Studies on the one-dimensional platinum atom chain compound Rb3(H3O)0.2[Pt(CN)4](O3SO·H·OSO3)0.5·0.8H2O

The variation of conductivity and thermopower with temperature for Rb₃(H₃O)_0.2[Pt(CN)₄](O₃SO·H·OSO₃)_0.5·0.8H₂O is reported. The abrupt falls in conductivity at low temperature previously reported have been carefully studied and from the non-reproducible nature of the phenomena, it is deduced that these result from cracks in the sample rather than a phase change in the material.     

Folding at the Microscale: Enabling Multifunctional 3D Origami‐Architected Metamaterials

Mechanical metamaterials inspired by the Japanese art of paper folding have gained considerable attention because of their potential to yield deployable and highly tunable assemblies. The inherent foldability of origami structures enlarges the material design space with remarkable properties such as auxeticity and high deformation recoverability and deployability, the latter being key in applications where spatial constraints are pivotal. This work integrates the results of the design, 3D direct laser writing fabrication, and in situ scanning electron microscopic mechanical characterization of microscale origami metamaterials, based on the multimodal assembly of Miura‐Ori tubes. The origami‐architected metamaterials, achieved by means of microfabrication, display remarkable mechanical properties: stiffness and Poisson’s ratio tunable anisotropy, large degree of shape recoverability, multistability, and even reversible auxeticity whereby the metamaterial switches Poisson’s ratio sign during deformation. The findings here reported underscore the scalable and multifunctional nature of origami designs, and pave the way toward harnessing the power of origami engineering at small scales.     

The effect of plasma treatment on flexible self-standing supercapacitors composed by carbon nanotubes and multilayer graphene composites

Journal of Materials Science - Flexible self-standing supercapacitor devices (FSSS) have attracted great attention in several areas due to their potential use in a wide range of applications, such...     

Plane Gravitational Waves,the Kinetic Energy of Free Particles and the Memory Effect

It is shown that in the passage of a short burst of nonlinear plane gravitational wave, the kinetic energy of free particles may either decrease or increase. The decrease or increase of the kinetic energy crucially depends on the initial conditions (position and velocity) of the a particle. Therefore a plane gravitational wave may extract energy from a physical system.     

Biodegradation of PHBV/GNS nanocomposites by Penicillium funiculosum

Biodegradable polymer nanocomposites are an essential alternative to minimize the generation of polymeric solid waste that shows short shelf life and difficult degradation. In this study, nanocomposites based on poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) were prepared by the incorporation of different contents, 0.25, 0.50, 0.75, and 1.00 wt % of graphite nanosheets (GNS), using a solution casting method. The investigation of the PHBV samples biodegradation was made using filamentous fungi (Penicillium funiculosum) in solid medium. Characterization of the material was performed by weight loss, differential scanning calorimetry, carbonyl index determined by Fourier transformed infrared spectroscopy, contact angle, roughness, and scanning electron microscopy. Results revealed that PHBV/GNS nanocomposites can be totally degraded in the presence of Penicillium funiculosum; however, it will be necessary high incubation period. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44234.     

Direct ink writing of ceramic matrix composite structures

We present the development of an ink containing chopped fibers that is suitable for direct ink writing (DIW), enabling to obtain ceramic matrix composite (CMC) structures with complex shape. We take advantage of the unique formability opportunities provided by the use of a preceramic polymer as both polymeric binder and ceramic source. Inks suitable for the extrusion of fine filaments (<1 mm diameter) and containing a relatively high amount of fibers (>30 vol% for a nozzle diameter of 840 μm) were formulated. Despite some optimization of ink rheology still being needed, complex CMC structures with porosity of ~75% and compressive strength of ~4 MPa were successfully printed. The process is of particular interest for its ability to orient the fibers in the extrusion direction due to the shear stresses generated at the nozzle tip. This phenomenon was observed in the production of polymer matrix composites, but it is here employed for the first time for the production of ceramic matrix ones. The possibility to align high aspect ratio fillers using DIW opens the path to layer‐by‐layer design for optimizing the mechanical and microstructural properties within a printed object, and could potentially be extended to other types of fillers.     

Kinetics of elimination and distribution in blood and liver of biocompatible ferrofluids based on Fe3O4 nanoparticles: An EPR and XRF study

In this study, we evaluated the biodistribution and the elimination kinetics of a biocompatible magnetic fluid, Endorem™, based on dextran-coated Fe₃O₄ nanoparticles endovenously injected into Winstar rats. The iron content in blood and liver samples was recorded using electron paramagnetic resonance (EPR) and X-ray fluorescence (XRF) techniques. The EPR line intensity at g = 2.1 was found to be proportional to the concentration of magnetic nanoparticles and the best temperature for spectra acquisition was 298 K. Both EPR and XRF analysis indicated that the maximum concentration of iron in the liver occurred 95 min after the ferrofluid administration. The half-life of the magnetic nanoparticles (MNP) in the blood was (11.6 ± 0.6) min measured by EPR and (12.6 ± 0.6) min determined by XRF. These results indicate that both EPR and XRF are very useful and appropriate techniques for the study of kinetics of ferrofluid elimination and biodistribution after its administration into the organism.     

An Evolutionary Method for Synthesizing Low-Sensitivity Lossless Matching Networks

Whereas the present practice of designing matching networks for antennas is limited to conventional topologies, requiring a significant amount of domain knowledge, evolutionary algorithms can be used for automatically identifying unconventional designs that are more effective than would otherwise be developed. In this work, an automatic method to design lossless matching networks driven by an evolutionary algorithm (EA) that considers the sensitivities of the network parameters during the synthesis process is presented. To this end, a closed-form expression for the transducer power gain (TPG) sensitivity with respect to the component values is employed in such a way that the effects of the components tolerance on the matching network performance can easily be quantified. A 3D data structure based on the adjacency matrix is conveniently used to represent any type of network topologies. The proposed EA employs a novel set of topology variation operators, tailored for changing the circuit topology, and an association step, with the aim of reducing the number of nodes of the matching circuit. The efficiency of the proposed EA is tested in the synthesis of an impedance matching network for a VHF monopole whip antenna. This study’s results indicate a matching bandwidth improvement, a more uniformly distributed TPG along the operation frequency band and a more stable TPG regarding the components tolerance compared to the results obtained by previous approaches.