Biodegradable blends of amorphous poly(lactic acid) (aPLA) and polycaprolactone (PCL) and nanocomposites of these blends were developed by melt blending. A morphological study of the bioblends was ...carried out by means of WAXS and SEM showing immiscible behavior. The nanocomposites were also characterized morphologically by WAXS, TEM and SEM, revealing high degree of interaction of the nanoclays with the aPLA. Mechanical, thermal and gas barrier properties of the different blends and nanocomposites were studied and the effect of blending and clay addition on the above‐mentioned properties was evaluated.
This paper reports on a novel route to develop EVOH-kaolinite nanocomposites by a melt intercalation process and on some relevant nanocomposite properties as a function of composition. The kaolinite ...clay used is a very cheap raw material of the tile industry and as such needed to be refined and chemically modified prior to the melt intercalation step. The modification was carried out with dimethyl-sulfoxide, methanol and octadecylamine in order to increase the basal plane distance of the original clay by a factor of more than three. Melt blended nanocomposites were characterized by WAXS, TEM, DSC, TGA and oxygen transmission rate. From the early results, partial exfoliation and intercalation of the clay platelets was the dominant morphology attained. An increase in thermal resistance, glass transition temperature, crystallinity and barrier properties to oxygen were also observed for mass clay loadings below 8%.
This paper deals with the influence of water on the mechanical performance of ethylene-vinyl alcohol copolymers. A comparative study on the mechanical properties of six EVOH food packaging commercial ...grades with different ethylene contents has been carried out as a function of relative humidity by DMA and tensile testing. Two different cooling rates, i.e. fast and slow cooling, were used in order to study the effect of cooling speed on water/EVOH interactions. In agreement with the water transport results of a previous study, the current results indicate that there is a surprising anomalous antiplasticization regime for some mechanical properties below 30% RH, and that beyond this point further moisture sorption acts as the well reported effective plasticization agent for the mechanical properties.
This paper presents a novel planar filtering antenna (filtenna) with simple layout based on tightly-coupled different-length monopoles. Its design methodology is based on an even-mode/odd-mode ...decomposition of the monopole currents, and the combination of both modes in a multimodal circuit model that facilitates the design and tuning of the antenna and the accompanying feeding network, since most of the process is performed using fast circuit simulations. The circuit model casts light into the interaction between conducting and radiating modes in the bulk of the antenna, and on how this interaction can be used to propose feedback loops that increase and define the radiation band. Using these modal tools, a filtenna was designed and fabricated to fully cover the new 5G frequency bands (n77, n78 and n79) from 3 to 5 GHz that are currently being adopted by many countries for high-capacity data transmission. It features a 62.9% FWB, dipole-like radiation patterns, good out-of-band rejection up to 10 GHz, and a very good trade-off between design/structural-simplicity and bandwidth.
Cyclic nucleotide cAMP is a ubiquitous secondary messenger involved in a plethora of cellular responses to biological agents involving activation of adenylyl cyclase. Its intracellular levels are ...tightly controlled by a family of cyclic nucleotide degrading enzymes, the PDEs. In recent years, cyclic nucleotide phosphodiesterase type 4 (PDE4) has aroused scientific attention as a suitable target for anti-inflammatory therapy in respiratory diseases, particularly in the management of asthma and COPD. Here we describe our efforts to discover novel, highly potent inhaled inhibitors of PDE4. Through structure based design, with the inclusion of a variety of functional groups and physicochemical profiles in order to occupy the solvent-filled pocket of the PDE4 enzyme, we modified the structure of our oral PDE4 inhibitors to reach compounds down to picomolar enzymatic potencies while at the same time tackling successfully an uncovered selectivity issue with the adenosine receptors. In vitro potencies were demonstrated in a rat lung neutrophilia model by administration of a suspension with a Penn-Century MicroSprayer Aerosolizer.
A virtual tool (electronic book) for antenna theory and electromagnetic propagation is presented. A variety of radiation and electromagnetic problems ranging from linear antennas to arrays, radiation ...in time domain, microstrip antennas, smart antennas, and reflectors can be simulated. The material is useful both at undergraduate and graduate engineering courses. The education tool uses a user-friendly interface thanks to Mathcad reg software package which has been used to develop the electronic book. Moreover, navigation throughout the book follows the same rules used by internet users, therefore, no extra knowledge have to be introduced on how to use the present tool. Besides the user-friendly interface, the book also features visualization capabilities, 3D representations and videos, which play a significant role in teaching. The electronic book comes with several exercise sections having twofold objectives: first, students can check their own progress, and second, data from such exercises is provided to professor/mentor. This data is extremely useful to determine whether a given section can be considered completely understood or some extra emphasize needs to be done. All the material presented in the book can be complemented by extra peer review scientific papers given at the end of each section, most of them can be downloaded (obviously, depending on the contract between university and editorial). The book has been tested using objective data resulting in good acceptance.
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