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•ZrO2 and YSZ aerogels derived by combining sol-gel method and supercritical drying.•Evolution of crystallinity was observed by in-situ XRD measurements up to 1200 °C.•Phase ...transformation of zirconia (ZrO2) is affected by crystallite size growth.•Yttria-stabilized zirconia (YSZ) aerogel forms stable single-phase t-ZrO2 at 455 °C.
Monolithic, structurally stable zirconia (ZrO2) aerogels can be used in high temperature applications and as medical implants. The macroscopic properties of these solids can be fine-tuned by the appropriate thermal treatment of the amorphous aerogels. Herein, we investigate the thermally induced phase transitions of ZrO2 and yttria-stabilized zirconia (YSZ) monolithic aerogels. All aerogels were produced by an acid-catalyzed sol-gel technique and subsequent supercritical drying (SCD). A complete reaction mechanism is proposed for the formation of the wet gel network. Also, the phase transformations taking place during calcination were followed as function of temperature by in-situ X-ray diffraction measurements. Composition and size of the forming crystallites were calculated from the XRD data. Phase transition is controlled by the temperature-dependent growth of crystallite size during calcination up to 1200 °C. Both tetragonal and monoclinic zirconia form in pure ZrO2 aerogels, and a single tetragonal phase forms in YSZ aerogels.
The aim of our study was to investigate the effects of a 24-week-long training program on changes in static body posture, as well as the characteristics of anterior shoulder pain in youth swimmers, ...and the relationship between changes in whole-body posture and the frequency and intensity of anterior shoulder pain. Competitive young swimmers (n = 54, 13.9 ± 1.79 years) were divided into experimental group and control group and both groups performed their usual swimming training. In addition, the experimental group performed a 24-week-long whole-body posture correction program. Before and after the implemented training, whole-body posture was analyzed using the PostureScreen (version 13.7) mobile application, and subjective intensity of pain was determined using the swimmer’s functional pain scale. Significant changes were found between the two groups in numerous measured postural parameters. A significant reduction in the prevalence of shoulder pain and score of the pain scale was observed after the posture correction program in the experimental group. Our results may imply that more optimal biomechanical conditions may indirectly reduce the incidence of swimmer’s shoulder in terms of prevention. Analysis and monitoring of body posture of swimmers using an on-field mobile application continuously, and the application of preventive training programs, may help to avoid developing injuries.
•Details on the preparation of titania–silica aerogels with no crystalline anatase phase.•Investigation of the structure and the photocatalytic activity of highly amorphous titania–silica aerogels ...with mesopores.•The fast adsorption of methylene blue and salicylic acid reduces the rates of their photocatalytic degradations.•An elaborate kinetic model which incorporates both adsorption and photocatalysis.
Titania–silica composite aerogels with 16–29% Ti-content by the mass were synthesized by the sol–gel method from different Ti-precursors, and calcined at 500°C. These aerogels are highly amorphous as no crystalline TiO2 phase can be detected in them by X-ray diffraction methods, and show the dominating presence of either mesopores or macropores. The incorporation of Ti into the silica structure is shown by the appearance of characteristic IR transitions of SiOTi vibrations. The characteristic band-gap energies of the different aerogels are estimated to be between 3.6 and 3.9eV from UV reflection spectra. Band-gap energy decreases with decreasing pore-size. When suspended in solution, even these highly amorphous aerogels accelerate the photodegradation of salicylic acid and methylene blue compared to simple photolysis. Kinetic experiments were conducted under illumination, and also in the dark to study the adsorption of the substrates onto the suspended aerogels. We assume that the fast in situ adsorption of the organic substrates mask the suspended aerogel particles from UV photons, which reduces the rate of photocatalysis. We managed to mathematically separate the parallel processes of photocatalysis and adsorption, and develop a simple kinetic model to describe the reaction system.
Nanogold is widely used in many areas of physics and chemistry due to its environment-sensitive plasmon resonance absorption. The immobilization of gold nanoparticles in highly porous silica aerogel ...offers an attractive alternative to liquid gold solutions as they show a mechanically stable structure, are permeable to gases, and can even be used at elevated temperatures. We have found that the commercially available citrate-stabilized 10 nm gold nanoparticles may suffer from aggregation prior to or under the base-catalyzed gelation process of tetramethoxy silane. In the wet gels, Au particles increased in size, changed shape, and demonstrated the loss of plasmon resonance absorption, due to the formation of larger aggregates. We have studied a range of water-miscible organic solvents, stabilizing agents, and the gelation conditions to minimize changes from occurring in the aerogel setting and the supercritical drying process. It has been found that atmospheric carbon dioxide has a significant effect on aggregation, and it cannot be entirely excluded under normal synthetic conditions. Methanol resulted in an increase in the particle size only, while dimethyl sulfoxide, dimethylformamide, and urea changed the shape of nanoparticles to rod-like shapes, and diols led to an increase in both size and shape. However, using the polymeric stabilizer poly(vinyl pyrrolidone) efficiently prevented the aggregation of the particles, even in the presence of high concentrations of carbon dioxide, and allowed the production of nanoAu containing silica aerogels in a single step, without the modification of technology.
β-Tricalcium phosphate was combined with silica aerogel in composites prepared using the sol-gel technique and supercritical drying. The materials were used in this study to check their biological ...activity and bone regeneration potential with MG63 cell experiments. The composites were sintered in 100 °C steps in the range of 500-1000 °C. Their mechanical properties, porosities, and solubility were determined as a function of sintering temperature. Dissolution studies revealed that the released Ca-/P molar ratios appeared to be in the optimal range to support bone tissue induction. Cell viability, ALP activity, and type I collagen gene expression results all suggested that the sintering of the compound at approximately 700-800 °C as a scaffold could be more powerful in vivo to facilitate bone formation within a bone defect, compared to that documented previously by our research team. We did not observe any detrimental effect on cell viability. Both the alkaline phosphatase enzyme activity and the type I collagen gene expression were significantly higher compared with the control and the other aerogels heat-treated at different temperatures. The mesoporous silica-based aerogel composites containing β-tricalcium phosphate particles treated at temperatures lower than 1000 °C produced a positive effect on the osteoblastic activity of MG63 cells. An in vivo 6 month-long follow-up study of the mechanically strongest 1000 °C sample in rat calvaria experiments provided proof of a complete remodeling of the bone.
Renewable energy sources are can play an important role both in fulfilling the increasing demands for energy and in reduction of the emissions of the greenhouse gases and other air pollutants. For ...these reasons their energy yield increases dynamically. Renewable energy sources are available in different ratios in different regions of the continents. Every regions has its own features what result in different utilisation methods. This paper presents a solar energy potential estimating model what can be used at any locations over the Earth. Examinations were carried out on a remote controlled system composed of 64 solar panels in the Renewable Energy Park Research Center in Debrecen, Hungary. Results revealed that the agreement between the model and the values in our database is over 90% thus using the model the production of the solar panel systems could be predicted taking into account specific local conditions as well.
Mesoporous silica aerogel particles of ca. 5 μm in diameter can be conveniently produced by grinding in an aqueous phosphate buffer at pH 7. The pores in the suspended aerogel particles are spherical ...and their diameter is 18–20 nm, as measured by NMR cryoporometry. NMR diffusiometry revealed that diffusion of water is hindered inside the pores of the aerogel. In spite of steric hindrance, bulk water and pore water exchange rapidly on the millisecond timescale in the suspension, indicating a highly interconnected pore network. The adsorption of methylene blue (MB), as a model compound, was studied on the silica aerogel particles. The process was followed by on-line UV-Vis spectrophotometry after injecting the dye into the aerogel suspension. Biphasic kinetics were observed with the first process complete in ca. 80 s and the second in ca. 600 s. A detailed kinetic model was developed for the interpretation of the results. It postulates a relatively fast adsorption process with Langmuir-type kinetics, and the aggregation of aerogel particles covered by the dye on a longer timescale. The aggregates are involved in a reversible sedimentation process which actually removes MB from the suspension.
Abstract Carotid body tumors (CBTs) are rare types of extra-adrenal paragangliomas, which originate from the neuroendocrine cells of the adventitial layer of carotid bifurcation. An 8-year-old girl ...was admitted to our department with left-sided and pulsating neck swelling, which progressively grew over several months. The patient had no family history of CBTs. Computed tomography (CT) and CT angiography (CTA) scans revealed a contrast material enhancing, hypervascularized mass involving the left carotid bifurcation, internal carotid artery (ICA), and external carotid artery (ECA), respectively. Preoperative embolization and surgical resection were performed. Histopathological examination later confirmed a benign CBT. Current follow-up examination revealed no evidence of residual or recurrent tumor. A systemic review of the literature indicates that early diagnosis, and experienced multi-disciplinary management is required in case of unilateral, resectable forms of CBTs with no distant metastasis, in order to provide a long-time survival of patients. Surgical intervention of unilateral, solitary CBTs with preoperative embolization is a relatively safe procedure, allowing complete tumor removal with minimal morbidity and low recurrence rate.
Formation of iron oxyhydroxide aerogel and xerogel by hydrolysis of FeCl3 ∙ 6 H2O was studied in organic media using water available solely from the starting iron salt. Ethylene glycol (EGLY), ...dimethyl sulfoxide (DMSO) and dimethyl formamide (DMFA) solvents were used. Products were analysed with specific surface area and TEM measurements. Early stages of hydrolysis and progress of gelation were followed by Mössbauer spectroscopy of frozen reaction mixtures. Presence of transient species and increase of the probability of the Mössbauer effect was observed in the early phase (0 – 60 min). Hydrolysis and gelation were the faster in EGLY, proceeded with medium rate in DMSO and were the slowest in DMFA.
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