Intercalation and dynamics of hydrated Fe2+ in the vermiculites from Santa Olalla and Ojén

Although the intercalation of Fe3+ into layered phyllosicilicates-especially into smectites-attracted much attention in the past two decades, the information about Fe2+ loaded phyllosilicates is sparse. Here we present an investigation of the Fe2+ exchanged vermiculites from Santa Olalla and Ojén (Andalusia, Spain) by means of Mössbauer spectroscopy. The room temperature Mössbauer spectra are very similar to those of the starting compounds (Na forms) except for a decrease of the contribution of structural Fe3+ and a concomitant increase of the contribution of Fe2+ sites, indicating an internal redox process. The extent of this redox reaction is different for the two vermiculites. Thus, the intercalated Fe2+ acts as an electron mediator from the external medium to the structural Fe3+ ions. A new component attributable to intercalated Fe2+ is practically invisible in the room temperature Mössbauer spectra, but increases strongly and continuously during cooling to 4.2 K, where it is the dominant feature of the Mössbauer patterns. At 4.2 K, its quadruple splitting amounts to 3.31 mm/s, which is in excellent agreement with the quadrupole slitting of Fe2+ coordinated to six water molecules in a highly symmetric octahedral arrangement. The strong decrease of the Mössbauer-Lamb factor of this component with increasing temperature indicates a weak bonding of the Fe 2+ in the interlayer space

Nonlinear elasto–plastic performance prediction of materials stabilized with bitumen emulsion in rural road pavements

[Abstract:] This article presents numerical modelling of rural road pavement sections recycled in situ with two materials stabilized with bitumen emulsion. The two materials stabilized with bitumen emulsion are base course materials comprising 25% reclaimed asphalt pavement and 75% natural aggregates with and without 1% cement. A 3D-finite difference model was used to determine the response of these pavement sections when subjected to two types of loads with four types of soil subgrades of varying resistances. A nonlinear elasto–plastic Mohr-Coulomb model was used in the two materials stabilized with bitumen emulsion, and a nonlinear model was adopted in the four soil subgrades. Both the resilient and permanent behaviours of these materials were modelled. An analysis was conducted on rutting and fatigue resistances of the base course materials. The base course material containing 1% cement is more resistant and is apt for use in lightly trafficked rural roads. Both base course materials stabilized with bitumen emulsion will first fail from rutting before fatigue

Mechanical properties and behaviour of in situ materials which are stabilised with bitumen emulsion

[Abstract:] This article presents a critical review of the mechanical properties of in situ materials which are stabilised with bitumen emulsion. A description is provided of the types of materials that are stabilised with bitumen emulsion presently available and different hypotheses about their behaviour and different properties are put forth. The two main categories of mechanical properties investigated in the laboratory by means of mechanical test are addressed: (a) properties similar to those of granular materials in accordance with their stress-dependent behaviour and (b) properties resembling hot mix asphalt materials in accordance with their temperature and time-dependent viscoelastic behaviour. The article concludes with several final remarks on the structural behaviour and mechanical properties of these materials

Modelización numérica en 3D de materiales reciclados en frío in situ con emulsión bituminosa en carreteras de bajo tráfico de la República Sudafricana

Esta XII Jornada tuvo lugar en Madrid, el 30 y 31 de mayo de 2017.[Resumen:] En esta comunicación se hace una modelización numérica de secciones de firme recicladas “in situ” con emulsión asfáltica. Se analizan firmes constituidos por un 25 % de material bituminoso fresado (Reclaimed Asphalt Pavement, RAP) y un 75 % de áridos naturales (capa granular), tanto con un 1 % de cemento como sin él. Se modeliza el comportamiento resiliente y permanente de estos materiales. Se calculan las respuestas del firme bajo una carga de ruedas gemelas, con cuatro tipos de explanadas de diversas características. Se obtiene la ley de variación del módulo resiliente para las cuatro explanadas y para los dos materiales reciclados (con cemento y sin cemento). Se analiza finalmente la deformación permanente de estos materiales reciclados

Numerical Simulation of Bitumen Emulsion-Stabilised Base Course Mixtures With C&D Waste Aggregates Considering Nonlinear Elastic Behaviour

[Abstract:] This study presents the numerical modelling of a load-volume road pavement section with bitumen emulsion-stabilised base courses. The base courses used natural and construction and demolition aggregates. A 3D finite difference model was used to determine the peak responses of the pavement sections when subjected to loads. Three nonlinear models were adopted in the two base courses. The response predictions of the three models were similar. Both the resilient and permanent behaviours of these materials were modelled. An analysis was conducted on the rutting resistance of the base course materials. Both base courses were suitable for use in low-volume roads. The base course made with construction and demolition aggregates was more resistant to rutting.Ministerio de Economía y Competitividad; BIA2016-80317-

Thermal characterization of Montmorillonite clays saturated with various cations

Emanation thermal analysis (ETA), thermogravimetry and high temperature XRD were used to characterize the thermal behavior during dehydration of natural Na montmorillonite (Upton Wyoming, USA) and homoionic montmorillonite (MMT) samples saturated with different cations, i.e. Li+, Cs+, NH 4 +, Mg2+ and Al3+. ETA results characterized radon mobility and microstructure changes that accompanied the mass loss of the samples due to dehydration on heating in air. A collapse of interlayer space between the silicate sheets after water release from the MMT samples was characterized by a decrease of the radon release rate, ΔE. Decreases in c-axis basal spacing (d 001) values determined from XRD patterns for the different montmorillonite samples follow the sequence: Mg−MMT>Al−MMT>Li−MMT>Na−MMT>NH4−MMT>Cs−MMT The decrease of the radon release rate (ΔE) determined by ETA that characterized microstructure changes due to collapse of interlayer space corresponded well to differences in the c-axis basal spacing (Δd 001) values determined from the XRD patterns before and after samples dehydration.Peer Reviewe

On the presence of Heterocarpus ensifer Milne Edwards, 1881 (Decapoda, Pandalidae) in the Spanish Mediterranean

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Indium(III)-Catalyzed Stereoselective Synthesis of Tricyclic Frameworks by Cascade Cycloisomerization Reactions of Aryl 1,5-Enynes

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUGThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.joc.1c00825 (https://pubs.acs.org/doi/suppl/10.1021/acs.joc.1c00825/suppl_file/jo1c00825_si_001.pdf)[Abstract] The indium(III)-catalyzed cascade cycloisomerization reaction of 1,5-enynes with pendant aryl nucleophiles is reported. The reaction proceeds in cascade under mild reaction conditions, using InI₃ (5 mol %) as a catalyst with a range of 1,5-enynes furnished with aryl groups (phenyl and phenol) at alkene (E and Z isomers) and with terminal and internal alkynes. Using 1-bromo-1,5-enynes, a one-pot sequential indium-catalyzed cycloisomerization and palladium-catalyzed cross-coupling with triorganoindium reagents were developed. The double cyclization is stereospecific and operates via a biomimetic cascade cation-olefin through 1,5-enyne cyclization (6-endo-dig) and subsequent C–C hydroarylation or C–O phenoxycyclization. Density functional theory (DFT) computational studies on 1,5-enynyl aryl ethers support a two-step mechanism where the first stereoselective 1,5-enyne cyclization produces a nonclassical carbocation intermediate that evolves to the tricyclic reaction product through a SᴇAr mechanism. Using this approach, a variety of tricyclic heterocycles such as benzo[b]chromenes, phenanthridines, xanthenes, and spiroheterocyclic compounds are efficiently synthesized with high atom economy.We thank the Spanish Ministerio de Ciencia, Innovación y Universidades (PGC2018-097792-B-I00 and PID 2019-110008GB-I00), Xunta de Galicia (GRC2018/039), IZO-SGI SGIker of UPV/EHU, and EDRF funds for financial and human supportXunta de Galicia; GRC2018/039https://pubs.acs.org/doi/suppl/10.1021/acs.joc.1c00825/suppl_file/jo1c00825_si_001.pd

Estabilidad política, terrorismo y medios de comunicación. Un análisis de la incidencia de percepciones mediáticas en el turismo receptivo.

The present research seeks to analyze the existing relationship between terrorist attacks, political instability, discourse from international media outlets and news agencies in receptive tourism. To accomplish this, four countries that have different internal situations will be studied in the period 2012- 2015: Egypt, Tunisia, Venezuela and Spain combining quantitative methodologies using official data from international and national organisms, with journalistic discourse analysis from 4 international news agencies and 4 international media outlets through the use of the MAXQDA (v. 11.0.11) software tool. The results have shown that the information spread by media about terrorist attacks have more effects on tourism than those about political and economic instability

Estabilidad política, terrorismo y medios de comunicación. Un análisis de la incidencia de percepciones mediáticas en el turismo receptivo.

The present research seeks to analyze the existing relationship between terrorist attacks, political instability, discourse from international media outlets and news agencies in receptive tourism. To accomplish this, four countries that have different internal situations will be studied in the period 2012- 2015: Egypt, Tunisia, Venezuela and Spain combining quantitative methodologies using official data from international and national organisms, with journalistic discourse analysis from 4 international news agencies and 4 international media outlets through the use of the MAXQDA (v. 11.0.11) software tool. The results have shown that the information spread by media about terrorist attacks have more effects on tourism than those about political and economic instability