Decoherence of Excitons in Multichromophore Systems: Thermal Line Broadening and Destruction of Superradiant Emission

We study the temperature-dependent dephasing rate of excitons in chains of chromophores, accounting for scattering on static disorder as well as acoustic phonons in the host matrix. From this we find a powerlaw temperature dependence of the absorption line width, in excellent quantitative agreement with experiments on dye aggregates. We also propose a relation between the line width and the exciton coherence length imposed by the phonons. The results indicate that the much debated steep rise of the fluorescence lifetime of pseudo-isocyanine aggregates above 40 K results from the fact that this coherence length drops below the localization length imposed by static disorder.Comment: 4 pages, 2 figure

Thermal broadening of the J-band in disordered linear molecular aggregates: A theoretical study

We theoretically study the temperature dependence of the J-band width in disordered linear molecular aggregates, caused by dephasing of the exciton states due to scattering on vibrations of the host matrix. In particular, we consider inelastic one- and two-phonon scattering between different exciton states (energy-relaxation-induced dephasing), as well as elastic two-phonon scattering of the excitons (pure dephasing). The exciton states follow from numerical diagonalization of a Frenkel Hamiltonian with diagonal disorder; the scattering rates between them are obtained using the Fermi Golden Rule. A Debye-like model for the one- and two-phonon spectral densities is used in the calculations. We find that, owing to the disorder, the dephasing rates of the individual exciton states are distributed over a wide range of values. We also demonstrate that the dominant channel of two-phonon scattering is not the elastic one, as is often tacitly assumed, but rather comes from a similar two-phonon inelastic scattering process. In order to study the temperature dependence of the J-band width, we simulate the absorption spectrum, accounting for the dephasing induced broadening of the exciton states. We find a power-law (T^p) temperature scaling of the effective homogeneous width, with an exponent p that depends on the shape of the spectral density of host vibrations. In particular, for a Debye model of vibrations, we find p ~ 4, which is in good agreement with experimental data on J-aggregates of pseudoisocyanine [J. Phys. Chem. A 101, 7977 (1997)].Comment: 14 pages, 7 figure

Notitie Denktank Overlijdensschade. Nieuwe richting benadering en berekening overlijdensschade

In 2009 is een werkgroep onder de naam Denktank Overlijdensschade gestart met het bestuderen van een ander, aan de huidige tijd aangepast model voor de berekening van overlijdensschade. Doelstelling was te komen tot een, ook voor nabestaanden, transparantie systematiek welke recht doet aan de vorderingsgerechtigdheid van de nabestaanden. In 2014 heeft de Denktank Overlijdensschade haar werkzaamheden voltooid met het opleveren van een nieuwe rekenmethodiek. In deze Notitie wordt beschreven hoe de Denktank tot deze nieuwe benadering van het berekenen van overlijdensschade is gekomen, welke onderzoeken daaraan ten grondslag liggen en wat de uiteindelijke rekenregel is, die nu voorgesteld wordt. Kern van de nieuwe methodiek is het uitgangspunt dat het gezin als economische eenheid wordt beschouwd, voor én na het overlijden

Ocean currents shape the microbiome of Arctic marine sediments

Prokaryote communities were investigated on the seasonally stratified Alaska Beaufort Shelf (ABS). Water and sediment directly underlying water with origin in the Arctic, Pacific or Atlantic oceans were analyzed by pyrosequencing and length heterogeneity-PCR in conjunction with physicochemical and geographic distance data to determine what features structure ABS microbiomes. Distinct bacterial communities were evident in all water masses. Alphaproteobacteria explained similarity in Arctic surface water and Pacific derived water. Deltaproteobacteria were abundant in Atlantic origin water and drove similarity among samples. Most archaeal sequences in water were related to unclassified marine Euryarchaeota. Sediment communities influenced by Pacific and Atlantic water were distinct from each other and pelagic communities. Firmicutes and Chloroflexi were abundant in sediment, although their distribution varied in Atlantic and Pacific influenced sites. Thermoprotei dominated archaea in Pacific influenced sediments and Methanomicrobia dominated in methane-containing Atlantic influenced sediments. Length heterogeneity-PCR data from this study were analyzed with data from methane-containing sediments in other regions. Pacific influenced ABS sediments clustered with Pacific sites from New Zealand and Chilean coastal margins. Atlantic influenced ABS sediments formed another distinct cluster. Density and salinity were significant structuring features on pelagic communities. Porosity co-varied with benthic community structure across sites and methane did not. This study indicates that the origin of water overlying sediments shapes benthic communities locally and globally and that hydrography exerts greater influence on microbial community structure than the availability of methane

Spatial distribution of isobaric androgens in target tissues using chemical derivatization and MALDI-2 on a trapped ion mobility quadrupole time-of-flight instrument

Prostate cancer is initially treated via androgen deprivation therapy (ADT), a highly successful treatment in the initial pursuit of tumour regression, but commonly restricted by the eventual emergence of a more lethal ‘castrate resistant’ (CRPC) form of the disease. Intracrine pathways that utilize dehydroepiandrosterone (DHEA) or other circulatory precursor steroids are thought to generate relevant levels of growth-stimulating androgens such as testosterone (T) and dihydrotestosterone (DHT). Decoding this tissue-specific metabolic pathway is key for the development of novel therapeutic treatments. Mass spectrometry imaging (MSI) is an analytical technique that allows the visualization of the distribution of numerous classes of biomolecules within tissue sections. The analysis of androgens by liquid chromatography mass spectrometry (LC/MS)-based methods however presents a challenge due to their generally poor ionization efficiency and low physiological endogenous levels. In MSI, on-tissue chemical derivatization (OTCD) has enabled the limits of steroids to be imaged within tissues to be pushed by overcoming poor ionization performance. However, isobaric interference of key androgen derivatives such as T and DHEA can severely hamper studying the intracrinology in several diseases. Here, we have evaluated the use of laser induced post-ionization (MALDI-2) combined with trapped ion mobility separation (TIMS) and orthogonal time-of-flight (QTOF) MS for the visualization of isobaric derivatized androgens in murine tumour xenograft at about 50 μm spatial resolution. With this combination, isobaric T and DHEA were separated in tissue sections and the signals of derivatized steroids enhanced by about 20 times. The combination of TIMS and MALDI-2 thus shows unique potential to study tissue intracrinology within target tissues. This could offer the opportunity for many novel insights into tissue-specific androgen biology

Closing the gap between screening and depression prevention:a qualitative study on barriers and facilitators from the perspective of public health professionals in a school-based prevention approach

Background: The prevalence of depression has increased among adolescents in western countries. Prevention is needed to reduce the number of adolescents who experience depression and to avoid negative consequences, including suicide. Several preventive interventions are found to be promising, especially multi-modal approaches, for example combining screening and preventive intervention. However, an important bottleneck arises during the implementation of preventive intervention. Only a small percentage of adolescents who are eligible for participation actually participate in the intervention. To ensure that more adolescents can benefit from prevention, we need to close the gap between detection and preventive intervention. We investigated the barriers and facilitators from the perspective of public health professionals in screening for depressive and suicidal symptoms and depression prevention referral in a school-based setting. Methods: We conducted 13 semi-structured interviews with public health professionals, who execute screening and depression prevention referral within the Strong Teens and Resilient Minds (STORM) approach. The interviews were recorded, transcribed verbatim, and coded in several cycles using ATLAS.ti Web. Results: Three main themes of barriers and facilitators emerged from the interviews, namely “professional capabilities,” “organization and collaboration,” and “beliefs about depressive and suicidal symptoms and participation in prevention”. The interviews revealed that professionals do not always feel sufficiently equipped in terms of knowledge, skills and supporting networks. Consequently, they do not always feel well able to execute the process of screening and prevention referral. In addition, a lack of knowledge and support in schools and other cooperating organizationorganizations was seen to hinder the process. Last, the beliefs of public health professionals, school staff, adolescents, and parents —especially stigma and taboo—were found to make the screening and prevention referral process more challenging. Conclusions: To further improve the process of screening and prevention referral in a school-based setting, enhancing professional competence and a holding work environment for professionals, a strong collaboration and a joint approach with schools and other cooperating organizations and society wide education about depressive and suicidal symptoms and preventive intervention are suggested. Future research should determine whether these recommendations actually lead to closing the gap between detection and prevention.</p

Spatial distribution of isobaric androgens in target tissues using chemical derivatization and MALDI-2 on a trapped ion mobility quadrupole time-of-flight instrument

Prostate cancer is initially treated via androgen deprivation therapy (ADT), a highly successful treatment in the initial pursuit of tumour regression, but commonly restricted by the eventual emergence of a more lethal 'castrate resistant' (CRPC) form of the disease. Intracrine pathways that utilize dehydroepiandrosterone (DHEA) or other circulatory precursor steroids are thought to generate relevant levels of growth-stimulating androgens such as testosterone (T) and dihydrotestosterone (DHT). Decoding this tissue-specific metabolic pathway is key for the development of novel therapeutic treatments. Mass spectrometry imaging (MSI) is an analytical technique that allows the visualization of the distribution of numerous classes of biomolecules within tissue sections. The analysis of androgens by liquid chromatography mass spectrometry (LC/MS)-based methods however presents a challenge due to their generally poor ionization efficiency and low physiological endogenous levels. In MSI, on-tissue chemical derivatization (OTCD) has enabled the limits of steroids to be imaged within tissues to be pushed by overcoming poor ionization performance. However, isobaric interference of key androgen derivatives such as T and DHEA can severely hamper studying the intracrinology in several diseases. Here, we have evaluated the use of laser induced post-ionization (MALDI-2) combined with trapped ion mobility separation (TIMS) and orthogonal time-of-flight (QTOF) MS for the visualization of isobaric derivatized androgens in murine tumour xenograft at about 50 mu m spatial resolution. With this combination, isobaric T and DHEA were separated in tissue sections and the signals of derivatized steroids enhanced by about 20 times. The combination of TIMS and MALDI-2 thus shows unique potential to study tissue intracrinology within target tissues. This could offer the opportunity for many novel insights into tissue-specific androgen biology.Proteomic

Evaluatie fysieke vaardigheidstoets politie

The physical skills test (abbreviated in Dutch as ‘FVT’) was developed to determine the fitness of police personnel. This test measures whether participants are in good enough physical condition and have the physical skills required to perform police work adequately. The aim of the study was to obtain insight into the practical implementation and degree to which the Physical Skills Test (FVT) achieves the goal set. The study concentrated on the following three principal questions:To what extent is the practical implementation of the FVT progressing as envisioned by the Police FVT Regulations?To what extent are the policy goals of the FVT being achieved?How can the FVT be improved? Index  In de Politie-CAO is afgesproken dat de fitheid en gezondheid van het politie-personeel een cruciaal onderdeel van het HRM-beleid is. Om de fitheid van het politiepersoneel vast te stellen is de fysieke vaardigheidstoets (FVT) ontwikkeld. Met deze toets wordt gemeten of deelnemers over voldoende fysieke conditie en vaardigheden beschikken om op adequate wijze het politiewerk te kunnen uitvoeren. Na een periode van vrijwillige deelname, is deelname aan de FVT sinds 2012 verplicht voor alle operationele politie-medewerkers die vallen onder de Regeling toetsing geweldsbeheersing politie (RTGP) en een geweldscode van 3 of hoger hebben (bijna 40.000 mede-werkers). Deze verplichtstelling is op 1 januari 2015 bekrachtigd met een ministeriële regeling. Aan het niet behalen van de FVT binnen de vastgestelde normen zijn vooralsnog geen gevolgen verbonden. Het onderzoek had als doel om inzicht te verkrijgen in de uitvoeringspraktijk en doelbereiking van de Fysieke Vaardigheidstoets (FVT). De volgende drie hoofdvragen stonden hierbij centraal: In hoeverre verloopt de uitvoeringspraktijk van de FVT zoals beoogd met de Regeling FVT politie? In hoeverre worden de beleidsdoelen van de FVT behaald? Hoe kan de FVT worden verbeterd? INHOUD: 1. Inleiding 2. Achtergrond Fysieke Vaardigheidstoets 3. Deelname- en slagingspercentages 4. Ervaringen met de FVT in de praktijk 5. Normering van de FVT 6. Samenvatting en conclusi

Excitation Dynamics and Relaxation in a Molecular Heterodimer

The exciton dynamics in a molecular heterodimer is studied as a function of differences in excitation and reorganization energies, asymmetry in transition dipole moments and excited state lifetimes. The heterodimer is composed of two molecules modeled as two-level systems coupled by the resonance interaction. The system-bath coupling is taken into account as a modulating factor of the energy gap of the molecular excitation, while the relaxation to the ground state is treated phenomenologically. Comparison of the description of the excitation dynamics modeled using either the Redfield equations (secular and full forms) or the Hierarchical quantum master equation (HQME) is demonstrated and discussed. Possible role of the dimer as an excitation quenching center in photosynthesis self-regulation is discussed. It is concluded that the system-bath interaction rather than the excitonic effect determines the excitation quenching ability of such a dimer