Capas finas de ZrO2 para mejorar la resistencia química de los vidriados mates de calcio

La resistencia al ataque químico de vidriados cerámicos susceptibles al mismo, concretamente formulados a partir de una frita mate de calcio, se ha mejorado depositando en la superficie una capa delgada de óxido de circonio. Un sol de circonio estabilizado es el precursor de la capa, el cual se deposita mediante aerografía sobre el vidriado cocido y con un tratamiento térmico suave (Tmax ≈ 400 ºC), es transformado en ZrO2 y anclado a la superficie. Los ensayos de resistencia química demuestran que el vidriado protegido no sufre un ataque apreciable visualmente por parte del ácido clorhídrico concentrado, condiciones en las que el mismo vidriado sin el recubrimiento resulta gravemente dañado. El precursor utilizado genera una capa de óxido de circonio que protege el vidriado subyacente, de modo que el ataque químico por parte del ácido clorhídrico queda confinado al entorno de las grietas y discontinuidades de la capa depositadaPeer reviewe

A Multi-signal Variant for the GPU-based Parallelization of Growing Self-Organizing Networks

Among the many possible approaches for the parallelization of self-organizing networks, and in particular of growing self-organizing networks, perhaps the most common one is producing an optimized, parallel implementation of the standard sequential algorithms reported in the literature. In this paper we explore an alternative approach, based on a new algorithm variant specifically designed to match the features of the large-scale, fine-grained parallelism of GPUs, in which multiple input signals are processed at once. Comparative tests have been performed, using both parallel and sequential implementations of the new algorithm variant, in particular for a growing self-organizing network that reconstructs surfaces from point clouds. The experimental results show that this approach allows harnessing in a more effective way the intrinsic parallelism that the self-organizing networks algorithms seem intuitively to suggest, obtaining better performances even with networks of smaller size.Comment: 17 page

Electronic structure and experimental benchmarking of aluminum spinels for solar water splitting

A computational methodology for screening aluminum-based spinel oxides for photoelectrochemical water splitting has been developed by combining HSE06 and PBE + U calculations. The method, which can be extended to other ternary oxides, provides values for formation energies, band gaps, band edge positions, and carrier effective masses. The formation energies indicate that the Al spinels of Mg, Co, Ni, and Zn (successfully synthesized using a sol-gel method) are among the most stable in the series. Except for the Mg and Zn cases, the electronic structures of the spinels are rather similar, with band gaps separating occupied and empty 3 d metal states. The charge-transfer band gap values are found to be above 3 eV, limiting the use of these materials in solar water splitting, although an estimate of the band edge positions indicates that, in general, both conduction band electrons and valence band holes can promote water reduction and oxidation, respectively. The effective masses of the charge carriers suggests that the spinels are n-type semiconductors as experimentally demonstrated. Importantly, both the UV–vis spectra and the photoelectrochemical results qualitatively agree with the theoretical electronic structure. In general vein, this work demonstrates the potential of theoretical screening for the development and selection of new photoelectrode materials based on ternary oxides for their application in solar water splitting.The authors gratefully acknowledge funding from the European Union’s Horizon 2020 research and innovation program under grant agreement no. 760930 (FotoH2 project). This research was also partially funded by the Ministerio de Ciencia e Innovación/Agencia Estatal de Investigación/Fondos FEDER through project PID2021-128876OB-I00 and by the Generalitat Valenciana through project PROMETEO/2020/089. F.J.P. also acknowledges the Spanish Ministry of Education for the award of an FPU grant

Spectroelectrochemical Study of the Photoinduced Catalytic Formation of 4,4′-Dimercaptoazobenzene from 4-Aminobenzenethiol Adsorbed on Nanostructured Copper

Surface-enhanced raman scattering (SERS) spectra of self-assembled monolayers of 4-aminobenzenethiol (4-ABT) on copper (Cu) and silver (Ag) surfaces decorated with Cu and Ag nanostructures, respectively, have been obtained with lasers at 532, 632.8, 785, and 1064 nm. Density functional theory (DFT) has been used to obtain calculated vibrational frequencies of the 4-ABT and 4,4′-dimercaptoazobenzene (4,4′-DMAB) molecules adsorbed on model Cu surfaces. The features of the SERS spectra depend on the electrode potential and the type and power density of the laser. SERS spectra showed the formation of the 4,4′-DMAB on the nanostructured Cu surface independently of the laser employed. For the sake of comparison SERS spectra of a self-assembled monolayer of the 4-ABT on Ag surfaces decorated with Ag nanostructures have been also obtained with the same four lasers. When using the 532 and 632.8 nm lasers, the 4,4′-DMAB is formed on Cu surface at electrode potentials as low as −1.0 V (AgCl/Ag) showing a different behavior with respect to Ag (and others metals such as Au and Pt). On the other hand, the surface-enhanced infrared reflection absorption (SEIRA) spectra showed that in the absence of the laser excitation the 4,4′-DMAB is not produced from the adsorbed 4-ABT on nanostructured Cu in the whole range of potentials studied. These results point out the prevalence of the role of electron–hole pairs through surface plasmon activity to explain the obtained SERS spectra.Financial support from Ministerio de Economía y Competitividad (Projects CTQ2013-48280-C3-3-R and CTQ2013-44083-P), Fondos Feder, and the University of Alicante are greatly acknowledged

Biopolymer additives to reduce erosion-induced soil losses during irrigation

A series of biopolymers added to irrigation water were tested for their efficacy in reducing shear-induced erosion in a laboratory-scale mini-furrow. Suspensions of chitosan, starch xanthate, cellulose xanthate, and acid-hydrolyzed cellulose microfibrils, at concentrations of 20, 80, 80, and 120 ppm, respectively, reduced suspended solids by more than 80%. None of these biopolymers, however, exhibited the > 90% runoff sediment reduction shown by the present industry standard, synthetic polyacrylamide polymers, PAM. PAM is effective at concentrations as low as 5 ppm. In field tests, chitosan solutions were only marginally effective in reducing runoff from the end of a 137 m long furrow, with indications that results were dependent on the length of the furrow. Sediment runoff of some clay-rich Northern California soils was reduced by up to 85% by increasing the concentration of exchangeable calcium to > 2.5mM. Calcium improved the sedimentation of the polyelectrolytic polymers in this study

Modal analysis of β-Ga₂O₃:Cr widely tunable luminescent optical microcavities

Optical microcavities are key elements in many photonic devices, and those based on distributed Bragg reflectors (DBRs) enhance dramatically the end reflectivity, allowing for higher quality factors and finesse values. Besides, they allow for wide wavelength tunability, needed for nano-and microscale light sources to be used as photonic building blocks in the micro- and nanoscale. Understanding the complete behavior of light within the cavity is essential to obtaining an optimized design of properties and optical tunability. In this work, focused ion-beam fabrication of high refractive-index contrast DBR-based optical cavities within Ga₂O₃:Cr microwires grown and doped by the vapor-solid mechanism is reported. Room-temperature microphotoluminescence spectra show strong modulations from about 650 nm up to beyond 800 nm due to the microcavity resonance modes. Selectivity of the peak wavelength is achieved for two different cavities, demonstrating the tunability of this kind of optical system. Analysis of the confined modes is carried out by an analytical approximation and by finite-difference-time-domain simulations. A good agreement is obtained between the reflectivity values of the DBRs calculated from the experimental resonance spectra, and those obtained by finite-difference-time-domain simulations. Experimental reflectivities up to 70% are observed in the studied wavelength range and cavities, and simulations demonstrate that reflectivities up to about 90% could be reached. Therefore, Ga₂O₃:Cr high-reflectivity optical microcavities are shown as good candidates for single-material-based, widely tunable light emitters for micro- and nanodevices

An NMR-based scoring function improves the accuracy of binding pose predictions by docking by two orders of magnitude

Low-affinity ligands can be efficiently optimized into high-affinity drug leads by structure based drug design when atomic-resolution structural information on the protein/ligand complexes is available. In this work we show that the use of a few, easily obtainable, experimental restraints improves the accuracy of the docking experiments by two orders of magnitude. The experimental data are measured in nuclear magnetic resonance spectra and consist of protein-mediated NOEs between two competitively binding ligands. The methodology can be widely applied as the data are readily obtained for low-affinity ligands in the presence of non-labelled receptor at low concentration. The experimental inter-ligand NOEs are efficiently used to filter and rank complex model structures that have been pre-selected by docking protocols. This approach dramatically reduces the degeneracy and inaccuracy of the chosen model in docking experiments, is robust with respect to inaccuracy of the structural model used to represent the free receptor and is suitable for high-throughput docking campaigns

Polymer additives in irrigation water to reduce erosion and better manage water infiltration

Water-soluble polyacrylamide (PAM) was identified as an environmentally safe and highly effective erosion preventing and infiltration-enhancing polymer when applied in furrow irrigation water at 1-10 g m-3, i.e. 1-10 ppm. The agricultural use of polyacrylamide, PAM, as an additive in irrigation water has grown rapidly since commercial introduction in 1995 because it improves water infiltration and reduces erosion-induced soil losses up to 97%, saving tons of topsoil per hectare per year. Various polymers and biopolymers have long been recognized as viable soil conditioners because they stabilize soil surface structure and pore continuity. The new strategy of adding the conditioner, high molecular weight anionic PAM, to the irrigation water in the first several hours of irrigation enables a significant costs savings over traditional application methods of tilling soil conditoner into the entire (15 cm deep) soil surface layer. By adding PAM to the irrigation water, soil structure is Unproved in the all-important 1-5 mm thick layer at the soil/water interface of the 25 to 30% of field surface contacted by flowing water. Recent studies with biopolymers such as chitosan, charged polysaccharides, whey, and industrial cellulose derivatives show potential as biopolymer alternatives to PAM. Their success will depend on production economics