New synthesis approach for hybrid Gd(III)-loaded Nanocrystalline TiO2 as potential magnetic resonance imaging contrast agents

A new aqueous "in situ and one pot" method to elaborate surface-functionalized Gd(III)-doped anatase TiO2 nanoparticles, starting from heterometallic/heteroleptic Gd-Ti alkoxides, is reported. Full characterization and thermal behaviour of the nanomaterials demonstrate that this molecular approach offers the convenience of working under soft temperature and pH conditions in order to allow fine tuning of the organic surface functionalization and gadolinium doping. In vitro phantom images exhibit potential MRI T1-contrast agent properties.     

The correct application of total active reflection coefficient to evaluate MIMO antenna systems and its generalization to N ports

Several papers published by prestigious Journals on Antennas and Microwave Techniques have disseminated misconceptions about total active reflection coefficient (TARC), a meaningful metric to characterize multiple‐input multiple‐output antenna arrays, and the misapprehension has been spread over the years. In this article, an extrapolation to calculate TARC for N‐antennas systems is derived and applied to published results for illustration purposes. Moreover, the inaccurate and correct TARC equations are put in context by means of its physic and mathematical insight, demonstrating the divergence of results when the interport RF isolation is comparable or higher than the port matching. The importance of assessing multiantenna systems using TARC is explained.     

Development of rigid toughened photocurable epoxy foams

This study present a fast and efficient method for preparing photocurable rigid epoxy foams. A system based on the anionic photopolymerization of diglycidyl ether of bisphenol A (DGEBA) combined with a thiol-ene photopolymerization, was used. A tertiary diamine curing agent functionalized with four allyl groups was used in conjunction with a multifunctional thiol. The presence of several basic species, like tertiary amines, thiolates, polythioethers and alkoxide groups induced the anionic ring opening polymerization of the epoxy groups. At the same time the double bonds of the curing agent reacted with the multifunctional thiol generating polythioethers. The flexibility of the polythioethers modified the properties of the epoxy polymers, improving their toughness. Benzenesulfonyl hydrazide as foaming agent and zinc oxide as activator were added to DGEBA to produce the epoxy foams. The photopolymerization kinetics showed that conversion of the epoxide groups reached 80% in 600 s. Thermal curing studies performed by DSC showed that the main curing exotherm were determined at 84–89 °C, which match the temperature at which the photocuring was carried out in the UV light chamber (85 °C). It was found that the viscosity of the formulations plays a key role in the pore size of the foamed polymer, the higher the viscosity the larger the pore sizes. It was also determined that the impact resistance of the produced foams increased with increasing concentration of the thiol-ene system, as a consequence of a greater amount of polythioethers present in the co-network.     

Localized CO2 laser damage repair of fused silica optics

A technique has been developed for the localized treatment of laser damage sites in fused silica optics by CO2 laser melt-flow smoothing, by using a 50 to 125 microm diameter beam in a regime that avoids mass removal by ablation. A detailed calibration of the laser irradiance for the threshold ablation of craters was carried out for a range of beam diameters and pulses in the 20 micros to 200 ms range. The results agree with a thermal model that also provides estimates of the melt depth for the different irradiation conditions. Smoothing trials for glass melting at irradiance values just below the ablation threshold irradiance were conducted to determine the optimum conditions and limits for the smoothing process. The technique has been found to remove damage pits up to a depth of 0.5 microm, while the small melt depth associated with localized treatment limits the smoothing to a 相似文献   

Plant growth-promoting bacteria for phytostabilization of mine tailings

Eolian dispersion of mine tailings in arid and semiarid environments is an emerging global issue for which economical remediation alternatives are needed. Phytostabilization, the revegetation of these sites with native plants, is one such alternative. Revegetation often requires the addition of bulky amendments such as compost which greatly increases cost. We report the use of plant growth-promoting bacteria (PGPB) to enhance the revegetation of mine tailings and minimize the need for compost amendment. Twenty promising PGPB isolates were used as seed inoculants in a series of greenhouse studies to examine revegetation of an extremely acidic, high metal contenttailings sample previously shown to require 15% compost amendment for normal plant growth. Several isolates significantly enhanced growth of two native species, quailbush and buffalo grass, in tailings. In this study, PGPB/compost outcomes were plant specific; for quailbush, PGPB were most effective in combination with 10% compost addition while for buffalo grass, PGPB enhanced growth in the complete absence of compost. Results indicate that selected PGPB can improve plant establishment and reduce the need for compost amendment. Further, PGPB activities necessary for aiding plant growth in mine tailings likely include tolerance to acidic pH and metals.