Manganese ferrite-polyaniline hybrid materials: Electrical and magnetic properties

Magnetic MnFe₂O₄ nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe₂O₄ using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe₂O₄ powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe₂O₄ powders and are higher by comparison to those of the MnFe₂O₄/PANI hybrid materials. The values of saturation magnetization in case of MnFe₂O₄ powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe₂O₄ powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe₂O₄ powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σ_DC = 54.5·10^?5S?m^?1) which was close to that of PANI (σ_DC = 61.2·10^?5 S?m^?1). The fact that the magnetic and electric properties of the synthesized MnFe₂O₄/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications.     

Intelligent Monitoring for Adaptation in Grid Applications

Grid applications access distributed, and often shared, resources. One consequence of this resource sharing is that measured application performance can vary widely and in unexpected ways. Determining the causes of poor performance, due to either anomalous application behavior or contention for shared resource use, and adapting to changing circumstances are critical to creation of robust Grid applications. Performance contracts and real-time adaptive control are two mechanisms to realize soft performance guarantees in Grid environments. Performance contracts formalize the relationship between application performance needs and resource capabilities. During execution, contract monitors use performance data to verify that expectations are met. When the contracted specifications are not satisfied, the system can choose to either adapt the application to available resources or reschedule the application on a new set of resources that can satisfy the original contract specifications. We describe an infrastructure for Grid application contract development and monitoring. This infrastructure, based on the Autopilot toolkit, provides flexible and scalable tools to assess both application and system behavior.     

Measurement of the working parameters of an air-post vertical-cavity surface-emitting laser

We present a complete experimental evaluation of the effective parameters necessary to describe the dynamical behavior of an air-post vertical-cavity surface-emitting lasers, on the basis of theoretical equations which are also derived in this paper. The experimental investigation is composed of several steps, including power versus current measurement, noise spectrum analysis, linewidth evaluation. The complete set of parameters derived, in particular the linewidth-enhancement factor and the spontaneous emission factor, is particularly important for accurate comparisons of theoretical models on the laser dynamics with experiments.     

Probing the thermal decomposition process of layered double hydroxides through in situ <Superscript>57</Superscript>Fe Mössbauer and in situ X-ray diffraction experiments

The thermal decomposition properties of Mg–Fe hydrotalcites were studied through in situ ⁵⁷Fe Mössbauer spectroscopy and in situ X-ray diffraction. Abrupt changes in the quadrupolar splitting measured in the Mössbauer spectra revealed a phase transition from the starting lamellar structure to a new crystalline arrangement. By analyzing the Mössbauer parameters we show that the material is highly disordered in the 300–400 °C temperature range. This hypothesis is confirmed by the X-ray results whose diffractograms indicated the collapse of the lamellar structure and the formation of a solid solution.     

Generalized Nakagami-m phase crossing rate

This paper provides simple, exact, new closed-form expressions for the generalized phase crossing rate of Nakagami-m fading channels. Sample numerical results obtained by simulation are presented that validate the formulations developed here. A special case of this formulation is the Rayleigh case, whose result agrees with that obtained elsewhere in the literature. In passing, several new closed-form results concerning the statistics of the envelope, its in-phase and quadrature components, phase, and their time derivatives are obtained.     

Utilization of chopped and long alfalfa by dairy heifers

Two physical forms of alfalfa hay, chopped and long, were fed at maintenance and for ad libitum consumption to dairy heifers to determine effects upon digestibility and energy utilization. Ad libitum intake was associated with lower digestibility of dry matter (56 versus 58%), neutral detergent fiber (45 versus 58%), and acid detergent fiber (45 versus 52%). Energy balance was 1.77 Mcal/day at ad libitum versus .08 Mcal/day at maintenance. Dry matter intake was similar for chopped (5.4 kg/day) versus long alfalfa (5.5 kg/day). Digestibilities of dry matter, neutral detergent fiber, acid detergent fiber, and cellulose were 7 to 10 percentage units lower when heifers were fed the chopped alfalfa. Metabolizable energy intake generally reflected digestible energy intake, which was about 2 Mcal/day less for heifers consuming chopped alfalfa. Heat production was similar for the two physical forms. Consequently, heifers consuming chopped alfalfa had lower energy balance. Reducing particle size of the alfalfa resulted in lower dry matter and energy digestibility, presumably because of increased rate of passage. Increased intake to compensate for depressed energy utilization of the chopped alfalfa did not occur; effects upon animal gain could not be assessed.     

Eigenschaften von binären mischungen aus polyethylenen hoher dichte mit ultrahoher und normaler molmasse

The study is on two component blends of high density polyethylenes, having normal and ultra-high molecular weight. The polyethylenes were homogenized by two routes: in powder state or by rolling in melt, then pressed at temperatures in the range from 140°C to 220°C. Comparative studies showed that the way of homogenizing of the components does practically not affect the main mechanical properties of the blends when pressed at temperatures ≥ 160°C. Of special interest are the characteristics of those systems where ultra-high molecular weight polyethylene is the matrix component.     

Late effects of radiotherapy in children

PURPOSE: To examine benzoporphyrin derivative angiography as a modality for studying photosensitizer biodistribution in experimental choroidal melanomas. METHODS: A liposomal preparation of benzoporphyrin derivative was used in this study. Digital benzoporphyrin derivative angiograms were performed in 10 rabbits (six for experimental choroidal melanomas, two for normal choroids, and two for irides) using a Topcon ImageNet H1024 digital imaging system, a Kodak Megaplus video camera, and a Topcon TRC-50-VT fundus camera. Only one eye from each rabbit was used. Filters specifically designed for benzoporphyrin derivative (peak absorption at 580 nm and peak emission at 695 nm) were used. Benzoporphyrin derivative (1 mg/kg) was injected into an ear vein while images of tumor, normal choroid, or iris were being obtained. Follow-up images were obtained during the first 3 hours and at 24 hours after injection. Fluorescence microscopy was performed in all 10 rabbits using 1 mg/kg of benzoporphyrin derivative. Tumor-bearing eyes were enucleated at the same time points that angiograms were performed, and the two sets of results were compared for maximum dye accumulation. RESULTS: Digital angiography demonstrated that maximal benzoporphyrin derivative fluorescence occurred in tumors 15 to 45 minutes after injection. Fluorescence photometry corroborated these results. CONCLUSION: Photosensitizer angiography is a valid modality for determining the optimum treatment time for photodynamic therapy.