The mechanism of intramolecular energy transfer in terminally substituted polyene molecules

Absorption, fluorescence and excitation spectra of different terminally substituted polyenes have been recorded in the UV-Vis region. The observed intramolecular unidirectional energy transfer from a donor substituent to an acceptor at the other end of the chain is influenced but not inhibited by incorporation of a spacer into the polyene chain. In molecules without a spacer, internal conversion within the supermolecule can explain the observed transfer of energy. In molecules with a spacer interrupting the polyene chain the observed intramolecular energy transfer can be explained in terms of Förster transfer

Intramolecular energy transfer through linear polyenes : effect of spacers

The optical properties of linear polyenes terminally substituted with different molecules (mainly anthryl- and TPP-substituents) have been studied. Bicyclic spacers within the polyene chain affect the quantum yields but do not interrupt intramolecular energy transfer between the endgroups

Dual fluorescence of 9-anthryl-substituted oligothiophenes in nonpolar environment

9-Anthryl-oligothiophenes (9A-Tn, n = 1–4) have been studied in n-hexane solution between helium and room temperature using absorption, fluorescence emission and excitation spectra and time resolved fluorescence measurements. These compounds are reference systems for studies on intramolecular energy and charge transfer in donor/acceptor-substituted conjugated chain molecules. The absorption spectra show contribution of both substituents anthracene and oligothiophene, but no additional bands due to mixed electronic states. Dual fluorescence is observed at Tgreater-or-equal, slanted 120 K for the compounds 9A-Tn (n = 1–3), but not for 9A-T4. Time resolved spectroscopy reveals a dynamical coupling between the two emission components whose relative quantum yields are strongly temperature dependent. The occurrence of the dual fluorescence is explained by an intramolecular torsional motion between the two molecular subunits

Female sex, young and old age, northern German residency, high HbA1c and insulin use predict depressed mood in 35,691 T2D patients

Background and aims: A bidirectional relationship between type 2 diabetes (T2D) and depressive symptoms has been reported. The primary aim was to analyze predictors of depressed mood in T2D. Secondly, the odds ratio of developing a clinically recognized depression in patients with conspicuous screening result was evaluated. Materials and methods: 35,691 T2D patients aged ≥18 years (median [IQR]: 68.9 [59.2-76.5] years) from the German/Austrian multicenter prospective diabetes follow-up registry (DPV) were analyzed. All patients had completed the WHO-5 questionnaire, a reliable and validated 5-item screening tool for depression (score ≤7: likely depression). Logistic regression modeling (SAS 9.4) was applied to study potential predictors (e.g. demographics, regional aspect, diabetes therapy, glycemic S414 Diabetologia (2015) 58 (Suppl 1):S1–S607 control) for depressed mood as well as the risk of developing clinically recognized depression. Results: Depressed mood was present in 11.2% (n=4,000) of patients screened and thereby significantly more prevalent compared to the adult German population (DEGS study: 8.1%, p<0.001). Patients with likely depression had a later diabetes onset (60.5 [49.6-70.2] vs. 58.3 [49.1- 67.7] years, p<0.001) and were more often female (54.0 vs. 48.0%, p< 0.001) compared to patients with inconspicuous results. Duration of diabetes did not differ significantly between groups (7.6 [2.4-12.9] vs. 7.0 [2.1-13.5] years, p=0.76). Young and very old age as well as female sex were associated with depressed mood (table 1, model 1). Moreover, living in northern federal states of Germany, poor glycemic control (HbA1c ≥58 mmol/mol) and insulin treatment were significantly related to depressed mood in T2D (table 1). Overall, the odds of developing a clinical diagnosis of depression was 1.95 (95%CI: 1.66-2.29) times higher in patients scored ≤7 in the WHO-5 questionnaire. Conclusion: Depressed mood is a frequent psychological comorbidity in adult T2D patients. In clinical care, routinely screening for psychological problems as recommended by guidelines is absolutely advisable, especially in high-risk patients

Vegetation type is an important predictor of the arctic summer land surface energy budget

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994-2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm(-2)) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types.An international team of researchers finds high potential for improving climate projections by a more comprehensive treatment of largely ignored Arctic vegetation types, underscoring the importance of Arctic energy exchange measuring stations.Peer reviewe

Vegetation type is an important predictor of the arctic summer land surface energy budget

Despite the importance of high-latitude surface energy budgets (SEBs) for land-climate interactions in the rapidly changing Arctic, uncertainties in their prediction persist. Here, we harmonize SEB observations across a network of vegetated and glaciated sites at circumpolar scale (1994–2021). Our variance-partitioning analysis identifies vegetation type as an important predictor for SEB-components during Arctic summer (June-August), compared to other SEB-drivers including climate, latitude and permafrost characteristics. Differences among vegetation types can be of similar magnitude as between vegetation and glacier surfaces and are especially high for summer sensible and latent heat fluxes. The timing of SEB-flux summer-regimes (when daily mean values exceed 0 Wm−2) relative to snow-free and -onset dates varies substantially depending on vegetation type, implying vegetation controls on snow-cover and SEB-flux seasonality. Our results indicate complex shifts in surface energy fluxes with land-cover transitions and a lengthening summer season, and highlight the potential for improving future Earth system models via a refined representation of Arctic vegetation types

Lowest excited singlet states of &#945;-9-anthrylpolyenes

Properties of the electronically excited states of &#945;-9-anthrylpolyenes are studied in n-hexane solutions by using optical absorption, emission and fluorescence excitation spectroscopy. The absorption spectra reveal a complex structure with contributions of both anthracene and polyene type bands but also of bands with mixed anthracence/polyene character. Small amounts of remaining impurities are chemically not separable but can be detected via fluorescence measurements. By computer-aided decomposition of spectra measured under variable selective excitation the actual, clearly chain-length dependent, fluorescences could be obtained