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Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 ≤ y ≤ 2.00 were deposited by reactive DC magnetron sputtering and were subjected to electrochemical intercalation of Li+-ions and charge-balancing electrons to obtain LixTiOy films with 0.12 ≤ x ≤ 0.34. Dispersion analysis was applied to calculate the complex dielectric function ϵ(ħω)≡ϵ1(ħω)+iϵ2(ħω) from numerical inversion of optical transmittance and reflectance spectra; a superposition of Tauc-Lorentz and Lorentz oscillator models was used for this purpose. Data on ϵ2(ħω) were employed to calculate the optical conductivity and fit this property to a smallpolaron model for disordered systems with strong electron-phonon interaction and involving transitions near the Fermi level. The introduction of oxygen vacancies and/or Li+ insertion yielded band gap widening by ~0.20–0.35 eV, and both processes induced similar low-energy optical absorption. The small-polaron-based analysis indicated increases in the Fermi level by ~0.15–0.3 eV for sub-stoichiometric and/or Li+-inserted films. This suggests the existence of polaronic Ti3+ states in the lower part of the conduction band arising from transfer of electrons from oxygen vacancies and/or inserted Li+ species. The present article is a sequel to an earlier paper on oxygen-deficient and/or Li+-inserted amorphous WOy thin films and forms part of a comprehensive investigation of optical absorption in amorphous transition metal oxides with different valence states of the metallic ions. [ABSTRACT FROM AUTHOR]

Optical absorption in oxygen-deficient and Li+-ion inserted titanium oxide films was studied in the framework of small-polaron hopping. Non-stoichiometric TiOy films with 1.68 ≤ y ≤ 2.00 were deposited by reactive DC magnetron sputtering and were subjected to electrochemical intercalation of Li+-ions and charge-balancing electrons to obtain LixTiOy films with 0.12 ≤ x ≤ 0.34. Dispersion analysis was applied to calculate the complex dielectric function ε(ℏω) ≡ ε1(ℏω) + iε2 (ℏω) from numerical inversion of optical transmittance and reflectance spectra; a superposition of Tauc-Lorentz and Lorentz oscillator models was used for this purpose. Data on ε2 (ℏω) were employed to calculate the optical conductivity and fit this property to a small-polaron model for disordered systems with strong electron-phonon interaction and involving transitions near the Fermi level. The introduction of oxygen vacancies and/or Li+ insertion yielded band gap widening by ∼0.20-0.35 eV, and both processes induced similar low-energy optical absorption. The small-polaron-based analysis indicated increases in the Fermi level by ∼0.15-0.3 eV for sub-stoichiometric and/or Li+-inserted films. This suggests the existence of polaronic Ti3+ states in the lower part of the conduction band arising from transfer of electrons from oxygen vacancies and/or inserted Li+ species. The present article is a sequel to an earlier paper on oxygen-deficient and/or Li+-inserted amorphous WOy thin films and forms part of a comprehensive investigation of optical absorption in amorphous transition metal oxides with different valence states of the metallic ions. [ABSTRACT FROM AUTHOR]

Thin films of LixWO3-z with 0 ≤ x ≤ 0.27 and 0 ≤ z ≤ 0.27 were prepared by sputter deposition followed by electrochemical lithiation. Kramers-Kronig-consistent complex dielectric functions were obtained for these films by numerical inversion of experimental spectra of optical transmittance and reflectance by using a superposition of Tauc-Lorentz and Lorentz oscillator models. Low-energy optical absorption bands were induced by oxygen vacancies and/or by electrochemical intercalation of Li+ species together with charge compensating electrons. The experimental optical conductivity was fitted to a small-polaron model for disordered systems with strong electron-phonon interaction, taking into account transitions near the Fermi level. The optical absorption is due to small-polaron hopping and associated with the formation of W5+ states due to transfer of electrons from oxygen vacancies and/or insertion of Li+ species. The results also show increases in the Fermi level, caused by oxygen deficiency or Li+ insertion, which occur along with a band gap shift towards higher energies for the Li+ intercalated films. [ABSTRACT FROM AUTHOR]

The development of reliable water oxidation catalysts (WOCs) is essential for implementing artificial photosynthesis on a large technological scale. WOC research has evolved into two major branches, namely molecular and heterogeneous catalysts. Manifold design principles and plenty of mechanistic insights have been developed in these individual fields after decades of investigations. Over the past years, a growing need for knowledge transfer between both sides has emerged in order to expedite the development and optimization of next-generation WOCs. In this review, we first provide selected recent highlights in the area of molecular WOCs with different nuclearities, together with current mechanistic insight. WOCs offering molecular integrity under operational conditions are ideal platforms for elucidating reaction mechanisms and well-defined structure–function correlations at the atomic level. Next, recent mechanistic advances and design strategies for heterogeneous WOCs are illustrated for representative examples, together with a discussion of their inherent limitations in mechanistic studies. Finally, illustrative cases of knowledge transfer between molecular and heterogeneous WOCs are discussed to highlight the advantages of combining the best of both catalyst types. For the sake of conciseness, this review focuses primarily on WOCs based on the first-row transition metals, which are attracting increasing attention for both fundamental studies and economic applications. [ABSTRACT FROM AUTHOR]

Current catalysis undergoes a paradigm shift from molecular and heterogeneous realms towards new dynamic catalyst concepts. This calls for innovative strategies to understand the essential catalytic motifs and true catalysts emerging from oxidative transformation processes. Polyoxometalate (POM) clusters offer an inexhaustible reservoir for new noble metal-free catalysts and excellent model systems whose structure–activity relationships and mechanisms remain to be explored. Here, we first introduce a new {ZnnNa6−n(B-α-SbW9O33)2} (n = 3–6) catalyst family with remarkable tuning options of the Zn-based core structure and high activity in H2O2-assisted catalytic alcohol oxidation as a representative reaction. Next, high level solution-based computational modelling of the intermediates and transition states was carried out for [Zn6Cl6(SbW9O33)2]12− as a representative well-defined case. The results indicate a radical-based oxidation process with the involvement of tungsten and adjacent zinc metal centers. The {ZnnNa6−n(B-α-SbW9O33)2} series indeed efficiently catalyses alcohol oxidation via peroxotungstate intermediates, in agreement with strong spectroscopic support and other experimental evidence for the radical mechanism. Finally, the high performance of [Zn6Cl6(SbW9O33)2]12− was traced back to its transformation into a highly active and robust disordered Zn/W-POM catalyst. The atomic short-range structure of this resting pre-catalyst was elucidated by RMC modelling of the experimental W-L3 and Zn-K edge EXAFS spectra and supported with further analytical methods. We demonstrate that computational identification of the reactive sites combined with the analytical tracking of their dynamic transformations provides essential input to expedite cluster-based molecular catalyst design. [ABSTRACT FROM AUTHOR]

Transition metal carbodiimides MNCN (M = Co, Ni, Co0.9Ni0.1, Mn and Cu), were studied by simultaneous operando Raman and X-ray absorption spectroscopy (XAS) with focus on surface oxide detection during electrocatalytic water oxidation. As a proof of concept, easily modifiable screen-printed electrodes were used in this unified operando synchrotron setup for a trade-off between convenience of electrochemical anodization and spectroscopic data acquisition. Monitoring of chemical and structural transformations at the electrode surface during initial anodic electrode polarization shows stability for MNCN with M = Co, Ni, Co0.9Ni0.1 and Mn. While MnNCN is inactive, CoNCN emerges as the most active representative of the series. CuNCN displays pronounced side reactions and the formation of a surface copper oxide layer leading to lower current density attributed to water oxidation, as evident from an irreversible variation of the CuNCN redox behaviour in rotating ring-disc voltammetry. Furthermore, the accompanying structural and vibrational spectroscopy properties of the different MNCN compounds were explored with complementary ex situ analytical methods. [ABSTRACT FROM AUTHOR]

Brain atlases are tools based on comprehensive studies used to locate biological characteristics (structures, connections, proteins, and gene expression) in different regions of the brain. These atlases have been disseminated to the point where tools have been created to store, manage, and share the information they contain. This study used the data published by the Allen Mouse Brain Atlas (2004) for mice (C57BL/6J) and Allen Human Brain Atlas (2010) for humans (6 donors) to compare the expression of serotonin-related genes. Genes of interest were searched for manually in each case (in situ hybridization for mice and microarrays for humans), normalized expression data (z-scores) were extracted, and the results were graphed. Despite the differences in methodology, quantification, and subjects used in the process, a high degree of similarity was found between expression data. Here we compare expression in a way that allows the use of translational research methods to infer and validate knowledge. This type of study allows part of the relationship between structures and functions to be identified, by examining expression patterns and comparing levels of expression in different states, anatomical correlations, and phenotypes between different species. The study concludes by discussing the importance of knowing, managing, and disseminating comprehensive, open-access studies in neuroscience. [ABSTRACT FROM AUTHOR]

Parkinson’s disease (PD) is a neurodegenerative condition, which compromises the motor functions and causes the alteration of some executive brain functions. The presence of changes in cognitive symptoms in PD could be due to the procedure of deep brain stimulation (DBS). We searched in several databases for studies that compared performance in executive function tests before and after the DBS procedure in PE and then performed a meta-analysis. After the initial search, there were 15 articles that specifically evaluated the functions of verbal fluency, working memory, cognitive flexibility, abstract thinking, and inhibition. It was found that there were differences in the evaluation of the cognitive functions in terms of the protocols, which generated heterogeneity in the results of the meta-analysis. Likewise, a tendency to diminish functions like verbal fluency and inhibition was found, being this consistent with similar studies. In the other functions evaluated, no difference was found between pre- and postsurgery scores. Monitoring of this type of function is recommended after the procedure. [ABSTRACT FROM AUTHOR]

The design of spectrally encoded fiber Bragg grating (FBG) sensors is proposed in order to incorporate more information in the optical measurement system. This information can provide full distinction between sensors operating at the same wavelength range. The encoded sensors are inspired by Optical Code Division Multiplexing (OCDM) techniques, specifically, we used Optical Orthogonal Codes (OOC) in order to define the spectral shape of the FBG sensors, providing them with a unique spectral signature. As a result we demonstrated the detection and tracking of the proposed sensors which allows effective measurement of temperature or strain even under overlapping conditions. The interrogation of the proposed encoded sensors could be performed easily and in real time through the autocorrelation product between the reflected spectrum and each sensor codeword. A simple addition to this identification method is implemented in order to remove any error in the interrogation process. Furthermore, a simulation of the proposed sensors under overlapping conditions is performed in order to test the distinction capability of the system. Finally the manufacturing and measurement of the sensors is described. [ABSTRACT FROM AUTHOR]

We present a study of the maximum stress supported by elastics bands of nitrile as a function of the natural length and the load time. The maximum tension of rupture and the corresponding variation in length were found by measuring the elongation of an elastic band when a mass is suspended from its free end until it reaches the breaking point. The work done by non-conservative forces was calculated by means of mechanical hysteresis cycles. Measurement of the hysteresis cycle was performed by the controlled addition and subtraction of masses to produce the band's stretching and contraction processes. It was found that the tension of rupture of an elastic band is independent of its natural length and that it decreases linearly with increasing load time. The mechanical work lost in the hysteresis cycle increases linearly with the natural length of the elastic band. An analysis using a state equation of the thermodynamics of rubber bands was performed obtaining good agreement with the experimental results. Also shown is the dependence on the work done by non-conservative forces in repetitive processes of cyclic hysteresis. This experiment is suitable to be implemented in experimental physics courses as an example of showing the characteristics of elastic materials; furthermore it can be done with inexpensive equipment. [ABSTRACT FROM AUTHOR]