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Objetivo: Describir las aptitudes físicas en niños futbolistas entre los siete a 11 años. Metodología: Estudio descriptivo con 41 participantes seleccionados de forma no probabilística. La fuerza, resistencia, velocidad y flexibilidad fueron medidas. Resultados: A los siete años, el 66.6 % se encuentra entre el percentil (P) P50 y P97 en la flexibilidad; en la resistencia, entre el P50 y P75; mientras que la prueba de velocidad de reacción obtuvo un bajo desempeño (66.6 %). En los ocho años, se clasificó entre el P50 y P97 en las pruebas de lanzamiento atrás y lanzamiento horizontal, pero en la prueba de velocidad de 20 m el 66 % fue pobre. Un 75 % de los deportistas de nueve años, en la prueba de velocidad, se encuentran en un P menor a 25; en contraste, en la flexibilidad, el 50 % fue bueno. En la velocidad de reacción, los niños de 10 años están entre el P75 y P97, con un 46.6 %, mientras que en la resistencia el 66.6 % fue pobre. Los niños de 11 años, en las pruebas de salto horizontal y velocidad de 20 m, fueron extremadamente buenos. Al analizar la resistencia y flexibilidad no se encontraron diferencias significativas (p > .05). Por el contrario, entre la velocidad máxima, velocidad de reacción y fuerza explosiva hubo diferencias estadísticas (p < .05) al comparar entre las edades. Conclusiones: El desempeño mejora a medida que aumenta la edad, sin incluir la prueba de velocidad de 20 m y la resistencia en 1000 m, que tuvieron una relación inversa a la edad. Abstract. Objective: To describe the physical aptitudes in children between seven and 11 years. Methods: Descriptive cross-sectional design with 41 participants selected in a non-probabilistic way. Strength, endurance, speed, and flexibility were measured. Results: At the age of seven, 66.6% are between the 50th and 97th percentile in flexibility; endurance the same amount between the 50th and 75th percentile, while the reaction speed test obtained a low performance in 66.6%. At the age of 8 years 66% were classified between the 50th and 97th percentile in the back throw and horizontal throw tests, but in the 20 m speed test 66% were poor. 75% of the nine-year-old participants in a lower than 25th percentile for speed, in contrast to flexibility, 50% were good. In reaction speed, 10-year-old children are between the 75th and 97th percentile with 46.6%, while in endurance, 66.6% was poor. The 11-year-olds in the horizontal jump and 20-meter sprint tests were extremely good (44%) and good (55.5%). When analyzing endurance and flexibility, no statistically significant differences were found (p > .05) between the seven and 11 years. While the aptitudes of maximum speed, reaction speed, strength and explosive strength, there were statistically significant differences (p < .05) when comparing the ages. Conclusions: Performance improves as age increases, not including the 20 m speed test and the 1000 m endurance which was inversely related to age.

Herein, we report an efficient metal-free system for the transfer hydrogenation of esters and carbonates with ammonia borane as hydrogen donor, by-passing the otherwise ubiquitous formation of transesterification side-products.

The utilization and valorization of agricultural waste is a key strategy for the implementation of a sustainable economy to lessen the environmental footprint of human activities on Earth. This work describes the use of rice husk (RH) from agricultural waste to prepare a highly active catalyst for the reduction of nitro compounds. RH was impregnated with various cobalt complexes bearing N-donor ligands, then pyrolyzed and the resulting composite was etched with a base to remove the silica domains. The composition and morphology of the prepared materials were investigated by IR, AAS, ICP-OES, XRD, BET, XPS and SEM technics. The material showed excellent activity and selectivity in the hydrogenation of nitro groups in aromatic and aliphatic substrates. A remarkable selectivity towards nitro groups was found in the presence of various reactive functionalities, including halogens, carbonyls, borates, and nitriles. Apart from their excellent activity and selectivity, these catalysts showed remarkable stability, allowing their easy recovery and multiple reuse without requiring re-activation.

El objetivo de este análisis es determinar la responsabilidad con la verdad que deben tener los periodistas. Esta investigación cobra relevancia en un contexto de posverdad, en el cual circulan fugaz y masivamente noticias falsas. La metodología aplicada fue la línea jurisprudencial. Así se pudo establecer que la Corte Constitucional colombiana considera que los reporteros tienen la obligación de mostrar diligencia en sus pesquisas.

Herein, we report an efficient metal-free system for the transfer hydrogenation of esters and carbonates by-passing the otherwise ubiquitous formation of transesterification side-products. The Lewis acid B(C

Objetivo: caracterizar desde el punto de vista microbiológico las infecciones periprotesicas (IP) de los pacientes sometidos a remplazo articular de rodilla o cadera, en la IPS universitaria Clínica León XIII, y evidenciar los patrones más comunes de resistencia a los antibióticos, en el periodo 2015-2018. Metodología: se recolectó información de 25 pacientes llevados a remplazo articular de rodilla o cadera en la IPS universitaria, sede Clínica León XIII, durante el periodo de 2015-2018, que desarrollaron IP. Se obtuvo información sobre características demográfica, clínicas y patrones de resistencia (según antibiograma), y sobre los criterios usados para diagnosticarla. Los datos se registraron, según la naturaleza y distribución de la variable, en medias o medianas para las variables cuantitativas, y en frecuencias para las cualitativas. Resultados: entre 2015 y 2018 se realizaron 541 remplazos articulares, la incidencia de infección periprotésica fue de 4.6% (25 pacientes), 22 casos (88%) con crecimiento microbiológico. El germen más frecuente fue el S. aureus, con patrón alto de resistencia para meticilina (SAMR), en el 44%. Seguido por K. pneumoniae, con un patrón de resistencia por producción de betalactamasas de espectro extendido (BLEE) de 83%. Ninguno tuvo resistencia a los carbapenémicos. Conclusiones: los resultados son similares a los reportados en la literatura internacional. Sigue siendo el S. aureus el principal causante de la infección periprotésica, seguido de los gérmenes gram negativos.

Reactions that form C–C bonds are at the heart of many important transformations, both in industry and in academia. From the myriad of catalytic approaches to achieve such transformations, those relying on C–H functionalization are gaining increasing interest due to their inherent sustainable nature. In this short review, we showcase the most recent advances in the field of C–C bond formation via C–H functionalization, but focusing only on those methodologies relying on copper catalysts. This coinage metal has gained increased popularity in recent years, not only because it is cheaper and more abundant than precious metals, but also thanks to its rich and versatile chemistry.1 Introduction2 Cross-Dehydrogenative Coupling under Thermal Conditions2.1 C(sp3)–C(sp3) Bond Formation2.2 C(sp3)–C(sp2) Bond Formation2.3 C(sp2)–C(sp2) Bond Formation2.4 C(sp3)–C(sp) Bond Formation3 Cross-Dehydrogenative Coupling under Photochemical Conditions3.1 C(sp3)–C(sp3) Bond Formation3.2 C(sp3)–C(sp2) and C(sp3)–C(sp) Bond Formation4 Conclusion and Perspective

Furanic di-carboxylate derivatives of 5-Hydroxymethylfurfural (HMF) are nowadays important in the polymer industry as they are used as building blocks for bio-based polyesters. The high reactivity of HMF compels to avoid harsh synthetic conditions. Therefore, developing mild catalytic processes for its selective oxidation is a challenging task. Herein, we report the first oxidative esterification of HMF to dimethyl furan-2,5-dicarboxylate (FDCM) under flow conditions using oxygen as oxidant. For that purpose, a new series of nitrogen-doped carbon-supported bimetallic Co/Ru heterogeneous catalysts were prepared and characterized by XRD, XPS and N2 physisorption. These analyses revealed that the porosity of the materials and order of impregnation of the metals to the carbon supports lead to varying catalytic activities. Under optimized conditions the flow reactor showed a 15-fold increase on the production of FDCM compared to batch conditions. �� 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

A convenient method for the hydrogenative depolymerization of silicon-modified polyureas was developed using simple transition metal catalysis. The method is considered sustainable, as it uses H2 as a clean reductant and allows for silicon recycling.

A series of hybrid porous polymers (HPPs) based on polyhedral oligomeric silsesquioxane (POSS) were synthesized, characterized, and successfully used as metal-free heterogeneous photocatalysts for cross-dehydrogenative coupling reactions (CDC), for which the aza-Henry coupling of tetrahydroisoquinolines and nitroalkanes was studied as the model reaction. The reactions run smoothly at room temperature under visible (blue) light irradiation using gaseous oxygen as an oxidant under atmospheric pressure. These novel metal-free heterogeneous photocatalysts can be readily recovered and reused without a significant loss of reactivity. Mechanistic investigations revealed the intermediacy of 1O2, obtained from 3O2 sensitization (energy transfer) by the photoexcited catalyst.

Catalytic allylation reactions are important methodologies to introduce the versatile allyl functionality into molecules to produce fine chemicals and synthetic building blocks. Since the first reports by Tsuji and Trost, many improvements on allylation technologies have been reported. The introduction of photocatalytic techniques marked one of the major breakthroughs in this field, complementing the existing thermal chemo-catalyzed protocols, providing high selectivity under milder conditions. This review discloses state-of-the-art photocatalyzed allylation methodologies, their reaction mechanisms, and synthetic applications. The reactions are classified according to the employed catalysts, namely single photocatalyst and dual-catalytic approaches. Finally, each methodology is individually presented and evaluated based on the performance of the reaction.

Silicones and silicone rubbers are ubiquitous in our daily lives, being used in a broad range of applications ranging from consumer products and adhesives to medicinal and electronic devices. The chemistry and synthesis of these versatile materials have been reviewed so many times that it is difficult to have a comprehensive overview. Hence, with this tutorial review we aim to provide a concise account of the most important reactions and industrial processes to furnish silicones, focusing specially on reactive silicones, specifically in telechelic OH-terminated polysiloxanes, which represent one of the most relevant members of this important materials family.

C.Li thanks the Prof. & Mrs Purdie Bequests Scholarship and AstraZeneca PhD Studentship. A family of six structurally related heteroleptic copper(I) complexes of the form of [Cu(N^N)(P^P)]+ bearing a 2,9-dimethyl-1,10-phenanthroline diimine (N^N) ligand and a series of electronically tunable xantphos (P^P) ligands have been synthesized and their optoelectronic properties characterized. The reactivity of these complexes in the copper-photocatalyzed Aza-Henry reaction of N-Phenyltetrahydroisoquinoline was evaluated, while the related excited state kinetics were comprehensively studied. By subtlety changing the electron-donating properties of the P^P ligands with neglegible structural differences, we could tailor the photoredox properties and relate it to their reactivity. Moreover, depending on the exited-state redox potential of the catalysts, the preferred mechanism can shift between reductive quenching, energy transfer and oxidative quenching pathways. A combined study of structural modulation of copper(I) photocatalysts, optoelectronic properties and photocatalytic reactivity resulted in a clearer understanding of both the rational design of the photocatalyst and the complexity of competing photoinduced electron and energy transfer mechanisms. Publisher PDF

An efficient, novel photocatalyzed allylic-alkynylation methodology via copper-based cross-dehydrogenative coupling (CDC) is described. Different types of 1,4-enyne compounds were synthesized in one step at room temperature using copper(I) terpyridyl complex as photocatalyst/initiator. This procedure is an improvement and to some extent complementary to previously reported thermal CDC methods. Preliminary investigations on the reaction mechanism are also presented.

Herein we re-evaluate the synthesis of Poly(e-caprolactone) (PCL) by ring-opening polymerization (ROP) using simple dialkylmagnesium compounds as catalysts. This old reaction has been never studied thoroughly before and a consensus on the intervening mechanism is lacking, being an anionic pathway proposed in the classic literature. In our hands, all tested catalysts exhibit high efficiency and complete conversion was achieved within a few hours with high yield and high number-average molecular weight (Mn) in a living fashion. Moreover, kinetic studies revealed that the ROP of e-CL has a first order dependency on monomer (e-CL) as well as catalyst concentration. Furthermore, mechanistic studies of the ROP demonstrated that the reaction follows a coordination-insertion mechanism where the alkyl group initiates the polymerization and is incorporated as one of the terminal groups in the polymer chain.

The development of strategies for the sustainable management and valorization of agricultural waste is of outmost importance. With this in mind, we report the use of rice husk (RH) as feedstock for the preparation of heterogeneous catalysts for hydrogenation reactions. The catalysts were prepared by impregnating the milled RH with a silver nitrate solution followed by carbothermal reduction. The composition and morphology of the prepared catalysts were fully assessed by IR, AAS, ICP-MS, XPS, XRD and STEM techniques. This novel bio-genic silver-based catalysts showed excellent activity and remarkable selectivity in the hydrogenation of nitro groups in both aromatic and aliphatic substrates, even in the presence of reactive functionalities like halogens, carbonyls, borate esters or nitriles. Recycling experiments showed that the catalysts can be easily recovered and reused multiple times without significant drop in performance and without requiring re-activation. © 2021 The Authors. ChemCatChem published by Wiley-VCH GmbH

Herein we report the synthesis of isotactically enriched poly(cyclohexene carbonate) (PCHC) by the bulk alternating copolymerization of meso-cyclohexene oxide and carbon dioxide using dialkylmagnesium compounds as catalyst. These simple achiral catalysts showed good activity for the isoselective copolymerization, with high yield and high carbonate-linkage contents, in a controlled manner under mild conditions and atmospheric CO2 pressure. The triad sequences in the 13C NMR spectra of these polymers were assigned using Bernoullian statistical methods in order to determine the tacticity of the copolymer. Differential scanning calorimetry analysis confirmed the formation of highly isotactic polycarbonate. Furthermore, kinetic studies and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry investigations allowed us to shed light on the reaction mechanism of the polymerization process.

Hypervalent iodine (III) five-membered heterocycles have found broad application as atom-transfer reagents for organic synthesis. Among them, 1-Phenyl-1,2-benziodoxol-3-(1H)-one is known as a traditional benzyne precursor, but no further synthetic applications have been reported. Herein, we report the first synthetic application of 1-phenylbenzidoxole to the synthesis of Phthalides using only CuI as catalyst. High selectivity and yield were achieved under mild reaction conditions with good functional group tolerance. During our investigations, the efficiency of different CuI and CuII catalysts under various reaction conditions were studied. The nature of the leaving group, the substituents on the substrate and temperature, play an important role on both yield and selectivity. Moreover, a plausible mechanistic pathway for this transformation was proposed based on our observations and previous literature reports.

An efficient and green synthetic method for the preparation of N,N-disubstituted tetramethylpyrazinium radical cations was developed, which does not require any solvent or strong alkylating agents. The investigation by UV/Vis and electron paramagnetic resonance (EPR) spectroscopy proved the stability of the prepared radical cation. Moreover, it was shown for the first time that the prepared N,N-disubstituted tetramethylpyrazine can act as a powerful metal-free catalyst for the selective oxidative homocoupling of amines to the corresponding imines under solvent-free conditions. Furthermore, oxygen or even air can be employed as an efficient oxidative reagent.

This Focus Review describes state-of-the-art methods for the preparation of antimicrobial silicones. Given the diversity of antimicrobial activity and their mechanisms, the performance of these materials is highly dependent on the characteristics of the polymeric matrix. Therefore, different synthetic routes have been developed, such as 1) physical treatments, 2) chemical transformations, and 3) copolymerization. This classification is not exclusive, so some products belong to more than one class. Herein, we attempt to present a handy overview of the development of antimicrobial silicones, their most important application fields, the most relevant antimicrobial assays, and, as the title suggests, an overview of the most relevant preparation methods.

Introduction: Circular polarization antennas (CPA) are able to reduce the “Faraday rotation” effect due to the ionosphere, which causes a significant power losses compared to the case of using linear polarization antennas (LPA) [1]-[2]. Therefore, these antennas are widely used for space telemetry applications of satellites, space probes and ballistic missiles among others [2]. Furthermore, suspended plate antennas (SPA) offer the possibility to obtain largest levels of maximum gain and impedance bandwidth compared to those obtained with conventional technologies. Likewise, it is useful to be able to select the most appropriate sense of rotation, depending on the propagation conditions in the up/down links. Objective: To design a CPA with configurable sense of rotation for small satellite applications, using SPA technology, such that it has gain and bandwidth levels higher than those obtained with conventional technologies. Method: The antenna design is based on models proposed in the literature, through which an initial geometry consisting of a suspended patch with an L-shaped feeder and a hybrid coupler is designed. Subsequently, geometry optimization by parametric analysis is carried out with appropriate electromagnetic simulators. Results: The proposed design has an impedance bandwidth of 34.39% and a maximum gain of 8.75 dBi at a frequency of 2.35GHz. Conclusions: The L-shaped feeder technique for suspended patches improves the behavior of the antenna in axial ratio, impedance and maximal gain.

5-Hydroxymethylfurfural (HMF) has become a benchmark chemical as it can be obtained by the processing of renewable biomass, making its downstream modification an important topic both in industry an...

Due to the richness of the field of cross-dehydrogenative coupling reactions and the plethora of applications toward the synthesis and derivatization of heterocyclic molecules, there is an increasing amount of synthetic methodologies which spread across different catalytic fields and hence, yield to a huge variety of operating mechanisms. Although all the pathways follow the same underlying principles, they can be easily differentiated according to the type of activation (thermal of photocatalyzed) and the type of catalyst (metallic or metal-free). In this account, we have summarized the most recent and relevant examples under the aforementioned categories, focusing especially on those presenting the most compelling and better understood mechanisms.

Phenazine radical cations (PhRCs) were used for the first time as efficient metal-free catalysts for the oxidative homo- and cross-coupling of a variety of different amines. A series of functional PhRCs were prepared, characterized with X-ray diffraction, and their radical character was investigated with DFT calculations. They were tested as catalysts under neat conditions with low oxygen pressure to prepare homo- and cross-coupled aliphatic and aromatic imines in high yields. Although all synthesized phenazines were catalytically active, the highest reaction rates and the best selectivity were achieved using the 5,10-dihydro-5,10-dimethylphenazine radical cation. By means of fluorescence, UV-vis and EPR spectroscopy, a mechanism of the oxidative amine coupling, catalyzed by PhRCs, is proposed.

C-H bond functionalization is a well-developed concept that has been thoroughly studied and gives entry to rather complex molecules without the need for previous derivatization of the substrates. The use of copper complexes in allylic C-H bond functionalization under oxidative conditions as an alternative to the well-established palladium-based methodologies remains largely underdeveloped. Here, we show for the first time a selective cross-dehydrogenative coupling reaction between underivatized allylic substrates and terminal alkynes to produce 1,4-enynes in high yields in a single step, using an in situ synthesized copper catalyst and an oxidant.

La anomia en la novela de crímenes en Colombia propone una teoría de esta clase de novela de los últimos tiempos que sigue la tradición occidental instaurada en Europa y los Estados Unidos y que se ocupa, ante todo, de indagar en torno al sentido del crimen en las sociedades contemporáneas.

Silicones and silicone rubbers are omnipresent in household and industrial products such as lubricants, coatings, sealants, insulators, medical devices, etc. This plethora of applications arises from their unparalleled properties including hydrophobicity, low surface energy, chemical inertness, extreme temperature stability, elasticity, and biocompatibility. Even though silicones have been known for more than five decades, their chemistry is still far from fully understood. Industrially, the vast majority of processes for their synthesis, transformation, and use are based on rather well established, alas outdated technologies, which are frequently empirical and poorly investigated. This review attempts to summarize the different approaches for the synthesis of silicone rubbers by vulcanization or curing of silicone polymers, the catalysts used, and the corresponding reaction mechanisms. Apart from the well-known methods (radical, hydrosilylation, and metal-based condensation), novel approaches such as organo- and bio-catalysis are also addressed.

Investigations on synthesis of cyanopropyl-functionalized poly(dimethyl-co-methylhydro)siloxane were done to determine the correlation between conversion of SiH groups and further parameters such as nature of reactants, catalyst, stoichiometry and reaction temperature. A study on the kinetics of hydrosilylation with various siloxane starting materials and allyl cyanide were carried out between 60 and 80 °C showing that the overall reaction with polymeric siloxanes was of the second-order. Converselly, small cyclosiloxanes show first reaction order dependence. Furthermore, a two-phase kinetic behavior on the hydrosilylation reaction was observed, most likely due to catalysts deactivation.