RESUMEN
The solvothermal synthesis of metal-organic frameworks (MOFs) often proceeds through competing crystallization pathways, and only partial control over the crystal nucleation and growth rates is possible. It challenges the use of MOFs as functional devices in free-space optics, where bulk single crystals of millimeter dimensions and high optical quality are needed. We develop a synthetic protocol to control the solvothermal growth of the MOF [Zn(3-ptz)2] n (MIRO-101), to obtain large single crystals with projected surface areas of up to 25 mm2 in 24 h, in a single reaction with in situ ligand formation. No additional cooling and growth steps are necessary. We propose a viable reaction mechanism for the formation of MIRO-101 crystals under acidic conditions, by isolating intermediate crystal structures that directly connect with the target MOF and reversibly interconverting between them. We also study the nucleation and growth kinetics of MIRO-101 using ex situ crystal image analysis. The synthesis parameters that control the size and morphology of our target MOF crystal are discussed. Our work deepens our understanding of MOF growth processes in solution and demonstrates the possibility of building MOF-based devices for future applications in optics.
RESUMEN
Resumen El virus Sars-Cov-2 ha provocado inevitablemente la enfermedad Covid-19. Ha sido una de las peores noticias que le ha acontecido a la humanidad en estos duros inicios del siglo XXI. Los daños materiales y pérdidas de vidas humanas han sido significativos, así como los efectos colaterales desde el punto de vista social y psicológico. En respuesta a contener o contrarrestar estas elevadas afectaciones, diversas áreas del saber y de la actividad humana se activan, se multiplican y crean nuevas estrategias de mitigación. Una de las áreas que más ha aportado durante los períodos de cuarentena y posteriores a este, es el área de la Cultura Física, el deporte y específicamente la didáctica de la Educación Física. El objetivo de este trabajo es realizar una sistematización sobre un grupo de publicaciones científicas referidas a la actividad física, el deporte y la Educación Física en tiempos de COVID, enfocadas en el entorno virtual y el empleo de las TICs. Con este estudio, se pretende realizar un análisis sobre las principales posiciones de los autores en función de obtener un criterio sobre las potencialidades de la Educación Física virtual para enfrentar los embates de la COVID-19. Unido a esta periodización se añadirá un grupo de recomendaciones metodológicas dirigidas a perfeccionar el trabajo del docente de Educación Física con el empleo de las Tics en estos momentos excepcionales que atraviesa la humanidad.
Resumo O vírus Sars-Cov-2 levou inevitavelmente à doença de Covid-19. Tem sido uma das piores notícias que tem acontecido à humanidade nestes duros começos do século XXI. Os danos materiais e a perda de vidas humanas têm sido significativos, bem como os efeitos colaterais do ponto de vista social e psicológico. Em resposta a conter ou contrariar estes elevados impactos, várias áreas do conhecimento e da atividade humana são ativadas, multiplicando-se e criando novas estratégias de mitigação. Uma das áreas que mais contribuiu durante os períodos de quarentena e pós quarentena foi a área da Cultura Física, desporto e especificamente o ensino da Educação Física. O objetivo deste trabalho é sistematizar um grupo de publicações científicas relacionadas com a atividade física, desporto e Educação Física no tempo da COVID, centrando-se no ambiente virtual e na utilização das TIC. O objetivo deste estudo é analisar as principais posições dos autores a fim de obter um critério sobre o potencial da Educação Física virtual para enfrentar os ataques da COVID-19. Juntamente com esta periodização, será acrescentado um grupo de recomendações metodológicas, destinadas a aperfeiçoar o trabalho do professor de Educação Física com a utilização das TIC nestes momentos excepcionais que a humanidade está a atravessar.
Abstract The Sars-Cov-2 virus has inevitably caused the Covid-19 disease. It has been one of the worst news that has happened to humanity at the beginning of the 21st century. The material damage and loss of human life has been significant, as well as the collateral effects from the social and psychological point of view. In response to contain or counteract these high affectations, various areas of knowledge and human activity are activated, multiplying and creating new mitigation strategies. One of the areas that has contributed the most during the quarantine periods and after it, is the area of Physical Culture, sports and specifically the didactics of Physical Education. The aim of this work is to systematize a group of scientific publications referred to physical activity, sport and Physical Education in times of COVID, focused on the virtual environment and the use of ICTs. With this study, it is intended to carry out an analysis of the main positions of the authors in order to obtain a criterion about the potentialities of virtual Physical Education to face the COVID-19 attacks. Together with this periodization, a group of methodological recommendations will be added, aimed at perfecting the work of Physical Education teachers with the use of ICTs in these exceptional moments that humanity is going through.
RESUMEN
We describe the structure and properties of [Zn(C6H4N5)N3] n , a new nonporous three-dimensional high-energy metal-organic framework (HE-MOF) with enhanced thermal stability. The compound is synthesized by the hydrothermal method with in situ ligand formation under controlled pH and characterized using single-crystal X-ray diffraction, elemental analysis, and Fourier transform infrared. The measured detonation temperature (T det = 345 °C) and heat of detonation (ΔH det = -0.380 kcal/g) compare well with commercial explosives and other nitrogen-rich HE-MOFs. The velocity and pressure of denotation are 5.96 km/s and 9.56 GPa, respectively. Differential scanning calorimetry analysis shows that the denotation of [Zn(C6H4N5)N3] n occurs via a complex temperature-dependent mechanism.
RESUMEN
Hexa-aqua-zinc(II) dinitrate 5-(pyridinium-3-yl)tetra-zol-1-ide, [Zn(H2O)6](NO3)2·2C6H5N5, crystallizes in the space group P . The asymmetric unit contains one zwitterionic 5-(pyridinium-3-yl)tetra-zol-1-ide mol-ecule, one NO3- anion and one half of a [Zn(H2O)6]2+ cation ( symmetry). The pyridinium and tetra-zolide rings in the zwitterion are nearly coplanar, with a dihedral angle of 5.4â (2)°. Several O-Hâ¯N and N-Hâ¯O hydrogen-bonding inter-actions exist between the [Zn(H2O)6]2+ cation and the N atoms of the tetra-zolide ring, and between the nitrate anions and the N-H groups of the pyridinium ring, respectively, giving rise to a three-dimensional network. The 5-(pyridinium-3-yl)tetra-zol-1-ide mol-ecules show parallel-displaced π-π stacking inter-actions; the centroid-centroid distance between adjacent tetra-zolide rings is 3.6298â (6)â Å and that between the pyridinium and tetra-zolide rings is 3.6120â (5)â Å.
RESUMEN
We report the synthesis and structural diversity of Zn(II) metal-organic framework (MOF) with in situ formation of tetrazole ligand 3-ptz [3-ptz = 5-(3-pyridyl)tetrazolate] as a function pH. By varying the initial reaction pH, we obtain high-quality crystals of the noncentrosymmetric three-dimensional MOF Zn(3-ptz)2 , mixed phases involving the zinc-aqua complex [Zn(H2O)4(3-ptz)2]·4H2O, and two-dimensional MOF crystals Zn(OH)(3-ptz) with a tunable microrod morphology, keeping reaction time, temperature, and metal-ligand molar ratio constant. Structures are characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV-vis spectroscopy. We discuss the observed structural diversity in terms of the relative abundance of hydroxo-zinc species in solution for different values of pH.
RESUMEN
BACKGROUND: Pneumomediastinum is the presence of free air around mediastinal structures, which may be spontaneous or secondary, and can occur in 10% of patients with blunt chest trauma, with the Macklin effect being its main pathophysiology. CLINICAL CASE: A 21 year old male, hit by motor vehicle, with alvéolopalatal fracture and blunt chest trauma, who, 72 hrs after admission, shows subcutaneous emphysema in the anterior chest. A simple tomography of the chest and abdomen was performed, finding a pneumomediastinum, bilateral pulmonary contusions and pneumoperitoneum. Oesophageal, tracheobronchial or intra-abdominal viscera injuries were ruled out, establishing the cause of pneumomediastinum and pneumoperitoneum due to the Macklin effect. This required conservative management in intensive care unit, with a favourable clinical course and discharged after a 10 day hospital stay. DISCUSSION: Macklin effect is caused by dissection of air medially along the bronchoalveolar sheath (interstitial emphysema), secondary to alveolar breakdown and extending into mediastinal and other anatomical structures (pneumoperitoneum). It has been documented in blunt trauma, as well as in acute asthma, positive pressure ventilation, or after Valsalva manoeuvres. The imaging method of choice is computed tomography, and its characteristic findings, interstitial emphysema adhering to a bronchus and pulmonary blood vessel. CONCLUSIONS: In the presence of pneumomediastinum and pneumoperitoneum is necessary to rule out oesophageal and tracheobronchial injury before establishing the Macklin effect as its cause. The diagnosis is made with computed tomography and managed conservatively.
Asunto(s)
Enfisema Mediastínico/etiología , Neumoperitoneo/etiología , Alveolos Pulmonares/lesiones , Enfisema Subcutáneo/etiología , Traumatismos Torácicos/complicaciones , Heridas no Penetrantes/complicaciones , Accidentes de Tránsito , Aire , Tratamiento Conservador , Cuidados Críticos/métodos , Humanos , Masculino , Enfisema Mediastínico/diagnóstico por imagen , Enfisema Mediastínico/fisiopatología , Neumoperitoneo/diagnóstico por imagen , Neumoperitoneo/fisiopatología , Respiración Artificial , Rotura , Enfisema Subcutáneo/fisiopatología , Traumatismos Torácicos/fisiopatología , Tomografía Computarizada por Rayos X , Heridas no Penetrantes/fisiopatología , Adulto JovenRESUMEN
The effect of high concentrations of sulphate on the reductive decolourisation of different azo dyes by anaerobic sludge was studied in batch cultures. Sludge cultures were pre-incubated under sulphate-reducing conditions prior addition of dyes. Little or no effects of sulphate (5-10 g sulphate l(-1)) on the rate of decolourisation of Reactive Orange 14 (RO14), Direct Blue 53 (DB53) and Direct Blue 71 (DB71) were observed when no external redox mediator was provided. However, an increase in sulphate concentration, in the presence of riboflavin (20 microM), enhanced the decolourisation of all dyes. The first-rate constant of decolourisation (k) was increased up to 2-, 3.6- and 2-fold for RO14, DB53 and DB71, respectively, by supplying high sulphate concentrations, compared to the controls lacking sulphate, in the presence of the redox mediator. Sulphate reduction did not take place during the course of azo reductions, but was only evident before dye addition and after complete decolourisation, suggesting azo dyes reduction out-competed sulphate reduction for the available reducing equivalents. The experimental data suggest that reduction of azo dyes by riboflavin, which had been reduced by biogenic sulphide, was the major mechanism implicated during decolourisations, which was corroborated by abiotic incubations. Riboflavin greatly accelerated the abiotic reduction of RO14, so that the k value was increased up to 44-fold compared to the control lacking riboflavin.