Search

Over the last two decades, a remarkable number of studies have examined the role of engineering education in supporting knowledge and skill building among children. In this paper, we present a synthesis of this literature to evaluate the added value of pre-college engineering design experiences at the elementary level, and ways researchers have gathered evidence of children’s development of this knowledge and skills. We have conducted a systematic literature review. The initial search across four different databases with relevant keywords resulted in over 3000 journal articles and conference papers. In a two-rounds screening, by applying the inclusion criteria first to titles and abstracts, and then to the full text, 78 peer-reviewed publications were included in this systematic literature review. We summarized and synthesized empirical evidence of student learning and engagement in engineering design activities, and approaches they were assessed and elicited. The thematic analysis revealed five categories of knowledge and skills: (1) disciplinary content knowledge; (2) engineering design practices, (3) engineering thinking skills; (4) professional skills; and (5) career awareness. Additionally, the assessment and evaluation approaches that were used for each of these categories were identified and discussed. The findings provide collective evidence of variety in student learning opportunities but also suggest the need to carefully define these knowledge and skills. Since a wide range of evaluation approaches were used to capture similar outcomes, we conclude that it is imperative to develop a shared research agenda by carefully defining the knowledge and skills we expect children to learn.

X-ray diffraction is a phenomenon that stems from the interaction of the electron density of a crystalline material and the electric field of the X-ray waves. The product of this interaction, the diffraction pattern, provides a picture of the reciprocal space of the atomic distribution in terms of intensities of certain scattering wavevectors. In this manner, a correlation between those intensities seen in a diffraction pattern and the electronic properties of a material is suggested. This correlation, if it exists, may not be directly proposed using analytical expressions. This article shows for the first time the feasibility of assessing the band gap of metal–organic frameworks (MOFs) and organic and inorganic materials from their X-ray powder diffraction pattern. The band gaps were assessed with convolutional neural networks (CNNs). These CNNs were developed using simulated X-ray powder diffraction patterns and the band gaps calculated with density functional theory. The diffraction patterns were simulated with different crystal sizes, from 10 nm to the macrocrystalline size. In addition, the reported band gaps of MOFs and organic compounds in the Quantum MOF Database and the Organic Materials Database data sets were used, which were calculated with the PBE functional. Furthermore, the band gaps calculated by Kim et al. [Sci. Data (2020), 7, 387] for inorganic compounds with the HSE functional were used. The developed CNNs were tested with simulated diffraction patterns of compounds different from those used to train the CNNs, as well as with experimentally recorded diffraction patterns. The developed CNNs allowed the assessment of the band gap of the compounds with a root-mean-square error as low as 0.492 eV after training with over 64 000 diffraction patterns.

Este artí­culo es una contribución para pensar el quehacer del Trabajo social en perspectiva ambiental, mediante experiencias de gestión colectiva del agua. Los resultados que se presentan interpretan el sólido sentimiento comunitario en el territorio que surgen cuando la gente con sus propios recursos construye canales de riego, piletas, tanques de almacenamiento e instala tuberí­as para distribuir agua con destino al consumo humano. Experiencias comunitarias como la gestión colectiva del agua aportan teórica y metodológicamente al ejercicio de investigación-intervención realizado por el Trabajo Social en la dimensión ambiental. Así­ mismo, con la investigación se valora el aporte sociopolí­tico de inclusión y reconocimiento social que tiene la estrategia colectiva de acceso al agua para consumo humano, entre pobladores rurales y urbanos marginados de la atención estatal para acceso al servicio público de acueducto.

The development of numerous biomass-derived carbon catalysis toward the oxygen reduction reaction (ORR) have been reported in the last decade. The catalytic activity for the ORR improves with heteroatom doping and is notably high when Fe-N-C type bonds are present. In this work, we developed a novel method to obtain Fe-N-C self-doped sewage sludge-derived biocarbons (SSBs) by intermittent microwave heating (IMH) technique. The effect of IMH on the structural and textural properties of SSBs, and their correlation with the catalytic activity for ORR was studied. The most active biocarbon was labeled as SSF, which was obtained by two-step process: chemical activation using KOH and then it was functionalized with methanol by IMH. Therefore, the obtained SSF micro-mesoporous biocarbon had high surface area (1127 m2 g-1) and quaternary-N and thiophene-S species. In addition, Fe-N-C bonds were detected on the surface of SSF. On the other hand, it was observed that IMH treatment improved the electrochemical parameters such as the on-set potential (E0), current density (j), electron transfer number (n) and %HO2 - production. In this regard, SSF shows the best performance toward the ORR (E0= 0.89 V vs RHE, j= -3.01 mA cm-2, n= 3.4 and %HO2 - = 25.85). These results indicate that sewage sludge could be used as raw material for the manufacture of cathodes, and that the treatment by IMH seems a promising eco-friendly alternative.

This article focuses on the petrographic and microfacial characterization of the building stones, buildings, monuments, and quarries of the archeological site of Calakmul to document aspects of composition, lithologies, and stone exploitation. Microfacial analysis shows that the used building rocks are highly recrystallized biosparudites (grainstones to packstones) with the presence of reef and shallow waters fauna (boundstones). These rocks have an intermediate porosity (10–20% pore volume values) and XRD analysis confirms that the mineral composition is mainly calcite, but also dolomite. Microfacies analysis demonstrate that limestone of the stelae and the SubIIc-1 main façade come from the same quarry and have fine texture corroborate that these stones are suitable materials for carving and lime production. Samples from St. XX Gran Acropolis and from Chan Chi’ich Group come from a different quarry. These results help us to know the origin of the rocks, their use in the different buildings and monuments studied, and to contribute to the knowledge of their lithological characteristics and their response to weathering and thus provide important information that will help in taking decisions in case of probable measures of restoration and conservation of the rocks in the Calakmul region.

In recent years, resistant starch (RS) and slowly digestible starch (SDS) have been linked to the prevention of chronic noncommunicable diseases, such as obesity and its complications. Southern Mexico has an important role in the tuber crop production of M. esculenta and I. batatas, which contain considerable amounts of starch. The aim of this study was to evaluate the morphological and physicochemical changes of M. esculenta and I. batatas after pyrodextrinization, including the production of RS and SDS. The factors used in this study were the starch/acid ratio (2.2 HCl) (80:1 and 160:1 p/v); temperature (90 °C and 110 °C) and reaction time (1 and 3 h). The highest production of RS in M. esculenta was obtained with the highest starch/acid ratio and temperature, and the lowest reaction time. For pyrodextrins, loss of crystallinity and an increase in swelling power and water absorption capacity were observed. The highest production of RS in I. batatas was obtained with the highest starch/acid ratio and reaction time, and the lowest temperature. Crystallinity and enthalpy of gelatinization decreased in modified starches. The solubility, swelling power and water absorption capacity increased in both sources.

In the present work, N-TiO2−x/Pt was synthesized using a homemade nitrogen plasma (AC) discharge system. The overall procedure use of low-power nitrogen plasma (100 watts) with 1 and 2 h of plasma discharge to successfully impregnate platinum nanoparticles on P25 titanium dioxide. The obtained samples were characterized using X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results reveal the incorporation of metallic Pt up to 2.9% on the surface of TiO2 by increasing the duration of plasma discharge by up to two hours with a constant power of 100 watts. Likewise, the incorporation of nitrogen atoms into a lattice crystal was also favored, confirming a direct relationship between the amount of Pt and nitrogen atoms introduced in TiO2 as a function of the duration of plasma treatment. By characterizing nanoparticles loaded on a N-TiO2−x/Pt surface, we show that joined platinum nanoparticles have two different patterns, and the boundary between these two regions coalesces. The results demonstrate that the use of nitrogen plasma to impregnate platinum nanoparticles on the surface of TiO2 to obtain N-TiO2−x/Pt allows wide and relevant physics and chemistry applications.

Color-induced changes in stones due to heating can be useful in determining the degree of degradation generated in their components and structure. We evaluate the effect of heating in three types of limestones, useful in building and restoration, corresponding to biomicrite (BC), biosparite (BS), and intramicrite (IM), in the range of temperature from 100°C to 600°C. Our analyses indicate that the strongest changes in reflectance occur in the samples of intramicrite, followed by biomicrite, being biosparite showing the smallest ones. Additionally, IM samples suffer the largest modifications in effective porosity due to the thermal treatment; in contrast, BS and BC samples show smaller temperature-induced alterations associated with smaller changes in reflectance. Moreover, we reveal that most of the thermally induced variations are associated, in this range of temperature, to the dehydroxylation of goethite that transforms into hematite, as well as by the burning and partial release of the organic matter present in the rock. Colorimetry analyses show that the sequence of thermally induced changes can be followed by the evolution of the three coordinates, L ∗ (lightness), a ∗ (red-green), and b ∗ (yellow-blue), of the CIE 1976 L ∗ a ∗ b ∗ space.

In this work, low-Pt content nanocatalysts (≈ 5 wt. %) supported on Hollow Carbon Spheres (HCS) were synthesized by two routes: i) colloidal conventional polyol, and ii) surfactant-free Bromide Anion Exchange (BAE). The nanocatalysts were labelled as Pt/HCS-P and Pt/HCS-B for polyol and BAE, respectively. The physicochemical characterization of the nanocatalysts showed that by following both methods, a good control of chemical composition was achieved, obtaining in addition well dispersed nanoparticles of less than 3 nm TEM average particle size (d) on the HCS. Pt/HCS-B contained more Pt0 species than Pt/HCS-P, an effect of the synthesis method. In addition, the structure of the HCS remains more ordered after BAE synthesis, compared to polyol. Regarding the catalytic activity for the Oxygen Reduction Reaction (ORR) in 0.5 M KOH, Pt/HCS-P and Pt/HCS-B showed a similar performance in terms of current density (j) at 0.9 V vs. RHE than the benchmark commercial 20 wt. % Pt/C. However, Pt/HCS-P and Pt/HCS-B demonstrated a 6 and 5-fold increase in mass catalytic activity compared to Pt/C, respectively. A positive effect of the high specific surface area of the HCS and its interactions with metal nanoparticles and electrolyte, which promoted the mass transfer, increased the performance of Pt/HCS-P and Pt/HCS-B. The high catalytic activity showed by Pt/HCS-B and Pt/HCS-P for the ORR, even with a low-Pt content, make them promising cathode nanocatalysts for Anion Exchange Membrane Fuel Cells (AEMFC).

This work reports the synthesis and characterization of metal-free electrocatalysts made from Brosimum alicastrum waste as the carbon source. The residues were washed and grounded to a fine powder. The thermogravimetric analysis carried out on the raw sample showed that the optimal synthesis temperature is 700 °C. Thus, the raw sample was pyrolyzed at 700 °C and activated with potassium hydroxide (KOH) in a 2:1 ratio (KOH/fine power) to improve its properties. Afterwards, hydrazine was used as the nitrogen source for doping. The physicochemical characteristics of pyrolyzed, activated, and doped carbons were studied and their electrochemical properties were determined using cyclic and linear voltammetry techniques. The electrochemical measurements indicate that the sample doped at 140 °C has an acceptable onset potential (0.854 V vs. RHE), while the one doped at 160 °C shows the highest current density among the synthesized electrocatalysts (2.61 mA cm-2). Although the catalyst performance is lower compared to commercial 20% Pt/C, this biomass precursor favors the oxygen reduction reaction in alkaline media.

Cities occupy a relatively small percentage of the Earth’s surface. However, they influence the entire biosphere, affect biodiversity and environmental conditions, which end up affecting human health and well-being. Therefore, it is necessary to evaluate the level of contamination by heavy metals in urban environments, as well as the possible ecological and human health risks. In this study, the urban dust of six Mexican cities was analyzed and it was found that all studied cities were contaminated, except for Mérida, when soil world background value was used as reference. In contrast, Mérida and Morelia were the most contaminated when a local background was used (decile 1). The concentrations in the cities for the metals Cu, Pb and Zn, decreased in the order CDMX > San Luis Potosí > Toluca > Morelia-Ensenada > Mérida. In the particular case of Cu and Pb, SLP accompanied CDMX as the most polluted city. For Mn and Fe concentrations, the order was CDMX > Toluca > Ensenada > SLP > Morelia-Mérida. No potential ecological risk was found due to contamination by Cu, Pb, and Zn, in the urban dust of the studied cities. However, the higher metal contribution to the potential ecological risk in all the cities was from Pb; and it represented a moderate ecological risk of more than 25% on CDMX, SLP, and Toluca sites. Pb can also be a potential risk for children’s health. In addition, chronic exposure to Fe and Mn could trigger many ailments. In the future, it is important to identify the main sources of Pb in cities and seek mitigation strategies to reduce the possible adverse effects that this metal may be causing.

In the search of insight concerning the interaction of molecules of different complexity with the desulfurization and hydrogenation sites, a series of NiMo sulfided catalysts with active particles of different morphology were tested in the hydrodesulfurization of dibenzothiophene, 4,6-dimethyldibenzothiophene, and in the hydrogenation of naphthalene and cyclohexene. The size and stacking of the NiMoS nanoparticles were modified both by increasing the Mo loading and by decreasing the metal-support interaction. The results show that not all the hydrogenation reactions take place at the same type of site, and that the hydrogenating sites at the top basal plane have greater hydrogenating power than those at the edge. The direct desulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene takes place at coordinatively unsaturated sites (CUS), whereas for the hydrogenation-desulfurization reaction route, the site where the rate controlling step takes place is influenced by the structure and reactivity of the reacting molecule. For dibenzothiophene, the rate controlling step takes place at hydrogenating sites at the top basal plane while for 4,6-dimethyldibenzothiophene it takes place at CUS. Therefore, to efficiently eliminate sulfur from molecules like 4,6-dimethyldibenzothiophene, as required in ultra-low sulfur fuels, the catalyst must have good hydrogenating capacity but more importantly, a high number of CUS.

Industrial and vehicular emissions of particles cause multiple damages to human health due to concentration, size, and composition. These emissions contain magnetic particles; therefore, low-cost properties allow tracking and monitoring them. This study is aimed at identifying the primary sources of magnetic material in 100 samples of urban road dust from San Luis Potosi, Mexico, analyzing the influence of land use and the type of road on these particles. Magnetic susceptibility (χlf) and isothermal remanent magnetization at 0.7 T (IRM0.7T) were determined, as well as the iron and manganese content using X-ray fluorescence. The distribution of particles was examined by land use and type of road through geostatistical maps and variance analysis. The results showed that the iron and manganese content, χlf, and IRM0.7T were positively correlated, indicating a possible common origin. The primary sources identified were the iron smelter and laminator in the industrial park. Urban land use influenced the content of iron, manganese, and magnetic material in urban road dust. The land uses with the more significant transformation (industrial and mixed) presented the highest values of iron, manganese, χlf, and IRM0.7T. On the other hand, vehicular traffic was indirectly assessed through the type of road, influencing the magnetic signal of urban road dust and finding the highest signals in primary and secondary roads. Then, the magnetic properties allowed the tracking and monitoring of magnetic particles from industrial and vehicle emissions.

Biodegradable films based on agar with glycerol (GLY) as a plasticizer were developed by incorporating hydroalcoholic garlic extract (HGE) on the film surface. The effect of GLY content (0, 15, or 30 wt%) and different concentrations of HGE (0, 0.5, 1, or 1.5 μg/mL) on the physicochemical and transport properties of the films was evaluated. The optical (color and transparency), mechanical (tensile test), transport (diffusion and water vapor transmission rate), thermal (thermogravimetric analysis) structural (infrared spectroscopy and X-ray diffraction), and morphological (scanning electron microscope) properties were analyzed. The impregnation of HGE increased the transparency values and decreased the luminosity, tensile strength, elastic modulus, and crystallinity of the agar films. The formulation of 30 wt% GLY with 1.5 μg/mL HGE, identified as 30 GLY [1.5], showed a similar thermal stability that of a neat agar film. The agar films with 30 wt% GLY showed the lowest diffusion coefficient and water vapor transmission rate, indicating that volatile compounds are slowly released. From the results the formulation 30 GLY [1.5] could be used as a film to transport and to release HGE which is supported by a biodegradable matrix and this system has a potential use as insect semiochemical for plague control.

Zn is an essential trace metal in living beings. However, excessive concentrations can cause toxic effects even in the aquatic biota. Zn is widely used in different industrial sectors, which has increased its presence in aquatic environments. To assess the acute toxicity of Zn, bioassays were performed with the fish Gambusia sexradiata for a 96-h exposure using ZnCl2 (0 and 15 salinity) and ZnO nanomaterials (0 salinity). The mean lethal concentrations (LC50–96 h) for ZnCl2 were 25.36 (19.64–32.76) and 177.91 (129.39–244.63) mg Zn L−1 to 0 and 15 salinity, respectively. The increased concentration of ZnCl2 showed a dose-response relationship; similarly, the increase in salinity significantly reduces the toxicity of Zn. Characterisation of ZnO nanomaterials was carried out by FTIR, DRX, SEM, DLS and zeta potential. The FTIR spectra showed the characteristic band of Zn-O vibration at 364 cm−1, while DRX presents the hexagonal wurtzite structure with an average crystallite size of 40 nm. SEM micrographs reveal rod-like shapes with lengths and diameters of 40–350 nm and 90 nm, respectively. Agglomerates of 423 nm in water suspension were obtained by DLS and zeta potential of + 14.4 mV. Under these conditions, no mortality was observed due to the rapid flocculation/precipitation of ZnO nanomaterials, which involved brief interaction periods of Zn in the water column with the fish. Gambusia sexradiata is affected by increased Zn concentrations in hard water conditions, and salinity changes modified Zn toxicity, placing it as a suitable model for toxicity tests for this type of particles.

The ethanol dehydration and subsequent ethylene oligomerization to short-chain olefins using catalysts based on ZSM-5 zeolite was studied in detail. P, Fe, and Ni were added by incipient wetness impregnation on zeolites with two SiO2/Al2O3 molar ratios (50 and 80). The catalysts were characterized by N2 adsorption–desorption, XRD, SEM–EDX, FTIR spectroscopy of adsorbed pyridine, and XPS techniques, while the catalytic activity was evaluated using an isothermal fixed-bed reactor. The impregnation of P, Fe, and Ni significantly improved the formation of the desired C3+ olefins (olefins having three or more C atoms). Particularly, the zeolite with SiO2/Al2O3 molar ratio = 50 and impregnated with P, exhibited the highest selectivity (C3+ olefins > 45 wt% at TOS = 5 h) in comparison with the rest of the evaluated catalysts. On the contrary, catalysts with SiO2/Al2O3 molar ratio = 80 showed lower selectivity to C3+ olefins, producing more side products (i.e. paraffins, aromatics and diethyl-ether).

The intervention - investigation of the Social Work in the environmental dimension is an area of the knowledge and an ethical - political imperative. In this paper are explained the arguments that base that relation and are presented some challenges that raise these two connotations. For it, the writing emphasizes the need that has the profession to value multiple forms of expression of human life and not human life, resulting of the socio-environmental correlations in diverse scenarios. The approach of some challenges allow to elucidate the immense possibilities that the Social Work has of thinking the environment as an articulatory category in the professional activity. The challenges proposed for the profession are framed in the theoretical and methodological approach of the political ecology and in the concept of sustainability in the environmental dimension. Likewise, the reflection calls on to consider analytical and practical categories of conflict and environmental education for the critical and reflexive action of the relations culture - nature, collective management for the access to natural resources, and finally patrimonial conception of the nature.

The Maya sites Balamkú, Calakmul, Becán, Chicanná, Xpuhil, Hormiguero, Muñeca, and Chactún are located in the south area of the Mexican State of Campeche, immerse in a tropical subhumid climate. Surrounded by jungle vegetation, these archeological sites preserve some of the best examples of sculptural elements from the pre-Classic (1800 b. C. – 250 a. C.) to the terminal Classic (1000 d. C.) periods. These sites display how the Maya used sculptures as architectural elements in order to emphasize their cosmogony and political beliefs. The main purpose of this research is to comprehend the technology of paint layer materials and to register the chromatic palettes by using surface and microscopic analytical techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer system (EDS), X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) in order to analyze and interpret the pictorial technique used for the architectural sculpture decoration.

An extensive range of spinel-like solid solutions was found in the system Zn7Sb2O12–Li3Zn3Sb3O12 with general formula Li3xZn7-4xSb2+xO12: 0.25 ≤ x ≤ 0.65. These solid solutions are isostructural with the spinel α-Zn7Sb2O12. The Li3Zn3Sb3O12 (LiZnSbO4) end-member shows two polymorphic forms: high-temperature α-Li3Zn3Sb3O12 with an orthorhombic cell and low-temperature β-Li3Zn3Sb3O12 with a monoclinic cell. These polymorphs show a reversible transformation at 1275 ± 25 °C. The α-Li3Zn3Sb3O12 was also prepared as a metastable phase by direct synthesis at low temperatures, 900 °C. The sub-solidus phase diagram of Li2O–ZnO–Sb2O5 has been determined. Additionally, the thermal and optical properties of Li3xZn7-4xSb2+xO12 (0.35 ≤ x ≤ 0.65) solid solutions were measured. The thermal properties of sintered samples iso-structural to α-Zn7Sb2O12 displayed a heat dissipation related to Li+ and Sb5+ content having a maximum at x = 0.55. The optical band-gap showed a linear shift toward higher energies as the Li+ and Sb5+ content increased.

O objetivo do estudo foi verificar o nível de atividade física e os fatores associados em adolescentes. Foi realizado um estudo transversal com 114 indivíduos (14 a 21 anos), estudantes do ensino médio, da cidade de Morro Redondo - RS. A atividade física foi mensurada pelo questionário de prática de atividade física para adolescentes (PAQ-A). Os resultados apontaram que na atividade física total, 55,7% dos adolescentes alcançaram as recomendações de atividade física (300 minutos por semana). Sujeitos que relataram percepção de saúde excelente apresentaram uma probabilidade 140% maior de praticar atividade física total quando comparados aos com percepção de saúde regular/ruim. Estudantes que já fumaram em algum momento da vida (RP=1,44; IC 95%= 1,06; 1,96) e aqueles que ingeriram mais de cinco doses de bebidas alcoólicas nos últimos 30 dias foram mais ativos que seus pares (RP=1,40; IC 95%= 1,01; 1,96). Na atividade física de lazer, 43,4% foram considerados ativos. Indivíduos de cor da pele não branca apresentaram 85% mais probabilidade de praticar atividade física no lazer (RP = 1,85; IC 95% = 1,26; 2,72), e a medida que melhora a percepção de saúde dos adolescentes, maior foi a chance de serem ativos. A atividade física mais praticada foi a caminhada como meio de transporte (57,9 %), seguida de andar de bicicleta (33,3%), correr (33,3 %) e jogar futebol (32,5%). Conclui-se que a prevalência de atividade física de lazer e total é semelhante à de estudos com adolescentes em diferentes cidades do país, e sua prática esteve associada a percepção de saúde positiva, ao consumo de bebidas alcóolicas e tabaco. A atividade mais realizada foi a caminhada como meio de transporte.

The present work lies in the framework of designing polymeric fibre reinforced materials to be used in nanosatellite structures (CubeSat). In the design of any structural system for a space mission the balance between mass, stiffness and strength must be taken into account, also the used materials have to be appropriated for the space environmental conditions. The CubeSat are exposed to high radiation levels (because of the sun irradiance), and so, the accurate determination of the thermal and radiation properties are a key issue for the materials design used in such applications. This work reports the thermal and radiation performance of a biphasic epoxy resin system incorporating two types of ceramic nanoparticles: zinc oxide and graphene, chosen as potential fillers to improve the thermal properties of the epoxy system. Materials are exposed to Gamma and UV radiation at rates of 1 kGy and 10 kGy and characterized after exposure. Different characterization techniques (Thermogravimetric analysis - TGA, Scanning Electron Microscopy - SEM and Colorimetry) are performed to determine thermal properties and possible material degradation after radiation exposure. The influence of the different nanofiller in the thermal and radiation response of the epoxy system are discussed. Thermal properties found are also added to the Finite Element Analysis of a CubeSat composite structure to estimate more accurately its performance under the thermal load and service conditions during satellite life cycle.

In this work a first approximation to obtain non-noble metal electrocatalysts from onion skin wastes is reported. Biocarbon were obtained at a range of 600–800 °C of pyrolysis temperature activated by chemical treatment with HNO3. It was observed that the pyrolysis temperature has a direct effect on the structural and textural properties, besides the morphology of the onion skin waste-derived biocarbon, which shows to have influence on the catalytic activity for the oxygen reduction reaction ORR. AOB700 was the non-noble metal electrocatalyst with the best performance for the ORR evaluated in alkaline electrolyte (0.5 mol L−1 KOH), which had the highest surface area (242 m2g-1) and a current density of −2.35 mA cm−2 with an onset potential of 0.82 V/RHE. The chemical surface composition shows that N-pyridinic, N-amine, N-quaternary and N-pyrrolic nitrogen species are present on this electrocatalysts. The use of onion skin waste as raw material in the production of non-noble metal electrocatalysts is a sustainable solution to avoid the disposal of abundant biomass residues as onion skins.

In this work, high surface area N-doped carbon synthesis from Sargassum spp. is reported as a low cost alternative for electrocatalysts production for the oxygen reduction reaction (ORR). First, Sargassum spp. was activated with potassium hydroxide (SKPH) and then doped with hydrazine (SKPHD). As a result of the activation process, SKPH obtained a high surface area (2289 m2 g−1), 0.16% nitrogen and 2.63% sulfur content; it also showed four-electron-transfer mechanism when tested as electrocatalyst in alkaline medium. Besides, SKPHD presented 3.60% nitrogen content in the bulk and higher ORR activity (0.838 V onset potential vs. RHE and 4.59 mA cm−2 current density) very close to 20% Pt/C (5.25 mA cm−2). Results indicate that using seaweeds as a synthesis precursor is an alternative for the Sargassum spp. disposal in the Caribbean due to its high availability and efficiency towards ORR.

The respiration chamber method is considered to be the most precise approach for measuring enteric methane emissions in cattle. A set of experimental runs was carried out in which increasing volumes of pure methane (168.5, 194.9, 234.9, 264.9, 301.0, 339.8, and 375.7 L per run) were gravimetrically released into open-circuit respiration chambers to simulate the volumes of methane eructated by cattle of different weights. The aim was to assess the effect of the volume of methane released into the chambers on percentage of methane recovered at the exit by the infrared methane analyzer. It was found that as the volume of methane released into the respiration chambers was decreased, methane recovery percentages were concomitantly reduced. The recovery percentages ranged from 103.7% down to 18.3% and from 102.7% down to 31.6% for chambers one and two, respectively. It can be concluded that the slow stabilization of methane inside the large volume chamber, when injected at low rates from the cylinder, led to low recoveries of the gas at an air extraction rate of 300 L/min. As a result, the recovery of methane was constrained, leading to underestimation of the actual volumes released from the pure methane cylinders. Poor mixing of air inside the chambers did also constrain the recovery of methane with the experimental approach employed. The possible implications for methane measurements in respiration chambers under in vivo conditions with cattle are discussed.

Background Drug-related problems (DRPs) are highly prevalent in chronic kidney disease (CKD) patients. Community pharmacists are ideally positioned to manage these DRPs. However, little is known about the factors influencing their interventions with CKD patients. Objectives Using the theory of planned behavior (TPB), this qualitative study sought to: (1) explore the behavioral beliefs (perceived advantages and disadvantages), normative beliefs (perceived expectations of significant others) and control beliefs (perceived barriers and facilitators) influencing community pharmacists' interventions related to identifying and managing DRPs in CKD; and (2) compare these beliefs among three DRPs prevalent in CKD patients. Methods Community pharmacists in Quebec, Canada participated in face-to-face individual semi-structured interviews. The topic guide was based on the TPB. Three vignettes were presented to stimulate community pharmacists' thoughts about their interventions regarding: (1) the use of an inappropriate over-the-counter laxative; (2) prescriptions of anti-inflammatory medications; and (3) non-adherence to antihypertensive medication. Integral transcripts of audio recordings were analyzed using thematic analysis. The findings on each of the three DRPs were systematically compared. Results Fifteen community pharmacists participated in the study. All expressed a positive attitude toward DRP management, mentioning advantages such as gaining the patient's loyalty as a client and avoiding CKD complications. Participants mentioned that patients and physicians generally approve their interventions, but the dynamics of these relationships may vary depending on the DRP. Common barriers in the management of the three DRPs were the pharmacists' limited time and heavy workloads. The pharmacists felt that the main disadvantage is that these interventions interrupt the workflow in the pharmacy. Conclusion Community pharmacists hold positive views of their interventions in CKD. However, enhancing community pharmacists' involvement in CKD care may require measures to facilitate pharmacists' proactivity, inter-professional collaboration and a work organization adapted to clinical activities.

"Siete millones de personas mueren al año por cáncer relacionado con la contaminación ambiental. El polvo urbano (PU) contiene partículas < 10 µm que afectan la salud humana. En la Ciudad de México (CDMX) existe sólo un estudio de PU. El objetivo de este estudio fue identificar las zonas de la CDMX con mayor probabilidad de contaminación por metales pesados (MP) en el PU. Se recolectaron 89 muestras de PU y se midió la concentración de MP por fluorescencia de rayos X. El análisis espacial se realizó mediante interpolación con kriging indicador. El porcentaje de la superficie con mayor probabilidad de que los MP superen los límites máximos permitidos (LMP) fueron: Cr (LMP 280 mg/kg), 0.55 %, suroeste; Cr (LMP 64 mg/kg), 89 %, toda la CDMX y la mayoría de las áreas conurbadas (AC); Cu, 17 %, 11 delegaciones y AC del norte; Ni, 13 %, centro y suroeste; Pb (LMP 140 mg/kg), 17.5 %, delegaciones céntricas y AC del noroeste; Pb (LMP 400 mg/kg), 2.2 %, delegaciones céntricas y AC del noroeste; V, 26 %, delegaciones céntricas y del sur, así como AC del noreste; Zn, 21 %, delegaciones céntricas y AC del norte. Los elementos con mayor número de sitios y superficie contaminada son: Cr, Zn, Cu y Pb. Los sitios con mayor superficie de sobreposición de MP son aquellos con asociaciones entre Cu y Zn (15 %), y Cu y Pb (13 %). Las delegaciones Cuauhtémoc, Venustiano Carranza y Gustavo A. Madero son las más contaminadas con metales pesados."

This study presents the synthesis and physicochemical characterization of functionalized carbon-based materials prepared from cassava residues (Manihot esculenta). Cassava residues were obtained from a local market, washed, dried and ground to small particle size. This powder was mixed with different aqueous media: diluted sulfuric acid (0.2 M), nejayote and deionized water. These mixtures were treated in an autoclave at 200 °C for 4 h. The physicochemical characteristics of samples were studied by SEM, TGA, FTIR, XPS and elemental analysis. The chemical composition of C:O was similar among groups, but TGA suggested that the hydrochar prepared with sulphuric acid presented a better thermal stability, with a decomposition peak at 435 °C, which was 80 °C higher than samples prepared with deionized water. The acid sample also had lower mass loss (47.3%). The SEM images showed that sulphuric acid promoted the formation of small needle-like structures, while samples prepared using nejayote and water showed agglomerates with a few spherical shapes. The proximate analysis indicated that there was a carbon enrichment from 41% from the original sample to 62% after the hydrothermal process.

In this work, a pH-responsive drug-carrier based on chitosan-silica nanospheres was developed as a carrier for Albendazole (ABZ), a poorly water-soluble anthelmintic drug. Spherical silica nanoparticles were obtained by Stöber method and further etched to obtain mesoporous particles with sizes ranging from 350 to 400 nm. The specific BET area of nanoparticles increased from 15 m2/g to 150 m2/g for etched silica, which also exhibited a uniform pore size distribution. X-ray powder diffraction showed the presence of amorphous phase of silica and a low-intensity peak attributed to ABZ for the drug-loaded nanoparticles. A uniform layer of chitosan was obtained ranging from 10 to 15 nm in thickness due to the small concentration of chitosan used (0.45 mg of chitosan/mg of SiO2). The in vitro evaluation of hybrid nanoparticles was performed using four cervical cancer cell lines CaSki, HeLa, SiHa and C33A, showing a significant reduction in cell proliferation (&gt, 85%) after 72 h. Therefore, we confirmed the encapsulation and bioavailability of the drug, which was released in a controlled way, and the presence of chitosan delayed the release, which could be of interest for the development of prolonged release drug delivery systems.

Objectives Polymedication and medication hoarding in patients’ homes may increase the risk of drug-related problems (DRPs). Community pharmacists can prevent DRPs through medication reconciliation and review. This study aims to (1) develop a tool for community pharmacists to perform domiciliary medication review (ReMeDo) and (2) assess the interrater and test–retest reliability and acceptability of the tool. Methods The ReMeDo tool was first developed 6 years before this study to perform medication review during pharmacist home visits. A literature review was performed to update the content of the existing tool. Ten pharmacy students participated in the assessment of the interrater and test–retest reliability using three vignettes based on former ReMeDo patients. Test–retest reliability coefficients were calculated for the entire tool and each segment. Global and individual interrater reliability coefficients were also computed. Acceptability was assessed through a satisfaction survey. Key findings The ReMeDo tool was structured to guide the collection of information before, during and after the pharmacist home visit. The global kappa coefficients for interrater and test–retest reliability were 0.70 (95% confidence interval (CI), 0.67 to 0.73) and 0.71 (95% CI, 0.68 to 0.74), respectively. The test–retest reliability coefficients for each segment and the interrater reliability coefficients for participants were higher than 0.60 (except for one participant), demonstrating a moderate to substantial level of agreement. The tool was deemed acceptable by participants. Conclusions The ReMeDo tool proved to be reliable and acceptable for use by community pharmacists to perform medication review in patients’ homes.

The funerary rites of particular members of the pre-Hispanic Mayan society included the pigmentation of the corpse with a red color. In order to understand this ritual, it is first necessary to identify the constituents of the pigment mixture and then, based on its properties, analyze the possible form and moment of application. In the present approach, 1H-NMR analysis was carried to detect organic components in the funerary pigments of Xcambó, a small Maya settlement in the Yucatan Peninsula. The comparison of the spectra belonging to the pigment found in the bone remains of seven individuals, and those from natural materials, led to the identification of beeswax and an abietane resin as constituents of the pigment, thus conferring it agglutinant and aromatic properties, respectively. The 1H-NMR analysis also allowed to rule out the presence of copal, a resin found in the pigment cover from paramount chiefs from the Mayan society. Additionally, a protocol for the extraction of the organic fraction from the bone segment without visible signs of analysis was developed, thus broadening the techniques available to investigate these valuable samples.

Ruminants are the main source of methane emissions from the agricultural sector. Emission inventories and mitigation strategies require reliable technics of measurement. The respiration chamber methodology is a precise approach for measuring enteric methane emissions in cattle. A set of experiments was carried out to validate two respiration chambers for measuring enteric methane emissions of cattle. The chambers were calibrated considering three main components: the methane analyzer, the air duct and air extraction system, and the chamber itself, by evaluating linearity and response time of the analyzer, plateau variability and high purity methane recoveries in chambers. Recovery test calculations carried out after releasing high purity methane into the chambers gave calibration factors of 0.95 ± 0.05 and 1.03 ± 0.03 for the complete system of respirations chambers one and two, respectively, with corresponding uncertainties of 4.87 and 2.49%. Thus, the respiration chambers for enteric methane measurements of cattle at the University of Yucatan, Mexico function with precision and accuracy. This technique can be used to establish methane inventories and methane mitigation strategies in cattle.

El objetivo fue la evaluación del color como técnica rápida para la identificación de muestras de suelos urbanos contaminados con metales pesados en la Ciudad de México. Las concentraciones de los metales pesados se midieron por fluorescencia de rayos X, y el color se determinó con las tablas Munsell y con un colorímetro. A partir de los valores Hue, Value y Croma se formaron cinco grupos de suelo por color: I, Café rojizo oscuro, 5YR 4/2; II, Gris oscuro, 7.5YR 4/1; III, Gris olivo, 5Y 5/2; IV, Gris, 5YR 5/1; V, Gris rosáceo, 7.5YR 6/2. Con los valores colorimétricos en el sistema Rojo, Verde y Azul (RGB) se calcularon tres índices de color: Índice Hue, Índice de Rojez e Índice de saturación. La validación de los grupos de suelo formados con las tablas Munsell fue mayor con los índices de color que con los metales pesados. Los grupos de muestras de suelo urbano I y II de colores oscuros tuvieron las concentraciones mayores del Cr, Cu, Pb, Zn; también tuvieron los más altos porcentajes de Fe2O3, MnO, y TiO2. Por el contrario, los grupos IV y V con colores claros tuvieron los porcentajes mayores de Al2O3, MgO y SiO2. El grupo III tuvo valores intermedios de Cr, Cu, Pb, Zn, Fe2O3, MnO, y TiO2. Por primera vez se reporta que el color del suelo urbano de la Ciudad de México puede ser utilizado como técnica de análisis rápido para la identificación de sitios contaminados con metales pesados.

Zn is an essential trace metal in living beings. However, excessive concentrations can cause toxic effects even in the aquatic biota. Zn is widely used in different industrial sectors, which has increased its presence in aquatic environments. To assess the acute toxicity of Zn, bioassays were performed with the fish Gambusia sexradiata for a 96-h exposure using ZnCl

This report presents the results of a research project that analyzes the feasibility of learning from experiences of the Kenyan productive peasant developments in farming insect for animal feed to develop insect farming in Colombia, specifically to foster the current reincorporation process of ex-insurgents. The research, carried out by scientists from the Universidad Nacional de Colombia and Wageningen University & Research, develops an initial stage of knowledge exchange among countries of the global south. With a qualitative/quantitative methodology, the research employs documental analysis and focus groups to identify current features of the ex-insurgent population. The document highlights the conditions, suggested by ex-insurgent population, under which a similar project might be developed and presents some recommendations for a further implementation of a project in Colombia that is inspired by the experiences in Kenya. Dit rapport presenteert de resultaten van een onderzoeksproject naar de mogelijkheid om de ervaringen opgedaan in Kenya met het ontwikkelen van insectenproductie voor veevoer in samenwerking met locale boeren te benutten om insectenproductie in Colombia te initiëren. In dit project is specifiek de nadruk gelegd op de mogelijkheden van insectenproductie voor veevoer om de reïntegratie van exopstandelingen te bevorderen. Het onderzoek, uitgevoerd door onderzoekers van de Universidad Nacional de Colombia en Wageningen University & Research, heeft de eerste fase ontwikkeld van kennisuitwisseling tussen landen uit het zuiden. Met een kwalitatief-kwantitatieve methodologie gebruikt het project een analyse van documenten en interactie met focusgroepen om de huidige karakteristieken van de ex-opstandelingenpopulatie te identificeren. Dit rapport richt zich met name op de voorwaarden, benoemd door de ex-opstandelingen, waaronder zo’n project zou kunnen worden ontwikkeld en presenteert aanbevelingen voor verdere implementatie van een project in Colombia dat is geïnspireerd door de ervaringen in Kenya.