Microstructural and magnetic characterization of nanostructured alpha-Fe2O3 and CuO mixtures obtained by ball milling

We have subjected powder mixtures of (0.5x)alpha -Fe2O3 and (1 - x) CuO to ball milling for a fixed period of 10 h for several x across the whole range of concentrations. No phases other than the initial ones in their nanostructural form were detected within the resolution of the several experimental techniques employed. The grain size of the CuO nanoparticles is not observed to depend notably upon x and the microstrain is three times higher than that found for haematite, In contrast, the alpha -Fe2O3 grain size varies with the haematite content of the mixtures and a minimum size of D approximate to 70 Angstrom was observed for 0.50 less than or equal to x less than or equal to 0.95. The high-field susceptibility can be expressed as the weighted sum of the milled CuO and alpha -Fe2O3 individual susceptibilities. For low x, a Cu(Fe)O solid solution is formed. An increase in the overall magnetization is observed for intermediate concentrations. In addition, within this x range, a broad Mossbauer sextet related to grain boundary regions is found coexisting with a bulk alpha -Fe2O3 signal at 30 K. The relative area of this broad signal is a maximum for x = 0.67, a sample that also shows an anomalous magnetic hysteresis. We associate these facts to a state of spin disorder linked to the grain boundaries of the nanocrystalline material

Probing the structure of nanograined CuO powders

The microstructural properties of polycrystalline CuO powders and their evolution during controlled high energetic ball milling (HEBM) were studied using conventional X-ray diffraction (XRD) techniques and in situ temperature-dependent small and wide angle scattering (SAXS–WAXS) synchrotron radiation experiments. Volume weighted average grain size, unit cell expansion, oxygen deficiency, and microstrain values as a function of milling time were obtained from XRD. SAXS data revealed different nanostructures for samples synthesized by one-step solid-state reaction (SSR) or HEBM-treated powders. The latter presented the characteristics of a multilayered nanoscale solid system with surface fractal behavior. Correlation of the XRD microstructural parameters and the power law exponent of the SAXS curves as a function of temperature and milling time provided a coherent picture of the structure of HEBM-treated powders. The overall structural information presented in this article may shed some light on the macroscopic physical properties of CuO nanostructures.Facultad de Ciencias Exacta

Modeling and Characterization of the Passive Bending Stiffness of Nanoparticle-Coated Sperm Cells using Magnetic Excitation

Of all the various locomotion strategies in low- (Formula presented.), traveling-wave propulsion methods with an elastic tail are preferred because they can be developed using simple designs and fabrication procedures. The only intrinsic property of the elastic tail that governs the form and rate of wave propagation along its length is the bending stiffness. Such traveling wave motion is performed by spermatozoa, which possess a tail that is characterized by intrinsic variable stiffness along its length. In this paper, the passive bending stiffness of the magnetic nanoparticle-coated flagella of bull sperm cells is measured using a contactless electromagnetic-based excitation method. Numerical elasto-hydrodynamic models are first developed to predict the magnetic excitation and relaxation of nanoparticle-coated nonuniform flagella. Then solutions are provided for various groups of nonuniform flagella with disparate nanoparticle coatings that relate their bending stiffness to their decay rate after the magnetic field is removed and the flagellum restores its original configuration. The numerical models are verified experimentally, and capture the effect of the nanoparticle coating on the bending stiffness. It is also shown that electrostatic self-assembly enables arbitrarily magnetizable cellular segments with variable stiffness along the flagellum. The bending stiffness is found to depend on the number and location of the magnetized cellular segments. © 2022 The Authors. Advanced Theory and Simulations published by Wiley-VCH GmbH

Assessment of the subjective benefit of electric acoustic stimulation with the abbreviated profile of hearing aid benefit

This study demonstrates that electric-acoustic stimulation (EAS) significantly decreases the subjective impairment in speech perception

MPP5 recruits MPP4 to the CRB1 complex in photoreceptors

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