Impact of Functionalized Polystyrenes as the Electron Injection Layer on Gold and Aluminum Surfaces: A Combined Theoretical and Experimental Study

At metal/organic interfaces, the insertion of an organic monolayer can significantly modify the surface properties of the substrate, especially in terms of charge injection across the interface. Herein, we study the formation of an insulating monolayer of morpholine or amine-functionalized polystyrene on Al(111) and Au(111) surfaces and its impact on surface work-function and charge injection. First-principles calculations based on Density Functional Theory have been carried out and point to a significant decrease in the work-function of modified metal surfaces; this is in very good agreement with ultraviolet photoemission spectroscopy measurements performed on the Au(111) surface. In addition, a bilayer cathode, consisting of a thin film of high-work-function metal, such as Al and Au, and a layer of amine-functionalized polystyrene, was also fabricated and tested in organic light-emitting diodes. Such bilayer structures exhibit substantially enhanced efficiency when compared with controls without the functionalized polymers. Our combined theoretical and experimental investigation gives insight into how a thin layer of a commodity polymer can be used to transform rather high-work-function metals into high-performance cathodes to provide efficient electron injection.     

Color–concept associations: A cross‐occupational and ‐cultural study and comparison

This study used a questionnaire survey to examine color–concept associations in two occupational groups from Hebei Province in China: steel workers (n = 139) and managerial staff (n = 74). The color stereotypes held by these two groups were also compared to those held by three other cultural groups studied elsewhere (Hong Kong Chinese, Yunnan Chinese, and Americans). The participants were presented with 16 concepts and asked to choose one of 10 colors to represent each concept. The chi‐square test results showed that each concept was significantly associated with at least one color. Both the steel workers and the managerial staff primarily associated green with “go” and “safe” and red with “stop” and “danger.” The cross‐group comparisons indicated that the steel workers and the managerial staff produced stronger color associations than those produced by the Yunnan Chinese and the Hong Kong Chinese subjects, but weaker than those produced by the US subjects. Our findings build on existing knowledge of population stereotypes for color–concept associations and provide guidelines for the design of color displays and products for global users. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 630–635, 2014     

Generation of Rho Zero Cells: Visualization and Quantification of the mtDNA Depletion Process

Human mitochondrial DNA (mtDNA) is located in discrete DNA-protein complexes, so called nucleoids. These structures can be easily visualized in living cells by utilizing the fluorescent stain PicoGreen^®. In contrary, cells devoid of endogenous mitochondrial genomes (ρ⁰ cells) display no mitochondrial staining in the cytoplasm. A modified restriction enzyme can be targeted to mitochondria to cleave the mtDNA molecules in more than two fragments, thereby activating endogenous nucleases. By applying this novel enzymatic approach to generate mtDNA-depleted cells the destruction of mitochondrial nucleoids in cultured cells could be detected in a time course. It is clear from these experiments that mtDNA-depleted cells can be seen as early as 48 h post-transfection using the depletion system. To prove that mtDNA is degraded during this process, mtDNA of transfected cells was quantified by real-time PCR. A significant decline could be observed 24 h post-transfection. Combination of both results showed that mtDNA of transfected cells is completely degraded and, therefore, ρ⁰ cells were generated within 48 h. Thus, the application of a mitochondrially-targeted restriction endonuclease proves to be a first and fast, but essential step towards a therapy for mtDNA disorders.     

Corrosion of NiTi Wires with Cracked Oxide Layer

Corrosion behavior of superelastic NiTi shape memory alloy wires with cracked TiO₂ surface oxide layers was investigated by electrochemical corrosion tests (Electrochemical Impedance Spectroscopy, Open Circuit Potential, and Potentiodynamic Polarization) on wires bent into U-shapes of various bending radii. Cracks within the oxide on the surface of the bent wires were observed by FIB–SEM and TEM methods. The density and width of the surface oxide cracks dramatically increase with decreasing bending radius. The results of electrochemical experiments consistently show that corrosion properties of NiTi wires with cracked oxide layers (static load keeps the cracks opened) are inferior compared to the corrosion properties of the straight NiTi wires covered by virgin uncracked oxides. Out of the three methods employed, the Electrochemical Impedance Spectroscopy seems to be the most appropriate test for the electrochemical characterization of the cracked oxide layers, since the impedance curves (Nyquist plot) of differently bent NiTi wires can be associated with increasing state of the surface cracking and since the NiTi wires are exposed to similar conditions as the surfaces of NiTi implants in human body. On the other hand, the potentiodynamic polarization test accelerates the corrosion processes and provides clear evidence that the corrosion resistance of bent superelastic NiTi wires degrades with oxide cracking.     

Growing a list

It is easy to find expert knowledge on the Internet on almost any topic, but obtaining a complete overview of a given topic is not always easy: information can be scattered across many sources and must be aggregated to be useful. We introduce a method for intelligently growing a list of relevant items, starting from a small seed of examples. Our algorithm takes advantage of the wisdom of the crowd, in the sense that there are many experts who post lists of things on the Internet. We use a collection of simple machine learning components to find these experts and aggregate their lists to produce a single complete and meaningful list. We use experiments with gold standards and open-ended experiments without gold standards to show that our method significantly outperforms the state of the art. Our method uses the ranking algorithm Bayesian Sets even when its underlying independence assumption is violated, and we provide a theoretical generalization bound to motivate its use.     

On probability polynomials of 1D quantum walk

We investigate a set of polynomials arising from one dimensional quantum walk with a single-parameter coin operator. In the process, explicit hypergeometric function expressions for these polynomials are presented. An explicit expression is also given for a limit probability for the special case of Hadamard walk.     

The Impact of Selective Oxidation on the Phase Transformation in the Sub‐Surface of Advanced High Strength Steels

The present paper contributes in the discussion of heterogeneous gas/metal reactions by discussing the influence of the dew point (dp) during intercritical annealing on the sub‐surface constitution. Annealing trials with different Advanced High Strength Steels (AHSS) were carried out and the element distribution within the sub‐surface was analysed by glow discharge optical emission spectrometer (GD‐OES). For modelling purpose the gained element distribution data were adjusted in a way that the selective oxidation products were considered within the sub‐surface element profiles. Several transformation temperatures along the depth profiles according to the adjusted GD‐OES data have been computed for the dp ?30 °C and +5 °C. In all cases the according models have been implemented in Matlab. The thermodynamic data have been obtained via the Matlab‐ThermoCalc interface. Empirical equations have been applied for the determination of the bainite and martensite start temperatures. It is shown that the sub‐surface constitution and the transformation temperature differ significantly. In most cases the change of the transformation temperature within the surface and sub‐surface reaches up to 100 °C compared to the bulk. For a Dual‐Phase (DP) Steel with C(0.15%)Mn(1.7%)Al(1.7%)Cr(0.5%), the change of the A_e1‐temperature is with 300 °C significantly higher. However one has to keep in mind that the 2‐phase composition can not be assumed to be constant during intercritical annealing. It is therefore concluded that for the purpose of simulating the selective oxidation processes during intercritical annealing of AHSS the continuous change of the sub‐surface constitution must be incorporated in the future work.     

Spatial Wavefunction-Switched (SWS) InGaAs FETs with II–VI Gate Insulators

This paper presents the implementation of a novel InGaAs field-effect transistor (FET), using a ZnSe-ZnS-ZnMgS-ZnS stacked gate insulator, in a spatial wavefunction-switched (SWS) structural configuration. Unlike conventional FETs, SWS devices comprise two or more asymmetric coupled quantum wells (QWs). This feature enables carrier transfer vertically from one quantum well to another or laterally to the wells of adjacent SWS-FET devices by manipulation of the gate voltages (V _g). Observation of an extra peak (near both accumulation and inversion regions) in the capacitance–voltage data in an InGaAs-AlInAs two-quantum-well SWS structure is presented as evidence of spatial switching. The peaks are attributed to the appearance of carriers first in the lower well and subsequently their transfer to the upper well as the gate voltage is increased. The electrical characteristics of a fabricated SWS InGaAs FET are also presented along with simulations of capacitance–voltage (C–V) behavior, showing the effect of wavefunction switching between wells. Finally, logic operations involving simultaneous processing of multiple bits in a device, using coded spatial location of carriers in quantum well channels, are also described.