation to corrosion resistance, compositional changes of the outermost surface film of the stainless steel and to measurements of the effective surface area and roughness. The total metal release decreased in the following sequence: 2D > 2B ≈ BA, and was primarily related to the electrochemically active surface area. No direct correlation was observed between corrosion resistance and metal release rates.     

NETMAN: The design of a collaborative wearable computer system

This paper presents a wearable groupware system designed to enhance the communication and cooperation of highly mobile network technicians. It provides technicians in the field with the capabilities for realtime audioconferencing, transmission of video images back to the office, and contextsensitive access to a shared notebook. An infrared locationtracking device allows for the automatic retrieval of notebook entries depending on the user's current location.     

Two-Dimensional Palladium Diselenide with Strong In-Plane Optical Anisotropy and High Mobility Grown by Chemical Vapor Deposition

Two-dimensional (2D) palladium diselenide (PdSe₂) has strong interlayer coupling and a puckered pentagonal structure, leading to remarkable layer-dependent electronic structures and highly anisotropic in-plane optical and electronic properties. However, the lack of high-quality, 2D PdSe₂ crystals grown by bottom-up approaches limits the study of their exotic properties and practical applications. In this work, chemical vapor deposition growth of highly crystalline few-layer (≥2 layers) PdSe₂ crystals on various substrates is reported. The high quality of the PdSe₂ crystals is confirmed by low-frequency Raman spectroscopy, scanning transmission electron microscopy, and electrical characterization. In addition, strong in-plane optical anisotropy is demonstrated via polarized Raman spectroscopy and second-harmonic generation maps of the PdSe₂ flakes. A theoretical model based on kinetic Wulff construction theory and density functional theory calculations is developed and described the observed evolution of “square-like” shaped PdSe₂ crystals into rhombus due to the higher nucleation barriers for stable attachment on the (1,1) and (1,−1) edges, which results in their slower growth rates. Few-layer PdSe₂ field-effect transistors reveal tunable ambipolar charge carrier conduction with an electron mobility up to ≈294 cm² V⁻¹ s⁻¹, which is comparable to that of exfoliated PdSe₂, indicating the promise of this anisotropic 2D material for electronics.     

Modeling the maximum power output of a distributed PV fleet

In areas with a high (photovoltaic) PV penetration, the installed PV capacity is the decisive factor in network planning. This article discusses meteorological impacts on distribution networks in these areas. The focus thereby is to determine the maximum feed‐in power of a distributed PV fleet. Therefore, a meteorological classification of the situations with maximum feed‐in is presented. With these results, the maximum feed‐in power is calculated for Germany. The maximum feed‐in of a distributed PV fleet is found for clear sky situations with a limit of 85% of the installed standard test condition power. This limit could be confirmed by the analysis of measured PV power feed‐in and its impact on the voltage levels in a distribution grid. The investigations are based on the analysis of data from a very detailed measurement campaign in a distribution grid with very high PV penetration in southern Germany. Copyright © 2014 John Wiley & Sons, Ltd.     

多球果型马尾松形态及生殖生物学特征研究

多球果型马尾松是马尾松种群内的一个具特异性状的变异体.在多球果型马尾松雌性生殖枝上,能够着生40～80个球果(大孢子叶球),有的甚至可以达到193个以上.而在常见型马尾松的雌性生殖枝上,通常只着生有1～8个球果,最常见的着生2-4个球果.本文对多球果型马尾松和常见型马尾松在生长状态、形态结构、生殖发育等方面的差异进行了研究和分析.     

Megahertz-class printed high mobility organic thin-film transistors and inverters on plastic using attoliter-scale high-speed gravure-printed sub-5 μm gate electrodes

High performance organic thin-film transistors and inverters operating at MHz frequencies at 10 V are fabricated on plastic with high throughput (printing speed up to 1.0 m/s) using attoliter-scale high-speed gravure printing. The high performance of the devices is achieved using highly scaled gravure printed features (smaller than 5 μm) and optimizing a high mobility organic semiconductor for the short-channel gravure printed devices (>0.5 cm²/V s) to realize record performance levels.