Stability of Surface Complexes Formed at the TiO2/Water Interface

TiO2 surface complexation by bidentate organic ligands is analysed in terms of the ligand Brønstead and Lewis basicities. The complexation and basicity constants comply with linear Gibbs Energy relationships (LGERs). For dicarboxylic acids, the surface chelate bond makes an approximately constant contribution to the stability. The proton transfer to the surface modulates the pH dependence of stability. A correlation exists between the surface complexation constant of the neutral acid H2L and the ligand first acidity constant. On the other hand, the surface complexation constants of dianions L2- of cathecols and aminophenols are positively correlated with the ligand second acidity constant. Apparent stability is determined by the competition of H+ and surface metal ions for the ligand. Stability trends are strongly influenced by the Brønstead acid base reaction between the acid ligands H2L and the surface, whereas the stability of the surface chelate contributes to the overall stability

Electrokinetic Behaviour and Interaction with Oxalic Acid of Different Hydrous Chromium(III) Oxides

Three samples of hydrous chromium(III) oxide have been prepared by different procedures, and their electrokinetic mobilities have been measured. In mineral media, isoelectric points were found to be 8.45 ±0.15. This value is shifted from the solution isoelectric point by –0.35 ±0.15, due to the contribution of solvation energy to the energy of ionic adsorption. On the basis of a simple model, it is suggested that the two successive surface acidity constants of hydrous chromium(III) oxide are pKS a1 = 7.17 and pKS a2 = 9.72. The influence of oxalic acidity on mobility may be described in terms of two successive adsorption equilibria, the first one conducive to the neutralization of positive protonic charge, and the second one originating a charge reversal. It is shown that the apparent affinity for this latter mode is lower in one of the samples, suggesting that surface complexation constants may in fact be sensitive to the history of hydrous chromium(III) oxide particles. The three samples show similar dissolution behaviour but the specific rates differ, in one case by two orders of magnitude. This difference is explained in terms of the influence of crosslinking on the reactivity

Electrokinetic Behaviour and Interaction with Oxalic Acid of Different Hydrous Chromium(III) Oxides

Three samples of hydrous chromium(III) oxide have been prepared by different procedures, and their electrokinetic mobilities have been measured. In mineral media, isoelectric points were found to be 8.45 ±0.15. This value is shifted from the solution isoelectric point by –0.35 ±0.15, due to the contribution of solvation energy to the energy of ionic adsorption. On the basis of a simple model, it is suggested that the two successive surface acidity constants of hydrous chromium(III) oxide are pKS a1 = 7.17 and pKS a2 = 9.72. The influence of oxalic acidity on mobility may be described in terms of two successive adsorption equilibria, the first one conducive to the neutralization of positive protonic charge, and the second one originating a charge reversal. It is shown that the apparent affinity for this latter mode is lower in one of the samples, suggesting that surface complexation constants may in fact be sensitive to the history of hydrous chromium(III) oxide particles. The three samples show similar dissolution behaviour but the specific rates differ, in one case by two orders of magnitude. This difference is explained in terms of the influence of crosslinking on the reactivity

Effects of periodic forcing in chaotic scattering

The effects of a periodic forcing on chaotic scattering are relevant in certain situations of physical interest. We investigate the effects of the forcing amplitude and the external frequency in both the survival probability of the particles in the scattering region and the exit basins associated to phase space. We have found an exponential decay law for the survival probability of the particles in the scattering region. A resonant-like behavior is uncovered where the critical values of the frequencies omega aprox. 1 and omega aprox. 2 permit the particles to escape faster than for other different values. On the other hand, the computation of the exit basins in phase space reveals the existence of Wada basins depending of the frequency values. We provide some heuristic arguments that are in good agreement with the numerical results. Our results are expected to be relevant for physical phenomena such as the effect of companion galaxies, among others

Irradiancia e irradiación UV-A a partir de medidas con radiómetros a 380 nm para aplicaciones ambientales de la energía solar

El correcto dimensionamiento de plantas de tratamiento por fotocatálisis solar requiere del conocimiento del recurso solar UV (280-400 nm) a nivel de la superficie terrestre. El UV-B (280-315nm), sólo constituye el 10% del total y se transmite sólo el 55% al ingresar al reactor, mientras que el UV-A(315-400 nm) se transmite en un 89%. En este trabajo se presenta y evalúa un método para calcular la irradiancia e irradiación UV-A a partir de mediciones a 380nm por medio del uso de un factor de escala dependiente del ángulo cenital solar. Los errores en la irradiancia calculada van del 18% a θ = 90º hasta 4% a θ =10º. El error en la irradiación UV-A calculada es del 10.2% para las integrales diarias. Estos errores están dentro del rango de incertidumbre aceptable para la mayoría de los sistemas fotocatalíticos solares y pueden ser usadas para los estudios de factibilidad.Proper dimensioning of plants for photocatalytic treatment of wastewaters require the knowledge of the UV solar resource availability. In this work, a method to calculate UV-A irradiance and irradiation from measurements at 380 nm by means of a scale factor dependant only on the solar zenith angle is proposed and evaluated. Errors in the calculated UV-A irradiance range from 18% at θ = 90º to 4% at θ =10º. Errors in the calculated UV-A irradiation are less than 11% for daily integrals. These errors are well within the range of acceptable uncertainty for most photocatalytic systems dimensioning and the procedure may be use for other applications as well. The next step is the establishment of relationships between UV-A and global solar radiation, and a map of the solar UV-A resource for Argentina.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Irradiancia e irradiación UV-A a partir de medidas con radiómetros a 380 nm para aplicaciones ambientales de la energía solar

El correcto dimensionamiento de plantas de tratamiento por fotocatálisis solar requiere del conocimiento del recurso solar UV (280-400 nm) a nivel de la superficie terrestre. El UV-B (280-315nm), sólo constituye el 10% del total y se transmite sólo el 55% al ingresar al reactor, mientras que el UV-A(315-400 nm) se transmite en un 89%. En este trabajo se presenta y evalúa un método para calcular la irradiancia e irradiación UV-A a partir de mediciones a 380nm por medio del uso de un factor de escala dependiente del ángulo cenital solar. Los errores en la irradiancia calculada van del 18% a θ = 90º hasta 4% a θ =10º. El error en la irradiación UV-A calculada es del 10.2% para las integrales diarias. Estos errores están dentro del rango de incertidumbre aceptable para la mayoría de los sistemas fotocatalíticos solares y pueden ser usadas para los estudios de factibilidad.Proper dimensioning of plants for photocatalytic treatment of wastewaters require the knowledge of the UV solar resource availability. In this work, a method to calculate UV-A irradiance and irradiation from measurements at 380 nm by means of a scale factor dependant only on the solar zenith angle is proposed and evaluated. Errors in the calculated UV-A irradiance range from 18% at θ = 90º to 4% at θ =10º. Errors in the calculated UV-A irradiation are less than 11% for daily integrals. These errors are well within the range of acceptable uncertainty for most photocatalytic systems dimensioning and the procedure may be use for other applications as well. The next step is the establishment of relationships between UV-A and global solar radiation, and a map of the solar UV-A resource for Argentina.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Irradiancia e irradiación UV-A a partir de medidas con radiómetros a 380 nm para aplicaciones ambientales de la energía solar

El correcto dimensionamiento de plantas de tratamiento por fotocatálisis solar requiere del conocimiento del recurso solar UV (280-400 nm) a nivel de la superficie terrestre. El UV-B (280-315nm), sólo constituye el 10% del total y se transmite sólo el 55% al ingresar al reactor, mientras que el UV-A(315-400 nm) se transmite en un 89%. En este trabajo se presenta y evalúa un método para calcular la irradiancia e irradiación UV-A a partir de mediciones a 380nm por medio del uso de un factor de escala dependiente del ángulo cenital solar. Los errores en la irradiancia calculada van del 18% a θ = 90º hasta 4% a θ =10º. El error en la irradiación UV-A calculada es del 10.2% para las integrales diarias. Estos errores están dentro del rango de incertidumbre aceptable para la mayoría de los sistemas fotocatalíticos solares y pueden ser usadas para los estudios de factibilidad.Proper dimensioning of plants for photocatalytic treatment of wastewaters require the knowledge of the UV solar resource availability. In this work, a method to calculate UV-A irradiance and irradiation from measurements at 380 nm by means of a scale factor dependant only on the solar zenith angle is proposed and evaluated. Errors in the calculated UV-A irradiance range from 18% at θ = 90º to 4% at θ =10º. Errors in the calculated UV-A irradiation are less than 11% for daily integrals. These errors are well within the range of acceptable uncertainty for most photocatalytic systems dimensioning and the procedure may be use for other applications as well. The next step is the establishment of relationships between UV-A and global solar radiation, and a map of the solar UV-A resource for Argentina.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Genome-wide association analysis of dementia and its clinical endophenotypes reveal novel loci associated with Alzheimer's disease and three causality networks : The GR@ACE project

Introduction: Large variability among Alzheimer's disease (AD) cases might impact genetic discoveries and complicate dissection of underlying biological pathways. Methods: Genome Research at Fundacio ACE (GR@ACE) is a genome-wide study of dementia and its clinical endophenotypes, defined based on AD's clinical certainty and vascular burden. We assessed the impact of known AD loci across endophenotypes to generate loci categories. We incorporated gene coexpression data and conducted pathway analysis per category. Finally, to evaluate the effect of heterogeneity in genetic studies, GR@ACE series were meta-analyzed with additional genome-wide association study data sets. Results: We classified known AD loci into three categories, which might reflect the disease clinical heterogeneity. Vascular processes were only detected as a causal mechanism in probable AD. The meta-analysis strategy revealed the ANKRD31-rs4704171 and NDUFAF6-rs10098778 and confirmed SCIMP-rs7225151 and CD33-rs3865444. Discussion: The regulation of vasculature is a prominent causal component of probable AD. GR@ACE meta-analysis revealed novel AD genetic signals, strongly driven by the presence of clinical heterogeneity in the AD series

Genetic Cross-Interaction between APOE and PRNP in Sporadic Alzheimer's and Creutzfeldt-Jakob Diseases

Alzheimer's disease (AD) and Creutzfeldt-Jakob disease (CJD) represent two distinct clinical entities belonging to a wider group, generically named as conformational disorders that share common pathophysiologic mechanisms. It is well-established that the APOE ε4 allele and homozygosity at polymorphic codon 129 in the PRNP gene are the major genetic risk factors for AD and human prion diseases, respectively. However, the roles of PRNP in AD, and APOE in CJD are controversial. In this work, we investigated for the first time, APOE and PRNP genotypes simultaneously in 474 AD and 175 sporadic CJD (sCJD) patients compared to a common control population of 335 subjects. Differences in genotype distribution between patients and control subjects were studied by logistic regression analysis using age and gender as covariates. The effect size of risk association and synergy factors were calculated using the logistic odds ratio estimates. Our data confirmed that the presence of APOE ε4 allele is associated with a higher risk of developing AD, while homozygosity at PRNP gene constitutes a risk for sCJD. Opposite, we found no association for PRNP with AD, nor for APOE with sCJD. Interestingly, when AD and sCJD patients were stratified according to their respective main risk genes (APOE for AD, and PRNP for sCJD), we found statistically significant associations for the other gene in those strata at higher previous risk. Synergy factor analysis showed a synergistic age-dependent interaction between APOE and PRNP in both AD (SF = 3.59, p = 0.027), and sCJD (SF = 7.26, p = 0.005). We propose that this statistical epistasis can partially explain divergent data from different association studies. Moreover, these results suggest that the genetic interaction between APOE and PRNP may have a biological correlate that is indicative of shared neurodegenerative pathways involved in AD and sCJD

Common variants in Alzheimer’s disease and risk stratification by polygenic risk scores

Funder: Funder: Fundación bancaria ‘La Caixa’ Number: LCF/PR/PR16/51110003 Funder: Grifols SA Number: LCF/PR/PR16/51110003 Funder: European Union/EFPIA Innovative Medicines Initiative Joint Number: 115975 Funder: JPco-fuND FP-829-029 Number: 733051061Genetic discoveries of Alzheimer's disease are the drivers of our understanding, and together with polygenetic risk stratification can contribute towards planning of feasible and efficient preventive and curative clinical trials. We first perform a large genetic association study by merging all available case-control datasets and by-proxy study results (discovery n = 409,435 and validation size n = 58,190). Here, we add six variants associated with Alzheimer's disease risk (near APP, CHRNE, PRKD3/NDUFAF7, PLCG2 and two exonic variants in the SHARPIN gene). Assessment of the polygenic risk score and stratifying by APOE reveal a 4 to 5.5 years difference in median age at onset of Alzheimer's disease patients in APOE ɛ4 carriers. Because of this study, the underlying mechanisms of APP can be studied to refine the amyloid cascade and the polygenic risk score provides a tool to select individuals at high risk of Alzheimer's disease