ZnO Nanoplatelets with Controlled Thickness: Atomic Insight into Facet-Specific Bimodal Ligand Binding Using DNP NMR

Colloidal nanoplatelets (NPLs) and nanosheets with controlled thickness have recently emerged as an exciting new class of quantum-sized nanomaterials with substantially distinct optical properties compared to 0D quantum dots. Zn-based NPLs are an attractive heavy-metal-free alternative to the so far most widespread cadmium chalcogenide colloidal 2D semiconductor nanostructures, but their synthesis remains challenging to achieve. The authors describe herein, to the best of their knowledge, the first synthesis of highly stable ZnO NPLs with the atomically precise thickness, which for the smallest NPLs is 3.2 nm (corresponding to 12 ZnO layers). Furthermore, by means of dynamic nuclear polarization-enhanced solid-state ¹⁵N NMR, the original role of the benzamidine ligands in stabilizing the surface of these nanomaterials is revealed, which can bind to both the polar and non-polar ZnO facets, acting either as X- or L-type ligands, respectively. This bimodal stabilization allows obtaining hexagonal NPLs for which the surface energy of the facets is modulated by the presence of the ligands. Thus, in-depth study of the interactions at the organic–inorganic interfaces provides a deeper understanding of the ligand–surface interface and should facilitate the future chemistry of stable-by-design nano-objects.     

Simultaneous handover scheme for IEEE 802.11 WLANs with IEEE 802.21 triggers

Handover performance in wireless networks is important, especially nowadays, when multimedia services are becoming increasingly available over the wireless devices. However, users expect uncompromised mobility when using the service. Thus, the support of multimedia services is not possible if handover is inefficient. At the same time it is clear that a strict separation between IP Layer and the Link Layer results in built-in sources of delay. The paper discusses the IEEE 802.11 and Mobile IPv4 handover performance in practical scenarios. We introduce a new simultaneous handover scheme with IEEE 802.21 triggers. In order to verify the handover performance, simulation experiments have been conducted, whose results are also presented and discussed.     

Adaptive transform skipping for improved coding of motion compensated residuals

New generations of video compression algorithms, such as those included in the under development High Efficiency Video Coding (HEVC) standard, provide substantially higher compression compared to their ancestors. The gain is achieved by improved prediction of pixels, both within a frame and between frames. Novel coding tools that contribute to the gain provide highly uncorrelated prediction residuals for which classical frequency decomposition methods, such as the discrete cosine transform, may not be able to supply a compact representation with few significant coefficients. To further increase the compression gains, this paper proposes transform skip modes which allow skipping one or both 1-D constituent transforms (i.e., vertical and horizontal), which is more suitable for sparse residuals. The proposed transform skip mode is tested in the HEVC codec and is able to provide bitrate reductions of up to 10% at the same objective quality when compared with the application of 2-D block transforms only. Moreover, the proposed transform skip mode outperforms the full transform skip currently investigated for possible adoption in the HEVC standard.     

A Roadmap for Controlled and Efficient n‐Type Doping of Self‐Assisted GaAs Nanowires Grown by Molecular Beam Epitaxy

N‐type doping of GaAs nanowires has proven to be difficult because the amphoteric character of silicon impurities is enhanced by the nanowire growth mechanism and growth conditions. The controllable growth of n‐type GaAs nanowires with carrier density as high as 10²⁰ electron cm^?3 by self‐assisted molecular beam epitaxy using Te donors is demonstrated here. Carrier density and electron mobility of highly doped nanowires are extracted through a combination of transport measurement and Kelvin probe force microscopy analysis in single‐wire field‐effect devices. Low‐temperature photoluminescence is used to characterize the Te‐doped nanowires over several orders of magnitude of the impurity concentration. The combined use of those techniques allows the precise definition of the growth conditions required for effective Te incorporation.     

Evolutionary approach to development of collaborative teleconsultation system for imaging medicine

This paper presents an evolution of a modern collaborative teleconsultation system called TeleDICOM over the period of several years. We show how new features (required from a medical point of view) can be provided, which barriers have been identified, and how these factors influence the system's architecture. A turning point in the evolution of our system was the formulation of a new architecture, fully facilitating service-oriented architecture paradigm guidelines. We therefore show how the knowledge and experience gathered during utilization of previous versions of TeleDICOM positively stimulate procedures of service-based system decomposition and business processes definition.     

Behavioral Fault Modeling and Simulation Using VHDL-AMS to Speed-Up Analog Fault Simulation

One of the main requirements for generating test patterns for analog and mixed-signal circuits is fast fault simulation. Analog fault simulation is much slower than the digital equivalent. This is due to the fact that digital circuit simulators use less complex algorithms compared with transistor-level simulators. Two of the techniques to speed up analog fault simulation are: fault dropping/collapsing, in which faults that have similar circuit responses compared with the fault-free circuit response and/or with another faulty circuit response are considered equivalent; and behavioral/macro modeling, whereby parts of the circuit are modeled at a more abstract level, therefore reducing the complexity and the simulation time. This paper discusses behavioral fault modeling to speed-up fault simulation for analog circuits.     

Determination of electrical and mechanical parameters in capacitive MEMS accelerometers using electrical measurements

This paper describes a simple technique for characterization of capacitive MEMS accelerometers. The method is based on electrical impedance (admittance) measurements of capacitive MEMS accelerometers treated as electrostatically-driven microelectromechanical resonators. By using this method, it is possible to determine some electrical and mechanical parameters including the shunt capacitance, the mechanical resonance frequency and quality factor. These parameters may serve as measures of structural integrity of the tested structures and their packages during reliability testing, for instance.     

Effective Number of Samples and Pseudo-Random Nonlinear Distortions in Digital OFDM Coded Signal

This paper concerns the theoretical modeling of OFDM coded signal’s degradation caused by pseudo-random nonlinear distortions introduced by an analog-to-digital or digital-to-analog converter. A new quantity, the effective number of samples, is defined and used for the derivation of accurate expressions for the autocorrelation function and the total power of the distortions. The derivation is based on a probabilistic model of the signal and its transition probability. It is shown that for digital (discrete and quantized) signals the effective number of samples replaces the total number of samples and is the proper quantity defining their properties.     

Polychlorinated phenols in total diet

A method has been developed for the isolation, separation and determination of chlorinated phenols in total diet. The isolation takes place following acid hydrolysis of the conjugates and is performed by simultaneous extraction and distillation with water vapour and toluene. The isolated chlorophenols are removed by clean-up on a Florisil column using a mixture of 15% dichloromethane in toluene for elution. The separation and determination is carried out by capillary gas chromatography with electron capture detection. The recovery of the method ranged between 70.1±5 and 96.8±4.9% for the individual chlorophenols. The determination limits were 0.5 to 1.0 g·kg^–1. The method was applied in a study aimed at estimating the chlorophenol burden in two population groups (children up to the age of 6 years and students up to the age of 18 years). In two succesive years, 80 total diet samples were analysed. Average contents of the individual chlorophenols were from 0.7 to 33.5 g·kg^–1 and were higher for the dichlorophenol isomers. The calculated average daily intake ranged from 0.04 to 1.69 g·kg^–1 body weight for the individual phenols.

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Polychlorierte Phenole im Gesamtverzehr

Zusammenfassung Das hier beschriebene Verfahren dient zur Isolierung, Trennung und Bestimmung von chlorierten Phenolen im Gesamtverzehr. Dieser wurde sauer hydrolysiert, die Phenole wurden durch eine simultane Wasserdampfdestillation und ein Extraktionsverfahren mit Toluol isoliert. Beim anschließenden Derivatisierungsverfahren mit Pentafluorobenzylbromid entstanden auch Störungssubstanzen, sie wurden mittels Säulenchromatographie an Florisil abgetrennt. Die chromatographische Trennung und Bestimmung erfolgte unter Anwendung der Kapillargaschromatographie mit ECD. Die Wiederfindungsrate variierte zwischen 70.1±5 und 96.8±4.9% bei Nachweisgrenzen von 0.5 bis 1.0 g·kg^–1. Das Verfahren wurde zur Ermittlung der Exposition bei Kindern bis zu 6 Jahren und Jungen bis zu 18 Jahren verwendet. Im Laufe von 2 Jahren wurden 80 Proben des Gesamtverzehrs aus Kindereinrichtungen analysiert. Der Durchschnittsinhalt schwankte von 0.7 bis 33.5 g·kg^–1 mit Überwiegen von Dichlorophenolen. Die aus den bekannten Inhalten ermittelte Tagesaufnahme variiert zwischen 0.04 und 1.69 g·kg^–1 Körpermasse und Tag.