Emission Quenching in Tetraphenylfuran Crystal: Why This Propeller-Shaped Molecule Does Not Emit in the Condensed Phase

Due to their substantial fluorescence quantum yields in the crystalline phase, propeller-shaped molecules have recently gained significant attention as potential emissive materials for optoelectronic applications. For the family of cyclopentadiene derivatives, light-emission is highly dependent on the nature of heteroatomic substitutions. In this paper, we investigate excited state relaxation pathways in the tetraphenyl-furan molecule (TPF), which in contrast with other molecules in the family, shows emission quenching in the solid-state. For the singlet manifold, our calculations show nonradiative pathways associated with C-O elongation are blocked in both vacuum and the solid state. A fraction of the population can be transferred to the triplet manifold and, subsequently, to the ground state in both phases. This process is expected to be relatively slow due to the small spin-orbit couplings between the relevant singlet-triplet states. Emission quenching in crystalline TPF seems to be in line with more efficient exciton hopping rates. Our simulations help clarify the role of conical intersections, population of the triplet states and crystalline structure in the emissive response of propeller-shaped molecules

Does marine planning enable progress towards adaptive governance of marine systems? Lessons from Scotland’s regional marine planning process

Paul Tett was partly funded by H2020 project no. 774426, ‘The Blue Growth Farm’.This paper examines marine planning in Scotland and the extent to which it constrains or enables change towards adaptive governance. An in-depth case study of the partnership-based regional marine planning process is presented, based on interviews and documentary analysis. Drawing on adaptive governance theory, analysis focussed on key themes of: (1) local governance and integration across scales; (2) participation and collaboration; (3) learning, innovation and adaptability; and (4) self-organisation. Results present regional marine planning as an interface between hierarchical and collaborative governance based on empowerment of regional actors, and an attempt to enable co-existence of ‘top-down’ arrangements with experimentation at smaller scales. In this system, national government provides legal legitimacy, economic incentives and policy oversight; while the partnerships support collaboration and innovation at the regional level, based on strong leadership and participation. Contrasting experience of partnership-working is evident between the large and complex region of the Clyde and the island region of Shetland, where devolved powers and a more cohesive and community-based stakeholder group better facilitate adaptive governance. Overall findings of the study show the tensions of institutionalising adaptive governance and provide insights into how marine planning contributes to governance of marine systems. Firstly, vertical integration between central and decentralised authority in multi-level marine planning arrangements is challenged by an unclear balance of power and accountability between national government and regional marine planning partnerships. Secondly, the interaction between marine planning and existing policy, planning and management emerged as critical, because marine plans may only operate as an instrument to ‘guide’ management and prevailing, limited adaptive capacity in broader management structures constrains adaptive outcomes. Lastly, adaptive governance requires incremental and rapid response to change, but limited financial and technical resources constrain the depth and scale of reflection and ability to act. Understanding the contribution of marine planning requires clarification of the interaction between marine planning and other management (the extent to which it can influence decision-making in other domains) and, in addressing governance deficiencies, attention is also required on the adaptive capacity of existing and emerging legislative frameworks which govern decision-making and management of activities at sea.Publisher PDFPeer reviewe

Role of Conical Intersections on the Efficiency of Fluorescent Organic Molecular Crystals

Organic molecular crystals are attractive materials for luminescent applications because of their promised tunability. However, the link between the chemical structure and emissive behavior is poorly understood because of the numerous interconnected factors which are at play in determining radiative and nonradiative behaviors at the solid-state level. In particular, the decay through conical intersection dominates the nonadiabatic regions of the potential energy surface, and thus, their accessibility is a telling indicator of the luminosity of the material. In this study, we investigate the radiative mechanism for five organic molecular crystals which display a solid-state emission, with a focus on the role of conical intersections in their photomechanisms. The objective is to situate the importance of the accessibility of conical intersections with regards to emissive behavior, taking into account other nonradiative decay channels, namely, vibrational decay, and exciton hopping. We begin by giving a brief overview of the structural patterns of the five systems within a larger pool of 13 crystals for a richer comparison. We observe that because of the prevalence of sheet like and herringbone packing in organic molecular crystals, the conformational diversity of crystal dimers is limited. Additionally, similarly spaced dimers have exciton coupling values of a similar order within a 50 meV interval. Next, we focus on three exemplary cases, where we disentangle the role of nonradiative decay mechanisms and show how rotational minimum energy conical intersections in vacuum lead to puckered ones in the crystal, increasing their instability upon crystallization in typical packing motifs. In contrast, molecules with puckered conical intersections in vacuum tend to conserve this trait upon crystallization, and therefore, their quantum yield of fluorescence is determined predominantly by other nonradiative decay mechanisms

Scalable, Time-Responsive, Digital, Energy-Efficient Molecular Circuits using DNA Strand Displacement

We propose a novel theoretical biomolecular design to implement any Boolean circuit using the mechanism of DNA strand displacement. The design is scalable: all species of DNA strands can in principle be mixed and prepared in a single test tube, rather than requiring separate purification of each species, which is a barrier to large-scale synthesis. The design is time-responsive: the concentration of output species changes in response to the concentration of input species, so that time-varying inputs may be continuously processed. The design is digital: Boolean values of wires in the circuit are represented as high or low concentrations of certain species, and we show how to construct a single-input, single-output signal restoration gate that amplifies the difference between high and low, which can be distributed to each wire in the circuit to overcome signal degradation. This means we can achieve a digital abstraction of the analog values of concentrations. Finally, the design is energy-efficient: if input species are specified ideally (meaning absolutely 0 concentration of unwanted species), then output species converge to their ideal concentrations at steady-state, and the system at steady-state is in (dynamic) equilibrium, meaning that no energy is consumed by irreversible reactions until the input again changes. Drawbacks of our design include the following. If input is provided non-ideally (small positive concentration of unwanted species), then energy must be continually expended to maintain correct output concentrations even at steady-state. In addition, our fuel species - those species that are permanently consumed in irreversible reactions - are not "generic"; each gate in the circuit is powered by its own specific type of fuel species. Hence different circuits must be powered by different types of fuel. Finally, we require input to be given according to the dual-rail convention, so that an input of 0 is specified not only by the absence of a certain species, but by the presence of another. That is, we do not construct a "true NOT gate" that sets its output to high concentration if and only if its input's concentration is low. It remains an open problem to design scalable, time-responsive, digital, energy-efficient molecular circuits that additionally solve one of these problems, or to prove that some subset of their resolutions are mutually incompatible.Comment: version 2: the paper itself is unchanged from version 1, but the arXiv software stripped some asterisk characters out of the abstract whose purpose was to highlight words. These characters have been replaced with underscores in version 2. The arXiv software also removed the second paragraph of the abstract, which has been (attempted to be) re-inserted. Also, although the secondary subject is "Soft Condensed Matter", this classification was chosen by the arXiv moderators after submission, not chosen by the authors. The authors consider this submission to be a theoretical computer science paper

An Infrastructure for acquiring high quality semantic metadata

Because metadata that underlies semantic web applications is gathered from distributed and heterogeneous data sources, it is important to ensure its quality (i.e., reduce duplicates, spelling errors, ambiguities). However, current infrastructures that acquire and integrate semantic data have only marginally addressed the issue of metadata quality. In this paper we present our metadata acquisition infrastructure, ASDI, which pays special attention to ensuring that high quality metadata is derived. Central to the architecture of ASDI is a erification engine that relies on several semantic web tools to check the quality of the derived data. We tested our prototype in the context of building a semantic web portal for our lab, KMi. An experimental evaluation omparing the automatically extracted data against manual annotations indicates that the verification engine enhances the quality of the extracted semantic metadata

A GIS-based Approach for Modeling the Spatial and Temporal Development of Night-time Lights

One of the few directly observable indicators of human activity in spatially explicit form are night-time satellite imagery data. Nocturnal lighting can be regarded as one of the defining features of concentrated human activity, such as flaring of natural gas in oil field

Will Brexit raise the cost of living?

This paper considers two aspects of this question. First, Brexit has already induced a devaluation of sterling of around 14 per cent since June 2016, which has started to work through to consumer prices: between June 2016 and July 2017 consumer prices increased by around 2.5 per cent. Second, while it is not government policy, nor the desire of the UK public, that the outcome of negotiations is a ‘MFN Brexit’, this remains a distinct possibility. Thus we ask how the imposition of tariffs on imports from the EU will work through into consumer prices. Making very conservative assumptions, we conclude that ‘MFN Brexit’ will increase the average cost of living by around 1 per cent and increase it for 8 per cent of households by 2 per cent or more. We present results for different groups of households according to their employment and structural characteristics and show that the impact will generally be largest on unemployed, single parent and pensioner households

Catch-up growth in children with chronic kidney disease started on enteral feeding after 2 years of age

BACKGROUND: Enteral feeding by tube in chronic kidney disease (CKD) before 2 years of age improves growth. Whether it is effective after this age is unknown. We assessed whether height and weight SDS changed after tube feeding was started in children with CKD above 2 years of age. METHODS: Retrospective study of pre-transplant, pre-pubertal children (< 11 years) with CKD stages 2–5 started on nasogastric tube or gastrostomy feeds for the first time after age 2 years. Children were identified by searching dietetic records and the renal database. Children on growth hormone were excluded. Height, weight, and BMI were documented 1 year prior to and at the start of tube feeds, and after 1 and 2 years. Data collection ceased at transplantation. RESULTS: Fifty children (25 male) were included. The median (range) age at start of tube feeds was 5.6 (2.1–10.9) years. Sixteen children were dialysed (1 haemodialysis, 15 peritoneal dialysis); 34 predialysis patients had a median (range) eGFR of 22 (6–88) ml/min/1.73 m2. Overall height SDS (Ht SDS) improved from − 2.39 to − 2.27 at 1 year and − 2.18 after 2 years (p = 0.02). BMI SDS improved from − 0.72 to 0.23 after 1 year and was 0.09 after 2 years of enteral feeding (p < 0.0001). Height SDS improved more in children aged 2–6 years (− 2.13 to − 1.68, p = 0.03) and in children not on dialysis (− 2.33 to − 1.99, p = 0.002). CONCLUSIONS: Enteral tube feeding commenced after 2 years of age in prepubertal children with CKD improves height and weight SDS, with stability of BMI during the second year. Younger children and those not on dialysis had the greatest benefit