A graphical vector autoregressive modelling approach to the analysis of electronic diary data

<p>Abstract</p> <p>Background</p> <p>In recent years, electronic diaries are increasingly used in medical research and practice to investigate patients' processes and fluctuations in symptoms over time. To model dynamic dependence structures and feedback mechanisms between symptom-relevant variables, a multivariate time series method has to be applied.</p> <p>Methods</p> <p>We propose to analyse the temporal interrelationships among the variables by a structural modelling approach based on graphical vector autoregressive (VAR) models. We give a comprehensive description of the underlying concepts and explain how the dependence structure can be recovered from electronic diary data by a search over suitable constrained (graphical) VAR models.</p> <p>Results</p> <p>The graphical VAR approach is applied to the electronic diary data of 35 obese patients with and without binge eating disorder (BED). The dynamic relationships for the two subgroups between eating behaviour, depression, anxiety and eating control are visualized in two path diagrams. Results show that the two subgroups of obese patients with and without BED are distinguishable by the temporal patterns which influence their respective eating behaviours.</p> <p>Conclusion</p> <p>The use of the graphical VAR approach for the analysis of electronic diary data leads to a deeper insight into patient's dynamics and dependence structures. An increasing use of this modelling approach could lead to a better understanding of complex psychological and physiological mechanisms in different areas of medical care and research.</p

An all-chromium single electron transistor:a possible new element of single electronics

The realization of an all‐chromium single electron tunneling (SET) transistor is reported. Chromium was chosen as a normal metal with small grain structure forming the oxide layer with a low potential barrier and great chemical and thermal stability. The transistor showed classical I‐V curves with an offset voltage of 450 μV and an amplitude of gate modulation of 160 μV. Fitting a tunnel current expression in the experimental I‐V curve gave a height of the potential barrier φ=170 meV and a width of the barrier d=16 Å. The SET transistor showed a charge sensitivity of 7×10−4 e/Hz1/2 at 10 Hz