Al/Fe-, Al/Cu- and Al/(Fe-Cu)-pillared clays: Structural features at low Atomic Active Metal Ratios (AMR)

A set of Al/Fe-, Al/Cu- and Al/(Fe-Cu)-pillared clays were prepared from a Colombian bentonite in sodium or natural (Ca/Mg) form as starting materials. The effect of the loading of the second metal(s) (Fe and/or Cu) related to Al (AMR) in the intercalating solutions at low range of values ≤ 10%, on the main physicochemical properties was investigated. The insertion of the active metals rose almost linearly with AMR for both binary, Al/Fe- and Al/Cu- mixed metal systems. For the three-metal Al/(Fe-Cu)- mixed system, the stabilization of copper behaved randomly as a function of AMR, while the stabilization of Fe was almost not affected by the presence of Cu. On the basis of the ionic radii of the metals involved, a possible competition of the two active metals for the octahedral sites available in the Al13 polycationic structure is proposed for the three-metal system (ionic radii values: Al3+ = 0.68 Å; Fe3+ = 0.67 Å; Cu2+ = 0.73 Å), but also as a good explanation for the efficiency of stabilization for iron around 15 times higher than copper in the binary metal systems. A clear dependence of the compensation of the cationic exchange capacity by polycations with the AMR value was found only for the system Al/Fe-, which was explained in terms of the opposite changes in the final pH obtained in the intercalating solutions, induced by the active metals in the Keggin-like polycations. The change in the basal spacings obtained in the XRD patterns from oriented glasses as a function of AMR was interpreted in terms of the opposite effect expected on the molecular size of the polycations as higher amounts of Fe or Cu would isomorphically substitute Al into the Al13 framework, allowing to propose that both, iron and copper are able to carry out such a substitution, although in different extent. The hydrogen consumption in the H2-TPR analysis of the materials was mainly distributed between two broad peaks: one from about 250ºC to 580ºC, and a second one from about 750ºC to 950ºC. Despite the several metal oxide species that are possible to form, the first signal in samples modified with the Al/Fe- system may correspond with the sequential overlapped reduction of Fe2O3 in up to three steps: (1) Fe2O3 → Fe3O4; (2) Fe3O4 → FeO; and (3) FeO → Fe, and to two sequential reduction effects in the range of 210-260 ºC for Cu2+→ Cu+ and Cu+→ Cu0 at higher temperatures of ca. 400 ºC to 700 ºC. In the Al/Fe- system two shoulders were observed at around 600ºC and 850ºC, whose intensity grow as the active metal loading increases, seem to be related to two kinds of metal sites repeatedly claimed in the literature as responsible for the high catalytic activity displayed by these materials in Fenton-like reactions; Fe “decorating” Al pillars and true mixed Al/Fe pillars, respectively. The textural analysis of the natural modified samples suggest that at AMR below 5.0 %, a discrete maximum exist for the systems Al/Fe- and Al/Cu- over which the sorption capacity starts to be significantly affected. Simultaneous thermal analysis (DSC/TGA) demonstrated that the addition of a second metal in the intercalating system enhanced more the fraction of physisorbed water and decreased the maximum temperature for such a thermal event than intercalation with simple Al- polycations. SEM micrographs showed significant changes in morphology of the particles as AMR increased from 2.0 to 5.0%; as the amount of iron and/or copper added to the system increased, a greater amount of tiny particles deposited on the clay surface was seen, may be corresponding with external oxide aggregates. Likewise, the ratio Fe/Al obtained from the semi-quantitative surface chemical EDX analysis of the samples modified with the system Al/Fe- indicated that the AMR increasing also leads to higher fraction of the iron inserted represented in intercalated, possibly less aggregated mixed species in the materials. Acknowledgements: Financial support from MEC and FEDER funds (Ref. MAT2007-66439-C02)

Inclusive Nucleon Emission Induced by Quasi--Elastic Neutrino--Nucleus Interactions

We study the quasi--elastic contribution to the inclusive $(\nu_l,\nu_l N)$, $(\nu_l,l^- N)$, $({\bar \nu}_l,{\bar \nu}_l N)$ and $({\bar \nu}_l,l^+ N)$ reactions in nuclei using a Monte Carlo simulation method to account for the rescattering of the outgoing nucleon. As input, we take the reaction probability from the microscopical many body framework developed in Phys. Rev. {\bf C70} (2004) 055503 for charged-current induced reactions, while for neutral currents we use results from a natural extension of the model described in that reference. The nucleon emission process studied here is a clear signal for neutral--current neutrino driven reactions, that can be used in the analysis of future neutrino experiments.Comment: 23 pages, 17 figures; Version 2: few typos correcte

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causal theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done, the methodology developed in this paper could be extended to apply to these other problems.Comment: 27 pages, 14 figures, Published version JCA

Heuristic Techniques for the Design of Steel-Concrete Composite Pedestrian Bridges

[EN] The objective of this work was to apply heuristic optimization techniques to a steel-concrete composite pedestrian bridge, modeled like a beam on two supports. A program has been developed in Fortran programming language, capable of generating pedestrian bridges, checking them, and evaluating their cost. The following algorithms were implemented: descent local search (DLS), a hybrid simulated annealing with a mutation operator (SAMO2), and a glow-worms swarm optimization (GSO) in two variants. The first one only considers the GSO and the second combines GSO and DLS, applying the DSL heuristic to the best solutions obtained by the GSO. The results were compared according to the lowest cost. The GSO and DLS algorithms combined obtained the best results in terms of cost. Furthermore, a comparison between the CO2 emissions associated with the amount of materials obtained by every heuristic technique and the original design solution were studied. Finally, a parametric study was carried out according to the span length of the pedestrian bridge.The authors acknowledge the financial support of the Spanish Ministry of Economy and Business, along with FEDER funding (DIMALIFE Project: BIA2017-85098-R).Yepes, V.; Dasí-Gil, M.; Martínez-Muñoz, D.; López Desfilis, VJ.; Martí Albiñana, JV. (2019). Heuristic Techniques for the Design of Steel-Concrete Composite Pedestrian Bridges. Applied Sciences. 9(16):1-18. https://doi.org/10.3390/app9163253S118916Liu, S., Tao, R., & Tam, C. M. (2013). Optimizing cost and CO2 emission for construction projects using particle swarm optimization. Habitat International, 37, 155-162. doi:10.1016/j.habitatint.2011.12.012Sarma, K. C., & Adeli, H. (1998). Cost Optimization of Concrete Structures. Journal of Structural Engineering, 124(5), 570-578. doi:10.1061/(asce)0733-9445(1998)124:5(570)Adeli, H., & Kim, H. (2001). Cost optimization of composite floors using neural dynamics model. Communications in Numerical Methods in Engineering, 17(11), 771-787. doi:10.1002/cnm.448Kravanja, S., & Šilih, S. (2003). Optimization based comparison between composite I beams and composite trusses. Journal of Constructional Steel Research, 59(5), 609-625. doi:10.1016/s0143-974x(02)00045-7Senouci, A. B., & Al-Ansari, M. S. (2009). Cost optimization of composite beams using genetic algorithms. Advances in Engineering Software, 40(11), 1112-1118. doi:10.1016/j.advengsoft.2009.06.001Kaveh, A., & Shakouri Mahmud Abadi, A. (2010). Cost optimization of a composite floor system using an improved harmony search algorithm. Journal of Constructional Steel Research, 66(5), 664-669. doi:10.1016/j.jcsr.2010.01.009Ramires, F. B., Andrade, S. A. L. de, Vellasco, P. C. G. da S., & Lima, L. R. O. de. (2012). Genetic algorithm optimization of composite and steel endplate semi-rigid joints. Engineering Structures, 45, 177-191. doi:10.1016/j.engstruct.2012.05.051Martí, J. V., Gonzalez-Vidosa, F., Yepes, V., & Alcalá, J. (2013). Design of prestressed concrete precast road bridges with hybrid simulated annealing. Engineering Structures, 48, 342-352. doi:10.1016/j.engstruct.2012.09.014García-Segura, T., & Yepes, V. (2016). Multiobjective optimization of post-tensioned concrete box-girder road bridges considering cost, CO2 emissions, and safety. Engineering Structures, 125, 325-336. doi:10.1016/j.engstruct.2016.07.012García-Segura, T., Yepes, V., & Frangopol, D. M. (2017). Multi-objective design of post-tensioned concrete road bridges using artificial neural networks. Structural and Multidisciplinary Optimization, 56(1), 139-150. doi:10.1007/s00158-017-1653-0Soke, A., & Bingul, Z. (2006). Hybrid genetic algorithm and simulated annealing for two-dimensional non-guillotine rectangular packing problems. Engineering Applications of Artificial Intelligence, 19(5), 557-567. doi:10.1016/j.engappai.2005.12.003Penadés-Plà, V., García-Segura, T., & Yepes, V. (2019). Accelerated optimization method for low-embodied energy concrete box-girder bridge design. Engineering Structures, 179, 556-565. doi:10.1016/j.engstruct.2018.11.015Yepes, V., García-Segura, T., & Moreno-Jiménez, J. M. (2015). A cognitive approach for the multi-objective optimization of RC structural problems. Archives of Civil and Mechanical Engineering, 15(4), 1024-1036. doi:10.1016/j.acme.2015.05.001Martí, J. V., García-Segura, T., & Yepes, V. (2016). Structural design of precast-prestressed concrete U-beam road bridges based on embodied energy. Journal of Cleaner Production, 120, 231-240. doi:10.1016/j.jclepro.2016.02.024García-Segura, T., Yepes, V., Frangopol, D. M., & Yang, D. Y. (2017). Lifetime reliability-based optimization of post-tensioned box-girder bridges. Engineering Structures, 145, 381-391. doi:10.1016/j.engstruct.2017.05.013Penadés-Plà, V., García-Segura, T., Martí, J., & Yepes, V. (2016). A Review of Multi-Criteria Decision-Making Methods Applied to the Sustainable Bridge Design. Sustainability, 8(12), 1295. doi:10.3390/su8121295BEDEC ITEC Materials Database https://metabase.itec.cat/vide/es/bedecYepes, V., Martí, J. V., & García-Segura, T. (2015). Cost and CO2 emission optimization of precast–prestressed concrete U-beam road bridges by a hybrid glowworm swarm algorithm. Automation in Construction, 49, 123-134. doi:10.1016/j.autcon.2014.10.013Molina-Moreno, F., Martí, J. V., & Yepes, V. (2017). Carbon embodied optimization for buttressed earth-retaining walls: Implications for low-carbon conceptual designs. Journal of Cleaner Production, 164, 872-884. doi:10.1016/j.jclepro.2017.06.246Kirkpatrick, S., Gelatt, C. D., & Vecchi, M. P. (1983). Optimization by Simulated Annealing. Science, 220(4598), 671-680. doi:10.1126/science.220.4598.671Medina, J. R. (2001). Estimation of Incident and Reflected Waves Using Simulated Annealing. 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Effect of dopants on the structure of titanium oxide used as a photocatalyst for the removal of emergent contaminants

Photocatalysts composed of titanium dioxide modified with B, F, N and P have been synthesized, characterized and applied to the degradation of caffeine, diclofenac, ibuprofen and salicylic acid. The modified TiO2 samples were prepared by the sol–gel technique starting from titanium(IV) isopropoxide and using H3BO3, NH4F, N(C2H5OH)3 and H3PO4 as precursors of the modifiers, with the content varying between 0 and 5 wt%. Structural characterization was based on nitrogen physisorption at −196 °C, powder X-ray diffraction (PXRD), simultaneous thermogravimetric/differential thermal analysis (TG/DTA) and X-ray photoelectron spectroscopy (XPS). The structural properties of the modified TiO2 solids were significantly different depending on the nature and amount of modifiers and the calcination temperature. TiO2 in the anatase phase was obtained in all cases and was stable upon calcination at 400 °C. The photocatalytic degradation of caffeine, diclofenac, ibuprofen and salicylic acid by modified TiO2 was investigated under ultraviolet irradiation at 25 °C. The photocatalytic degradation behavior followed the order: caffeine > diclofenac = ibuprofen > salicylic acid. B-doped TiO2 was the most efficient catalyst in the degradation of these selected emerging contaminants

Microanatomical findings with relevance to trigeminal ganglion enhancement on post-contrast T1-weighted magnetic resonance images in dogs

Trigeminal ganglion contrast enhancement (TGCE) is reported to be a normal and a common finding on magnetic resonance imaging studies of dogs, cats and humans. The intent of the present study was to describe the anatomical characteristics of the trigeminal ganglion, its surrounding structures, and histological features that are relevant to explain or hypothesize on the reason for TGCE on T1-weighted post-contrast MRI studies of the brain in dogs. Eight dog cadavers were dissected to study the anatomy of the trigeminal ganglion. The presence and anatomy of vessels was studied by dissection and by histological techniques. Two trigeminal ganglia were isolated and stained with hematoxylin-eosin (HE). Two other trigeminal ganglia included in the trigeminal canal and trigeminal cavity were decalcified with formic acid/formalin for 12 weeks and stained with HE to study the related vessels. Additionally, a corrosion cast was obtained from a separate canine specimen. Leptomeninges and a subarachnoid space were identified at the level of the trigeminal nerve roots and the trigeminal ganglion. No subarachnoid space was identified and leptomeninges were no longer present at the level of the three trigeminal nerve branches. Small arterial vessels ran to and supplied the trigeminal ganglion, passing through the dura mater. No venous plexus was visualized at the level of the trigeminal ganglion in the dissections. A complex arterial vascular network was identified within the leptomeningeal covering of the trigeminal ganglion and was best appreciated in the corrosion cast. Histological examination revealed small-to moderate-sized blood vessels located in the epineurium around the ganglion; from there a multitude of arterioles penetrated into the perineurium. Small endoneurial branches and capillaries penetrated the ganglion and the trigeminal nerve branches. Limitations to this study include the limited number of canine specimens included and the lack of electron microscopy to further support current hypotheses included in our discussion. In conclusion, this study provides further support to the theory that TGCE in dogs may be due an incomplete blood-nerve barrier or blood-ganglion barrier at the interface between the central nervous system and the peripheral nervous system