Complex random matrices and Rician channel capacity

Eigenvalue densities of complex noncentral Wishart matrices are investigated to study an open problem in information theory. Specifically, the largest, smallest, and joint eigenvalue densities of complex noncentral Wishart matrices are derived. These densities are expressed in terms of complex zonal polynomials and invariant polynomials. A connection between the complex Wishart matrix theory and information theory is given. This facilitates evaluation of the most important information-theoretic measure, the so-called ergodic channel capacity. In particular, the capacity of multiple-input multiple-output (MIMO) Rician distributed channels is investigated. We consider both spatially correlated and uncorrelated MIMO Rician channels and derive exact and easily computable tight upper bound formulas for ergodic capacities. Numerical results are also given, which show how the channel correlation degrades the capacity of the communication system.Translated from Problemy Peredachi Informatsii, No. 1, 2005, pp. 3–27.Original Russian Text Copyright © 2005 by Ratnarajah, Vaillancourt, Alvo.This work was partially supported by the Natural Sciences and Engineering Research Council of Canada.     

Poly(ethylene oxide)-poly(butadiene) interpenetrated networks as electroactive polymers for actuators: A molecular dynamics study

Molecular dynamics (MD) techniques have been used to study ionic transport and coordination stability in an interpenetrating polymer (IPN) network used as electrolyte for actuator devices. The system consisted of poly(ethylene oxide) (PEO) and poly(butadiene) (PB) in a 80/20% weight ratio at a total polymer of 32%, immersed into propylene carbonate (PC) solutions of LiClO₄. The system has been studied for five different concentrations of LiClO₄ in PC: 0.25, 0.5, 0.75, 1.0 and 1.25 M, and with applied external electric fields of 0, 1 and 5 MV/m. It is shown that the polymer matrix has little involvement in the movement of ions and solvent, but that the polymer arrangement is important for the solvent phase nano-structure, and thereby influences the mobility. The mobility of PC is higher than of the other species in the system, but the charged species display higher mobility under external field. The field threshold level for conductivity processes is between 1 and 5 MV/m. It is argued that ion pairing, phase separation and coordination stability are important for the overall dynamic properties.     

Flexible supercapacitor-like actuator with carbide-derived carbon electrodes

Soft and flexible electric driven transducers based on carbide-derived carbon (CDC), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), polyvinylidenefluoride-co-hexafluoropropylene (PVdF(HFP)) are proposed, and electroactive performances of these materials are reported. By its nature, the synthesized device has two features when voltage is applied. Firstly, it is a bending-type electrochemical actuator. Besides the external change of shape, this device is also an electrochemical capacitor, providing opportunity to store a considerable amount of charge. Laminated actuators can work in open air at low voltages (1–3 V). Their operating frequency is between 5 × 10⁻³ – 1 × 10¹ Hz (it is from 5 millihertz to 200 hertz) and 10 Hz and the maximum strain calculated from transducer displacement is 0.6%. The gravimetric capacitance of CDC in actuator electrodes was found to be 119 F g⁻¹ at 1 mV s⁻¹ sweep rate of the applied triangle voltage. The effects of synthesis temperature of CDC and associated changes in the porosity and surface area on the actuator displacement are discussed. The results of this study demonstrated a great potential of CDC as an active material for actuator electrodes, especially in these applications where the performance of the actuator has to be standardized and highly predictable.     

Hepatic veno-occlusive disease associated to the use of azathioprine in a renal transplant recipient

We report a 30 years old male, recipient of a kidney allograft and treated with azathioprine, who eighteen days after transplantation had a clinically asymptomatic elevation of total bilirubin and alkaline phosphatases. Nineteen months later, he presented with mild ascites, with a total bilirubin of 3.5 mg/dl, alkaline phosphatases of 308 U/L (normal < 170 U/L) and a prothrombin time at 55% of control. A liver biopsy showed sinusoidal and perivenular fibrosis without inflammation, compatible with chronic venous obstruction. Hepatic veno-occlusive disease is an infrequent complication of azathioprine use.     

Renewable antioxidant properties of suspensible chitosan–polypyrrole composites

Conductive polymers have the ability to capture radicals and have become in focus for antioxidant applications of food packaging or biomedical applications. Unfortunately, the conducting polymers such as polypyrrole are difficult to suspense in solution after chemical or electrochemical polymerization. Chitosan, as a natural polymer from chitin, can be dissolved in diluted acetic acid solutions. In the present study, composites suspensible in diluted acetic acid solutions have been produced by the chemical polymerization of pyrrole in chitosan solution using ammonium persulfate (APS) as the oxidant. FTIR and UV–Vis measurements did identify an attachment of polypyrrole to chitosan.In order to optimize the activity and stability of the composites, the ratios of APS: polypyrrole: chitosan were analyzed. The chitosan–polypyrrole composites were formed as membranes (coatings); impedance measurements indicated their conductivity to be in the range of 10^?3–10^?7 S cm^?1. The antioxidant (radical scavenger activity) properties were determined by the di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (DPPH) assay. The radical scavenger activity of the composites was found renewable by means of electrochemical cycling.     

A Versatile Ionomer-Based Soft Actuator with Multi-Stimulus Responses,Self-Sustainable Locomotion,and Photoelectric Conversion

The prospects of endowing artificial robotics or devices with increasingly complex and emergent life-like behaviors have attracted growing interest in the soft functional materials that mimic the versatile motions of living creatures in the iridescent nature. However, despite the flourishing achievements so far, soft actuators capable of sensitive multi-stimulus responses and self-sustainable movements, have been extensively pursued to reduce control complexity yet remains a challenging target. Here, through material-structural synergistic design incorporating stress-mismatching structure, high pseudo-negative coefficient of thermal expansion of perfluoro-sulfonic acid ionomer, comprehensive converting properties of carbon nanotube, and anisotropic large thermal expansion of PE polymer, an ionomer-based bilayer actuator is proposed, presenting high-performance actuation of various forms and nice stability, responsive to light (including sunlight without focusing, LED light), low voltage, mild heating, and humidity/solvent change. With a built-in structural feedback loop, the actuation performances are further explored to realize intelligent systems, including: 1) self-sustainable locomotion under sunlight irradiation with adjustable photophobic and phototropic direction as well as adaption to different topographies and loading conditions, 2) self-sustainable oscillation and solar-electric generating, and 3) bionic floristic reaction according to environmental change. These diversified actuation modes allow promising following-up designs for bio-hybrid soft robotics fueled by and harmonized with natural environments.     

All-Printed Green Micro-Supercapacitors Based on a Natural-derived Ionic Liquid for Flexible Transient Electronics

The fabrication and characterization of green, flexible, and ultra-thin supercapacitors that are able to operate above 1.5 V is reported, using an all-printed fabrication process. The devices are produced by aqueous spray casting of a natural-derived electrolyte ionogel composed by 2-hydroxyethyl cellulose and by the ionic liquid choline lactate, while the electrodes are composed of highly porous nanostructured carbon films deposited by supersonic cluster beam deposition (SCBD). The obtained supercapacitors (device thickness < 10 μm) are stable to bending and they possess power values up to 120 kW kg^–1. The combination of aqueous spray casting and SCBD constitutes a versatile, scalable, and eco-friendly fabrication process able to directly print interconnected elements suitable for transient electronic systems.     

World science as an input-output system

World science can be characterized as the product of one scientist or nation — knowledge or published papers — used or consumed by other scientists or nations. In this sense, science can be viewed as an input-output system, analogous to the models used in economics. An input-output model of the citation patters of the 18 leading countries in international science was constructed. These countries produce most of the world's science. The large role of the United States in both producing and consuming scientific information is evident in the results. The models also show the role of other countries with respect to each other. For example, the multinational nature of science in countries like the Netherlands and Switzerland is evident. The model can be used to show which countries interact with others, and which do not. Both types of information are useful in discussing trans-national interactions in science.