Photon-electron coincidence experiments at synchrotron radiation facilities with arbitrary bunch modes

We report the adaptation of an electron–photon coincidence detection scheme to the multibunch hybrid mode of the synchrotron radiation source BESSY II (Helmholtz-Zentrum Berlin). Single-event-based data acquisition and evaluation, combined with the use of relative detection times between the coincident particles, enable the acquisition of proper coincidence signals from a quasi-continuous excitation pattern. The background signal produced by accidental coincidences in the time difference representation is modeled using the non-coincident electron and photon spectra. We validate the method by reproducing previously published results, which were obtained in the single bunch mode, and illustrate its usability for the multibunch hybrid mode by investigating the photoionization of CO2 into CO+2 B satellite states, followed by subsequent photon emission. The radiative lifetime obtained and the electron binding energy are in good agreement with earlier publications. We expect this method to be a useful tool to extend the versatility of coincident particle detection to arbitrary operation modes of synchrotron radiation facilities and other excitation sources without the need for additional experimental adjustments

Nature and impact of charge transfer to ground-state dications in atomic and molecular environments

Charge transfer processes between weakly bound entities play an important role in various chemical and biological environments. In this combined experimental and theoretical work, we investigate the nature of charge-transfer processes in homogeneous atomic and heterogeneous atomic-molecular clusters. Our results reveal fundamentally different processes to be at play in pure argon clusters compared to mixed argon-nitrogen systems: We demonstrate that the former species decay via photon-mediated charge transfer while a nonradiative direct process is found dominant in the atomic-molecular cases. Our results are of general interest for studies on charge redistribution in more complex and biologically relevant samples where molecules are involved

"CAN Stop" - Implementation and evaluation of a secondary group prevention for adolescent and young adult cannabis users in various contexts - study protocol

<p>Abstract</p> <p>Background</p> <p>Current research shows that overall numbers for cannabis use among adolescents and young adults dropped in recent years. However, this trend is much less pronounced in continuous cannabis use. With regard to the heightened risk for detrimental health- and development-related outcomes, adolescents and young adults with continuous cannabis use need special attention. The health services structure for adolescents and young adults with substance related problems in Germany, is multifaceted, because different communal, medical and judicial agencies are involved. This results in a rather decentralized organizational structure of the help system. This and further system-inherent characteristics make the threshold for young cannabis users rather high. Because of this, there is a need to establish evidence-based low-threshold help options for young cannabis users, which can be easily disseminated. Therefore, a training programme for young cannabis users (age 14-21) was developed in the "CAN Stop" project. Within the project, we seek to implement and evaluate the training programme within different institutions of the help system. The evaluation is sensitive to the different help systems and their specific prerequisites. Moreover, within this study, we also test the practicability of a training provision through laypersons.</p> <p>Methods/Design</p> <p>The CAN Stop study is a four-armed randomized wait-list controlled trial. The four arms are needed for the different help system settings, in which the CAN Stop training programme is evaluated: (a) the drug addiction aid and youth welfare system, (b) the out-patient medical system, (c) the in-patient medical system and (d) prisons for juvenile offenders. Data are collected at three points, before and after the training or a treatment as usual, and six months after the end of either intervention.</p> <p>Discussion</p> <p>The CAN Stop study is expected to provide an evidence-based programme for young cannabis users seeking to reduce or quit their cannabis use. Moreover, we seek to gain knowledge about the programme's utility within different settings of the German help system for young cannabis users and information about the settings' specific clientele. The study protocol is discussed with regard to potential difficulties within the different settings.</p> <p>Trial registration</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN57036983">ISRCTN57036983</a></p

Fully automated and standardized segmentation of adipose tissue compartments via deep learning in 3D whole-body MRI of epidemiological cohort studies.

Fully automated and fast assessment of visceral and subcutaneous adipose tissue compartments using whole-body MRI is feasible with a deep learning network; a robust and generalizable architecture was investigated that enables objective segmentation and quick phenotypic profiling.PurposeTo enable fast and reliable assessment of subcutaneous and visceral adipose tissue compartments derived from whole-body MRI.Materials and MethodsQuantification and localization of different adipose tissue compartments derived from whole-body MR images is of high interest in research concerning metabolic conditions. For correct identification and phenotyping of individuals at increased risk for metabolic diseases, a reliable automated segmentation of adipose tissue into subcutaneous and visceral adipose tissue is required. In this work, a three-dimensional (3D) densely connected convolutional neural network (DCNet) is proposed to provide robust and objective segmentation. In this retrospective study, 1000 cases (average age, 66 years ± 13 [standard deviation]; 523 women) from the Tuebingen Family Study database and the German Center for Diabetes research database and 300 cases (average age, 53 years ± 11; 152 women) from the German National Cohort (NAKO) database were collected for model training, validation, and testing, with transfer learning between the cohorts. These datasets included variable imaging sequences, imaging contrasts, receiver coil arrangements, scanners, and imaging field strengths. The proposed DCNet was compared to a similar 3D U-Net segmentation in terms of sensitivity, specificity, precision, accuracy, and Dice overlap.ResultsFast (range, 5–7 seconds) and reliable adipose tissue segmentation can be performed with high Dice overlap (0.94), sensitivity (96.6%), specificity (95.1%), precision (92.1%), and accuracy (98.4%) from 3D whole-body MRI datasets (field of view coverage, 450 × 450 × 2000 mm). Segmentation masks and adipose tissue profiles are automatically reported back to the referring physician.ConclusionAutomated adipose tissue segmentation is feasible in 3D whole-body MRI datasets and is generalizable to different epidemiologic cohort studies with the proposed DCNet

Core level interatomic Coulombic decay in van der Waals clusters

We report on the experimental observation of the direct decay of a core vacancy in van der Waals clusters byemission of a fast electron from a neighboring atom. The process can be regarded as an interatomic Coulombicdecay of core holes (core-level ICD). We identify it unambiguously by electron-electron and electron-electron-photon coincidence spectroscopy of the decay of 2pvacancies in Ar clusters. While several earlier works reportedthe absence of this channel, we find core-level ICD to be of considerable significance and quantify the branchingratio of this nonlocal electron emission to conventional local Auger decay as (0.8±0.2)%. Our results aresupported by calculations on smaller clusters and show a reasonable agreement. This report on a successfullyperformed electron-electron-photon coincidence experiment provides a perspective for explorations of matterexposed to ionizing radiation. The observed core-level ICD is proposed to be of general importance for studieson charge redistribution after core-level photoionization where van der Waals clusters are often used as prototypesystems

Experimental quantification of site specific efficiency of Interatomic Coulombic Decay after inner shell ionization

Interatomic Coulombic Decay ICD and related interatomic and intermolecular autoionization mechanisms are ubiquitous decay processes of excited atoms and molecules in an environment. It is commonly accepted that the efficiency of ICD of an ionized atom in a cluster increases with an increasing number of nearest neighbors. Here, we present a method for experimental validation of this assumption by a site specific and quantitative comparison of ICD and its main competitor, Auger decay, in core level ionized Kr clusters. Our results are in quantitative agreement with scaled theoretical calculations on Kr