M. van der Meer

Femtosecond fluorescence upconversion studies of barrierless bond twisting of auramine in solution

Femtosecond fluorescence upconversion studies have been performed for auramine (a diphenylmethane dye), dissolved in ethanol, as a function of temperature. It is found that the (sub)picosecond decay components in the fluorescence slow down as the temperature is lowered from 293 K to 173 K. From the observation of a residual fluorescence, with a viscosity-dependent lifetime of about 30 ps (or longer at higher viscosity), and transient absorption results it is concluded that the two-state sink function model [B. Bagchi, G. R. Fleming, and D. W. Oxtoby, J. Chem. Phys. 78, 7375 (1983)] does not apply in the case of auramine. Comparison of the auramine fluorescence kinetics in ethanol and decanol shows that diffusional twisting and not solvation is the main cause for the (sub)picosecond excited state relaxation. To explain the experimental results, adiabatic coupling between a locally excited emissive state (F) and a nonemissive excited state (D) is considered. Torsional diffusion motions of the phenyl groups ...

Subpicosecond fluorescence upconversion measurements of primary events in yellow proteins

Abstract The primary step in the photocycle of photoactive yellow protein (PYP) has been investigated by means of the subpicosecond fluorescence upconversion technique. The nature of the chromophore is found to affect the fluorescence decay dynamics: upon replacement of the coumaric acid chromophore by 7-hydroxy-coumarin-3-carboxylic acid, the fluorescence decay becomes much longer (with typical decay times larger than 60 ps), whereas the 700 fs and 3 ps components have disappeared. It is discussed that the obtained results are strong support for the idea that the initial step in the photocycle involves trans–cis isomerization inside the coumaric acid chromophore in native PYP.

Illness perceptions and work participation: a systematic review.

PurposeSelf-regulatory processes play an important role in mediating between the disease and the health outcomes, and potentially also work outcomes. This systematic review aims to explore the relationship between illness perceptions and work participation in patients with somatic diseases and complaints.MethodsThe bibliographic databases Medline, PsycINFO and Embase were searched from inception to March 2008. Included were cross-sectional or longitudinal studies, patients with somatic diseases or complaints, illness perceptions based on at least four dimensions of the common sense model of self-regulation, and work participation.ResultsTwo longitudinal and two cross-sectional studies selected for this review report statistically significant findings for one or more illness perception dimensions in patients with various complaints and illnesses, although some dimensions are significant in one study but not in another. Overall, non-working patients perceived more serious consequences, expected their illness to last a longer time, and reported more symptoms and more emotional responses as a result of their illness. Alternatively, working patients had a stronger belief in the controllability of their condition and a better understanding of their disease.ConclusionsThe limited number of studies in this review suggests that illness perceptions play a role in the work participation of patients with somatic diseases or complaints, although it is not clear how strong this relationship is and which illness perception dimensions are most useful. Identifying individuals with maladaptive illness perceptions and targeting interventions toward changing these perceptions are promising developments in improving work participation.

Femto- and picosecond fluorescence studies of solvation and non-radiative deactivation of ionic styryl dyes in liquid solution

Abstract A comparative study of the solvation and non-radiative relaxation dynamics of bridged and unbridged ionic styryl dye compounds is reported. Femto- and picosecond fluorescence transient measurements reveal solvation dynamics on a picosecond timescale of the solutes in ethanol, benzonitrile and decanol. Bridging is found to strongly affect the lifetime of the emissive state. It is shown that the presence of unbridged styryl-group single bonds allows for an effective non-radiative decay process. This decay process is suppressed by double chemical bridging.

The sociospatial diversity in the leisure activities of older people in the Netherlands

Leisure activities afford an important way for old people to continue to take part in society and have a positive effect on personal wellbeing. The types and number of leisure activities in which older people participate are highly diverse. This diversity is associated not only with personal characteristics, but also with those of the environment in which old people live. Using cross sectional data selected in 2002-2003, differences are presented between regions, cities and villages, and between prosperous and deprived neighbourhoods. The characteristics of the region and of the urban or rural environment show a clear relationship wit the intrinsic orientation in leisure. The diversity is smallest among older adults who live in deprived neighbourhoods and among the very old. They take part in fewer activities (contraction), which leads to a more similar activity pattern in and around the home (convergence).

Femtosecond studies of twisting dynamics of auramine in solution

Abstract Femtosecond fluorescence upconversion experiments as performed for photoexcited auramine (a diphenylaminemethane dye) in liquid solution are discussed. Upon pulsed laser excitation the solute shows a dynamic Stokes shift as well as a drop in fluorescence intensity in only a few picoseconds. From a study of the excited state dynamics as a function of solvent viscosity it is concluded that auramine undergoes a picosecond (quasi)-barrierless relaxation from an emissive state to a non-emissive excited state that decays to the ground state in about 30 ps. The relaxation is controlled by the torsional motions of the phenyl rings of the auramine molecule.

Fluorescence quenching of auramine in fluid solution: a femtosecond spectroscopic study.

The quenching of Auramine fluorescence in ethanol is studied by two ultrafast spectroscopy techniques. The gain band, probed by transient absorption spectroscopy, vanishes in a few picoseconds, while a transient absorption band rises and the ground-state repopulation is delayed. In up-conversion experiments, nonexponential wavelength-dependent fluorescence decays are observed. The average decay times increase with the wavelength and the reconstructed instantaneous spectrum exhibits a few hundred-wavenumber red shift and a broadening while its intensity drops. The previously proposed relaxation model, involving a barrierless internal twisting motion toward a transient dark state, is further examined. In particular, the extinction coefficients of the transient state are extracted from the differential absorption spectra. The band is found to lie in the same wavelength range as the dimethylaniline cation radical. This result is discussed as a possible support for an internal twisting process involving a charge shift.

Double Affine Hecke Algebras and Bispectral Quantum Knizhnik-Zamolodchikov Equations

We use the double affine Hecke algebra of type GLN to construct an explicit consistent system of q-difference equations, which we call the bispectral quantum Knizhnik‐ Zamolodchikov (BqKZ) equations. BqKZ includes, besides Cherednik’s quantum affine KZ equations associated to principal series representations of the underlying affine Hecke algebra, a compatible system of q-difference equations acting on the central character of the principal series representations. We construct a meromorphic self-dual solution � of BqKZ which, upon suitable specializations of the central character, reduces to symmetric self-dual Laurent polynomial solutions of quantum KZ equations. We give an explicit correspondence between solutions of BqKZ and solutions of a particular bispectral problem for Ruijsenaars’ commuting trigonometric q-difference operators. Under this correspondence, � becomes a self-dual Harish-Chandra series solution � + of the bispectral problem. Specializing the central character as above, we recover from � + the

E-health to improve work functioning in employees with rheumatoid arthritis in rheumatology practice: a feasibility study

Objectives: To evaluate the feasibility of an e-health intervention in rheumatology practice for employees with rheumatoid arthritis (RA) who experience problems with work functioning. Method: Twenty-three out of 90 patients with RA from a hospital rheumatology department, invited by letter, participated in a feasibility study. The 3-month internet e-health programme consisted of a self-management programme using a three-step problem-solving strategy: (step 1) analyse your work problems and opportunities; (step 3) identify solutions; and (step 3) work out a strategy (action plan). Support and personal feedback was provided by a rheumatology nurse. Patients completed assignments, received information, and actively worked on their goals. The main feasibility outcome included satisfaction with the programme. Other feasibility outcomes included usefulness, suitability, website use, and work functioning measured at baseline and/or 3 months using questionnaires, semi-structured interviews, and website data. Results: In total, 95% of the participants were satisfied with the programme, and 96% thought the programme was useful for working RA patients and would recommend the programme to other working RA patients (91%). On the website, all patients at least partially completed the assignments in step 1 and 12 patients completed at least one assignment in step 3. Patients judged the website as well arranged with clear tasks. Patients worked on a range of (individual) goals, resolving work challenges using different strategies and actions. Conclusions: The e-health intervention is a feasible intervention for rheumatology practice justifying further effectiveness evaluation while allowing for further improvements in the selection of RA patients and shaping the intervention.