Recent advances (2016 - 2020) in green synthesis of metal oxide nanoparticles: An overview

The development of products and processes which are more ecological has been a source of interest in research in recent decades. Thus, researchers have developed several methods to improve the synthesis of oxides and metals in a more ecological way. Green synthesis has become a method that is being widely used for presenting low temperature, low cost and great availability of raw material. Some biological sources such as fungi, bacteria and plants are used in this route, but plant extracts are the most used in the literature. Various parts of the plant such as the roots, bark, flowers, fruits, stem, seeds, and leaves are rich in secondary metabolites such as: flavonoids, phenols, steroids, terpenoids, alkaloids, saponins and phenolic compounds, which play an essential role in the complexation, polymerization, capping and stabilization processes that generate oxides. The methodology used in the synthesis process significantly interferes in some properties and characteristics of the same oxide as its morphology. In this sense, this paper presents a review on green synthesis in obtaining oxides and their morphologies.

Hybrid NOMA-Based ACO-FBMC/OQAM for Next-Generation Indoor Optical Wireless Communications Using LiFi Technology

The light fidelity (LiFi) has been successfully used to achieve high data transfer rates, high security, great availability, and low interference. In this paper, we propose a LiFi system consisting of a combination of non-orthogonal multi-access (NOMA), asymmetrically-clipped optical (ACO) and filter bank multicarrier (FBMC) techniques combined with offset quadrature amplitude modulation (OQAM). The paper also applies a $\mu$-law companding approach for a high peak to average power ratio (PAPR) reduction of the FBMC/OQAM scheme. The combination of NOMA, ACO-FBMC/OQAM, and $\mu$-law companding allows a significant increase in throughput and a significant reduction in non-served users. An appropriate algorithm is developed considering two scenarios, maximize the throughput and minimize the number of blocked (non-served) users. The results show that the throughput of the system can be increased by $1.8$ compared to FBMC and OFDM. Furthermore, the proposed system reduces the number of blocked users below $10\%$, while the system can provide $30\%$ or $60\%$ in case only the FBMC or OFDM is used, respectively.

Plasticity To Environmental Conditions And Substrate Colonization Mediates The Invasion of Dreissenid False Mussels In Brackish Systems

False mussels are recognized as the brackish water equivalent of zebra mussels, although the abiotic and habitat conditions that mediate these invaders’ success are barely known. In this context, we aimed to evaluate the native and non-native geographical distribution of Mytilopsis species worldwide and assess biological traits, environmental condition, and habitat associated with false mussels in native and invaded systems. Our hypothesis is that Mytilopsis invasion is driven by species plasticity to environmental conditions and substrate use in brackish systems, where the colonization of non-native populations is favored by great availability of artificial substrates and tolerance to wide ranges of environmental conditions. Besides, this study provides the occurrence range and distribution patterns of Mytilopsis species within their introduced and native areas and tracks the spread of introduced populations worldwide. Considering the five species evaluated, M. leucophaeata and M. sallei are the most widespread, while M. adamsi, M. trautwineana, and M. africana showed more restricted geographic distribution. In the last decades, M. leucophaeata and M. sallei consolidated and expanded their distributions. Environmental conditions were significantly different between native and non-native areas, where Mytilopsis populations presented significantly higher densities. Non-native populations exhibited remarkable plasticity concerning habitat colonization that was more frequent on artificial substrata. Mytilopsis populations presented significant differences on their biological traits, habitat environmental conditions, and substrate use between native and non-native areas. These species seem to adapt to the conditions of invaded systems, changing their preferences, which reflects plasticity and suggests a potential shift of their realized niches.

Synthesis and Comparative Characterization of Different Microparticles used as Biomaterials in Dentistry

A biomaterial must be biologically compatible, mechanical, functional, corrosion resistant and easily adapt to clinical and laboratory technologies. Dental biomaterials are materials used to replace a part of a living system or to work closely with living tissue. Many scientific articles present different polymeric biocomposites with possible application in dentistry and this is a proof of the opportunity of a research in a field in full ascent and with great availability in the promotion of materials destined to �work under biological constraint� and which must also meet the functional requirements of a dental implant. The objectives of this research were to obtain and to comparatively evaluate different polymeric microparticles that can be used in dentistry. The samples based on poly(lactic-co-glycolic acid) and respectively polyurethane microparticles were characterized by pH and Zetasizer measurements, and in vitro cytotoxicity assays. The results indicate the obtaining of particles with a neutral pH, medium homogeneity, and with different tendencies to form agglomerations. Their low cytotoxicity, tested on the primary human gingival fibroblasts by MTT and LDH techniques, indicates that these microparticles are safe to be tested in further clinical evaluations.

Properties of self-compacting mortar made with various mineralogical sources different types of sands and fillers

Purpose By its high fluidity, great deformability and rheological stability, the self-compacting mortar (SCM) is capable of ensuring the ability to be easily implemented without vibration. However, its formulation requires a large volume of fine materials with a high dosage of cement, which is necessary to ensure adequate workability and mechanical strengths, which is necessary to allow its flow. Current environmental considerations encourage reducing the production of cement, it is essential to use additions to replace the cement, because of their great availability and their moderate price. On another side, their use contributes to an economic sort to solve the problems related to the environment. Design/methodology/approach The formulations and characteristics of SCM made with two types of mineralogical sources (silica and limestone) were investigated. Different materials were used separately and in binary combinations; silica river sand (SRS), limestone quarry sand (LQS), silica fillers (SF) and limestone fillers (LF). The formulation starts with the self-compacting pastes (SCPs) then the SCMs at the SRS and the LQS whose the cement is partially replaced by volume contents of SF and LF with 15%, 30% and 45%. Findings The results obtained prove that the incorporation of LQS instead of SRS has a negative effect on the fluidity and deformability and a positive effect on the mechanical strengths of SCM. In addition, the incorporation of the SF and LF reduces the need for water and the saturation dose of superplasticizer in the pastes. Thus, the addition of the SF and LF in specific voluminal contents (15% SF and 30% LF) in the binder can have a beneficial effect on the parameters of the workability and the mechanical strengths of SCM. These results are very interesting to aspects such as technological, economic and environmental. Originality/value Influence of the different type of sands and fillers in improvements the properties of SCM made from various mineralogical sources.

Nanomaterial-Integrated Cellulose Platforms for Optical Sensing of Trace Metals and Anionic Species in the Environment

The development of disposable sensors that can be easily adapted to every analytical problem is currently a hot topic that is revolutionizing many areas of science and technology. The need for decentralized analytical measurements at real time is increasing for solving problems in areas such as environment pollution, medical diagnostic, food quality assurance, etc., requiring fast action. Despite some current limitations of these devices, such as insufficient detection capability at (ultra)trace level and risk of interferent effects due to matrix, they allow low-cost analysis, portability, low sample consumption, and fast response. In the last years, development of paper-based analytical devices has undergone a dramatic increase for on-site detection of toxic metal ions and other pollutants. Along with the great availability of cellulose substrates, the immobilization of receptors providing enhanced recognition ability, such as a variety of nanomaterials, has driven the design of novel sensing approaches. This review is aimed at describing and discussing the different possibilities arisen with the use of different nanoreceptors (e.g., plasmonic nanoparticles, quantum dots, carbon-based fluorescent nanoparticles, etc.) immobilized onto cellulose-based substrates for trace element detection, their advantages and shortcomings.

Optimization of the Mechanical Formulation of Typha Concrete

In order to address energy efficiency issues in the building sector, we conducted this study which focuses on the optimization of the mechanical characteristics of Typha concrete for its use in load-bearing structures of buildings. The fact that buildings are very energy-intensive makes it essential to develop new forms of construction based on bioclimatic architecture and the valorization of certain materials considered as waste in construction. To achieve these objectives, wehave targeted the use of Typha Australis thanks to its great availability and high thermalinsulation capacity. Thus, starting from the composition of a control concrete determined bythe DreuxGorisse formulation method with a characteristic compressive strength of 20 MPaat 28 days, Typha S1 series concretes are formulated with the substitution of sand up to 40, 50,and 60% of Typha. In order to increase the mechanical strength of Typha S1 series concretes,the cement class and G/S ratio are increased for the second S2 series.At the end of this research, the results obtained show that some of these concretes withdifferent proportions of Typha have good mechanical performance, which depends on theirstructural use.

THERMAL AND ECONOMIC ANALYSIS OF LIME PRODUCTION

The ore beneficiation process uses little technology, but mining companies have high economic performance. As an energy source, firewood plays a fundamental role due to its simple storage, low cost, great availability of forests, and lack of processing. Thus, the present work aims to analyze the consumption of firewood as fuel and possible improvements in the process for the production of lime in terms of harnessing raw materials and costs. Calcium oxide is obtained from the thermal decomposition of calcium and magnesium carbonates obtained from dolomitic deposits of limestone (CaCO3 : CaMgCO3). After CaO extraction, it is subjected to a calcination process, removing carbon dioxide (CO2) in ovens that work at temperatures between 900 and 1200°C. The source of energy applied to the calcination furnaces in the analyzed area is wood. The wood has a calorific value between 2,250 and 2,700 Kcal/Kg, but the moisture content responsible for the thermal variation must be considered. The firewood burning process was carried out in a ravine type oven where the temperature at which operators are exposed to heat was evaluated. The results indicated that the cooking time dropped by 20% as the amount of wood is fed into the oven. This increase represents a significant gain in lime production, thus leading to a higher profit for the company.

REUSE RESIDUAL SAND CASTING FOR PRODUCTION OF CONCRETE BLOCKS

The ore beneficiation process uses little technology, but mining companies have high economic performance. As an energy source, firewood plays a fundamental role due to its simple storage, low cost, great availability of forests, and lack of processing. Thus, the present work aims to analyze the consumption of firewood as fuel and possible improvements in the process for the production of lime in terms of harnessing raw materials and costs. Calcium oxide is obtained from the thermal decomposition of calcium and magnesium carbonates obtained from dolomitic deposits of limestone (CaCO3 : CaMgCO3). After CaO extraction, it is subjected to a calcination process, removing carbon dioxide (CO2) in ovens that work at temperatures between 900 and 1200°C. The source of energy applied to the calcination furnaces in the analyzed area is wood. The wood has a calorific value between 2,250 and 2,700 Kcal/Kg, but the moisture content responsible for the thermal variation must be considered. The firewood burning process was carried out in a ravine type oven where the temperature at which operators are exposed to heat was evaluated. The results indicated that the cooking time dropped by 20% as the amount of wood is fed into the oven. This increase represents a significant gain in lime production, thus leading to a higher profit for the company.

Use of office package of free software in high school of Santa Rosalía, BCS

The present article shows the results of the study carried to the junior high schools of Santa Rosalía Baja California Sur, to identify the level of knowledge that the students and teachers have about the free office software package, where the result obtained was a high percentage of ignorance. It should be noted the great availability and acceptance shown by students and teachers towards this software package based on free software. To carry out this study, it was used the exploratory and descriptive methods, where the study sample was a total of 135 students and 44 teachers who replied the surveys and interviews, which were conducted in two stages: the first one, was carried out to know the level of knowledge the school community has about of office programs of free software; the second one, was done to know the level of acceptance of it.