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Charge Transfer Characteristics of n-type In0.1Ga0.9N Photoanode across Semiconductor-Liquid Interface

  • Caccamo, Lorenzo
  • Fábrega, Cristian
  • Marschewski, Marcel
  • Fündling, Sönke
  • Gad, Alaaeldin
  • Casals Guillén, Olga
  • Lilienkamp, Gerhard
  • Hofft, Oliver
  • Prades García, Juan Daniel
  • Daum, Winfried
  • Waag, Andreas
Understanding the mechanisms of charge transfer across the semiconductor/liquid interface is crucial to realize efficient photoelectrochemical devices. Here, the interfacial charge transfer characteristics of n-type In0.1Ga0.9N photoanodes are investigated and correlated to their photo-activity properties measured in phosphate buffered saline solution (pH 7) under illumination conditions. Cyclic voltammetry measurements show evident photoactivity changes as the number of cycles increases. In particular, the photocurrent density reaches its maximum value after 49 voltammetric cycles; meanwhile, the photocurrent onset potential shifts toward more negative cathodic potentials. Electrochemical impedance measurements reveal that, first, the hole transfer process occurs mainly via localized states at the surface and the photocurrent onset potential is dependent on the energetic position of those states. Therefore, the observed initial photocurrent increase and cathodic shift of the photocurrent onset potential can be attributed to a decrease of the transfer resistance and partial passivation of the states at the surface. On the other hand, a gradual oxidation and corrosion of the InGaN surface arises, causing a consequential decrease of the photocurrent. At this point, the charge transfer process occurs predominantly from the valence band. This work provides a basic understanding of the charge transfer mechanisms across the InGaN/liquid interface which can be used to improve the overall photoanode efficiency.

Modernity and capitalism: Conceptual retrieval and comparative-historical analyses

  • Casassas, David
  • Wagner, Peter, 1956 setembre 18-
The terms modernity and capitalism remain in widespread use to characterize contemporary societies, but the distinction between them is much less antagonistic in current social theory than it used to be when a theory of 'modern society' was opposed to the theory of 'late capitalism'. Rather than seeing societies either on an evolutionary trajectory realizing the functionally efficient institutionalization of freedom or as determined by increasing contradictions due to the logics of capital and to class struggle, a key task of social theory today is to reconceptualize modernity and capitalism in such a way that the dynamics of historical transformations and the varieties of current socio-political constellations can be more adequately understood. This article contributes to addressing this task, introducing a special issue of the European Journal of Social Theory devoted to 'modernity and capitalism'. This introduction elaborates a concept of modernity focused on the interpretative self-understanding of societies and a concept of capitalism as a historically specific response to the question of satisfying human material needs. On this conceptual basis, a historical-comparative perspective is taken to analyze transformations in the self-understandings of societies and the institutional changes in organizing the economy related to the former, placing the comparative analysis of societies in the global context of transformations of modernity and capitalism.

Understanding the evolution and spread of chikungunya virus in the Americas using complete genome sequences

  • Sahadeo, N. S. D.
  • Allicock, O. M.
  • Martínez de Salazar, Pablo
  • Auguste, A. J.
  • Widen, S.
  • Olowokure, B.
  • Gutierrez, C.
  • Valadere, A. M.
  • Polson-Edwards, K.
  • Weaver, S. C.
  • Carrington, C. V. F.
Local transmission of chikungunya virus (CHIKV) was first detected in the Americas in December 2013, after which it spread rapidly throughout the Caribbean islands and American mainland, causing a major chikungunya fever epidemic. Previous phylogenetic analysis of CHIKV from a limited number of countries in the Americas suggests that an Asian genotype strain was responsible, except in Brazil where both Asian and East/Central/South African (ECSA) lineage strains were detected. In this study, we sequenced thirty-three complete CHIKV genomes from viruses isolated in 2014 from fourteen Caribbean islands, the Bahamas and two mainland countries in the Americas. Phylogenetic analyses confirmed that they all belonged to the Asian genotype and clustered together with other Caribbean and mainland sequences isolated during the American outbreak, forming an 'Asian/American' lineage defined by two amino acid substitutions, E2 V368A and 6K L20M, and divided into two well-supported clades. This lineage is estimated to be evolving at a mean rate of 5 x 10-4 substitutions per site per year (95% higher probability density, 2.9-7.9 x 10-4) and to have arisen from an ancestor introduced to the Caribbean (most likely from Oceania) in about March 2013, 9 months prior to the first report of CHIKV in the Americas. Estimation of evolutionary rates for individual gene regions and selection analyses indicate that (in contrast to the Indian Ocean Lineage that emerged from the ECSA genotype followed by adaptive evolution and with a significantly higher substitution rate) the evolutionary dynamics of the Asian/American lineage are very similar to the rest of the Asian genotype and natural selection does not appear to have played a major role in its emergence. However, several codon sites with evidence of positive selection were identified within the non-structural regions of Asian genotype sequences outside of the Asian/American lineage.

Metabolic profiling for the identification of Huntington biomarkers by on-line solid-phase extraction capillary electrophoresis mass spectrometry combined with advanced data analysis tools

  • Pont Villanueva, Laura
  • Benavente Moreno, Fernando J. (Julián)
  • Jaumot Soler, Joaquim
  • Tauler Ferré, Romà
  • Alberch i Vié, Jordi
  • Ginés Padrós, Silvia
  • Barbosa Torralbo, José
  • Sanz Nebot, María Victoria
In this work, an untargeted metabolomic approach based on sensitive analysis by on-line solid-phase extraction capillary electrophoresis mass spectrometry (SPE-CE-MS) in combination with multivariate data analysis is proposed as an efficient method for the identification of biomarkers of Huntington's disease (HD) progression in plasma. For this purpose, plasma samples from wild type (wt) and HD (R6/1) mice of different ages (8, 12 and 30 weeks), were analysed by C18-SPE-CE-MS in order to obtain the characteristic electrophoretic profiles of low molecular mass compounds. Then, multivariate curve resolution alternating least squares (MCR-ALS) was applied to the multiple full scan MS data sets. This strategy permitted the resolution of a large number of metabolites being characterised by their electrophoretic peaks and their corresponding mass spectra. A total number of 29 compounds were relevant to discriminate between wt and HD plasma samples, as well as to follow-up the HD progression. The intracellular signalling was found to be the most affected metabolic pathway in HD mice after 12 weeks of birth, when mice already showed motor coordination deficiencies and cognitive decline. This fact agreed with the atrophy and dysfunction of specific neurons, loss of several types of receptors and changed expression of neurotransmitters.

Thermodynamics, transport and relaxation in non-conformal theories

  • Attems, Maximilian
  • Casalderrey Solana, Jorge
  • Mateos, David (Mateos Solé)
  • Papadimitriou, Ioannis
  • Santos-Oliván, Daniel
  • Sopuerta, Carlos F.
  • Triana Iglesias, Miquel
  • Zilhão, Miguel
We study the equilibrium and near-equilibrium properties of a holographic five-dimensional model consisting of Einstein gravity coupled to a scalar field with a non-trivial potential. The dual four-dimensional gauge theory is not conformal and, at zero temperature, exhibits a renormalisation group flow between two different fixed points. We quantify the deviations from conformality both in terms of thermodynamic observables and in terms of the bulk viscosity of the theory. The ratio of bulk over shear viscosity violates Buchel's bound. We study relaxation of small-amplitude, homogeneous perturbations by computing the quasi-normal modes of the system at zero spatial momentum. In this approximation we identify two different relaxation channels. At high temperatures, the different pressures first become approximately equal to one another, and subsequently this average pressure evolves towards the equilibrium value dictated by the equation of state. At low temperatures, the average pressure first evolves towards the equilibrium pressure, and only later the different pressures become approximately equal to one another.

Resisting and tolerating P. falciparum in pregnancy under different malaria transmission intensities

  • Ndam, Nicaise Tuikue
  • Mbuba, Emmanuel
  • González, Raquel
  • Cisteró, Pau
  • Kariuki, Simon
  • Sevene, Esperança Júlia Pires
  • Rupérez, María
  • Fonseca, Ana Maria
  • Vala, Anifa
  • Maculuve, Sónia Amós
  • Jiménez, Alfons
  • Quintó, Llorenç
  • Ouma, Peter
  • Ramharter, Michael
  • Aponte, John J.
  • Nhacolo, Arsénio
  • Massougbodji, Achille
  • Briand, Valérie
  • Kremsner, Peter G.
  • Mombo-Ngoma, Ghyslain
  • Desai, Meghna
  • Macete, Eusébio
  • Cot, Michel
  • Menéndez, Clara
  • Mayor Aparicio, Alfredo Gabriel
Resistance and tolerance to Plasmodium falciparum can determine the progression of malaria disease. However, quantitative evidence of tolerance is still limited. We investigated variations in the adverse impact of P. falciparum infections among African pregnant women under different intensities of malaria transmission. Methods P. falciparum at delivery was assessed by microscopy, quantitative PCR (qPCR) and placental histology in 946 HIV-uninfected and 768 HIV-infected pregnant women from Benin, Gabon, Kenya and Mozambique. Resistance was defined by the proportion of submicroscopic infections and the levels of anti-parasite antibodies quantified by Luminex, and tolerance by the relationship of pregnancy outcomes with parasite densities at delivery. Results P. falciparum prevalence by qPCR in peripheral and/or placental blood of HIV-uninfected Mozambican, Gabonese and Beninese women at delivery was 6% (21/340), 11% (28/257) and 41% (143/349), respectively. The proportion of peripheral submicroscopic infections was higher in Benin (83%) than in Mozambique (60%) and Gabon (55%; P = 0.033). Past or chronic placental P. falciparum infection was associated with an increased risk of preterm birth in Mozambican newborns (OR = 7.05, 95% CI 1.79 to 27.82). Microscopic infections were associated with reductions in haemoglobin levels at delivery among Mozambican women (–1.17 g/dL, 95% CI –2.09 to –0.24) as well as with larger drops in haemoglobin levels from recruitment to delivery in Mozambican (–1.66 g/dL, 95% CI –2.68 to –0.64) and Gabonese (–0.91 g/dL, 95% CI –1.79 to –0.02) women. Doubling qPCR-peripheral parasite densities in Mozambican women were associated with decreases in haemoglobin levels at delivery (–0.16 g/dL, 95% CI –0.29 to –0.02) and increases in the drop of haemoglobin levels (–0.29 g/dL, 95% CI –0.44 to –0.14). Beninese women had higher anti-parasite IgGs than Mozambican women (P < 0.001). No difference was found in the proportion of submicroscopic infections nor in the adverse impact of P. falciparum infections in HIV-infected women from Kenya (P. falciparum prevalence by qPCR: 9%, 32/351) and Mozambique (4%, 15/417). Conclusions The lowest levels of resistance and tolerance in pregnant women from areas of low malaria transmission were accompanied by the largest adverse impact of P. falciparum infections. Exposure-dependent mechanisms developed by pregnant women to resist the infection and minimise pathology can reduce malaria-related adverse outcomes. Distinguishing both types of defences is important to understand how reductions in transmission can affect malaria disease.

Performance of a modified hybrid functional in the simultaneous description of stoichiometric and reduced TiO2 polymorphs

  • Ko, Kyoung Chul
  • Lamiel Garcia, Josep Oriol
  • Lee, Jin Yong
  • Illas i Riera, Francesc
Conventional density functionals with either the local density approximation (LDA) or the generalized gradient approximation (GGA) form of the exchange-correlation potential fail to describe the electronic structure of a large number of metal oxides. Both the LDA and the GGA grossly underestimate the band gaps of these materials which severely affect the description of oxygen vacancy point defect states in reduced samples. To find a pragmatic approach to simultaneously and accurately describe the atomic and electronic structures of the most common TiO2 polymorphs, we explore the effect of the percentage of exact, non-local, Fock exchange on the electronic structure of stoichiometric rutile and anatase. From these results, a modified hybrid functional is proposed to properly describe the atomic structures, formation enthalpies and electronic structures of rutile and anatase and, at the same time, the results of reduced samples are also in good agreement with the available experimental results. The present approach can be safely used to accurately describe numerous TiO2 based materials containing defects or realistic nanoparticles for which the required large unit cells or system sizes hinder the use of GW related techniques.

Effect of size and structure on the ground-state and excited-state electronic structure of TiO2 nanoparticles

  • Cho, Daeheum
  • Ko, Kyoung Chul
  • Lamiel Garcia, Josep Oriol
  • Bromley, Stefan Thomas
  • Lee, Jin Yong
  • Illas i Riera, Francesc
We investigated the influence of size and structure on the electronic structure of TiO2 nanoparticles 0.5-3.2 nm in diameter, in both vacuum and water, using density functional theory (DFT) calculations. Specifically, we tracked the optical and electronic energy gap of a set of (TiO2)(n) nanoparticles ranging from small non-bulklike clusters with n = 4, 8, and 16, to larger nanoparticles derived from the anatase bulk crystal with n = 35 and 84. As the difference between these two energy gaps (the exciton binding energy) becomes negligible in the bulk, this magnitude provides an indicator of the bulklike character of the electronic structure of the nanoparticles under study. Extrapolating our results to larger sizes, we obtain a rough estimate of the nanoparticle size at which the electronic structure will begin to be effectively bulklike. Our results generally confirmed that the electronic structure of the nanoparticle ground state and excited state has a more pronounced structure dependency than size dependency within a size range of 0.5-1.5 nm. We also showed that the thermodynamic preference for the photocatalytic species is the first S-1 exciton. This S-1 exciton is stable under vacuum but may evolve to free charge carriers upon structural relaxation in an aqueous environment for particles 0.5-1.5 nm in size studied in the present article. An analysis of ionization potentials and electron affinities, relative to the standard reduction potential for the water splitting half-reactions, revealed the importance of considering the structural relaxation in the excited states and the presence of water for assessing the thermodynamic conditions for photocatalytic water splitting.

When anatase nanoparticles become bulk-like: properties of realistic TiO2 nanoparticles in the 1-6 nm size range from all electron relativistic density functional theory based calculations

  • Lamiel Garcia, Josep Oriol
  • Ko, Kyoung Chul
  • Lee, Jin Yong
  • Bromley, Stefan Thomas
  • Illas i Riera, Francesc
All electron relativistic density functional theory (DFT) based calculations using numerical atom-centered orbitals have been carried out to explore the relative stability, atomic, and electronic structure of a series of stoichiometric TiO2 anatase nanoparticles explicitly containing up to 1365 atoms as a function of size and morphology. The nanoparticles under scrutiny exhibit octahedral or truncated octahedral structures and span the 1-6 nm diameter size range. Initial structures were obtained using the Wulff construction, thus exhibiting the most stable (101) and (001) anatase surfaces. Final structures were obtained from geometry optimization with full relaxation of all structural parameters using both generalized gradient approximation (GGA) and hybrid density functionals. Results show that, for nanoparticles of a similar size, octahedral and truncated octahedral morphologies have comparable energetic stabilities. The electronic structure properties exhibit a clear trend converging:to the bulk values as the size of the nanoparticles increases but with a marked influence of the density functional employed. Our results suggest that electronic structure properties, and hence reactivity, for the largest anatase nanoparticles considered in this study will be similar to those exhibited by even larger mesoscale particles or by bulk systems. Finally, we present compelling evidence that anatase nanoparticles become effectively bulklike when reaching a size of similar to 20 nm diameter.

Validity and reliability of strain gauge measurement of volitional quadriceps force in patients with COPD

  • Machado Rodrigues, Fernanda
  • Demeyer, Heleen
  • Hornikx, Miek
  • Camillo, Carlos Augusto
  • Calik-Kutukcu, Ebru
  • Burtin, Chris
  • Janssens, Wim
  • Troosters, Thierry
  • Osadnik, Christian
This study investigated the validity and reliability of fixed strain gauge measurements of isometric quadriceps force in patients with chronic obstructive pulmonary disease (COPD). A total cohort of 138 patients with COPD were assessed. To determine validity, maximal volitional quadriceps force was evaluated during isometric maximal voluntary contraction (MVC) manoeuvre via a fixed strain gauge dynamometer and compared to (a) potentiated non-volitional quadriceps force obtained via magnetic stimulation of the femoral nerve (twitch (Tw); n = 92) and (b) volitional computerized dynamometry (Biodex; n = 46) and analysed via correlation coefficients. Test-retest and absolute reliability were determined via calculations of intra-class correlation coefficients (ICCs), smallest real differences (SRDs) and standard errors of measurement (SEMs). For this, MVC recordings in each device were performed across two test sessions separated by a period of 7 days ( n = 46). Strain gauge measures of MVC demonstrated very large correlation with Tw and Biodex results ( r = 0.86 and 0.88, respectively, both p < 0.0001). ICC, SEM and SRD were numerically comparable between strain gauge and Biodex devices (ICC = 0.96 vs. 0.93; SEM = 8.50 vs. 10.54 N.m and SRD = 23.59 vs. 29.22 N.m, respectively). The results support that strain gauge measures of quadriceps force are valid and reliable in patients with COPD.

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