(Photo)Electrocatalytic CO2 Reduction at the Defective Anatase TiO2 (101) Surface

Excessive carbon dioxide (CO2) emissions by combustion of fossil fuels are linked to global warming and rapid climate change. One promising route to lowering the concentration of CO2 in the atmosphere is to reduce it to useful small molecules via photoelectrocatalytic hydrogenation, which would enable solar energy storage with a zero-carbon emission cycle and perform a more efficient separation of the photogenerated electron and hole pair than pure photocatalysis. Indeed, photoelectrocatalytic CO2 reduction has been an intense focus of research. Using the density functional theory (DFT), we studied the CO2 reduction reaction on the defective anatase TiO2 (101) surface, at both the solvent/catalyst and the electrolyte/catalyst interfaces. The analysis of the electronic structure of the surface shows a contrast between the solvent/catalyst and the electrolyte/catalyst interfaces, which results in the two corresponding catalytic cycles being distinct. Our study explains at the electronic and mechanistic levels why methanol is the main product in the presence of the electrolyte and why the overpotential is not only controlled by the reaction process but also by the diffusion process

Identification and characterization of thermophilic Synechococcus spp. isolates from Asian geothermal springs

Two thermophilic cyanobacterial strains, Ts and Bs, collected from Asian geothermal springs were identified morphologically and phylogenetically as Synechococcus in the order Chroococcales and were isolated into axenic cultures. In addition to the high similarities between their full 16S rRNA gene sequences, both strains also shared similar pigment profiles and fatty acid compositions but with varied ratios. Strain Ts had elevated levels of photoprotective pigments such as carotenoid and scytonemin even after prolonged culture under identical laboratory conditions, whereas strain Bs produced more chlorophyll a per unit cell volume, perhaps resulting from UV adaptation in the natural habitats. In addition, strain Ts had more content than strain Bs in terms of the total fatty acids and the proportion of unsaturated fatty acids. Neither isolate was able to fix nitrogen, and they had zero susceptibility to ampicillin and streptomycin. © 2007 NRC.published_or_final_versio

Vortex Depinning in a Two-Dimensional Superfluid

\ua9 The Author(s) 2024.We employ the Gross–Pitaevskii theory to model a quantized vortex depinning from a small obstacle in a two-dimensional superfluid due to an imposed background superfluid flow. We find that, when the flow’s velocity exceeds a critical value, the vortex drifts orthogonally to the flow before subsequently moving parallel to it away from the pinning site. The motion of the vortex around the pinning site is also accompanied by an emission of a spiral-shaped sound pulse. Through simulations, we present a phase diagram of the critical flow velocity for vortex depinning together with an empirical formula that illustrates how the critical velocity increases with the height and width of the pinning site. By employing a variety of choices of initial and boundary conditions, we are able to obtain lower and upper bounds on the critical velocity and demonstrate the robustness of these results

Writing CFT correlation functions as AdS scattering amplitudes

We explore the Mellin representation of conformal correlation functions recently proposed by Mack. Examples in the AdS/CFT context reinforce the analogy between Mellin amplitudes and scattering amplitudes. We conjecture a simple formula relating the bulk scattering amplitudes to the asymptotic behavior of Mellin amplitudes and show that previous results on the flat space limit of AdS follow from our new formula. We find that the Mellin amplitudes are particularly useful in the case of conformal gauge theories in the planar limit. In this case, the four point Mellin amplitudes are meromorphic functions whose poles and their residues are entirely determined by two and three point functions of single-trace operators. This makes the Mellin amplitudes the ideal objects to attempt the conformal bootstrap program in higher dimensions.Comment: 23 pages + appendice

Dislocation network at InN/GaN interface revealed by scanning tunneling microscopy

For heteroepitaxy of InN on GaN(0001) by molecular-beam epitaxy, the lattice misfit strain is relieved by misfit dislocations (MDs) formed at the interface between InN and GaN. Imaging by scanning tunneling microscopy (STM) of the surfaces of thin InN epifilms reveals line feature parallel to 〈112 0〉. Their contrast becomes less apparent for thicker epifilms. From the interline spacing as well as a comparison with transmission electron microscopy studies, it is suggested that they correspond to the MDs beneath the surface. The STM contrast originates from both the surface distortion caused by the local strain at MDs and the electronic states of the defects. © 2008 American Institute of Physics.published_or_final_versio

Joint PDF modelling of turbulent flow and dispersion in an urban street canyon

The joint probability density function (PDF) of turbulent velocity and concentration of a passive scalar in an urban street canyon is computed using a newly developed particle-in-cell Monte Carlo method. Compared to moment closures, the PDF methodology provides the full one-point one-time PDF of the underlying fields containing all higher moments and correlations. The small-scale mixing of the scalar released from a concentrated source at the street level is modelled by the interaction by exchange with the conditional mean (IECM) model, with a micro-mixing time scale designed for geometrically complex settings. The boundary layer along no-slip walls (building sides and tops) is fully resolved using an elliptic relaxation technique, which captures the high anisotropy and inhomogeneity of the Reynolds stress tensor in these regions. A less computationally intensive technique based on wall functions to represent boundary layers and its effect on the solution are also explored. The calculated statistics are compared to experimental data and large-eddy simulation. The present work can be considered as the first example of computation of the full joint PDF of velocity and a transported passive scalar in an urban setting. The methodology proves successful in providing high level statistical information on the turbulence and pollutant concentration fields in complex urban scenarios.Comment: Accepted in Boundary-Layer Meteorology, Feb. 19, 200

Observation of Faraday rotation from a single confined spin

Ability to read-out the state of a single confined spin lies at the heart of solid-state quantum information processing. While all-optical spin measurements using Faraday rotation has been successfully implemented in ensembles of semiconductor spins, read-out of a single semiconductor spin has only been achieved using transport measurements based on spin-charge conversion. Here, we demonstrate an all-optical dispersive measurement of the spin-state of a single electron trapped in a semiconductor quantum dot. We obtain information on the spin state through conditional Faraday rotation of a spectrally detuned optical field, induced by the polarization- and spin-selective trion (charged quantum dot) transitions. To assess the sensitivity of the technique, we use an independent resonant laser for spin-state preparation. An all-optical dispersive measurement on single spins has the important advantage of channeling the measurement back-action onto a conjugate observable, thereby allowing for repetitive or continuous quantum nondemolition (QND) read-out of the spin-state. We infer from our results that there are of order unity back-action induced spin-flip Raman scattering events within our measurement timescale. Therefore, straightforward improvements such as the use of a solid-immersion lens and higher efficiency detectors would allow for back-action evading spin measurements, without the need for a cavity

Evidence Base of Clinical Studies on Qi Gong: A Bibliometric Analysis

© 2020 The Authors Objective: This bibliometric study aimed to systematically and comprehensively summarize the volume, breadth and evidence for clinical research on Qigong. And this bibliometric analysis also can provide the evidence of this field. Design: Bibliometric analysis. Methods: All types of primary and secondary studies on humans were included: systematic reviews, randomized clinical trials, non-randomized controlled clinical studies, case series and case reports. Chinese Biomedical Literature Database, China National Knowledge Infrastructure, Chinese Scientific Journal Database, Chinese Academic Conference Papers Database and Chinese Dissertation Database, PubMed and the Cochrane Library were searched from the date of inception to December 10, 2018. Bibliometric information, such as publication information, disease/condition, Qigong intervention and research results were extracted and analyzed. Results: A total of 886 clinical studies were identified: including 47 systematic reviews, 705 randomized clinical trials, 116 non-randomized controlled clinical studies, 12 case series and 6 case reports. The studies were conducted in 14 countries. The top 15 diseases/conditions studied were: diabetes, chronic obstructive pulmonary disease, hypertension, stroke, cervical spondylosis, lumbar disc herniation, insomnia, knee osteoarthritis, low back pain, and osteoporosis, Coronary heart disease, breast cancer, periarthritis of shoulder, depression, metabolic syndrome. Of the various Qigong exercises reported in these 886 clinical studies, Ba Duan Jin was the most frequently researched in 492 (55.5%) studies, followed by Health Qigong 107 (12.1%), Dao Yin Shu 85 (9.6%), Wu Qin Xi 67 (7.6%) and Yi Jin Jing 66 (7.4%). The most frequently used comparisons in randomized trials were maintaining normal way of life unchanged 149 (18.1%), the remaining controls included conventional treatment, mainly western medicine, Chinese herbal medicine, acupuncture, health education, psychological therapy, Yoga, Tai Chi and other non-drug therapy. The most frequently reported outcomes were physical function, quality of life, symptoms, pain and mental health indicators. Beneficial results from practicing Qigong were reported in 97% of studies. Conclusions: Qigong research publications have been increasing gradually. Reports on study types, participants, Qigong Intervention, and outcomes are diverse and inconsistent. There is an urgent need to develop a set of reporting standards for various interventions of Qigong. Further trials of high methodological quality with sufficient sample size and real world studies are needed to verify the effects of Qigong in health and disease management