Modified and unmodified zinc oxide as coagent in elastomer compounds

The aim of this work was to study the activity of unmodifi ed and modifi ed ZnO in the peroxide crosslinking of hydrogenated acrylonitrile-butadiene elastomer (HNBR) and ethylene-propylene copolymer (EPM). In the first step, zinc oxide was obtained by emulsion precipitation. Maleic acid was introduced onto the surface of ZnO using an in situ method. The unmodifi ed and modifi ed zinc oxide was characterized using dispersive and morphological analysis, BET surface area analysis, and elemental, spectroscopic and thermal analysis. In the second stage of the research, the ZnO/MA systems were incorporated into the structure of elastomer compounds improving the kinetic and mechanical properties of vulcanizates. The proposed modifi cation method had a favorable effect on the physicochemical properties of the zinc oxide and on the kinetic and mechanical properties of the vulcanizates. This study demonstrated that modifi cation of zinc oxide by maleic acid is a promising technique

Transcriptome analysis of <i>Streptococcus gordonii </i>Challis DL1 indicates a role for the biofilm-associated <i>fruRBA </i>operon in response to <i>Candida albicans</i>

Multiple levels of interkingdom signaling have been implicated in maintaining the ecological balance between Candida albicans and commensal streptococci to assure a state of oral health. To better understand the molecular mechanisms involved in the initial streptococcal response to the presence of C. albicans that can initiate oral surface colonization and biofilm formation, hypha-forming cells were incubated with Streptococcus gordonii cells for 30 minutes to assess the streptococcal transcriptome response. A genome wide microarray analysis and quantitative PCR validation of S. gordonii transcripts identified a number of genes, the majority of which were involved in metabolic functions that were differentially expressed in the presence of hyphae. The fruR, fruB and fruA genes encoding the transcriptional regulator, fructose-1-phosphate kinase, and fructose-specific permease, respectively, of the phosphoenolpyruvate-dependent fructose phosphotransferase system, were consistently up-regulated. An S. gordonii mutant in which these genes were deleted by allelic replacement, formed an architecturally-distinct, less robust biofilm with C. albicans than did parental strain cells. Complementing the mutant with plasmid borne fruR, fruB and fruA genes caused phenotype reversion, indicating that the genes in this operon played a role in dual species biofilm formation. This genome wide analysis of the S. gordonii transcriptional response to C. albicans has identified several genes that have potential roles in interkingdom signaling and responses

Multifunctional Oxide-Based Materials: From Synthesis to Application

The book deals with novel aspects and perspectives in metal oxide and hybrid material fabrication

Advanced Hybrid Materials Based on Titanium Dioxide for Environmental and Electrochemical Applications

Constant technological progress, as well as the pursuit of “friendly” technologies, leads to intensive work on the development of a new generation of advanced products with strictly defined, unique physicochemical properties dedicated to specific applications. This group of materials includes hybrids based on titanium dioxide and its derivatives, characterised with specific, well-defined physicochemical and structural properties, chiefly determined during their synthesis. Different properties of titania nanoparticles depend on their morphology, crystallite size, and crystalline structure. Nanocrystalline titanium dioxide can be synthesised via different methods, among which chemical precipitation, microemulsion method (inversed micelles), sol-gel process and hydrothermal crystallisation are the most important ones. That is why, a crucial part of the following chapter will be paid to characterisation of synthesis routes used for titanium dioxide and titania-based hybrid production. Furthermore, application of TiO2-based materials, including mixed oxide systems as well as graphene oxide–based hybrids, in electrochemical (electrode material) and environmental (photocatalysis) aspects, will be described in detail

Enzyme immobilization by adsorption : a review

Endowed with unparalleled high catalytic activity and selectivity, enzymes offer enormous potential as catalysts in practical applications. These applications, however, are seriously hampered by enzymes’ low thermal and chemical stabilities. One way to improve these stabilities is the enzyme immobilization. Among various tested methods of this process that make use of different enzyme-carrier interactions, immobilization by adsorption on solid carriers has appeared most common. According to these findings, in this review we present a comparative analysis of the literature reports on the recent trends in the immobilization of the enzymes by adsorption. This thorough study was prepared in order to provide a deeper understanding of the process. Both carriers, carrier modifiers and procedures developed for effective adsorption of the enzymes are discussed. The review may thus be helpful in choosing the right adsorption scheme for a given enzyme to achieve the improvement of its stability and activity for a specific application

Depolymerization and Activation of Lignin: Current State of Knowledge and Perspectives

A very important topic in present-day research is the depolymerization of lignin, meaning the multi-parametric decomposition of the biopolymer into low-molecular-weight products (monomers) by breaking of the intermolecular bonds. Depolymerization can occur under many different factors, such as high temperature or catalysts, which determine the mechanism of disintegration. In the case of lignin, this process is carried out in order to obtain many valuable low-molecular-weight compounds. It is becoming more and more popular as a result of the use of ionic liquids, but methods using alkaline, acidic, and metallic catalysts, as well as pyrolysis and supercritical fluids, are also known. All of these methods will be described in detail in this chapter

Lignosulfonate as a byproduct of wood pulp production: A potential precursor for the preparation of functional hybrid materials

Functional hybrid materials based on magnesium lignosulfonate and silica were obtained and characterized. Magnesium lignosulfonate is a common waste product of the wood pulp industry, while silica is a well-known inorganic material with exceptional physicochemical properties. In this study, silicas with a spherical particle shape were synthesized using a sol-gel method and alternatively in a nonpolar medium. Silica was found to improve the thermal and electrokinetic properties of the final products. The resulting lignosulfonate/silica hybrid materials were analyzed with the use of advanced techniques and measuring methods: scanning electron microscopy, a laser diffraction method enabling particle size measurements, Fourier transform infrared spectroscopy, elemental analysis, thermogravimetry, electrophoretic light scattering, zeta potential measurements, low-temperature nitrogen sorption, and colorimetric analysis. The results enabled the hybrid materials to be characterized from the point of view of potential applications in various branches of industry (for example as polymer fillers, electroactive blends and biosorbents). We additionally indicate new methods for the utilization of waste products, a category to which lignosulfonate certainly belongs

Using the TL Single-Aliquot Regenerative-Dose Protocol for the Verification of the Chronology of the Teutonic Order Castle in Malbork

The Teutonic Order Castle in Malbork is one of the precious medieval monuments in Europe. Because of the lack of natural rock resources in Pomerania, its walls are built almost exclusively of bricks. The huge volume and rich historical knowledge about the Malbork Castle makes it a marvellous object for TL dating. The parts of well known age can serve for the verification and improvement of dating method. Subsequently, gained in such way knowledge and experience can be applied for discovering the history of the rest of the castle. Here, the preliminary results of investigations which are still in progress, are presented for 5 brick samples. The applied TL dating procedure is described in detail. The very good accuracy of equivalent dose is achieved by the TL single-aliquot regenerative-dose protocol. The effect of wall inhomogeneity connected with the difference between the activity of the brick and mortar is discussed

Sliding mode control design using generalized relative degree approach : aerospace application

The relative degree (RD) approach is a powerful tool, for obtaining a system’s input-output dynamics of an output tracking controller design with minimum phase dynamics. Designs using RD alone can fail due to insufficient control authority in minimum phase systems, and instability of internal/zero dynamics attributed to non-minimum phase systems. Generalized RD (GRD) in minimum phase systems can identify parasitic control terms (PCTs). An Alternate GRD (AGRD) is investigated, to determine the impact of discarding these PCTs. A novel definition for Practical GRD (PGRD) is proposed and used in concert with Sliding Mode Control (SMC) compensating system perturbations in minimum phase systems. Using known GRD in nonminimum phase systems allows for internal dynamics reduction. However, in-stability emerging in the corresponding control dynamic extension defeats any output tracking controller design. A novel methodology of using GRD for designing continuous SMC in nonminimum phase systems is presented. An approach for generating bounded solutions of the unstable dynamic extension is proposed and used in concert with SMC, allowing for a viable control design for nonminimum phase systems. The efficacy of the proposed GRD-based approaches is demonstrated for both minimum and nonminimum phase missile attitude control problems

Additives for Abrasive Materials

The overarching objective of the chapter is to acquaint the readers with the topic associated with the production of abrasive tools and presentation of the most significant research results regarding the determination of the most important functional properties of selected additives (described in the literature and established on the basis of authors’ own scientific experiences). The studies regarding various additives, which were characterized in detail in the literature, were mainly based on thorough physicochemical and microstructural analysis as well as the determination of basic strength and thermos-mechanic parameters. The attempt to implement alternative cross-linking agents, which would result in the limited release of volatile organic compounds, is also of great importance in terms of production of environmentally friendly final products. A subsequent aim is to attract the attention of a wide range of readers and popularize the topic associated with conventional abrasive materials and next-generation abrasive compositions