Complex Analysis of Vanillin and Syringic Acid as Natural Antimicrobial Agents against Staphylococcus epidermidis Biofilms

The presence of Staphylococcus epidermidis biofilms on medical devices is a major cause of nosocomial diseases and infections. Extensive research is directed at inhibiting the formation and maturation of such biofilms. Natural plant-derived phenolic compounds have promising antimicrobial effects against drug-resistant bacteria. The anti-biofilm activity of two selected phenolic compounds (vanillin and syringic acid) was tested against three biofilm-forming methicillin-resistant S. epidermidis strains with different genotypes. Resazurin assay combining crystal violet staining and confocal microscopy was used for biofilm and extracellular polymer substance (EPS) inhibition tests. Effects on EPS compounds such as proteins, extracellular DNA, and polysaccharides were also examined. Combined with quantitative real-time PCR of selected agr quorum-sensing systems and biofilm genetic determinants, our complex analysis of vanillin and syringic acid showed similar biofilm and EPS inhibition effects on S. epidermidis strains, reducing biofilm formation up to 80% and EPS up to 55%, depending on the genotype of the tested strain. Natural antimicrobial agents are thus potentially useful inhibitors of biofilms.     

The Influence of Induction Sintering on Microstructure and Deformation Behavior of Ti-5Al-5Mo-5V-3Cr Alloy

The influence of the induction sintering process at different temperatures on the behavior of the powder metallurgy Ti-5Al-5Mo-5V-3Cr alloy was investigated. Material for the research was produced by elemental powder blending, followed by the uniaxial cold compacting process. Powder compacts were induction heated and sintered within the temperature range of 1000 °C to 1300 °C. The influences of process parameters on the material behavior during sintering and its properties were studied. The microstructure examination was performed with particular attention to the pore size and distribution as well as the homogenization of the microstructure. The sintering temperature of 1200 °C proved to be critical for the dissolution of most alloying powder particles. Hot compression tests were performed to determine the formability of the obtained material. Significant differences in flow stress behavior between samples sintered at temperatures below and above 1200 °C were observed. The mechanical properties of the material before and after deformation were compared. The evolution of the microstructure of sintered Ti-5Al-5Mo-5V-3Cr alloy after hot deformation was analyzed with an emphasis on its influence on the material properties. Based on the conducted research, it was found that the adequate homogenization of the chemical composition and microstructure was achieved at the temperature of 1250 °C, and a further increase did not reflect in a significant improvement.

     

Tribo-mechanical properties of composites based on polyoxymethylene reinforced with basalt fiber and silicon carbide whiskers

This paper presents an analysis of the hybrid reinforcement of polyoxymethylene composites. Basalt fibers and monocrystalline silicon carbide fibers were used as reinforcement. Basic tests of mechanical properties were carried out, such as the static tensile and flexural test. The tests were repeated under external factors, such as the influence of water aging and a wide range of exploitation temperatures. The materials were also subjected to tribological tests, that is, determination of the friction coefficient and the specific wear rate. Strength tests revealed an increase in the stiffness of the material as well as a reduction the friction coefficient and abrasive wear. The addition of monocrystalline fibers significantly limited water absorption, stabilized the strength properties in the water environment as well as provided better material's resistance to dynamic impact.     

Structure and transport properties of the novel (Dy,Er,Gd,Ho,Y)3Fe5O12 and (Dy,Gd,Ho,Sm,Y)3Fe5O12 high entropy garnets

High-entropy, iron-containing, garnet-structured oxides with (Dy,Er,Gd,Ho,Y)₃Fe₅O₁₂ and (Dy,Gd,Ho,Sm,Y)₃Fe₅O₁₂ compositions are synthesized for the first time. A modified Pechini method followed by calcination at 700 °C and sintering at 1300 °C enables obtaining single-phase, homogenous materials of cubic structure with Ia-3d symmetry. High-temperature in-situ X-ray diffraction studies show excellent phase stability of the garnets, as well as moderate thermal expansion coefficient, ca. 11·10^?6 K^-1 in 25?1000 °C temperature range. Raman spectroscopy measurements indicate the presence of local distortion of structural polyhedra, likely associated with the high-entropy effect. The collected Mossbauer spectra confirm distorted character of the lattice. Influenced by the presence of Fe³⁺ in locally distorted octahedra and tetrahedra, the electrical conduction at low temperatures of both oxides remains much lower comparing to Y₃Fe₅O₁₂ (yttrium iron garnet - YIG), as well as to other rare-earth garnets up to 600 °C, where it reaches value similar to YIG.     

The role of geographic and cognitive proximity in knowledge networks: The case of joint R&D projects

This paper explores effect of proximities on R&D collaboration and focus on a prime mechanism of intentional search for knowledge—joint R&D projects—using data on R&D projects co-financed by various public sector bodies in the period 2003–2018. Our findings show that R&D collaboration based on cognitive proximity is intentional and firms prefer partners with technological distance smaller than expected based on a reference population. In the case of repeated R&D collaboration among the same companies in manufacturing, there is a statistically significant shift towards a higher cognitive proximity. As for geographical proximity, we found relatively low intra-regional R-D collaboration and high openness of regional innovation systems.     

Turning industrial aerobic fermentation plants into thermal power stations

The industrial aerobic bioprocess of baker's yeast production requires large amounts of water to cool down large bubble column bioreactors. As result, an appreciable quantity of low‐grade heat is generated. Because of the low temperature level of the water (~25°C) exiting the bioreactors cooling system, very little attention has been dedicated to heat recovery and conversion from this stream, which is usually released in rivers, streams, and canals. In this work, we simulated the generation of low‐grade heat (up to 14.4 MW) from an industrial baker's yeast production plant consisting of seven 150‐m³ bioreactors. Subsequently, a dedicated transcritical carbon dioxide heat pump system for the conversion of this low‐grade heat into fourth generation district heat (~16.2 MW) was successfully designed. Fourth generation district heat employs low‐temperature water (30‐70°C) as heat carrier and is expected to play a major role in future sustainable energy system. Finally, an economic study confirmed the feasibility and the applicability of our approach and a concept for long‐term energy storage including state‐of‐the‐art phase change material (PCM)–units was discussed.     

Prediction of elastic moduli of angle-ply laminates from various rhombohedral unit cells

The elastic properties of angle-ply laminates are investigated by using the numerical homogenization based on a rhombohedral unit cell. A discussion of the influence of fiber packing geometry on the elastic moduli is included. The efficiency of various fiber distributions is validated by comparing the results of homogenization analyses with the available analytical solutions. The prediction is performed for various values of fiber orientation, fiber volume fraction and ply thickness.     

An approximated decision-theoretic algorithm for minimization of the Tversky loss under the multi-label framework

Pattern Analysis and Applications - In this paper, we addressed the problem of building a decision-theoretic classifier tailored for minimizing the Tversky loss under the framework of multi-label...     

SVM with a neutral class

Pattern Analysis and Applications - In many real binary classification problems, in addition to the presence of positive and negative classes, we are also given the examples of third neutral class,...     

Translation of segment scale stiffening into macroscale reinforcement in polymer nanocomposites

Structuring of polymer nanocomposites (PNCs) with an aid of relatively weak external magnetic fields has been studied as a method for control of the nano- and microstructure. Magnetic nanoparticles (NPs) were assembled into high aspect ratio one-dimensional strings and unidirectionally oriented with the magnetic field (B = 0–50 mT) within the photopolymer matrix. The effect of the anisotropic MNPs assemblies on the mechanical properties was studied over a wide temperature range for the first time. The impact of various reinforcing mechanisms was distinguished with respect to the position of the glass transition temperature (T_g). The reinforcing effect exhibits temperature dependency with a maximum ~65°C above the glass transition and only negligible effect below the T_g. In addition, significant directional anisotropy of stiffness was observed. Composite micromechanics was applied to interpret the orientation and size-dependent reinforcement of PNCs, and temperature-dependent stiffness of the polymer-MNP structures was quantified. The presence of polymer chains with altered dynamics surrounding the MNPs inside the anisotropic assemblies was proposed to be an essential nanoscale mechanism mediating the stress transfer and contributing to mechanical robustness of the hybrid structures and PNCs. POLYM. ENG. SCI., 60:587–596, 2020. © 2019 Society of Plastics Engineers