Thermal Degradation Kinetics and Viscoelastic Behavior of Poly(Methyl Methacrylate)/Organomodified Montmorillonite Nanocomposites Prepared via In Situ Bulk Radical Polymerization

Nanocomposites of polymers with nanoclays have recently found great research interest due to their enhanced thermal and mechanical properties. Deep understanding of the kinetics of thermal degradation of such materials is very important, since the degradation mechanism usually changes in the presence of the nano-filler. In this investigation, poly(methyl methacrylate)/organomodified clay nanocomposite materials were prepared by the in situ free radical bulk polymerization technique. The thermal degradation of the products obtained was studied by means of thermogravimetric analysis at several heating rates. Isoconversional kinetic analysis was conducted in order to investigate the effect of degradation conversion on the activation energy. Both, pure poly(methyl methacrylate) (PMMA) and its nanocomposites were found to degrade through a two-step reaction mechanism. Data arising from a differential and an integral method were used to disclose the correlation between activation energies (Eα) and the extent of degradation (α). It was found that Eα value improved for all nanocomposites at α values higher than 0.3. Moreover, the viscoelastic behavior of the obtained nanocomposites was examined by means of dynamic mechanical thermal analysis. All nanocomposites exhibited higher storage modulus in comparison to the virgin PMMA at room temperature, while the increment of clay amount improved their stiffness gradually

Novel Benes Network Routing Algorithm and Hardware Implementation

Benes/Clos networks constitute a particularly important part of interconnection networks and have been used in numerous areas, such as multi-processor systems, data centers and on-chip networks. They have also attracted great interest in the field of optical communications due to the increasing popularity of optical switches based on these architectures. There are numerous algorithms aimed at routing these types of networks, with varying degrees of utility. Linear algorithms, such as Sun Tsu and Opferman, were historically the first attempt to standardize the routing procedure of this types of networks. They require matrix-based calculations, which are very demanding in terms of resources and in some cases involve backtracking, which impairs their efficiency. Parallel solutions, such as Lee’s algorithm, were introduced later and provide a different answer that satisfy the requirements of high-performance networks. They are, however, extremely complex and demand even more resources. In both cases, hardware implementations reflect their algorithmic characteristics. In this paper, we attempt to design an algorithm that is simple enough to be implemented on a small field programmable gate array board while simultaneously efficient enough to be used in practical scenarios. The design itself is of a generic nature; therefore, its behavior across different sizes (8 × 8, 16 × 16, 32 × 32, 64 × 64) is examined. The platform of implementation is a medium range FPGA specifically selected to represent the average hardware prototyping device. In the end, an overview of the algorithm’s imprint on the device is presented alongside other approaches, which include both hard and soft computing techniques

Synthesis and Characterization of Dental Nanocomposite Resins Filled with Different Clay Nanoparticles

Nanotechnology comprises a promising approach towards the update of dental materials.The present study focuses on the reinforcement ofdental nanocomposite resins with diverse organomodified montmorillonite (OMMT) nanofillers. The aim is to investigate whether the presence of functional groups in the chemical structure of the nanoclay organic modifier may virtually influence the physicochemical and/or the mechanical attitude of the dental resin nanocomposites. The structure and morphology of the prepared materials were investigated by means of wide angle X-ray diffraction and scanning electron microscopy analysis. Fourier transform infrared spectroscopy was used to determine the variation of the degree of conversion over time. Measurements of polymerization shrinkage and mechanical properties were conducted with a linear variable displacement transducer apparatus and a dynamometer, respectively. All the obtained nanocomposites revealed intercalated structures and most of them had an extensive filler distribution into the polymer matrix. Polymerization kinetics werefound to be influenced by the variance of the clay organomodifier, whilenanoclays with vinyl groups considerably increased the degree of conversion. Polymerization shrinkage was almost limited up to 50% by incorporating nanoclays. The absence of reactive groups in the OMMT structure may retain setting contraction atlow levels. An enhancement of the flexural modulus was observed, mainly by using clay nanoparticles decorated with methacrylated groups, along with a decrease in the flexural strength at a high filler loading. The overall best performance was found for the nanocomposites with OMMTs containing double bonds. The significance of the current work relies on providing novel information about chemical interactions phenomena between nanofillers and the organic matrix towards the improvement of dental restorative materials

ICT-based Innovation and Employability for Women

The utilization of ICTs in creating new jobs and eliminating gender based inequalities in employability and entrepreneurship, employs increasingly more researchers, governments and organizations around the world. In this article we analyze the current situation regarding the impact of ICTs, social networks and media on creating new opportunities for the employability of women. We also present the new market requirements, the new e-skills that will be acquired by women in order to take advantage of new labor market opportunities. Finally special reference is made to new trends in women's entrepreneurship as well as the supportive role of ICTs

Synthesis of Novel Dental Nanocomposite Resins by Incorporating Polymerizable, Quaternary Ammonium Silane-Modified Silica Nanoparticles

Diverse approaches dealing with the reinforcement of dental composite resins with quaternary ammonium compounds (QAC) have been previously reported. This work aims to investigate the physicochemical and mechanical performance of dental resins containing silica nanofillers with novel QAC. Different types of quaternary ammonium silane compounds (QASiC) were initially synthesized and characterized with proton nuclear magnetic resonance (1H-NMR) and Fourier transform infrared (FTIR) spectroscopy. Silica nanoparticles were surface modified with the above QASiC and the structure of silanized products (S.QASiC) was confirmed by means of FTIR and thermogravimetric analysis. The obtained S.QASiC were then incorporated into methacrylate based dental resins. Scanning electron microscopy images revealed a satisfactory dispersion of silica nanoclusters for most of the synthesized nanocomposites. Curing kinetics disclosed a rise in both the autoacceleration effect and degree of conversion mainly induced by shorter QASiC molecules. Polymerization shrinkage was found to be influenced by the particular type of S.QASiC. The flexural modulus and strength of composites were increased by 74% and 19%, while their compressive strength enhancement reached up to 19% by adding 22 wt% S.QASiC nanoparticles. These findings might contribute to the proper design of multifunctional dental materials able to meet the contemporary challenges in clinical practice

Effect of Silica Nanoparticles Silanized by Functional/Functional or Functional/Non-Functional Silanes on the Physicochemical and Mechanical Properties of Dental Nanocomposite Resins

Dental nanocomposite resins have been proposed as potential restorative materials that are inevitably challenged with dynamic oral conditions. This investigation focused on the contribution of miscellaneous silane blends, used as coupling agents, to the ultimate performance of dental nanocomposite dimethacrylate resins. Herein, silica nanoparticles were initially silanized with functional/functional or functional/non-fuctional silane mixtures (50/50 wt/wt). Fourier transforms infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) verified the modification of nanosilica. The organomodified nanoparticles were then inserted into Bis-GMA/TEGDMA based resins by hand spatulation process. Scanning electron microscopy (SEM) findings revealed a broad distribution of fillers in the polymer network when reactive silanes and their corresponding blends were used. Furthermore, optical profilometry results showed that the presence of functional/non-functional mixtures can produce relatively smooth composite surfaces. Polymerization shrinkage was found to be limited upon the decrease of the degree of conversion regarding all the tested silane mixtures. The functional/functional silane blend assured the highest flexural properties and the lowest solubility after the storage of the nanocomposite in water for 1 week at 37 °C. The above experimental data could contribute to the proper designing of dental nanocomposite resins which may fit the modern clinical applications

HPV16-Genotyper: A Computational Tool for Risk-Assessment, Lineage Genotyping and Recombination Detection in HPV16 Sequences, Based on a Large-Scale Evolutionary Analysis

Previous analyses have identified certain but limited evidence of recombination among HPV16 genomes, in accordance with a general perception that DNA viruses do not frequently recombine. In this evolutionary/bioinformatics study we have analyzed more than 3600 publicly available complete and partial HPV16 genomes. By studying the phylogenetic incongruence, similarity plots and the distribution patterns of lineage-specific SNPs, we identify several potential recombination events between the two major HPV16 evolutionary clades. These two clades comprise the (widely considered) phenotypically more benign (lower risk) lineage A and the (widely considered) phenotypically more aggressive (higher risk) non-European lineages B, C and D. We observe a frequency of potential recombinant sequences ranging between 0.3 and 1.2% which is low, but nevertheless considerable. Our findings have clinical implications and highlight that HPV16 genotyping and risk assessment based only on certain genomic regions and not the entire genome may provide a false genotype and, therefore, its associated risk estimate. Finally, based on this analysis, we have developed a bioinformatics tool that automates the entire process of HPV16 lineage genotyping, recombination detection and further identifies, within the submitted sequences, SNPs that have been reported in the literature to increase the risk of cancer

A Comparative Analysis of the Core Proteomes within and among the Bacillus subtilis and Bacillus cereus Evolutionary Groups Reveals the Patterns of Lineage- and Species-Specific Adaptations.

By integrating phylogenomic and comparative analyses of 1104 high-quality genome sequences, we identify the core proteins and the lineage-specific fingerprint proteins of the various evolutionary clusters (clades/groups/species) of the Bacillus genus. As fingerprints, we denote those core proteins of a certain lineage that are present only in that particular lineage and absent in any other Bacillus lineage. Thus, these lineage-specific fingerprints are expected to be involved in particular adaptations of that lineage. Intriguingly, with a few notable exceptions, the majority of the Bacillus species demonstrate a rather low number of species-specific fingerprints, with the majority of them being of unknown function. Therefore, species-specific adaptations are mostly attributed to highly unstable (in evolutionary terms) accessory proteomes and possibly to changes at the gene regulation level. A series of comparative analyses consistently demonstrated that the progenitor of the Cereus Clade underwent an extensive genomic expansion of chromosomal protein-coding genes. In addition, the majority (76-82%) of the B. subtilis proteins that are essential or play a significant role in sporulation have close homologs in most species of both the Subtilis and the Cereus Clades. Finally, the identification of lineage-specific fingerprints by this study may allow for the future development of highly specific vaccines, therapeutic molecules, or rapid and low-cost molecular tests for species identification

Impact of Mt. Olympus Honeys on Virulence Factors Implicated in Pathogenesis Exerted by <i>Pseudomonas aeruginosa</i>

The aim of this study was to examine the impact of twenty honey samples, harvested in Mt. Olympus (Greece), on the virulence factors implicated in P. aeruginosa pathogenesis. Six key virulence factors (protease and elastase activity, pyocyanin and pyoverdine concentration, biofilm formation, and swimming motility) were selected in order to assess the effect of the tested honeys compared with Manuka honey. All tested honeys demonstrated a significant inhibition of protease and elastase activity compared with the control. Six and thirteen honeys exerted superior protease (no inhibition zone) and elastase (values lower than 55%) activity, respectively, compared with Manuka honey. Seventeen tested honeys exhibited reduced pyoverdine production compared with the control; all tested honeys, except for one, showed an inhibitory effect on pyocyanin production compared with the control. Regarding swimming motility, nine tested honeys demonstrated significantly higher inhibition compared with Manuka honey. Honey concentrations (6% v/v and 8% v/v) had the most profound impact, as they reduced biofilm formation to less than 20% compared with the control. Overall, our data demonstrate a significant inhibition of the virulence factors in the tested Mt. Olympus honeys, highlighting the strong antimicrobial activity against P. aeruginosa, an antibiotic-resistant pathogen of growing concern, which is implicated in severe nosocomial infections globally