Stability of Modified Electroweak Strings

We discuss the stability of an electroweak string with axions in its core, which give to the configuration a quasi-topological property, and compare it with other modifications using instantons in the thin wall approximation.Comment: Minor changes and inclusion of one figure. To be published on Z. f. Physik C. 11 pages, 1 postcript figur

Vacuum correlations at geodesic distance in quantum gravity

The vacuum correlations of the gravitational field are highly non-trivial to be defined and computed, as soon as their arguments and indices do not belong to a background but become dynamical quantities. Their knowledge is essential however in order to understand some physical properties of quantum gravity, like virtual excitations and the possibility of a continuum limit for lattice theory. In this review the most recent perturbative and non-perturbative advances in this field are presented. (To appear on Riv. Nuovo Cim.)Comment: report U.T.F. 332, July 94. Plain TeX, 67 pp. (+ 1 table and 7 figures, available from the author

Inexpensive ionic liquids: [HSO₄]¯-based solvent production at bulk scale

Through more than two decades’ intensive research, ionic liquids (ILs) have exhibited significant potential in various areas of research at laboratory scales. This suggests that ILs-based industrial process development will attract increasing attention in the future. However, there is one core issue that stands in the way of commercialisation: the high cost of most laboratory-synthesized ILs will limit application to small-scale, specialized processes. In this work, we evaluate the economic feasibility of two ILs synthesized via acid–base neutralization using two scenarios for each: conventional and intensification processing. Based upon our initial models, we determined the cost price of each IL and compared the energy requirements of each process option. The cost prices of triethylammonium hydrogen sulfate and 1-methylimidazolium hydrogen sulfate are estimated as $1.24 kg−1 and$2.96–5.88 kg−1, respectively. This compares favourably with organic solvents such as acetone or ethyl acetate, which sell for $1.30–$1.40 kg−1. Moreover, the raw materials contribute the overwhelming majority of this cost and the intensified process using a compact plate reactor is more economical due to lower energy requirements. These results indicate that ionic liquids are not necessarily expensive, and therefore large-scale IL-based processes can become a commercial reality

Rotational molecular dynamics in the RI phase of n-nonadecane

info:eu-repo/semantics/publishe

Sustainable scale-up of negative emissions technologies and practices: where to focus

Most climate change mitigation scenarios restricting global warming to 1.5 oC rely heavily on Negative Emissions Technologies and Practices (NETPs). Here we updated previous literature reviews and conducted an analysis to identify the most appealing NETPs. We evaluated 36 NETPs configurations considering their technical maturity, economic feasibility, greenhouse gas removal potential, resource use, and environmental impacts. We found multiple trade-offs among these indicators, which suggests that a regionalised portfolio of NETPs exploiting their complementary strengths is the way forward. Although no single NETP is superior to the others in terms of all the indicators simultaneously, we identified 16 Pareto-efficient NETPs. Among them, six are deemed particularly promising: forestation, Soil Carbon Sequestration (SCS), enhanced weathering with olivine and three modalities of Direct Air Carbon Capture and Storage (DACCS). While the co-benefits, lower costs and higher maturity levels of forestation and SCS can propel their rapid deployment, these NETPs require continuous monitoring to reduce unintended side-effects – most notably the release of the stored carbon. Enhanced weathering also shows an overall good performance and substantial co-benefits, but its risks – especially those concerning human health – should be further investigated prior to deployment. DACCS presents significantly fewer side-effects, mainly its substantial energy demand; early investments in this NETP could reduce costs and accelerate its scale-up. Our insights can help guide future research and plan for the sustainable scale-up of NETPs, which we must set into motion within this decade.This project has received funding from the European Union's Horizon 2020 research and innovation program under Grant Agreement No. 869192 (NEGEM)

Rotational molecular dynamics in the R1 phase of n-nonadecane

Reorientational dynamics of n-nonadecane molecules in the R1 phase have been investigated by means of molecular dynamics computer simulations (MD) and incoherent quasielastic neutron scattering (IQNS) techniques. Models based on jump process and rotational diffusion are compared with the calculated intermediate scattering functions and with the experimental spectra. A four-site jump model must be ruled out while a model based on a fourfold potential with two different barriers could be used to interpret the data succesfully.SCOPUS: ar.jinfo:eu-repo/semantics/publishe