Hierarchical tantalum-graphene flakes reinforced zirconia (3Y-TZP) ceramic matrix composites were fabricated by wet processing route and freeze drying followed by spark plasma sintering (SPS). The ...microstructures and mechanical properties were investigated. The results show that graphene and Ta particles are homogeneously dispersed in the ceramic matrix and the optimum sintering temperature for complete densification of composites and thermal reduction of the graphene oxide is 1500 °C. The addition of dual reinforcements of tantalum microflakes and graphene nanoflakes results in significant improvement in the mechanical properties of the ZrO2 matrix. Approximately a 30% increase in flexural strength vs the zirconia-Ta composite and a 175% increase in fracture toughness vs the monolithic zirconia have been achieved by introducing 0.5 vol% GO and 20 vol% Ta particles.
The theoretical framework of the self-determination theory establishes that the satisfaction of basic psychological needs and more self-determined motivational forms are related to positive ...behavioral consequences and, therefore, may increase the intention to be physically active in Physical Education students. In this sense, the need for novelty has been proposed as a psychological need by recent scientific evidence, so it is necessary to prove its possible contribution to the prediction of young people's behavior. Therefore, the main objective of the study was to test a model that analyzed the power of prediction of the satisfaction of the needs for autonomy, competence, relatedness, and novelty as well as the motivation experienced in Physical Education on the intention to be physically active. A questionnaire was administered to 1665 Physical Education students with an average age of 12.43 years (SD = 1.87), of which 835 were boys and 830 were girls. An adaptation of the Spanish educational context of the Basic Psychological Needs in Exercise Scale (BPNES) that includes the need for novelty, the Perceived Locus of Causality Scale (PLOC), and the Intention to be Physically Active Scale (IPAS) was used. Path analysis results showed that the satisfaction of the psychological needs for autonomy, competence, relatedness, and novelty predicted autonomous motivation. On the other hand, the need for autonomy positively predicted controlled motivation, while the satisfaction of relatedness did so negatively. The need for competence and autonomous motivation positively predicted the intention to be physically active in Physical Education students, obtaining an explained variance of 33%. However, controlled motivation was not related in a statistically significant way to the intention to be physically active. In conclusion, the results of the hypothesized model highlight the importance of satisfying all the basic psychological needs (including novelty) and give special emphasis to the need for competence, since it predicts autonomous motivation and the intention to be physically active outside of the educational context.
Iron phthalocyanines (FePc) adsorbed onto a Ag(110) substrate self-assemble into different monolayer phases going from rectangular to different oblique phases, with increasing molecular density. We ...have investigated the oxygen uptake capability of the different phases and their associated magneto-structural changes. Our study combines scanning tunneling microscopy and spectroscopy (STM/STS), X-ray magnetic circular dichroism (XMCD), and density functional theory (DFT) calculations. STM measurements reveal that the oxygenation reaction of the FePc/Ag(110) generally involves a displacement and a rotation of the molecules, which affects the electronic state of the Fe centers. The oxygen intercalation between FePc and the substrate is greatly obstructed by the steric hindrance in the high-density phases, to the point that a fraction of oblique phase molecules cannot change their position after oxidizing. Depending on the oxidation state and adsoption geometry, the STS spectra show clear differences in the Fe local density of states, which are mirrored in the XAS and XMCD experiments. Particularly, XMCD spectra of the oxidized phases reflect the distribution of FePc species (nonoxygenated, oxygenated-rotated, and oxygenated-unrotated) in the different cases. Sum rule analysis yields the effective spin (m s eff) and orbital (m L) magnetic moments of Fe in the different FePc species. Upon oxygenation, the magnetic moment of FePc molecules increases about an order of magnitude, reaching m TOT ∼ 2.2 μB per Fe atom.
Introduction
This study aims to understand how emotions and motivation influence the academic achievement of physical education (PE) students and their future intention to practice physical activity ...(PA). Despite the influence on student’s behaviors and the reciprocal associations between motivation and emotion, the number of studies addressing both constructs at the same level is very limited.
Methods
A structural equation model was used with 799 students aged 11–17 years (
M
= 13.16; SD = 1.17).
Results and discussion
The results showed that the teacher support of the basic psychological needs (BPN) predicted students’ BPN satisfaction, which in turn predicted their autonomous motivation and positive emotions, and negatively predicted their negative emotions. Finally, autonomous motivation predicted students’ intention to be physically active, whereas academic achievement was predicted by both autonomous motivation and emotions. We conclude that to better understand the consequences of PE classes, it is necessary to consider both constructs.
Abstract Metals and ceramics are commonly used in orthopaedics, dentistry and other load bearing applications. However, the use of ceramic matrix composites reinforced with biocompatible metals for ...heavy load-bearing hard tissue replacement applications has not previously been reported. In order to improve the reliability and the mechanical properties of biomedical implants, new zirconia–Nb composites have been recently developed. The aim of this study was to investigate the biological tolerance of these new zirconia/Nb biocermets implants with both in vitro and in vivo approaches. At first, human bone marrow derived mesenchymal stem cells were cultured on sintered biocermet discs with polished surfaces and were compared with responses to niobium metal. In vitro, the biocermets showed no deleterious effect on cell proliferation, extra-cellular matrix production or on cell morphology. Furthermore, the biocermet showed a higher percentage of cell proliferation than Nb metal. On the other hand, the bone response to these new zirconia/Nb biocermets was studied. Cylinders of biocermets, as well as commercially Nb rod were implanted in the tibiae of New Zealand white rabbits. All the animals were euthanatized after 6 months. The specimens were processed to obtain thin ground sections. The slides were observed in normal transmitted light microscope. A newly formed bone was observed in close contact with material surfaces. No inflamed or multinucleated cells were present. This study concluded that zirconia/Nb composites are biocompatible and osteoconductive. The ceramic-metal composite has even better osteointegration ability than pure Nb. In conclusion, zirconia–Nb biocermet is suitable for heavy load-bearing hard tissue replacement from the point of view of both mechanical properties and biocompatibility.
Recently the new term ‘telocytes’ has been proposed for cells formerly known as interstitial Cajal‐like cells. In fact, telocytes are not really Cajal‐like cells, they being different from all other ...interstitial cells by the presence of telopodes, which are cell‐body prolongations, very thin, extremely long with a moniliform aspect. The identification of these cells is based on ultrastructural criteria. The presence of telocytes in others organs was previously documented. We reported for the first time, an ultrastructural study of telocytes in the lamina propria of rat duodenum. Our findings show that typical telocytes are present in the rat duodenum. Telocytes are located in the lamina propria, immediately below mucosal crypts. Telopodes frequently establish close spatial relationships with immune cells, blood vessels and nerve endings. On the basis of their distribution and morphology, we suggest that these cells may be involved in immune response and in our opinion, it may be possible that different locations of telocytes could be associated with different roles.
An evaluation is made of the complementarity between two non-invasive techniques, cuticle microhistological analysis (CMA) and PCR-capillary electrophoresis (PCR-CE) DNA-based analysis, for the ...determination of herbivore diet composition from faecal samples. Cuticle microhistological analysis is based on the different microanatomical characteristics of the epidermal fragments remaining in the faeces. The PCR-CE technique combines PCR amplification of a trnL(UAA) genomic DNA region with amplicon length determination by CE, with this length being characteristic for each species or taxon. A total of 37 fresh stool samples were analyzed, including 16 from feral goats (Capra hircus) from the Tramuntana mountain range (Mallorca, Baleares) and 11 from Bruna dels Pirineus cattle breed (Bos taurus) from the surrounding Montserrat mountain range (Barcelona, Spain). All the animals were in a free grazing Mediterranean pine habitat, dominated by Aleppo pine (Pinus halepensis). The results showed that both techniques detected a similar number of plant components in the faeces of goats and cows. In the case of goats, a positive correlation was obtained between the percentage of samples in which a particular taxon is detected by CMA and the percentage of samples in which that taxon is detected by PCR-CE. This correlation was not observed in the case of cows. It is concluded that PCR-CE is a fast and reliable method to detect the different plant components in the faeces of herbivores. However, it cannot be considered as an alternative to CMA, but as a complementary method, since both techniques can detect some taxa that are not detected by the other technique. In addition, CMA detected the presence of the different taxa in a greater number of samples, and at the same time, it enables quantitative data to be obtained for plant diet composition. The species of herbivore also seems to influence the results obtained by PCR-CE, so more studies are required to address this aspect.
Dense (>98 th%) and homogeneous ceramic/metal composites were obtained by spark plasma sintering (SPS) using ZrO2 and lamellar metallic powder of tantalum (20 vol%) as starting materials. Composites ...showed a fracture toughness value of 16 MPa m1/2 mainly due to crack bridging of the elastic–plastic deformations of ductile metal particles. This fracture toughness was accompanied by a simultaneous enhancement in damage tolerance and fatigue resistance of 3Y-TZP/Ta composites.
Besides exceptional mechanical properties, SPS sintered 3Y-TZP/Ta composites also showed the electrical conductivity suited to wire electrical discharge machining (WEDM). Therefore, they are suitable to be produced in mechanically performant, complex shape components with the required tolerance while reducing machining costs. The aim of this work was the study of the electrical properties of the materials as well as the characteristics of the machining process and the machined surfaces influence on the bending strength of composites. The results show that workpieces can be machined with high accuracy and without a drop in mechanical strength.
•Fully dense and homogeneous ceramic-metal composites were successfully fabricated.•Composites showed outstanding value of fracture toughness of 16 MPa m1/2.•3Y-TZP/Ta composites suited to wire electrical discharge machining (WEDM).•WEDM cut specimens showed insignificant degradation in the bending strength.
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