Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy

Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright 1La and 1Lb electronic states of 1\u3c0\u3c0* character and spectroscopically dark and dissociative 1\u3c0\u3c3* states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited 1La state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived 1Lb state or the 1\u3c0\u3c3* state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the 1\u3c0\u3c3* state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied.Peer reviewed: YesNRC publication: Ye

Blue hydrogen and industrial base products: The future of fossil fuel exporters in a net-zero world

Is there a place for today's fossil fuel exporters in a low-carbon future? This study explores trade channels between energy exporters and importers using a novel electricity-hydrogen-steel energy systems model calibrated to Norway, a major natural gas producer, and Germany, a major energy consumer. Under tight emission constraints, Norway can supply Germany with electricity, (blue) hydrogen, or natural gas with re-import of captured CO2. Alternatively, it can use hydrogen to produce steel through direct reduction and supply it to the world market, an export route not available to other energy carriers due to high transport costs. Although results show that natural gas imports with CO2 capture in Germany is the least-cost solution, avoiding local CO2 handling via imports of blue hydrogen (direct or embodied in steel) involves only moderately higher costs. A robust hydrogen demand would allow Norway to profitably export all its natural gas production as blue hydrogen. However, diversification into local steel production, as one example of easy-to-export industrial base products, offers an effective hedge against the possibility of lower European blue hydrogen demand. Looking beyond Europe, the findings of this study are also relevant for the world's largest energy exporters (e.g., OPEC+) and importers (e.g., developing Asia). Thus, it is recommended that large hydrocarbon exporters consider a strategic energy export transition to a diversified mix of blue hydrogen and climate-neutral industrial base products.publishedVersio

Substituent effects on the relaxation dynamics of furan, furfural and β-furfural: a combined theoretical and experimental approach

For the series furan, furfural and β-furfural we investigated the effect of substituents and their positioning on the photoinduced relaxation dynamics in a combined theoretical and experimental approach. Using time resolved photoelectron spectroscopy with a high intensity probe pulse, we can, for the first time, follow the whole deactivation process of furan through a two photon probe signal. Using the extended 2-electron 2-orbital model [Nenov et al., J. Chem. Phys., 2011, 135, 034304] we explain the formation of one central conical intersection and predict the influence of the aldehyde group of the derivatives on its geometry. This, as well as the relaxation mechanisms from photoexcitation to the final outcome was investigated using a variety of theoretical methods. Complete active space self consistent field was used for on-the-fly calculations while complete active space perturbation theory and coupled cluster theory were used to accurately describe critical configurations. Experiment and theory show the relaxation dynamics of furfural and β-furfural to be slowed down, and together they disclose an additional deactivation pathway, which is attributed to the nO lonepair state introduced with the aldehyde group

A matrix free, partitioned solution of fluid-structure interaction problems using finite volume and finite element methods

A fully-coupled partitioned finite volume–finite volume and hybrid finite volume–finite element fluid–structure interaction scheme is presented. The fluid domain is modelled as a viscous incompressible isothermal region governed by the Navier–Stokes equations and discretised using an edge-based hybrid-unstructured vertex-centred finite volume methodology. The structure, consisting of a homogeneous isotropic elastic solid undergoing large, non-linear deformations, is discretised using either an elemental/nodal-strain finite volume approach or isoparametric Q8 finite elements and is solved using a matrix-free dual-timestepping approach. Coupling is on the solver sub-iteration level leading to a tighter coupling than if the subdomains are converged separately. The solver is parallelised for distributed-memory systems using METIS for domain-decomposition and MPI for inter-domain communication. The developed technology is evaluated by application to benchmark problems for stronglycoupled fluid–structure interaction systems. It is demonstrated that the scheme results in full coupling between the fluid and solid domains, whilst furnishing accurate solutions.http://www.elsevier.com/locate/ejmflu2016-01-31hb201

An enhanced finite volume method to model 2D linear elastic structures

This paper details the evaluation and enhancement of the vertex-centred finite volume method for the purpose of modelling linear elastic structures undergoing bending. A matrix-free edge-based finite volume procedure is discussed and compared with the traditional isoparametric finite element method via application to a number of test-cases. It is demonstrated that the standard finite volume approach exhibits similar disadvantages to the linear Q4 finite element formulation when modelling bending. An enhanced finite volume approach is proposed to circumvent this and a rigorous error analysis conducted. It is demonstrated that the developed finite volume method is superior to both standard finite volume and Q4 finite element methods, and provides a practical alternative to the analysis of bending-dominated solid mechanics problems.http://www.elsevier.com/locate/apmhb201

Excited state non-adiabatic dynamics of pyrrole:A time-resolved photoelectron spectroscopy and quantum dynamics study

The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole's electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A2(\u3c0\u3c3 17) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A1(\u3c0\u3c0 17) and B2(\u3c0\u3c0 17) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole's electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B1(\u3c0\u3c3 17) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B1(\u3c0\u3c3 17) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A2(\u3c0\u3c3 17) state.Peer reviewed: YesNRC publication: Ye

Physiological function and catalytic versatility of bacterial multihaem cytochromescinvolved in nitrogen and sulfur cycling

Bacterial MCCs (multihaem cytochromes c) represent widespread respiratory electron-transfer proteins. In addition, some of them convert substrates such as nitrite, hydroxylamine, nitric oxide, hydrazine, sulfite, thiosulfate or hydrogen peroxide. In many cases, only a single function is assigned to a specific MCC in database entries despite the fact that an MCC may accept various substrates, thus making it a multifunctional catalyst that can play diverse physiological roles in bacterial respiration, detoxification and stress defence mechanisms. The present article briefly reviews the structure, function and biogenesis of selected MCCs that catalyse key reactions in the biogeochemical nitrogen and sulfur cycles

Модель Портера как стратегический инструмент анализа (на примере рынка мороженого Республики Беларусь)

Разработка стратегии предприятия основывается на анализе микросреды с помощью модели Портера, который позволяет сформулировать основные угрозы иразработать способы защиты от них. На примере рынка мороженого было проведено выявление и анализ угроз и сформулированы направления работы по защите

The LSST Camera Overview

The LSST camera is a wide-field optical (0.35-1um) imager designed to provide a 3.5 degree FOV with better than 0.2 arcsecond sampling. The detector format will be a circular mosaic providing approximately 3.2 Gigapixels per image. The camera includes a filter mechanism and, shuttering capability. It is positioned in the middle of the telescope where cross-sectional area is constrained by optical vignetting and heat dissipation must be controlled to limit thermal gradients in the optical beam. The fast, f/1.2 beam will require tight tolerances on the focal plane mechanical assembly. The focal plane array operates at a temperature of approximately -100 C to achieve desired detector performance. The focal plane array is contained within an evacuated cryostat, which incorporates detector front-end electronics and thermal control. The cryostat lens serves as an entrance window and vacuum seal for the cryostat. Similarly, the camera body lens serves as an entrance window and gas seal for the camera housing, which is filled with a suitable gas to provide the operating environment for the shutter and filter change mechanisms. The filter carousel can accommodate 5 filters, each 75 cm in diameter, for rapid exchange without external intervention