507 research outputs found
A GIS for flood risk management in Flanders
In the past decades, Flanders, a region of north Belgium that extends from the coastline inland (in northwest Europe), has suffered several serious riverine floods that caused substantial property damage. As Flanders is one of the most densely populated regions in the world, a solid water management policy is needed in order to mitigate the effects of this type of calamity. In the past, Flemish water managers chose to drain off river water as quickly as possible by heightening the dikes along the rivers. However, this method leads to a higher flood probability further downstream. Moreover, water defence infrastructure can always suffer from technical failures (e.g., breaching) creating even more damage than would have occurred if no defences were in place. In a search for a better solution to this recurring problem, the Flemish administration proposed a new approach in the 1990 s. This approach focuses on minimizing the consequences of flooding instead of attempting to prevent floods. To implement this approach, large amounts of data were gathered for the Flemish Region. Using a Geographic Information System (GIS), a risk-based methodology was created to quantitatively assess flood risk based on hydrologic models, land use information and socio-economic data. Recently, this methodology was implemented in a specifically designed GIS-based flood risk assessment tool called LATIS. By estimating the potential damage and number of casualties during a flood event, LATIS offers the possibility to perform risk analysis quickly and effectively. This chapter presents a concise overview of LATIS’ methodology and its implementation for flood risk management in Flanders
Vanadium (β-(Dimethylamino)ethyl)cyclopentadienyl Complexes with Diphenylacetylene Ligands
Reduction of the V(III) (β-(dimethylamino)ethyl)cyclopentadienyl dichloride complex [η5:η1-C5H4(CH2)2NMe2]VCl2(PMe3) with 1 equiv of Na/Hg yielded the V(II) dimer {[η5:η1-C5H4(CH2)2NMe2]V(µ-Cl)}2 (2). This compound reacted with diphenylacetylene in THF to give the V(II) alkyne adduct [η5:η1-C5H4(CH2)2NMe2]VCl(η2-PhC≡CPh). Further reduction of 2 with Mg in the presence of diphenylacetylene resulted in oxidative coupling of two diphenylacetylene groups to yield the diamagnetic, formally V(V), bent metallacyclopentatriene complex [η5:η1-C5H4(CH2)2NMe2]V(C4Ph4).
Versatile Coordination of Cyclopentadienyl-Arene Ligands and Its Role in Titanium-Catalyzed Ethylene Trimerization
Cationic titanium(IV) complexes with ansa-(η5-cyclopentadienyl,η6-arene) ligands were synthesized and characterized by X-ray crystallography. The strength of the metal-arene interaction in these systems was studied by variable-temperature NMR spectroscopy. Complexes with a C1 bridge between the cyclopentadienyl and arene moieties feature hemilabile coordination behavior of the ligand and consequently are active ethylene trimerization catalysts. Reaction of the titanium(IV) dimethyl cations with CO results in conversion to the analogous cationic titanium(II) dicarbonyl species. Metal-to-ligand backdonation in these formally low-valent complexes gives rise to a strongly bonded, partially reduced arene moiety. In contrast to the η6-arene coordination mode observed for titanium, the more electron-rich vanadium(V) cations [cyclopentadienyl-arene]V(NiPr2)(NC6H4-4-Me)+ feature η1-arene binding, as determined by a crystallographic study. The three different metal-arene coordination modes that we experimentally observed model intermediates in the cycle for titanium-catalyzed ethylene trimerization. The nature of the metal-arene interaction in these systems was studied by DFT calculations.
Intramolecular locking and coumarin insertion: a stepwise approach for TADF design
Three novel TADF (thermally activated delayed fluorescence) emitters based on the well-studied Qx-Ph-DMAC fluorophore are designed and synthesized. The photophysical properties of these materials are studied from a theoretical and experimental point of view, demonstrating the cumulative effects of multiple small modifications that combine to afford significantly improved TADF performance. First, an extra phenyl ring is added to the acceptor part of Qx-Ph-DMAC to increase the conjugation length, resulting in BQx-Ph-DMAC, which acts as an intermediate molecular structure. Next, an electron-deficient coumarin unit is incorporated to fortify the electron accepting ability, affording ChromPy-Ph-DMAC with red-shifted emission. Finally, the conjugated system is further enlarged by ‘locking’ the molecular structure, generating DBChromQx-DMAC with further red-shifted emission. The addition of the coumarin unit significantly impacts the charge-transfer excited state energy levels with little effect on the locally excited states, resulting in a decrease of the singlet–triplet energy gap. As a result, the two coumarin-based emitters show considerably improved TADF performance in 1 w/w% zeonex films when compared to the initial Qx-Ph-DMAC structure. ‘Locking’ the molecular structure further lowers the singlet–triplet energy gap, resulting in more efficient reverse intersystem crossing and increasing the contribution of TADF to the total emission
The benefits of statins in people without established cardiovascular disease but with cardiovascular risk factors: meta-analysis of randomised controlled trials
Objectives To investigate whether statins reduce all cause mortality and major coronary and cerebrovascular events in people without established cardiovascular disease but with cardiovascular risk factors, and whether these effects are similar in men and women, in young and older (>65 years) people, and in people with diabetes mellitus
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Sex differences in lifetime risk and first manifestation of cardiovascular disease: prospective population based cohort study
Objective: To evaluate differences in first manifestations of cardiovascular disease between men and women in a competing risks framework. Design: Prospective population based cohort study. Setting: People living in the community in Rotterdam, the Netherlands. Participants: 8419 participants (60.9% women) aged ≥55 and free from cardiovascular disease at baseline. Main outcome measures First diagnosis of coronary heart disease (myocardial infarction, revascularisation, and coronary death), cerebrovascular disease (stroke, transient ischaemic attack, and carotid revascularisation), heart failure, or other cardiovascular death; or death from non-cardiovascular causes. Data were used to calculate lifetime risks of cardiovascular disease and its first incident manifestations adjusted for competing non-cardiovascular death. Results: During follow-up of up to 20.1 years, 2888 participants developed cardiovascular disease (826 coronary heart disease, 1198 cerebrovascular disease, 762 heart failure, and 102 other cardiovascular death). At age 55, overall lifetime risks of cardiovascular disease were 67.1% (95% confidence interval 64.7% to 69.5%) for men and 66.4% (64.2% to 68.7%) for women. Lifetime risks of first incident manifestations of cardiovascular disease in men were 27.2% (24.1% to 30.3%) for coronary heart disease, 22.8% (20.4% to 25.1%) for cerebrovascular disease, 14.9% (13.3% to 16.6%) for heart failure, and 2.3% (1.6% to 2.9%) for other deaths from cardiovascular disease. For women the figures were 16.9% (13.5% to 20.4%), 29.8% (27.7% to 31.9%), 17.5% (15.9% to 19.2%), and 2.1% (1.6% to 2.7%), respectively. Differences in the number of events that developed over the lifespan in women compared with men (per 1000) were −7 for any cardiovascular disease, −102 for coronary heart disease, 70 for cerebrovascular disease, 26 for heart failure, and −1 for other cardiovascular death; all outcomes manifested at a higher age in women. Patterns were similar when analyses were restricted to hard atherosclerotic cardiovascular disease outcomes, but absolute risk differences between men and women were attenuated for both coronary heart disease and stroke. Conclusions: At age 55, though men and women have similar lifetime risks of cardiovascular disease, there are considerable differences in the first manifestation. Men are more likely to develop coronary heart disease as a first event, while women are more likely to have cerebrovascular disease or heart failure as their first event, although these manifestations appear most often at older ages
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