Three-dimensional tetra(oligothienyl)silanes as donor material for organic solar cells

Tetrahedral conjugated systems involving four conjugated oligothiophene chains fixed onto a central silicon node (1, 2) have been synthesized and used as donor materials in hetero-junction solar cells. Bilayer solar cells have been realized by thermal evaporation of compounds1 and 2 as donors and N,N′-bis-tridecylperylenedicarboxyimide as an acceptor. Comparison of the performances of these devices to those of a reference system based on dihexylterthienyl (H3T) shows that despite comparable effective conjugation lengths, the 3D compounds 1 and 2lead to a power conversion efficiency four–five times higher, suggesting better absorption of the incident light and better hole transport properties. Whereas fabrication of bulk hetero-junction with H3T was prevented by the lack of film forming properties, a prototype bulk hetero-junction based on compound 2 as the donor and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the acceptor has been realized. A short-circuit current density of 1.13 mA cm−2 and a power conversion efficiency of 0.30% has been measured under AM 1.5 simulated solar irradiation at 80 mW cm−2

Paradoxical effects of polyphenolic compounds from Clusiaceae on angiogenesis

Clusiaceae plants display high contents of xanthones and coumarins, the effects of which on endothelium, more particularly on angiogenesis, have not been assessed yet. We screened the capacity of six molecules from Clusiaceae – belonging to xanthones, coumarins and acid chromanes classes – to induce endothelium-dependent relaxation on mice aortic rings. Endothelial nitric oxide (NO) production was assessed in endothelial cell line using electron paramagnetic resonance technique. Then, the capacity of these molecules to induce capillary-like structures of endothelial cells was assessed. Cellular processes implicated in angiogenesis (adhesion, migration and proliferation) and Western blot analyses were then investigated. Among the tested molecules, isocalolongic acid (IA) and 2-deprenylrheediaxanthone (DRX) induced an endothelium-dependent relaxation of the aorta associated with an increase of NO production in endothelial cells. Using in vitro and ex vivo angiogenesis assays, it was shown that IA treatment promoted the formation of capillary-like network. In contrast, DRX prevented the ability of vascular endothelial growth factor (VEGF) to increase the formation of capillary-like network. IA increased endothelial cell proliferation while DRX decreased all cellular processes of angiogenesis. Western blot analysis showed that IA increased VEGF expression whereas DRX decreased ICAM-1 expression. Altogether, these data allowed identifying isolated molecules from Clusiaceae that exhibit a potential activity towards the modulation of endothelium-dependent relaxation involving NO release. Interestingly, they also highlighted paradoxical effects of the two compounds on cellular angiogenic processes, IA being pro-angiogenic and DRX anti-angiogenic

Molecular and supramolecular engineering of π-conjugated systems for photovoltaic conversion

Various series of conjugated systems have been used as donor in hetero-junction solar cells. The results obtained with EDOT-containing π-conjugated oligomers show that besides their direct effect on the electronic properties of the conjugated chain, the number and position of the EDOT units control to a large extent the orientation of the molecules on the substrate and hence the performances of the derived solar cells. The characteristics of the cells based on oligothienylenevinylenes donors show that in this case structural control of orientation can be achieved by means of substitution of the conjugated structure by alkyl chains. Donors based on star-shaped oligothiophenes provide another example of control of horizontal molecular orientation by design. The photovoltaic characteristics of bi-layer hetero-junctions show that the combined effects of controlled molecular orientation and planarization of the structure by the use of a fused tri-thienobenzene central core lead to power conversion efficiencies approaching 1%. In order to avoid the need to control molecular orientation first examples of bulk hetero-junctions based on PCBM and three-dimensional conjugated systems with isotropic electronic properties have been realized. A power conversion efficiency of 0.30% has been obtained under 79 mW cm− 2 white light illumination. This result obtained with a 3D donor based on a terthiophene conjugated chain with very limited absorption of the visible spectrum demonstrates the large potentialities of this novel concept

Does Charge Carrier Dimensionality Increase in Mixed-Valence Salts of Tetrathiafulvalene-Terminated Dendrimers?

In four new dendrimers terminated by 12 electroactive tetrathiafulvalenyl substituents, the tridimensional character of the inter- and intradendrimeric charge and electron transfer, and hence of the electroconductivity, is evidenced by examination of the electronic spectra of their corresponding neutral state and cation radical, dication, and mixed-valence salts, including a closed-shell anion

A review of carbon offset strategies with seaweed aquaculture – feasibility, current knowledge, and suggestions for future research. The Scottish Association for Marine Science, Oban, UK. Report prepared for the Scottish Government

In September 2022, a group of international collaborators gathered from six European countries (hereby referred to as the ‘working group’) to take part in a workshop at the Scottish Association for Marine Science (SAMS), Oban. The workshop was funded as part of Marine Scotland’s Blue Carbon International Policy Challenge (BCIPC). The main aim of the workshop was to produce a document outlining the potential for carbon offset by macroalgal aquaculture. The discussions held at the workshop focused on various concepts and hypotheses surrounding carbon drawdown by seaweed aquaculture and the potential for mitigation of atmospheric CO2. The key points of these discussions have been compiled into a policy brief which aims to highlight important areas for future research, uncertainties and challenges faced by the industry, policy makers and other stakeholders

Climate-driven regime shift of a temperate marine ecosystem.

Ecosystem reconfigurations arising from climate-driven changes in species distributions are expected to have profound ecological, social, and economic implications. Here we reveal a rapid climate-driven regime shift of Australian temperate reef communities, which lost their defining kelp forests and became dominated by persistent seaweed turfs. After decades of ocean warming, extreme marine heat waves forced a 100-kilometer range contraction of extensive kelp forests and saw temperate species replaced by seaweeds, invertebrates, corals, and fishes characteristic of subtropical and tropical waters. This community-wide tropicalization fundamentally altered key ecological processes, suppressing the recovery of kelp forests

Social welfare analysis of investment public-private partnership approaches for tansportation projects

This paper has two objectives: (1) to introduce a new approach to gaining widespread support for comprehensive road pricing; and (2) to develop a detailed social welfare analysis for road pricing schemes. We first describe a new approach to garnering support for system-wide road pricing, which we refer to as an investment public-private partnership, or IP3. This approach returns a significant portion of the economic value created by road pricing back to its citizen-owners. Next, we present a social welfare framework that estimates the benefits and costs of using the IP3 approach on an urban transportation network. Policy makers typically evaluate public-private partnership (P3) projects using Value for Money (VfM) analysis. However, a P3 project's impact on overall social welfare provides a more comprehensive evaluation criterion. Apart from several theoretical studies, a detailed social welfare analysis that includes all major P3 project stakeholders is lacking. Using Fresno City's transportation system as our case study, we show that system-optimal tolling scenarios favor average users, but that government¿and consequently taxpayers¿would pay for costly tolling systems. In contrast, unlimited profit-maximizing tolls raise substantial profits for government, for the infrastructure's citizen-owners, and for the private sector, but the average user is worse off. From a social welfare perspective, one should search for a Pareto-improvement under which all major stakeholders are better off. Our estimates indicate that a mixed private and public tolling scheme offers such an improvement. A mixed scheme results in the highest social welfare among all scenarios unless the weight placed on motorists' (i.e., transportation users') welfare is very low or the weight placed on residents' welfare is very high relative to the weight of other stakeholders

Movement of pulsed resource subsidies from kelp forests to deep fjords

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12 m), deep subtidal (12‒85 m), and deep fjord (400‒450 m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1 year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50 m (mean 11.8 m ± 8.5 SD) in 11‒17 days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.acceptedVersio