Improvement of digital Gabor holographic microscopy using a lens in plankton studies.

This work utilizes a Gabor Holographic Optical Scheme integrated with a microscope objective and a thin convex plane lens. This bi-telecentric lens system corrects spherical aberration from the objective, maintains consistent magnification across various reconstruction distances, and ensures a plane incidence on CMOS. Depending on the focal lengths of the objective and lens, the final image can be enlarged or reduced compared to the classic Gabor system, resulting in high-quality reconstructed phase images without spherical aberration. This setup was employed to capture phase distribution and intensity images of planktonic objects, such as copepods, achieving superior image quality.

Influence of Bentonite Particles on the Mechanical Properties of Polyester-Sisal Fiber Composites.

As a part of the mission to create materials that are more environmentally friendly, we present the following proposal, in which a study of the mechanical properties of composite materials comprising a polyester resin with sisal fiber and bentonite particles was conducted. Sisal fiber was added to a matrix in percentages ranging from 5% to 45% in relation to the polyester resin weight, while bentonite remained fixed at 7% in relation to the polyester resin weight. The specimens were manufactured by compression molding. The mechanical properties were analyzed by tensile, bending, impact, stepped creep, and relaxation tests. In addition, energy-dispersive X-ray spectroscopy and scanning electron microscopy analyses were carried out to analyze the composition and heterogeneity of the structure of the composite material. The results obtained showed that 7% of bentonite added to the matrix affects the tensile strength. Flexural strength increased by up to 21% in the specimens with a 20% addition of sisal fiber, while the elastic modulus increased by up to 43% in the case of a 20% addition of sisal fiber. The viscoelastic behavior was improved, while the relaxation stress was affected.

Parameter Identification of Fractional Index Viscoelastic Model for Vegetable-Fiber Reinforced Composite.

In the present work, parameters for adapting the behavior of the uniaxial three-element viscoelastic constitutive model with integer and fractional index derivatives to the mechanical evolution of an epoxy-composite material reinforced with long random henequen fibers, were determined. Cyclic loading-unloading with 0.1%, 0.2%, 0.3%, …, 1.0% controlled strain and staggered fluency experiments at 5 MPa, 10 MPa, and 15 MPa constant tension were performed in stages, and the obtained data were used to determine and validate the model's parameter values. The Inverse Method of Identification was used to calculate the parameters, and the Particle Swarm Optimization (PSO) method was employed to achieve minimization of the error function. A comparison between the simulated uniaxial results and the experimental data is demonstrated graphically. There exists a strong dependence between properties of the composite and the fiber content (0 wt%, 9 wt%, 14 wt%, 22 wt%, and 28 wt% weight percentage fiber/matrix), and therefore also of the model parameter values. Both uniaxial models follow the viscoelastic behavior of the material and the fractional index version presents the best accuracy. The latter method was noted to be adequate for determination of the aforementioned constants using non-large experimental data and procedures that are easy to implement.

Determinación de la bioactividad de capas de alginato de sodio en discos de hidroxiapatita / Determination of bioactivity in sodium alginate layers of hydroxyapatite disks

Objetivo: el propósito central de este trabajo es evaluar la bioactividad in vitro de capas de alginato de sodio en discos de hidroxiapatita. Métodos: los discos de hidroxiapatita fueron elaborados mediante procesos sucesivos de prensado y de sinterizado en un horno eléctrico. Las capas de alginato de sodio se obtuvieron empleando el método de sobrepresión y una disolución acuosa de alginato de sodio al 5 por ciento. En el ensayo de bioactividad las muestras a estudiar fueron sumergidas en fluido biológico simulado. La caracterización de las muestras se realizó empleando microscopia electrónica de barrido y energía dispersiva de rayos X. Resultados: en las muestras de hidroxiapatita sometidas al ensayo de bioactividad, con y sin capas de alginato de sodio, se observó la formación de precipitados ricos en calcio y fósforo. Además, se determinó que con el aumento del tiempo de inmersión en el fluido biológico simulado se incrementan las dimensiones de los aglomerados formados por partículas apatíticas. Conclusiones: los resultados experimentales corroboran que la hidroxiapatita es bioactiva y demuestran que las capas estudiadas de alginato de sodio en discos de hidroxiapatita poseen un comportamiento bioactivo(AU)

Objective: the main purpose of the study is to evaluate in vitro bioactivity in sodium alginate layers of hydroxyapatite disks. Methods: the hydroxyapatite disks were manufactured by successive pressing and sintering in an electric furnace. The sodium alginate layers were obtained by overpressure and a 5% sodium alginate aqueous solution. For the bioactivity assay, the study samples were soaked in simulated biological fluid. Characterization of the samples was conducted by scanning electron microscopy and energy dispersive X rays. Results: the bioactivity assay of hydroxyapatite samples with and without sodium alginate layers revealed the formation of precipitates rich in calcium and phosphorus. It was also found that an increase in the time of immersion in the simulated biological fluid brought about an increase in the size of agglomerates of apatite particles. Conclusions: experimental results show that hydroxyapatite is indeed bioactive, and that the sodium alginate layers of hydroxyapatite disks which were studied behave bioactively(AU)

Determinación de la bioactividad de capas de alginato de sodio en discos de hidroxiapatita / Determination of bioactivity in sodium alginate layers of hydroxyapatite disks

OBJETIVO: el propósito central de este trabajo es evaluar la bioactividad in vitro de capas de alginato de sodio en discos de hidroxiapatita. MÉTODOS: los discos de hidroxiapatita fueron elaborados mediante procesos sucesivos de prensado y de sinterizado en un horno eléctrico. Las capas de alginato de sodio se obtuvieron empleando el método de sobrepresión y una disolución acuosa de alginato de sodio al 5 %. En el ensayo de bioactividad las muestras a estudiar fueron sumergidas en fluido biológico simulado. La caracterización de las muestras se realizó empleando microscopia electrónica de barrido y energía dispersiva de rayos X. RESULTADOS: en las muestras de hidroxiapatita sometidas al ensayo de bioactividad, con y sin capas de alginato de sodio, se observó la formación de precipitados ricos en calcio y fósforo. Además, se determinó que con el aumento del tiempo de inmersión en el fluido biológico simulado se incrementan las dimensiones de los aglomerados formados por partículas apatíticas. CONCLUSIONES: los resultados experimentales corroboran que la hidroxiapatita es bioactiva y demuestran que las capas estudiadas de alginato de sodio en discos de hidroxiapatita poseen un comportamiento bioactivo.

OBJECTIVE: the main purpose of the study is to evaluate in vitro bioactivity in sodium alginate layers of hydroxyapatite disks. METHODS: the hydroxyapatite disks were manufactured by successive pressing and sintering in an electric furnace. The sodium alginate layers were obtained by overpressure and a 5% sodium alginate aqueous solution. For the bioactivity assay, the study samples were soaked in simulated biological fluid. Characterization of the samples was conducted by scanning electron microscopy and energy dispersive X rays. RESULTS: the bioactivity assay of hydroxyapatite samples with and without sodium alginate layers revealed the formation of precipitates rich in calcium and phosphorus. It was also found that an increase in the time of immersion in the simulated biological fluid brought about an increase in the size of agglomerates of apatite particles. CONCLUSIONS: experimental results show that hydroxyapatite is indeed bioactive, and that the sodium alginate layers of hydroxyapatite disks which were studied behave bioactively.