Low retinal noise in animals with low body temperature allows high visual sensitivity

The weakest pulse of light a human can detect sends about 100 photons through the pupil and produces 10−20 rhodopsin isomerizations in a small retinal area1,2. It has been postulated3 that we cannot see single photons because of a retinal noise arising from randomly occurring thermal isomerizations. Direct recordings have since demonstrated the existence of electrical 'dark' rod events indistinguishable from photoisomerization signals4−6. Their mean rate of occurrence is roughly consistent with the 'dark light' in psychophysical threshold experiments, and their thermal parameters justify an identification with thermal isomerizations5. In the retina of amphibians, a small proportion of sensitive ganglion cells have a performance-limiting noise that is low enough to be well accounted for by these events7−10. Here we study the performance of dark-adapted toads and frogs and show that the performance limit of visually guided behaviour is also set by thermal isomerizations. As visual sensitivity limited by thermal events should rise when the temperature falls, poikilothermous vertebrates living at low temperatures should then reach light sensitivities unattainable by mammals and birds with optical factors equal. Comparison of different species at different temperatures shows a correlation between absolute threshold intensities and estimated thermal isomerization rates in the retina

Electrical properties of TaN–Cu nanocomposite thin films

TaN–Cu nanocomposite thin films used as materials for TFR (thin film resistor) were prepared by reactive co-sputtering of Ta and Cu in the plasma of N2 and Ar. After deposition, the films were annealed using rapid thermal processing (RTP) at 400 °C for 2, 4, 8 min, respectively to induce the nucleation and grain growth of Cu. The results reveal that temperature coefficient of resistivity (TCR) values will increase with the increase of Cu content for both the as-deposited and annealed films. The increase of nitrogen will result in higher resistivity and more negative TCR. At a constant nitrogen flow rate, the resistivity and TCR may increase or decrease with the increase of annealing time depending on the Cu content. In general, to reach near-zero TCR value, more copper is needed to compensate the negative effect caused by Ta–N. Thus, electrical properties of thin films can be characterized as functions of N2 flow rate, Cu concentration and annealing time

Effect of food and pharmaceutical formulation on desmopressin pharmacokinetics in children

Introduction: Desmopressin is used for treatment of nocturnal enuresis in children. In this study, we investigated the pharmacokinetics of two formulations—a tablet and a lyophilisate—in both fasted and fed children. Methods: Previously published data from two studies (one in 22 children aged 6–16 years, and the other in 25 children aged 6–13 years) were analyzed using population pharmacokinetic modeling. A one-compartment model with first-order absorption was fitted to the data. Covariates were selected using a forward selection procedure. The final model was evaluated, and sensitivity analysis was performed to improve future sampling designs. Simulations were subsequently performed to further explore the relative bioavailability of both formulations and the food effect. Results: The final model described the plasma desmopressin concentrations adequately. The formulation and the fed state were included as covariates on the relative bioavailability. The lyophilisate was, on average, 32.1 % more available than the tablet, and fasted children exhibited an average increase in the relative bioavailability of 101 % in comparison with fed children. Body weight was included as a covariate on distribution volume, using a power function with an exponent of 0.402. Simulations suggested that both the formulation and the food effect were clinically relevant. Conclusion: Bioequivalence data on two formulations of the same drug in adults cannot be readily extrapolated to children. This was the first study in children suggesting that the two desmopressin formulations are not bioequivalent in children at the currently approved dose levels. Furthermore, the effect of food intake was found to be clinically relevant. Sampling times for a future study were suggested. This sampling design should result in more informative data and consequently generate a more robust model