Experimental noise in small-angle scattering can be assessed and corrected using the Bayesian Indirect Fourier Transformation

Small-angle X-ray and neutron scattering are widely used to investigate soft matter and biophysical systems. The experimental errors are essential when assessing how well a hypothesized model fits the data. Likewise, they are important when weights are assigned to multiple datasets used to refine the same model. Therefore, it is problematic when experimental errors are over- or underestimated. We present a method, using Bayesian Indirect Fourier Transformation for small-angle scattering data, to assess whether or not a given small-angle scattering dataset has over- or underestimated experimental errors. The method is effective on both simulated and experimental data, and can be used assess and rescale the errors accordingly. Even if the estimated experimental errors are appropriate, it is ambiguous whether or not a model fits sufficiently well, as the "true" reduced $\chi^2$ of the data is not necessarily unity. This is particularly relevant for approaches where overfitting is an inherent challenge, such as reweighting of a simulated molecular dynamics trajectory against a small-angle scattering data or ab initio modelling. Using the outlined method, we show that one can determine what reduced $\chi^2$ to aim for when fitting a model against small-angle scattering data. The method is easily accessible via a web interface

Pædagogiske læreplaner – og nye muligheder?

Dette arbejdsmateriale er udarbejdet som en del af forskningsprojektet 'Handlekompetencer i pædagogisk arbejde med socialt udsatte børn og unge - indsats og effekt' (HPA-projektet). Materialet er en del af en serie på i alt 14 tekster, der alle stammer fra projektet, som blev søsat i 2006.Projektets sigte er at udvikle metoder, der giver pædagoger mulighed for at udvikle deres pædagogiske handlekompetencer, så de kan fremme udsatte børns handlemuligheder og livschancer

Shape2SAS -- a web application to simulate small-angle scattering data and pair distance distributions from user-defined shapes

Shape2SAS is a web application that allows researchers and students to build intuition and understanding of small-angle scattering. It is available at https://somo.chem.utk.edu/shape2sas. The user defines a model of arbitrary shape by combining geometrical subunits, and Shape2SAS then calculates and displays the scattering intensity, the pair distance distribution as well as a visualization of the user-defined shape. Simulated data with realistic noise are also generated. We demonstrate how Shape2SAS can calculate and display the different scattering patterns for various geometrical shapes, such as spheres and cylinders. We also demonstrate how the effect of structure factors can be visualized. Finally, we show how multi-contrast particles can readily be generated, and how the calculated scattering may be used to validate and visualize analytical models generated in analysis software for fitting small-angle scattering data

Theory of electron energy-loss spectroscopy in atomically thin metallic films

We study strongly confined plasmons in ultrathin gold and silver films by simulating electron energy-loss spectroscopy (EELS). Plasmon dispersion relations are directly retrieved from the energy- and momentum-resolved loss probability under normal incidence conditions, whereas they can also be inferred for aloof parallel beam trajectories from the evolution of the plasmon features in the resulting loss spectra as we vary the impinging electron energy. We find good agreement between nonlocal quantum-mechanical simulations based on the random-phase approximation and a local classical dielectric description for silver films of different thicknesses down to a few atomic layers. We further observe only a minor dependence of quantum simulations for these films on the confining out-of-plane electron potential when comparing density-functional theory within the jellium model with a phenomenological experimentally-fitted potential incorporating atomic layer periodicity and in-plane parabolic bands of energy-dependent effective mass. The latter shows also a small dependence on the crystallographic orientation of silver films, while the unphysical assumption of energy-independent electron mass leads to spurious features in the predicted spectra. Interestingly, we find electron band effects to be more relevant in gold films, giving rise to blue shifts when compared to classical or jellium model simulations. In contrast to the strong nonlocal effects found in few-nanometer metal nanoparticles, our study reveals that a local classical description provides excellent quantitative results in both plasmon strength and dispersion when compared to quantum-mechanical simulations down to silver films consisting of only a few atomic layers, thus emphasizing the in-plane nearly-free conduction-electron motion associated with plasmons in these structures.Comment: 15 pages, 13 figures, 76 reference

KRONIK: Fremtidens lederprofil i udenrigstjenesten er musikalsk

Udenrigsministeriets lederprofil bør gentænkes. Den nuværende lederprofil fremhæver, at ”du er først og fremmest en god personaleleder”. I samtaler med danske diplomater, der samlet set har ledererfaring fra alle klodens kontinenter, er det tydeligt, at den gode leder i diplomatiet er mere og andet end personaleledelse. En ny lederprofil bør fremhæve: “Du er først og fremmest en musikalsk leder, der har blik for samspillet mellem dine medarbejderes trivsel og de faglige resultater, der skal opnås.

An Experimental Study on Transient Response of a Hybrid Thermoelectric–Photovoltaic System with Beam Splitter

In the current study, the electrical responses of a thermoelectric (TE) module and a photovoltaic (PV) cell are investigated in three different systems, namely, a PV-only system, TE-only system, and hybrid TE-PV system with a beam splitter (TE-PV-BS), under variable solar irradiations demonstrating partly cloudy weather conditions. To enhance the deployment of solar energy, a predesigned beam splitter combined with the amorphous silicon TE and PV system is used in the experiments. The impact of the spectral beam splitting technology on the conversion performance of the TE module and PV cell in the hybrid system is studied and compared to the performance of the TE-only and PV-only systems. The electrical output parameters of the TE module and PV cell are obtained for the studied systems, and they are discussed in detail. The results of this work show that the power generated by the PV cell has a stepwise fluctuation similar to the variation in the concentrated solar radiation. Affected by its heat capacity, the power variation is monotonous with the TE module. The results moreover indicate that there is more power generated by the PV cell in the TE-PV-BS hybrid system than by the PV-only system. In comparison, the TE-only system produces more power than the TE module in the hybrid system. Furthermore, the TE-PV-BS hybrid system generates higher and more stable electrical power than the TE-only and PV-only systems, showing a significant advantage of the spectrum management concept

Psychological Flexibility as a Buffer against Caregiver Distress in Families with Psychosis

Background: Research has shown that caregivers of persons with psychosis play an invaluable role in recovery, but unfortunately, often report high levels of distress. While cognitive models of caregiver distress have been well-supported, there is still limited knowledge of the psychological factors involved. Recent advances in cognitive behavioral therapy seem to converge on the importance of acceptance- and mindfulness based processes.Aim: To examine the impact of psychological flexibility on caregiver distress in the early phases of psychosis, while controlling for known predictors of caregiver distress.Method: Within a cross-sectional design, 101 caregivers of 38 persons with first-episode psychosis in a clinical epidemiological sample completed a series of self-report measures.Results: A linear mixed model analysis found that, after controlling for caregiver socio-demographic factors, service user symptoms, drug use and global functioning, psychological flexibility was a significant predictor of caregiver distress.Conclusion: Greater level of psychological flexibility in caregivers, seems to be related to lower levels of caregiver distress. This finding corresponds to studies within a broad range of emotional disorders. There may be important clinical implications in terms of facilitating the process of acceptance through interventions from the ‘third-wave’ or contextual cognitive behavioral therapies