Research Conducted Using Data Obtained through Online Communities: Ethical Implications of Methodological Limitations

An Essay by A. Cecile Janssens and Peter Kraft discusses the limitations inherent in research involving collection of self-reported data by self-selected participants, and makes proposals for upfront communication of such limitations to study participants

Direct current control of three magnon scattering processes in spin-valve nanocontacts

We have investigated the generation of spin waves in the free layer of an extended spin-valve structure with a nano-scaled point contact driven by both microwave and direct electric current using Brillouin light scattering microscopy. Simultaneously with the directly excited spin waves, strong nonlinear effects are observed, namely the generation of eigenmodes with integer multiple frequencies (2 \emph{f}, 3 \emph{f}, 4 \emph{f}) and modes with non-integer factors (0.5 \emph{f}, 1.5 \emph{f}) with respect to the excitation frequency \emph{f}. The origin of these nonlinear modes is traced back to three magnon scattering processes. The direct current influence on the generation of the fundamental mode at frequency \emph{f} can be related to the spin-transfer torque, while the efficiency of three-magnon-scattering processes is controlled by the Oersted field as an additional effect of the direct current

Performance of a demand controlled mechanical extract ventilation system for dwellings

The main aim of ventilation is to guarantee a goodindoor air quality, related to the energy consumed forheating and fan(s). Active or passive heat recoverysystems seem to focus on the reduction of heatingconsumption at the expense of fan electricityconsumption and maintenance. In this study, demandcontrolledmechanical extract ventilation systems ofRenson (DCV1 and DCV2), based on natural supply inthe habitable rooms and mechanical extraction in thewet rooms (or even the bedrooms), was analysed forone year by means of multi-zone Contam simulationson a reference detached house and compared withstandard MEV and mechanical extract ventilationsystems with heat recovery (MVHR). To this end, IAQ, total energy consumption,CO2 emissions and total cost of the systems aredetermined. The results show that DCV systems withincreased supply air flow rates or direct mechanicalextract from bedrooms can significantly improve IAQ,while reducing total energy consumption comparedto MEV. Applying DCV reduces primary heatingenergy consumption and yearly fan electricityconsumption at most by 65% to 50% compared toMEV. Total operational energy costs and CO2emissions of DCV are similar when compared toMVHR. Total costs of DCV systems over 15 years aresmaller when compared to MVHR due to lowerinvestment and maintenance costs

Argon tagging of doubly transition metal doped aluminum clusters: The importance of electronic shielding

The interaction of argon with doubly transition metal doped aluminum clusters, AlnTM2+ (n = 1–18, TM = V, Nb, Co, Rh), is studied experimentally in the gas phase via mass spectrometry. Density functional theory calculations on selected sizes are used to understand the argon affinity of the clusters, which differ depending on the transition metal dopant. The analysis is focused on two pairs of consecutive sizes: Al6,7V2+ and Al4,5Rh2+, the largest of each pair showing a low affinity toward Ar. Another remarkable observation is a pronounced drop in reactivity at n = 14, independent of the dopant element. Analysis of the cluster orbitals shows that this feature is not a consequence of cage formation but is electronic in nature. The mass spectra demonstrate a high similarity between the size-dependent reactivity of the clusters with Ar and H2. Orbital interactions provide an intuitive link between the two and further establish the importance of precursor states in the reactions of the clusters with hydrogen

Predictive genetic testing for the identification of high-risk groups: a simulation study on the impact of predictive ability

Background: Genetic risk models could potentially be useful in identifying high-risk groups for the prevention of complex diseases. We investigated the performance of this risk stratification strategy by examining epidemiological parameters that impact the predictive ability of risk models.Methods: We assessed sensitivity, specificity, and positive and negative predictive value for all possible risk thresholds that can define high-risk groups and investigated how these measures depend on the frequency of disease in the population, the frequency of the high-risk group, and the discriminative accuracy of the risk model, as assessed by the area under the receiver-operating characteristic curve (AUC). In a simulation study, we modeled genetic risk scores of 50 genes with equal odds ratios and genotype frequencies, and varied the odds ratios and the disease frequency across scenarios. We also performed a simulation of age-related macular degeneration risk prediction based on published odds ratios and frequencies for six genetic risk variants.Results: We show that when the frequency of the high-risk group was lower than the disease frequency, positive predictive value increased with the AUC but sensitivity remained low. When the frequency of the high-risk group was higher than the disease frequency, sensitivity was high but positive predictive value remained low. When both frequencies were equal, both positive predictive value and sensitivity increased with increasing AUC, but higher AUC was needed to maximize both measures.Conclusions: The performance of risk stratification is strongly determined by the frequency of the high-risk group relative to the frequency of disease in the population. The identification of high-risk groups with appreciable combinations of sensitivity and positive predictive value requires higher AUC