Efficient photosynthesis of carbon monoxide from CO2 using perovskite photovoltaics

Artificial photosynthesis, mimicking nature in its efforts to store solar energy, has received considerable attention from the research community. Most of these attempts target the production of H2 as a fuel and our group recently demonstrated solar-to-hydrogen conversion at 12.3% efficiency. Here, in an effort to take this approach closer to real photosynthesis, which is based on the conversion of CO2, we demonstrate the efficient reduction of CO2 to carbon monoxide driven solely by simulated sunlight using water as the electron source. Employing series-connected perovskite photovoltaics and high-performance catalyst electrodes, we reach a solar-to-CO efficiency exceeding 6.5%, which represents a new benchmark in sunlight-driven CO2 conversion. Considering hydrogen as a secondary product, an efficiency exceeding 7% is observed. Furthermore, this study represents one of the first demonstrations of extended, stable operation of perovskite photovoltaics, whose large open-circuit voltage is shown to be particularly suited for this process

Positioning, Articulating, and Crafting Conceptual Articles on Entrepreneurship

Conceptual Articles Are Important for Theory Building but the Special Challenges of Developing Conceptual Articles on Entrepreneurship Has Not Been Fully Considered. We Begin to Fill This Gap by Discussing the Nature of Conceptual Articles on Entrepreneurship, Particularly Those Geared for Publication in Entrepreneurship Theory and Practice. We Introduce Three Dimensions of the Entrepreneurship Discipline—uniqueness, Relevance, and Multiplicity—and Discuss How They Can Affect the Positioning of Conceptual Articles and the Articulation of their Contribution. We Also Enumerate Some Basic Principles for Crafting Good Conceptual Articles and Present Guidelines based on Our Discussion

The kinetics of metal oxide photoanodesfrom charge generation to catalysis

Generating charge carriers with lifetimes long enough to drive catalysis is a critical aspect for both photoelectrochemical and photocatalytic systems and a key determinant of their efficiency. This review addresses the charge carrier dynamics underlying the performance of metal oxides as photoanodes and their ability to drive photoelectrochemical water oxidation, alongside wider comparison with metal oxide function in photocatalytic and electrocatalytic systems. We start by highlighting the disparity between the ps–ns lifetimes of electron and holes photoexcited in bulk metal oxides versus the ms –s timescale of water oxidation catalysis. We go onto review recent literature of the dominant kinetic processes determining photoanode performance, namely charge generation, polaron formation and charge trapping, bulk and surface recombination, charge separation and extraction, and finally the kinetics of water oxidation catalysis. With each topic, we review current understanding and note areas of remaining uncertainty or controversy. We discuss the potential for material selection and examine approaches such as doping, nanostructuring, junction formation and/or co-catalyst deposition to enhance performance. Critically, we examine how such performance enhancements can be understood from analyses of carrier dynamics and propose design guidelines for further material or device optimisation

AMS measurements of cosmogenic and supernova-ejected radionuclides in deep-sea sediment cores

Samples of two deep-sea sediment cores from the Indian Ocean are analyzed with accelerator mass spectrometry (AMS) to search for traces of recent supernova activity around 2 Myr ago. Here, long-lived radionuclides, which are synthesized in massive stars and ejected in supernova explosions, namely 26Al, 53Mn and 60Fe, are extracted from the sediment samples. The cosmogenic isotope 10Be, which is mainly produced in the Earths atmosphere, is analyzed for dating purposes of the marine sediment cores. The first AMS measurement results for 10Be and 26Al are presented, which represent for the first time a detailed study in the time period of 1.7-3.1 Myr with high time resolution. Our first results do not support a significant extraterrestrial signal of 26Al above terrestrial background. However, there is evidence that, like 10Be, 26Al might be a valuable isotope for dating of deep-sea sediment cores for the past few million years.Comment: 5 pages, 2 figures, Proceedings of the Heavy Ion Accelerator Symposium on Fundamental and Applied Science, 2013, will be published by the EPJ Web of conference

Multiple dimensions of excessive daytime sleepiness

Background: In this study we investigated subjective measures of sleepiness and related our findings to dimensions of affect, fatigue, emotion, mood and quality of life based on a hypothetical multidimensional model of sleepiness. Methods: Patients referred to a sleep clinic were assessed regarding their excessive daytime sleepiness (EDS), sleep complaints, routine and symptoms. Age, gender and body mass index (BMI), the Epworth Sleepiness Scale (ESS), the Stanford Sleepiness Scale (SSS), the Samn-Perelli fatigue Scale (SPS), the Global Vigor and Affect Scale (GVS and GAS, respectively), the Hospital Anxiety and Depression Scale (HADS-A and HADS-D, respectively), and the Positive and Negative Affect Schedule (PAS and NAS, respectively) scores were recorded. Results: Fifty patients [25 male, 45.2 (18.7) years] completed the questionnaires. The ESS scores were positively correlated with SSS, SPS, HADS-A, HADS-D and NAS scores and negatively with GVS and GAS scores (P<0.05). The SPS (P<0.001) and HADS-A scores (P=0.002) were independently associated with the ESS scores (R2=0.532, adjusted R2 =0.4794, P<0.001). Conclusions: A model of sleepiness that assesses dimensions of fatigue and anxiety could explain the symptom of subjective sleepiness better than the isolated use of the ESS

Understanding the dynamic momentum aperture of the Advanced Light Source

The lifetime of a light source with small emittance like the Advanced Light Source (ALS) is usually limited by the momentum acceptance of the ring. Large momentum acceptances are reached by providing enough RF voltage and by avoiding a degradation of the dynamic momentum aperture. At the ALS the size of the momentum acceptance depends strongly on the transverse dynamics. It is very sensitive to machine conditions such as the tunes and chromaticities since depending on those conditions the Touschek scattered particles explore different resonance regions in the phase space. In this paper we show that by using a single-turn ’pinger’ magnet together with turn-byturn beam position monitors (BPM) one can identify the cause of a reduction in momentum acceptance and take steps to improve the acceptance

Acute ischaemic hemispheric stroke is associated with impairment of reflex in addition to voluntary cough

Cough function is impaired after stroke; this may be important for protection against chest infection. Reflex cough (RC) intensity indices have not been described after stroke. RC, voluntary cough (VC) and respiratory muscle strength were studied in patients within 2 weeks of hemispheric infarct. The null hypotheses were that patients with cortical hemisphere stroke would show the same results as healthy controls on: 1) objective indices of RC and VC intensity; and 2) respiratory muscle strength tests.Peak cough flow rate (PCFR) and gastric pressure (Pga) were measured during maximum VC and RC. Participants also underwent volitional and nonvolitional respiratory muscle testing. Nonvolitional expiratory muscle strength was assessed by measuring Pga increase after magnetic stimulation over the T10 nerve roots (twitch T10 Pga). Stroke severity was scored using the National Institutes of Health Stroke Scale (NIHSS; maximum = 31).18 patients (mean±SD age 62±15 yrs and NIHSS score 14±8) and 20 controls (56±16 yrs) participated. VC intensity was impaired in patients (PCFR 287±171 versus 497±122 L·min−1) as was VC Pga (98.5±61.6 versus 208.5±61.3 cmH2O; p&lt;0.001 for both). RC PCFR was reduced in patients (204±111 versus 379±110 L·min−1; p&lt;0.001), but RC Pga was not significantly different from that of controls (179.0±78.0 versus 208.0±77.4 cmH2O; p = 0.266). Patients exhibited impaired volitional respiratory muscle tests, but twitch T10 Pga was normal.VC and RC are both impaired in hemispheric stroke patients, despite preserved expiratory muscle strength. Cough coordination is probably cortically modulated and affected by hemispheric stroke

Symmetric achromatic low-beta collider interaction region design concept

We present a new symmetry-based concept for an achromatic low-beta collider interaction region design. A specially-designed symmetric Chromaticity Compensation Block (CCB) induces an angle spread in the passing beam such that it cancels the chromatic kick of the final focusing quadrupoles. Two such CCBs placed symmetrically around an interaction point allow simultaneous compensation of the 1st-order chromaticities and chromatic beam smear at the IP without inducing significant 2nd-order aberrations to the particle trajectory. We first develop an analytic description of this approach and explicitly formulate 2nd-order aberration compensation conditions at the interaction point. The concept is next applied to develop an interaction region design for the ion collider ring of an electron-ion collider. We numerically evaluate performance of the design in terms of momentum acceptance and dynamic aperture. The advantages of the new concept are illustrated by comparing it to the conventional distributed-sextupole chromaticity compensation scheme.Comment: 12 pages, 17 figures, to be submitted to Phys. Rev. ST Accel. Beam

Effectiveness of photodynamic therapy and sodium hypochlorite on root canal system infected with Enterococcus faecalis - an in vitro study

Portuguese title: Eficácia da terapia fotodinâmica e do hipoclorito de sódio sobre o sistema de canais radiculares infectado com Enterococcus faecalis - um estudo in vitro Abstract and Keywords also in Portuguese. Journal title in English: Journal of Dental Science.Objective: The purpose of this study was to evaluate, in vitro , the effectiveness of photodynamic therapy and sodium hypochlorite over root canal system infected with Enterococcus faecalis . Methods: The root canals of 45 single-rooted human extracted teeth were enlarged up to a file 60, autoclaved, inoculated with Enterococcus faecalis and incubated for 30 days. The samples were divided into five groups (G1 – n=5; G2-G5 – n=10) according to the protocol of decontamination: G1 (negative control) – no procedure was performed; G2 – distilled water; G3 – photodynamic therapy (PDT); G4 – 2.5% sodium hypochlorite (NaOCl); and G5 – 2.5% NaOCl+PDT. Scanning electron microscopy (SEM) were performed to evaluate the effectiveness of proposed treatments. The assessment was made by images of each third at 5000x magnification for the canal wall and 10000x for the exposed tubule area. The presence of bacteria was scored by position ranks from 1 to 45, where the higher the value, the cleanliness of the sample. Data were subjected to one-way ANOVA followed by post-hoc Tukey test ( α =0.05). Results: Group 4 (2.5% NaOCl) and 5 (2.5% NaOCl + PDT) had the highest mean of position ranks for all thirds of the root canal in the canal wall, which was statistically different from groups 1, 2 and 3 ( p <0.05). Group 3 (PDT), group 4 (2.5% NaOCl) and 5 (2.5% NaOCl+PDT) had the highest mean of position ranks in the exposed tubule area, which was statistically different from groups 1 and 2 ( p <0.05). Conclusion: the association of 2.5% sodium hypochlorite + photodynamic therapy can be considered an effective protocol for the elimination of Enterococcus faecalis. = Objetivo: o propósito deste estudo foi avaliar, in vitro, a eficácia da terapia fotodinâmica e do hipoclorito de sódio sobre o sistema de canais radiculares infectados com Enterococcus faecalis. Metodologia: Os canais radiculares de 45 dentes humanos extraídos unirradiculares foram ampliados até a lima 60, autoclavados, inoculados com Enterococcus faecalis e incubados por 30 dias. As amostras foram divididas em cinco grupos (G1 – n=5; G2-G5 – n=10) de acordo com o protocolo de descontaminação: G1 (controle negativo) – não foi realizado procedimento; G2 – água destilada; G3 – terapia fotodinâmica; G4 – hipoclorito de sódio 2,5%; G5 – hipoclorito de sódio 2,5%+terapia fotodinâmica. Microscopia eletrônica de varredura foi realizada para avaliar a eficácia dos tratamentos propostos. A avaliação foi feita através de imagens de cada terço a 5000x de magnificação nas paredes do canal e 10000x na profundidade dos túbulos dentinários. A presença de bacterias foi determinada por intermédio de rank de posições a partir de 1 até 45, onde quanto maior o valor, maior a limpeza da amostra. Os dados foram submetidos a one-way ANOVA seguido por post-hoc de Tukey (α=0.05). Resultados: Grupo 4 (NaOCl 2,5%) e 5 (NaOCl 2,5%+PDT) obtiveram a maior media de posição de ranks para todos os terços do canal radicular na parede do canal, o que foi estatisticamente diferente dos grupos 1, 2 e 3 (p<0.05). Grupo 3 (PDT), grupo 4 (NaOCl 2,5%) e 5 (NaOCl 2,5%+PDT) obtiveram a maior méida de posição de ranks para todos os terços do canal radicular na profundidade dos túbulos dentinários, o que foi estatisticamente diferente dos grupos 1 e 2 (p<0,05). Conclusão: A associação de hipoclorito de sódio.Matheus Albino Souza, Liviu Steier, Giampiero Rossi-Fedele, Valdir Barth Júnior, Silvia Dias de Oliveira, José Antônio Poli de Figueired

In situ observation of picosecond polaron self-localisation in α-Fe2O3 photoelectrochemical cells

Hematite (α-Fe2O3) is the most studied artificial oxygen-evolving photo-anode and yet its efficiency limitations and their origin remain unknown. A sub-picosecond reorganisation of the hematite structure has been proposed as the mechanism which dictates carrier lifetimes, energetics and the ultimate conversion yields. However, the importance of this reorganisation for actual device performance is unclear. Here we report an in situ observation of charge carrier self-localisation in a hematite device, and demonstrate that this process affects recombination losses in photoelectrochemical cells. We apply an ultrafast, device-based optical-control method to resolve the subpicosecond formation of small polarons and estimate their reorganisation energy to be ~0.5 eV. Coherent oscillations in the photocurrent signals indicate that polaron formation may be coupled to specific phonon modes (<100 cm-1). Our results bring together spectroscopic and device characterisation approaches to reveal new photophysics of broadly-studied hematite devices