Biochar production from cellulose under reductant atmosphere: influence of the total pyrolysis time.

Today's rising energy costs, coupled with increasing energy demand, make it necessary to search for more efficient energy processes. In recent years, there have been increasing efforts to develop efficient catalysts based on waste-derived char, by a single step where the carbon precursor and the metallic active phase one undergo a single common thermal process under a reductant atmosphere at high temperature. The use of a reductant atmosphere drives the formation of carbonaceous materials with different characteristics than those obtained under the standard nitrogen-inert one. Our work evaluates the influence of the residence time and the heating rate on the physicochemical properties of the biochar obtained. Relatively long residence times and slow heating rates, improve the yield to the resulting biochar, without increasing production cost, making the subsequent char-based metallic catalyst synthesis more efficient. The heating rate was shown to be key in improving the properties of the char in a smoother and more controlled way, unlocking a new working pathway for the efficient design and production of char-based catalysts in a one-pot synthesis.

Accidente cerebrovascular en una Unidad de Cuidados Intensivos Pediátricos. "11años de ACV en UCIP" / Stroke in a Pediatric Intensive Care Unit. "11 years of stroke in the PICU "

Introducción: La incidencia de ACV (Accidente Cerebrovascular) en niños es de 2-13/100.000 niños por año, siendo una de las 10 causas más frecuentes de muerte en la infancia. La misma varía entre 6-40% dependiendo de las series publicadas y de los subtipos de ACV. Existen diferencias importantes entre el ACV en niños y adultos, ya que las características neurológicas y de la hemostasia son muy distintas en cada grupo. En niños deben ser investigados múltiples factores de riesgo que a menudo se superponen entre sí. Materiales y métodos: Trabajo descriptivo retrospectivo por revisión de historias clínicas, de una población de niños con diagnóstico de ACV ingresados en UCIP en un período de 10 años. Resultados: Se confirmó el diagnóstico de ACV en un total de 84 pacientes. El 70,24% de la población correspondía a ACVH (Accidente Cerebrovascular Hemorrágico) y un 29,76% ACVI (Accidente Cerebrovascular Isquémico). El 60,71 % eran masculinos. La mediana del tiempo entre el inicio de los síntomas y el ingreso a UCIP, en ambos grupos fue de 1 día con rango entre 1-17 días para los ACVH y 1-9 para los ACVI. Se evaluaron variables clínicas, de diagnóstico y de tratamiento según ambos tipos de ACV. Conclusión: El ACV requiere de un abordaje multidisciplinario. La realización de neuro-imágenes es un pilar fundamental para el diagnóstico y no debe ser pospuesto. El monitoreo y tratamiento está enfocado en minimizar el daño en el parénquima cerebral circundante (AU)

Introduction: The incidence of stroke in children is 2-13/100,000 children a year, being one of the 10 most common causes of death in childhood. Mortality varies between 6 and 40% depending on the series reported and according to the different subtypes of stroke. There are important differences between childhood and adult stroke, as the neurological features and characteristics of hemostasis vary greatly. In children, multiple risk factors that often overlap should be investigated. Material and methods: A retrospective descriptive review of the clinical records of a series of patients with stroke admitted to the pediatric intensive care unit (PICU) over a period of 10 years was conducted. Results: The diagnosis of stroke was confirmed in 84 patients; 70.24% had hemorrhagic and 29.76% ischemic stroke. Overall, 60.71% were boys. Median time between symptom onset and admission to the PICU was one day in both groups, ranging from 1-17 días for those with hemorrhagic and from 1-9 days for those with ischemic stroke. Clinical, diagnostic, and treatment variables were evaluated for both types of stroke. Conclusion: Stroke requires a multidisciplinary approach. Neuroimaging is essential for the diagnosis and should not be postponed. Monitoring and treatment is focused on minimizing damage to the surrounding brain parenchyma (AU)

Fibrous MnO2 nanoparticles with (2 x 2) tunnel structures. Catalytic activity in the total oxidation of volatile organic compounds.

Manganese oxides having 2 x 2 tunnel structures (cryptomelanes) have been synthesized by a milling method in order to test their efficiency as catalysts for the abatement of volatile organic compounds, using toluene as probe molecule. These materials present excellent textural properties, arising from the nanofiber morphology and were active for toluene total oxidation. DRIFTS of the adsorbed phase allow proposing the role of lattice oxygen in the catalytic reaction.

Apatite and Portland/apatite composite cements obtained using a hydrothermal method for retaining heavy metals.

Apatite and Portland/apatite composite cements containing steelwork dusts have been prepared using a low temperature hydrothermal method (200 degrees C, 48h). The produced solids were characterized by means of XRD, IR, and SEM-EDX, and the remaining liquid was analyzed by ICP. The results clearly show the capability of these cements to inertise the heavy metals contained in steelwork dusts, that is Fe, Pb, Mo, Cr, Mn, Ni, and Zn. In the case of apatitic cements, Fe, Mg, Cr, Mn, and Pb coming from steel dust replaced Ca in the divalent cation position of the apatite structure, while Si and Mo replaced P in tetrahedral position. The average crystal size of the apatite-containing dust is smaller than in pure apatite synthesized using the same procedure, which is related to the magnesium content of the dust, since magnesium seems to inhibit the crystal growth. XRD diagrams of composite cements show only peaks corresponding to phases observed in the single cements, and in that no new phases are found. However, EDX analysis reveals the introduction of cations coming from Portland cement into the apatite structure. From the results of water analysis it could be concluded that the capability of retention is higher in composite matrices than in the pure apatite one. In conclusion, the obtained data allow stating that the proposed method, the hydrothermal synthesis of steelwork dust containing cement, is a reliable one for immobilization of toxic residues containing heavy leachable cations.

Fourier transform infrared spectroscopic study of surface acidity by pyridine adsorption on Mo/ZrO2-SiO2(Al2O3) catalysts.

Acidity of the oxidic molybdenum catalysts supported on mixed ZrO2-SiO2 and ZrO2-Al2O3 carriers was investigated by Fourier transform infrared spectroscopy of pyridine adsorption. Deposition of molybdenum on ZrO2-SiO2 and ZrO2-Al2O3 supports leads to formation of surface Brønsted acid sites. The number of the Brønsted and Lewis acid sites in supported-molybdenum catalysts depends on both the ZrO2 content and the type of the support. With increasing ZrO2 content, the Lewis acid sites increase for both series of catalysts. The Brønsted acid sites are higher for Mo/ZrO2-SiO2 samples compared to those for Mo/ZrO2-Al2O3 and also increase with zirconia.

Synthesis and Characterization of Hydrotalcite-like Compounds Containing V(3+) in the Layers and of Their Calcination Products.

The synthesis and full characterization of a new hydrotalcite-like compound with the formula [Mg(0.71)V(0.29)(OH)(2)](CO(3))(0.145).0.72H(2)O and with V(3+) in the layers are described. The influence of hydrothermal treatment and drying rate on the crystallinity of the materials obtained is discussed. The evolution to mixed oxides upon calcination at different temperatures (448, 548, 773, 1023, and 1273 K) under different atmosphere environments (air or nitrogen) for 2 h has been studied. Characterization of the original layered materials and of the calcination products has been carried out by X-ray diffraction, thermal analysis, Fourier-transform infrared spectroscopy, BET specific surface area determination, temperature-programmed reduction, and transmission electron microscopy. X-ray absorption spectroscopies (XANES and EXAFS) have also been used to assess the local geometry of vanadium ions in the different compounds prepared. All experimental data agree with a well-crystallized hydrotalcite-like compound after thermal treatment, and also a minor effect of the drying rate on the crystallinity has been found. Thermal decomposition yields poorly crystalline layered compound at 448 K that undergoes transformation to mostly amorphous materials when calcined at 548-773 K, finally leading to a mixture of MgO and Mg(3)V(2)O(8), which has increasing crystallinity as the calcination temperature increases. XAS results indicate the presence of V(3+) ions in an octahedral coordination in the parent sample calcined at 448 K and tetrahedrally coordinated V(5+) species for samples calcined at higher temperatures, calcination giving rise to a better ordering of the second coordination sphere. Similar results were found when calcination was performed in nitrogen, although higher temperatures were needed to achieve the same result.

The structural role of the carotenoid in the bacterial light-harvesting protein 2 (LH2) of Rhodonbacter capsulatus. A Fourier transform Raman spectroscopy and circular dichroism study.

In previous work (Zurdo J, Fernández-Cabrera C and Ramírez JM (1993) Biochem J 290: 531-537), it had been shown that selective extraction of the carotenoid from the light-harvesting protein 2 (LH2) of Rhodobacter capsulatus induced the dissociation of 800-nm absorbing bacteriochlorophyll (Bchl), a 10-nm red shift of 854-nm Bchl, and a decrease of the stability of the protein in detergent solution. In the present study, the Fourier transform Raman and near-infrared circular dichroism spectra of native and carotenoid-depleted LH2 membrane preparations were compared. It was found that while the coupled carbonyls of 854-nm Bchl remained specifically H-bonded to the peptides after carotenoid extraction, the optical activity of the near-infrared electronic transition was significantly altered. Given the excitonic origin of such optical activity, our data suggest that carotenoid extraction elicits a rearrengement of the chromophore cluster and of the associated polypeptide subunits. This implies a significant role of the carotenoid in maintaining the native quaternary structure of the protein, which would be consistent with the observed dissociation of 800-nm Bchl and the loss of solubilized LH2 stability that result from carotenoid removal. There is no evidence for a similar role of the carotenoid in the LH1 protein.