Electric Field Assisted Microfluidic Platform for Generation of Tailorable Porous Microbeads as Cell Carriers for Tissue Engineering

Injection of cell‐laden scaffolds in the form of mesoscopic particles directly to the site of treatment is one of the most promising approaches to tissue regeneration. Here, a novel and highly efficient method is presented for preparation of porous microbeads of tailorable dimensions (in the range ≈300–1500 mm) and with a uniform and fully interconnected internal porous texture. The method starts with generation of a monodisperse oil‐in‐water emulsion inside a flow‐focusing microfluidic device. This emulsion is later broken‐up, with the use of electric field, into mesoscopic double droplets, that in turn serve as a template for the porous microbeads. By tuning the amplitude and frequency of the electric pulses, the template droplets and the resulting porous bead scaffolds are precisely produced. Furthermore, a model of pulsed electrodripping is proposed that predicts the size of the template droplets as a function of the applied voltage. To prove the potential of the porous microbeads as cell carries, they are tested with human mesenchymal stem cells and hepatic cells, with their viability and degree of microbead colonization being monitored. Finally, the presented porous microbeads are benchmarked against conventional microparticles with nonhomogenous internal texture, revealing their superior performance.     

New calcium‐free Na2O–Al2O3–P2O5 bioactive glasses with potential applications in bone tissue engineering

Sodium aluminophosphate glasses were evaluated for their bone repair ability. The glasses belonging to the system 45Na₂O–xAl₂O₃‐(55‐x)P₂O₅, with x = (3, 5, 7, 10 mol%) were prepared by a melt‐quenching method. We assessed the effect of Al₂O₃ content on the properties of Na₂O–Al₂O₃–P₂O₅ (NAP) glasses, which were characterized by density measurements, DSC analyses, solubility, bioactivity in simulated body fluid and cytocompatibility with MG‐63 cells. To the best of our knowledge, this is the first investigation of calcium‐free Na₂O–Al₂O₃–P₂O₅ system glasses as bioactive materials for bone tissue engineering.     

High Temperature Corrosion of Chromium–Manganese Steels in Sulfur Dioxide

This work was aimed at explaining the corrosion mechanism of commercial Cr–Mn steels at 1073, 1173 and 1273 K in the atmospheres containing oxygen and sulfur. Three steels were selected for the investigations, two single-phase austenitic steels (Cr17Mn17 and Cr13Mn19SiCa) and a two-phase austenitic-ferritic steel Cr15Mn19. On all studied steels triplex scales were formed. The inner very thin, fine-grained part of the scale contained manganese, chromium and iron sulfides and oxides, the intermediate layer was built mainly of the MnCr₂O₄ spinel while MnO was the predominant constituent of the outer scale layer. According to the gravimetric measurements, after an initial incubation period, the oxidation of steel follows a parabolic rate law. Thermodynamic and kinetic aspects of the formation of oxide-sulfide and oxide layers were discussed. Oxidation was accompanied by depletion of the subscale region of the metallic core in manganese, which is the austenite former. Consequently austenite transformed into ferrite.     

Effects of Forming Pressure on Physicochemical Properties of YBCO Ceramics

This article details the solid-state synthesis of high-temperature superconducting YBa₂Cu₃O_7?x. Tests were carried out on samples formed at different pressures (200, 400, 600 and 800 MPa) before being annealed under pure oxygen. The X-ray diffraction method showed that, regardless of the forming pressure, the samples contain about 97 wt.% of Y-123 phase. SEM images showed a polycrystalline structure of samples of similar grain size and number of pores (intergranular spaces). The values of critical temperatures (T_c0), determined from magnetoresistance measurements, are about 91.5 K for all samples, and the T_c0 temperatures do not depend on sample-forming pressure. Magnetoresistance measurements have shown that samples formed with higher pressures exhibit smaller changes in T_c0 and superconducting transition width ΔT due to the influence of the H_DC magnetic field, than the samples formed with lower pressures. Values of specific resistance determined by the use of van der Pauw method at 300 K is about 2 mΩcm for all samples. The critical temperatures (T cintra) of grains and critical current densities at 77 K were determined from AC magnetic susceptibility measurements, and they are about 91.6 K and 400 A cm^?2, respectively.     

How do Attitudes Toward Globalization Influence Human Functioning?

ABSTRACT

This study shows the results of the research into the relationships between attitudes toward globalization (accepting, critical, fearful) and psychological factors: identity styles, attitudes toward the Internet, and the quality of friendship. The survey conducted among Polish adolescents and young adults revealed that attitudes toward globalization had a stronger influence on psychological functioning for young adults than for adolescents. The results may help to understand social acceptance factors or disapproval of technological and globalizational changes.     

Assessment of aliphatic poly(ester-carbonate-urea-urethane)s potential as materials for biomedical application

Selected mechanical and biological properties of biodegradable elastomeric poly(ester-carbonate-urea-urethane)s (PECUUs) point towards their potential to be applied as scaffolds in tissue engineering. Here we explore their medical applicability taking into account their hemocompatibility and cytotoxicity. The influence of the ester monomer (derivatives of adipic and succinic acids), as well as diisocyanate type (IPDI and HDI) on the investigated PECUUs properties is presented. The presence of aliphatic diisocyanates, cyclic IPDI or linear HDI, governs the adhesion of Candida cells to these polymers offering the possibility to control the biofilm formation on their surface. In comparison to the linear form, cyclic diisocyanates with pentamethylene succinate or adipate fragments had two to three times lower biofilm mass formation on their surface. Reduced hemoglobin release from red blood cells observed during incubation of tested polymers with human erythrocytes suspension indicates their potential biocompatibility with human tissues. PECUUs were also able to support the growth of human keratinocytes HaCaT on their surface when coated with collagen. In effect, IPDI derivatives might possess a high potential for use in biomedical applications.     

Dressing process in the grinding of aerospace blade root

Journal of Mechanical Science and Technology - This study investigates the grinding wheel dressing process in the grinding of aerospace blade root fir tree profile made from Inconel 718 alloy. This...     

Structure and properties of polyamides‐epoxidized elastomers blends

Blends of aliphatic polyamides (PA6, PA66, and PA12), containing 0–15 wt % nonepoxidized or epoxidized elastomers (statistical copolymer butadiene–styrene BS/EBS or linear block copolymer styrene–butadiene–styrene SBS/ESBS) were investigated. For PA6‐elastomer blends, taken as an example, it was shown that with increasing blending time, mechanical properties of blends increase, especially, if ESBS copolymer is used. It can be treated as an indirect sign of reactions between components. It was also found that in blends considerable changes of glass temperatures of components occur. Polyamides in blends with elastomers have smaller heats of fusion in comparison with virgin polyamides. It testifies to hindering of PA crystallization by elastomers. In some cases, significant shifts of melting points are also observed. Measurements of water contact angle show that all blends have very similar values of contact angles, which are lower than those of virgin polyamides. Elastomer content does not also affect the blend water uptake. However, it depends on the polyamide and elastomer type contrary to contact angle. Highest water uptake changes are observed in blends of PA66, especially for epoxidized elastomers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1872–1879, 2006