Nanostructured Biopolymer/Few‐Layer Graphene Freestanding Films with Enhanced Mechanical and Electrical Properties

In the present work, novel freestanding multilayered films based on chitosan (CHI), alginate (ALG), and functionalized few‐layer graphene are developed through layer‐by‐layer assembly. First, functionalized few‐layer graphene aqueous suspensions are prepared from graphite by a stabilizer‐assisted liquid phase exfoliation process, using a pyrene derivative as stabilizer. Afterward, the films are produced and their physical, morphological, thermal, and mechanical properties are evaluated. Furthermore, their degradation and swelling profiles, as well as their biological behavior, are assessed. The incorporation of functionalized few‐layer graphene results in films with a nanolayered structure, lower roughness than the control CHI/ALG films, and hydrophilic behavior. The mechanical characterization reveals an increase of the Young's modulus, ultimate tensile strength, and elongation at break due to the incorporation of the graphene derivative. A decrease in the electrical resistivity of the multilayered films is also observed. The biological assays reveal improved cytocompatibility toward L929 cells when functionalized few‐layer graphene is incorporated in the CHI/ALG matrix. Therefore, these new graphene‐reinforced multilayered films exhibit interesting properties and great potential for biomedical applications, particularly in wound healing and cardiac and bone tissue engineering.     

Nematode Root Herbivory in Tomato Increases Leaf Defenses and Reduces Leaf Miner Oviposition and Performance

The outcome of plant-mediated interactions among herbivores from several feeding guilds has been studied intensively. However, our understanding on the effects of nematode root herbivory on leaf miner oviposition behavior and performance remain limited. In this study, we evaluated whether Meloidogyne incognita root herbivory affects Tuta absoluta oviposition preference on Solanum lycopersicum plants and the development of the resulting offspring. To investigate the M. incognita-herbivory induced plant systemic responses that might explain the observed biological effects, we measured photosynthetic rates, leaf trypsin protease inhibitor activities, and analyzed the profile of volatiles emitted by the leaves of root-infested and non-infested plants. We found that T. absoluta females avoided laying eggs on the leaves of root-infested plants, and that root infestation negatively affected the pupation process of T. absoluta. These effects were accompanied by a strong suppression of leaf volatile emissions, a decrease in photosynthetic rates, and an increase in the activity of leaf trypsin protease inhibitors. Our study reveals that root attack by nematodes can shape leaf physiology, and thereby increases plant resistance.     

Calcium/chitosan spheres as catalyst for biodiesel production

Chitosan, an abundant biopolymer extracted from crustacean shells, can be used as a structuring agent by the insertion of calcium oxide and used as a catalyst in transesterification reactions. These calcium‐incorporated chitosan spheres were calcined in order to obtain a porous calcium catalyst without organic material. The materials were characterized using X‐ray diffraction, thermogravimetric analysis, Fourier transform infrared and X‐ray photoelectron spectroscopies, temperature‐programmed desorption of CO₂, scanning electron microscopy and specific surface area analysis. Afterwards the calcined calcium/chitosan spheres were used in the transesterification reaction of sunflower oil with methanol. The conversion of sunflower oil to methyl esters (Y_FAME), under optimized reaction conditions, which were determined by factorial experimental design (X_MR, 1:9; X_CAT, 3 wt%; time, 4 h; temperature, 60 °C; magnetic stirring, 1000 rpm), was 56.12 ± 0.32 wt%. These results show that chitosan can be used as a precursor for the formation of calcium/chitosan spheres, yielding a porous calcium oxide (with higher surface area) that can be used as an alkaline catalyst for biodiesel production. © 2014 Society of Chemical Industry     

Qualitative and quantitative analysis of social network data intended for brand management

Wireless Networks - The purpose of the paper is to point out the importance of analysing data obtained from social media through the qualitative data analysis software. The main goal of conducted...     

Generalized inverse spectral problem for pseudo-Jacobi matrices with mixed eigendata

In this paper, we investigate a generalized inverse eigenproblem for pseudo-Jacobi matrices with mixed eigendata. These matrices appear in non-Hermitian Quantum Mechanics and extend the well-known concept of Jacobi matrices. It is shown that a unique pseudo-Jacobi matrix may be recovered from certain prescribed mixed eigendata, i.e. its leading principal submatrix, two distinct real eigenvalues, and part of the corresponding eigenvectors. An algorithm is provided for the reconstruction of such a matrix, and illustrative numerical experiments are presented to test the algorithm. The recurrence relation involving leading principal minors is crucial for the problem solution.