Exploring energy landscapes: from molecular to mesoscopic systems

We review a comprehensive computational framework to survey the potential energy landscape for systems composed of rigid or partially rigid molecules. Illustrative case studies relevant to a wide range of molecular clusters and soft and condensed matter systems are discussed

Exploring energy landscapes: metrics, pathways, and normal mode analysis for rigid-body molecules

We present new methodology for exploring the energy landscapes of molecular systems, using angle-axis variables for the rigid-body rotational coordinates. The key ingredient is a distance measure or metric tensor, which is invariant to global translation and rotation. The metric is used to formulate a generalized nudged elastic band method for calculating pathways, and a full prescription for normal-mode analysis is described. The methodology is tested by mapping the potential energy and free energy landscape of the water octamer, described by the TIP4P potential

Financial toxicity in cancer patients treated with radiotherapy in Germany-a cross-sectional study

Purpose Financial toxicity arises in cancer patients from subjective financial distress due to objective financial burden from the disease or treatment. Financial toxicity associates with worse outcomes. It has not been described in cancer patients undergoing radiotherapy in Germany and its publicly funded health system. In this context, we therefore investigated the prevalence of financial toxicity, associated risk factors, and patient preferences on communication of financial burden. Methods We conducted a preregistered ( https://doi.org/10.17605/OSF.IO/KH6VX ) cross-sectional study surveying patients at the end of their course of radiotherapy in two institutions. Objective financial burden was assessed by direct costs and loss of income. Financial toxicity was measured by subjective financial distress per EORTC QLQ-C30. We used Spearman's correlation and Fisher's exact test for univariate analysis, an ordinal regression for multivariate analysis. A p-value < 0.05 was considered statistically significant. Results Of the 100 patients participating in the study, 68% reported direct costs, 25% loss of income, and 31% subjective financial distress. Per univariate analysis, higher subjective financial distress was significantly associated with active employment, lower quality of life, lower household income, higher direct costs, and higher loss of income. The latter three factors remained statistically significant in the multivariate analysis. A relative majority of the patients welcomed communication regarding financial burden with their radiation oncologist. Conclusion Financial toxicity is prevalent in cancer patients treated with radiotherapy in Germany. The reported risk factors may help to identify patients at risk. Future studies should validate these results and investigate interventions for financial toxicity to potentially improve outcomes

The wavefront of the radio signal emitted by cosmic ray air showers

Analyzing measurements of the LOPES antenna array together with corresponding CoREAS simulations for more than 300 measured events with energy above $10^{17}\,$eV and zenith angles smaller than $45^\circ$, we find that the radio wavefront of cosmic-ray air showers is of approximately hyperbolic shape. The simulations predict a slightly steeper wavefront towards East than towards West, but this asymmetry is negligible against the measurement uncertainties of LOPES. At axis distances $\gtrsim 50\,$m, the wavefront can be approximated by a simple cone. According to the simulations, the cone angle is clearly correlated with the shower maximum. Thus, we confirm earlier predictions that arrival time measurements can be used to study the longitudinal shower development, but now using a realistic wavefront. Moreover, we show that the hyperbolic wavefront is compatible with our measurement, and we present several experimental indications that the cone angle is indeed sensitive to the shower development. Consequently, the wavefront can be used to statistically study the primary composition of ultra-high energy cosmic rays. At LOPES, the experimentally achieved precision for the shower maximum is limited by measurement uncertainties to approximately $140\,$g/cm$^2$. But the simulations indicate that under better conditions this method might yield an accuracy for the atmospheric depth of the shower maximum, $X_\mathrm{max}$, better than $30\,$g/cm$^2$. This would be competitive with the established air-fluorescence and air-Cherenkov techniques, where the radio technique offers the advantage of a significantly higher duty-cycle. Finally, the hyperbolic wavefront can be used to reconstruct the shower geometry more accurately, which potentially allows a better reconstruction of all other shower parameters, too.Comment: accepted by JCA

On noise treatment in radio measurements of cosmic ray air showers

Precise measurements of the radio emission by cosmic ray air showers require an adequate treatment of noise. Unlike to usual experiments in particle physics, where noise always adds to the signal, radio noise can in principle decrease or increase the signal if it interferes by chance destructively or constructively. Consequently, noise cannot simply be subtracted from the signal, and its influence on amplitude and time measurement of radio pulses must be studied with care. First, noise has to be determined consistently with the definition of the radio signal which typically is the maximum field strength of the radio pulse. Second, the average impact of noise on radio pulse measurements at individual antennas is studied for LOPES. It is shown that a correct treatment of noise is especially important at low signal-to-noise ratios: noise can be the dominant source of uncertainty for pulse height and time measurements, and it can systematically flatten the slope of lateral distributions. The presented method can also be transfered to other experiments in radio and acoustic detection of cosmic rays and neutrinos.Comment: 4 pages, 6 figures, submitted to NIM A, Proceedings of ARENA 2010, Nantes, Franc