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    Stability of incommensurately modulated Ni50Mn27Ga22Fe1 10M martensite under uniaxial tensile stress
    (PERGAMON-ELSEVIER SCIENCE LTD, 2024-07-01) Vinogradova, Mariia; Sozinov, Alexei; Straka, Ladislav; Veřtát, Petr; Heczko, Oleg; Zelený, Martin; Chulist, Robert; Ullakko, Kari
    We investigate the incommensurately modulated crystal structure in the Ni50Mn27Ga22Fe1 magnetic shape memory alloy. We focus on temperature- and stress-induced changes, particularly measuring the a and b lattice parameters and the monoclinic angle. The in-situ XRD experiment shows that the thermally-induced commensurate-incommensurate (C-IC) transition coincides with the change of the average lattice symmetry from monoclinic to orthorhombic. The thermally-induced IC structure is stable under uniaxial tensile stress along the a-axis for deformation epsilon < 0.8 %. A mixture of the IC and C structures appears for epsilon > 0.8 % and the changes become irreversible. The volume fraction of the C structure further increases with increasing deformation. These results provide vital initial insights into the structural evolution of Ni-Mn-Ga alloys and enable us to establish the role of C and IC structures in their extraordinarily high mobility of twin boundaries.
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    Lumbar Interbody Fusion Conducted on a Porcine Model with a Bioresorbable Ceramic/Biopolymer Hybrid Implant Enriched with Hyperstable Fibroblast Growth Factor 2
    (MDPI, 2021-06-25) Krtička, Milan; Plánka, Ladislav; Vojtová, Lucy; Nekuda, Vladimír; Šťastný, Přemysl; Sedláček, Radek; Břínek, Adam; Kavková, Michaela; Göpfert, Eduard; Hedvičáková, Věra; Rampichová, Michaela; Křen, Leoš; Lišková, Květoslava; Ira, Daniel; Matulová, Jana; Suchý, Tomáš; Zikmund, Tomáš; Kaiser, Jozef; Starý, David; Faldyna, Martin; Trunec, Martin
    An experimental animal study was designed to investigate the intervertebral fusion efficiency and safety of a bioresorbable ceramic/biopolymer hybrid implant enriched with FGF2-STAB(R) in comparison with a tricortical bone autograft used as a gold standard. Twenty-four experimental pigs underwent L2/3 discectomy with implantation of either the tricortical iliac crest bone autograft or the bioresorbable hybrid implant (BHI) followed by lateral intervertebral fixation. The quality of spinal fusion was assessed by micro-computed tomography (micro-CT), biomechanical testing, and histological examination at both 8 and 16 weeks after the surgery.
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    Carboxymethyl starch as a reducing and capping agent in the hydrothermal synthesis of selenium nanostructures for use with three-dimensional-printed hydrogel carriers
    (ROYAL SOC, 2023-10-11) Vishakha, Vishakha; Abdellatif, Abdelmohsen Moustafa; Michalička, Jan; White, Paul B.; Lepcio, Petr; Tinoco Navarro, Lizeth Katherine; Jančář, Josef
    The hydrothermal method is a cost-effective and eco-friendly route for preparing various nanomaterials. It can use a capping agent, such as a polysaccharide, to govern and define the nanoparticle morphology. Elemental selenium nanostructures (spheres and rods) were synthesized and stabilized using a tailor-made carboxymethyl starch (CMS, degree of substitution = 0.3) under hydrothermal conditions. CMS is particularly convenient because it acts simultaneously as the capping and reducing agent, as verified by several analytical techniques, while the reaction relies entirely on green solvents. Furthermore, the effect of sodium selenite concentration, reaction time and temperature on the nanoparticle size, morphology, microstructure and chemical composition was investigated to identify the ideal synthesis conditions. A pilot experiment demonstrated the feasibility of implementing the synthesized nanoparticles into vat photopolymerization three-dimensional-printed hydrogel carriers based on 2-hydroxyethyl methacrylate (HEMA). When submersed into the water, the subsequent particle release was confirmed by dynamic light scattering (DLS), promising great potential for use in bio-three-dimensional printing and other biomedical applications.
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    Structure–Properties Relationship of Electrospun PVDF fibers
    (MDPI, 2020-06-23) Částková, Klára; Kaštyl, Jaroslav; Sobola, Dinara; Petruš, Josef; Šťastná, Eva; Říha, David; Tofel, Pavel
    Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers’ morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- and micro-sized fiber diameters were prepared by a controlled and reliable electrospinning process. The fibers with diameters from 276 nm to 1392 nm were spun at a voltage of 25 kV–50 kV from the pure PVDF solutions or in the presence of a surfactant—Hexadecyltrimethylammonium bromide (CTAB). Although the presence of the CTAB decreased the fibers’ diameter and increased the electroactive phase content, the piezoelectric performance of the PVDF material was evidently deteriorated. The maximum piezoelectric activity was achieved in the fibrous PVDF material without the use of the surfactant, when a piezoelectric charge of 33 pC N1 was measured in the transversal direction on a mean fiber diameter of 649 nm. In this direction, the material showed a higher piezoelectric activity than in the longitudinal direction.
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    Water-born 3Dnanofiber mats usingcost-effectivecentrifugal spinning: comparison with electrospinnig process: A complex study
    (WILEY, 2021-02-05) Říhová, Martina; Ince, Ahmet Erdem; Čičmancová, Veronika; Hromádko, Luděk; Částková, Klára; Pavliňák, David; Vojtová, Lucy; Macák, Jan
    A comparison of the electrostatic and centrifugal spinning of poly(vinyl alcohol) and poly(vinyl pyrrolidone) is shown in terms of the resulting fiber morphology and the process conditions. Specific parameters of centrifugal spinning, such rotational speed of spinneret and the relative humidity, were extensively investigated in details. Morphologies and diameters of resulting fiber mats were investigated by a scanning electron microscopy and compared between the two spinning techniques. The results revealed that formation of fibers is mainly affected by the initial polymer concentrations (and resulting viscosities) of polymeric solutions, which is in line with previous reports. However, the key novel finding of this work is that increasing relative humidity during centrifugal spinning process leads to greatly reduced fiber diameters to the levels typical for electrospinning. The obtained comparison is discussed and clearly shows technological advantages of the centrifugal spinning over electrospinning, enabling quantitative production of fibers with same or similar diameters.