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Controlling the growth of material is crucial in material processing for desired properties. Current approaches often involve sophisticated equipment for controlling precursors and monitoring material formation. Here we report a self-limiting material growth mechanism controlled by the experienced mechanical loading without the need for precise control over precursors or monitoring material growth. Material formation that reduces the driving force for growth is hypothesized to result in a saturation thickness that is dependent on the maximum driving force. Analytical relations based on the growth model are derived and verified using a piezoelectric substrate immersed in an electrolyte solution under fixed frequency cyclic loading to attract surrounding mineral ions to form mineral layers. Accumulating mineral layers decrease the driving force for further growth and the material eventually reaches a saturation thickness. This allows for loading force to control the saturation thickness of the self-limiting material growth. Experimental data supports the predicted exponential relations, offering guides to predict the saturation thickness and control the growth profile. The findings are envisioned to contribute to the fundamental understanding of the self-limiting material growth mechanism and could benefit a range of applications including coatings for orthopedic implants as well as marine surface and underwater vehicles.
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The life span of metals can be inferred from early microscopic deformation events.
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Electrospun nanofibrous materials serve as potential solutions for several biomedical applications as they possess the ability of mimicking the extracellular matrix (ECM) of tissues. Herein, we report on the fabrication of novel nanostructured composite materials for potential use in biomedical applications that require a suitable environment for cellular viability. Anodized TiO2 nanotubes (TiO2 NTs) in powder form, with different concentrations, were incorporated as a filler material into a blend of chitosan (Cs) and polyvinyl alcohol (PVA) to synthesize composite polymeric electrospun nanofibrous materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nanoindentation, Brunauer-Emmett-Teller (BET) analysis, and MTT assay for cell viability techniques were used to characterize the architectural, structural, mechanical, physical, and biological properties of the fabricated materials. Additionally, molecular dynamics (MD) modelling was performed to evaluate the mechanical properties of the polymeric PVA/chitosan matrix upon reinforcing the structure with TiO2 anatase nanotubes. The Young's modulus, shear and bulk moduli, Poisson's ratio, Lame's constants, and compressibility of these composites have been computed using the COMPASS molecular mechanics force fields. The MD simulations demonstrated that the inclusion of anatase TiO2 improves the mechanical properties of the composite, which is consistent with our experimental findings. The results revealed that the mineralized material improved the mechanical strength and the physical properties of the composite. Hence, the composite material has potential for use in biomedical applications.
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ZnO nanostructures (NS)/guar gum (GG) nanocomposites have been successfully synthesized and tested as sorbents for photodegradation, adsorption and antimicrobial activity for dye removal. The addition of ZnO improves the thermal stability of GG based on the ratio of the oxygen in the OH form and the total oxygen in the samples as indicated via XPS and FTIR analyses. Among all tested composites, the ZnO NPs/GG nanocomposite showed the highest photocatalytic activity and hence used in extended adsorption and degradation studies against the anionic dye reactive red (RR195) and the cationic dye Rhodamine B (RhB). The adsorption mechanism and kinetics were studied in details. The ZnO NPs/GG nanocomposite showed quite high removal efficiency for both dyes reaching about 96 degradation percent of the initial dye concentration as well as a high adsorption capacity reaching 70â¯mgâ¯g-1. The adsorption of both dyes on ZnO NPs/GG was found to obey the Freundlich adsorption model with pseudo-second-order kinetics. The antibacterial assay showed an enhanced antibacterial effect of ZnO/GG against E-Coli/TOP10 (PTA 10989) strain compared to pristine ZnO or pure guar gum. The obtained results were proved to be of high significance based on the statistical analysis using one-way ANOVA followed by Tukey's analysis.
Asunto(s)
Antibacterianos/química , Antibacterianos/farmacología , Colorantes/aislamiento & purificación , Nanocompuestos/química , Adsorción , Escherichia coli/efectos de los fármacos , Galactanos/química , Galactanos/farmacología , Cinética , Mananos/química , Mananos/farmacología , Oxígeno/química , Procesos Fotoquímicos , Gomas de Plantas/química , Gomas de Plantas/farmacología , Rodaminas/química , Termodinámica , Eliminación de Residuos Líquidos , Óxido de Zinc/química , Óxido de Zinc/farmacologíaRESUMEN
BACKGROUND: Virtually all plants and animals protect themselves from the sun using vitamins C and E. OBJECTIVE: The purpose of this study was to see if a combination of topical vitamins C and E is better for UV protection to skin than an equivalent concentration of topical vitamin C or E alone. METHODS: We developed a stable aqueous solution of 15% L-ascorbic acid (vitamin C) and 1% alpha-tocopherol (vitamin E). We applied antioxidant or vehicle solutions to pig skin daily for 4 days. We irradiated (1-5x minimal erythema dose) control- and antioxidant-treated skin using a solar simulator with a 295-nm band-pass filter. On day 5, we measured antioxidant protection factor, erythema, sunburn cells, and thymine dimers. RESULTS: The combination of 15% L-ascorbic acid and 1% alpha-tocopherol provided significant protection against erythema and sunburn cell formation; either L-ascorbic acid or 1% alpha-tocopherol alone also was protective but the combination was superior. Application during 4 days provided progressive protection that yielded an antioxidant protection factor of 4-fold. In addition, the combination of vitamins C and E provided protection against thymine dimer formation. CONCLUSION: Appreciable photoprotection can be obtained from the combination of topical vitamins C and E. We suggest that these natural products may protect against skin cancer and photoaging.