A novel ceramic matrix composite based on YNbO4–TiO2 for microwave applications

This work presents the dielectric properties of YNbO₄ (YNO)–TiO₂ composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO₂ to YNO results in the formation of a Y(Nb_0.5Ti_0.5)₂O₆ phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO₂. Moreover, the addition of TiO₂ results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C^?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO₂ composites are interesting candidates for microwave operating devices.     

Synthesis and Properties of New Cleavable Cationic Surfactants Containing Carbonate Groups

A novel series of cleavable alkyltrimethylammonium surfactants with different hydrocarbon chain lengths (C8–16) were synthesized. A carbonate break site inserted between the polar head and the hydrocarbon chain makes these compounds hydrolyzable. The reagents used are renewable, (bio)degradable, or reusable. The hydrolysis of these cleavable surfactants will lead to the generation of fatty alcohols and choline, which is an essential biological nutrient. The surface activities in aqueous solution of the synthesized carbonates fulfill the requirement of being good surfactants. In addition, the cleavable compounds containing n-decyl and n-dodecyl chains showed similar or higher antimicrobial activities when compared to a non-cleavable analog.     

Increasing the photocatalytic and fungicide activities of Ag3PO4 microcrystals under visible-light irradiation

The present study reports for the first time the performance of silver phosphate (Ag₃PO₄) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicans–C. albicans) under visible-light irradiation (455 nm). Ag₃PO₄ microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag₃PO₄ have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag₃PO₄ were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag₃PO₄ was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation.     

Nanocomposite powders of hydroxyapatite-graphene oxide for biological applications

The repair of bone fractures is a clinical challenge for patients with impaired healing, such as osteoporosis. Currently, different strategies have been developed to design new biomaterials, enhancing their interactions with biological systems and conducting the cellular behavior in the desired direction to help fracture healing. In the present work, hydroxyapatite-graphene oxide (HA-GO) nanocomposites were produced and the morphological and physicochemical influences of the addition of 0.5 wt%, 1.0 wt% and 1.5 wt% of GO to HA were observed. FEG-SEM and TEM analyses of HA-GO nanocomposites showed HA nanoparticles adhered to the surface of the GO sheets, suggesting an effective method to form nanostructured graphene-based biomaterials. As confirmation, physicochemical analyses by Raman, FTIR and TGA demonstrated a strong affinity between HA and GO, according to the increase of concentration from 0.5 wt% to 1.5 wt% GO in the HA-GO nanocomposites. Also, in order to evaluate the HA-GO nanocomposites behavior under biological microenvironment, in vitro bioactivity and indirect cytotoxicity tests were performed. FEG-SEM analyses confirmed the positive results for the bioactivity properties of HA-GO nanocomposite and indirect cytotoxicity demonstrated that even with a decrease in the hDPSCs viability and proliferation, when increasing to 1.5 wt% of GO concentration, high level of cell viability was exhibited by HA-GO nanocomposites. These biological results suggested the 0.5 wt% HA-GO nanocomposite as a potential bioactive bone graft and a promising biomaterial for bone tissue regeneration, when compared to the pure HA.     

A computational literature review of football performance analysis through probabilistic topic modeling

This research aims to illustrate the potential use of concepts, techniques, and mining process tools to improve the systematic review process. Thus, a review was performed on two online databases (Scopus and ISI Web of Science) from 2012 to 2019. A total of 9649 studies were identified, which were analyzed using probabilistic topic modeling procedures within a machine learning approach. The Latent Dirichlet Allocation method, chosen for modeling, required the following stages: 1) data cleansing, and 2) data modeling into topics for coherence and perplexity analysis. All research was conducted according to the standards of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses in a fully computerized way. The computational literature review is an integral part of a broader literature review process. The results presented met three criteria: (1) literature review for a research area, (2) analysis and classification of journals, and (3) analysis and classification of academic and individual research teams. The contribution of the article is to demonstrate how the publication network is formed in this particular field of research, and how the content of abstracts can be automatically analyzed to provide a set of research topics for quick understanding and application in future projects.

     

Functionalized-radiolabeled hydroxyapatite/tenorite nanoparticles as theranostic agents for osteosarcoma

Hydroxyapatite (HA) nanoparticles (NPs) doped with different radioisotopes for use as theranostic systems play an important role in scientific research nowadays due to their ability to simultaneously act in the treatment and diagnosis of various types of cancers. In this work, we describe the synthesis and characterization of a hydroxyapatite/tenorite nanocomposite functionalized with folic acid, representing a nanotheranostic material with potential for application as an agent in positron emission tomography imaging systems and to act specifically in the treatment and diagnosis of osteosarcoma. ⁶⁴Cu and ³²P were produced by nuclear activation in the TRIGA reactor at CDTN. The obtained samples were characterized by XRD with Rietveld refinement, XAFS, SEM, BET, TGA, FTIR, CHN, ICP-AES, XPS and gamma spectroscopy. We investigated how CuO grows in HA NPs, the stability of the interactions between CuO and HA constituents and the interactions between folic acid and the surface of the HA NPs. The results indicate the formation of a second phase (tenorite) besides hydroxyapatite, and that the interactions between the two phases are stable, resulting in a nanocomposite. Furthermore, the activation of ⁶⁴Cu and ³²P inside the HA matrix, through the exposition to a neutron flux, produces a theranostic material of interest for biological tests.     

Influence of Alkaline Additives and Buffers on Mineral Trapping of CO2 under Mild Conditions

Carbon dioxide (CO₂) gas is the main contributor to climate change. CO₂ storage in underground brines and oil‐field brines by mineral trapping has been considered as a promising alternative in order to reduce CO₂ emissions. However, permanent storage of CO₂ in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO₃/NaOH, Na₂HPO₄/NaOH, NH₄Cl/NH₄OH) on the mineral trapping of CO₂ under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH₄Cl/NH₄OH and KOH+NH₄Cl/NH₄OH mixtures promote precipitation mainly of calcium carbonate (CaCO₃).     

Software for Simulation of Second‐Generation Ethanol Production by a Simultaneous Saccharification and Fermentation Process

Environmental impacts associated with the consumption of fossil fuels and the need to generate power through renewable resources demands the usage of alternative materials. The objective is the production of clean energy from materials like lignocellulosic biomass to produce second‐generation (2G) ethanol. A software in the Matlab program is elaborated to simulate the simultaneous saccharification and fermentation (SSF) process of lignocellulosic biomass for the 2G ethanol production in batch reactors. Studying the effects of the process variables, it was found that the higher interference is caused by cellulose concentration. Higher concentrations of the product in batch processes are obtained with the maximum cellulose concentrations, cells, and enzyme.