Reliability of dose volume constraint inference from clinical data

Dose volume histogram points (DVHPs) frequently serve as dose constraints in radiotherapy treatment planning. An experiment was designed to investigate the reliability of DVHP inference from clinical data for multiple cohort sizes and complication incidence rates. The experimental background was radiation pneumonitis in non-small cell lung cancer and the DVHP inference method was based on logistic regression. From 102 NSCLC real-life dose distributions and a postulated DVHP model, an 'ideal' cohort was generated where the most predictive model was equal to the postulated model. A bootstrap and a Cohort Replication Monte Carlo (CoRepMC) approach were applied to create 1000 equally sized populations each. The cohorts were then analyzed to establish inference frequency distributions. This was applied to nine scenarios for cohort sizes of 102 (1), 500 (2) to 2000 (3) patients (by sampling with replacement) and three postulated DVHP models. The Bootstrap was repeated for a 'non-ideal' cohort, where the most predictive model did not coincide with the postulated model. The Bootstrap produced chaotic results for all models of cohort size 1 for both the ideal and non-ideal cohorts. For cohort size 2 and 3, the distributions for all populations were more concentrated around the postulated DVHP. For the CoRepMC, the inference frequency increased with cohort size and incidence rate. Correct inference rates  >[Formula: see text] were only achieved by cohorts with more than 500 patients. Both Bootstrap and CoRepMC indicate that inference of the correct or approximate DVHP for typical cohort sizes is highly uncertain. CoRepMC results were less spurious than Bootstrap results, demonstrating the large influence that randomness in dose-response has on the statistical analysis.

Wird sprachlicher Förderbedarf in der Grundschule sicher erkannt? Zur Klassifikationsgüte von diagnostischen Entscheidungen

Zusammenfassung. Additive Sprachfördermaßnahmen basieren auf einer vorgelagerten Entscheidung, ob bei einem Kind ein sprachlicher Förderbedarf besteht. Im vorliegenden Beitrag, in dem die Sprachförderdiagnostik in Grundschulen anhand von Daten der IQB-Ländervergleichsstudie 2011 betrachtet wird, gehen wir der Frage nach, welche diagnostische Güte solche Entscheidungen aufweisen. Darüber hinaus wird untersucht, inwieweit die Entscheidungsgüte mit der Nutzung bestimmter diagnostischer Informationsquellen (u.a. Beobachtungen durch Lehrkräfte, Schulnoten, sprachdiagnostische Verfahren) kovariiert. Unsere Ergebnisse zeigen, dass in den Schulen nur ein geringer Anteil der Kinder mit sprachlichem Förderbedarf korrekt identifiziert wird (geringe Sensitivität). Hingegen werden Kinder ohne Förderbedarf zumeist zuverlässig erkannt (hohe Spezifität). Positive Zusammenhänge mit der Diagnosegüte wurden lediglich für den Einsatz sprachdiagnostischer Verfahren (z.B. Tests) gefunden, wobei eine maßgebliche Verbesserung der Diagnosegüte offenbar nur dann erzielt wird, wenn sprachliche Kompetenzen nicht nur einmalig, sondern mehrfach erfasst werden.

Suppressed decomposition of organometal halide perovskites by impermeable electron-extraction layers in inverted solar cells

The area of thin-film photovoltaics has been overwhelmed by organometal halide perovskites. Unfortunately, serious stability concerns arise with perovskite solar cells. For example, methyl-ammonium lead iodide is known to decompose in the presence of water and, more severely, even under inert conditions at elevated temperatures. Here, we demonstrate inverted perovskite solar cells, in which the decomposition of the perovskite is significantly mitigated even at elevated temperatures. Specifically, we introduce a bilayered electron-extraction interlayer consisting of aluminium-doped zinc oxide and tin oxide. We evidence tin oxide grown by atomic layer deposition does form an outstandingly dense gas permeation barrier that effectively hinders the ingress of moisture towards the perovskite and—more importantly—it prevents the egress of decomposition products of the perovskite. Thereby, the overall decomposition of the perovskite is significantly suppressed, leading to an outstanding device stability.

The stability issue of perovskite-based solar cells is in part due to electrode corrosion. Here, Brinkmann et al. develop an impermeable bilayered electron-extraction layer between the active layer and the electrode, suppressing decomposition of the perovskite and preventing corrosion from the inside.