Subsoil <Superscript>15</Superscript>N-N<Subscript>2</Subscript>O Concentrations in a Sandy Soil Profile After Application of <Superscript>15</Superscript>N-fertilizer

Studies on emissions of nitrous oxide (N₂O) from agricultural soils mostly focus on fluxes between the soil and the atmosphere or are limited to the atmosphere in the topsoil. However, in soils with shallow water tables, significant N₂O formation may occur closer to the groundwater. The aims of this study were (i) to determine the importance of subsoil N₂O formation in a sandy soil; and (ii) to obtain a quantitative insight in the contribution of subsoil N₂O to the overall losses of N₂O to the environment. We applied ¹⁵N labeled fertilizer at a rate of 5.22 kg ¹⁵N ha⁻¹; 50% as Ca(NO₃)₂ and 50% as NH₄Cl, on a mesic typic Haplaquod seeded with potatoes (Solanum tuberosum L.), and traced soil N₂O concentrations and fluxes over a one-year period. Throughout the year, total N₂O and the amount of ¹⁵N recovered in soil N₂O were highest in the subsoil, with a maximum concentration at 48 cm depth in mid-February of 19900 μl m⁻³ and 24 μg ¹⁵N m⁻³, respectively. The maximum concentration coincided with the highest water-filled pore space of 71%. The cumulative flux of N₂O was 446 g N₂O-N ha⁻¹, the recovery of ¹⁵N in this flux was 0.06%. During the summer, maximum fluxes followed high soil N₂O concentrations. During winter, no such relation was found. We concluded that the formation of N₂O was the highest in the subsoil, largely controlled by water-filled pore space rather than NO₃⁻ concentration or temperature. Although high subsoil N₂O concentrations did not lead to high surface fluxes of N₂O in the winter, artificial draining may lead to high indirect N₂O emissions through supersaturated drainage water.     

Physics-guided machine learning from simulated data with different physical parameters

Knowledge and Information Systems - Physics-based models are widely used to study dynamical systems in a variety of scientific and engineering problems. However, these models are necessarily...     

Evaluation and comparison of satellite-based rainfall products in Burkina Faso,West Africa

The performance of seven operational high-resolution satellite-based rainfall products – Africa Rainfall Estimate Climatology (ARC 2.0), Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS), Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), African Rainfall Estimation (RFE 2.0), Tropical Applications of Meteorology using SATellite (TAMSAT), African Rainfall Climatology and Time-series (TARCAT), and Tropical Rainfall Measuring Mission (TRMM) daily and monthly estimates – was investigated for Burkina Faso. These were compared to ground data for 2001–2014 on a point-to-pixel basis at daily to annual time steps. Continuous statistics was used to assess their performance in estimating and reproducing rainfall amounts, and categorical statistics to evaluate rain detection capabilities. The north–south gradient of rainfall was captured by all products, which generally detected heavy rainfall events, but showed low correlation for rainfall amounts. At daily scale they performed poorly. As the time step increased, the performance improved. All (except TARCAT) provided excellent scores for Bias and Nash–Sutcliffe Efficiency coefficients, and overestimated rainfall amounts at the annual scale. RFE performed the best, whereas TARCAT was the weakest. Choice of product depends on the specific application: ARC, RFE, and TARCAT for drought monitoring, and PERSIANN, CHIRPS, and TRMM daily for flood monitoring in Burkina Faso.     

2‐D/3‐D displays based on switchable lenticulars

Abstract— An attractive concept for 3‐D displays is the one based on LCDs equipped with lenticular lenses. This enables autostereoscopic multiview 3‐D displays without a loss in brightness. A general issue in multiview 3‐D displays is their relatively low spatial resolution because the pixels are divided among the different views. To overcome this problem, we have developed switchable displays, using liquid‐crystal (LC) filled switchable lenticulars. In this way, it is possible to have a high‐brightness 3‐D display capable of fully exploiting the native 2‐D resolution of the underlying LCD. The feasibility of LC‐filled switchable lenticulars was shown in several applications. For applications in which it is advantageous to be able to display 3‐D and 2‐D content simultaneously, a 42‐in. locally switchable prototype having a matrix electrode structure was developed. These displays were realized using cylindrically shaped lenticular lenses in contact with LC. An alternative for these are lenticulars based on gradient‐index (GRIN) LC lenses. Preliminary results for such switchable GRIN lenses are presented as well.     

Improvement of luminance and luminous efficacy in PDPs

Abstract— The dependence of PDP luminance and efficacy on the input power was investigated for several Xe‐Ne gas mixtures. The input power was varied in two ways: namely, by changing the dielectric‐layer capacitance (thickness) and by changing the sustain voltage. A distinctly different behavior was found; for increasing capacitance the efficacy decreases markedly, whereas for increasing sustain voltage the efficacy increases. A design window comprising the combination of a high Xe concentration and a high sustain voltage was suggested. In this window, a high luminance and a high efficacy are concurrent. A 4‐in. test panel with 10% Xe in Ne has been realized showing a white luminance of 2040 cd/m² and an efficacy of 2.3 lm/W for continuous sustaining at 50 kHz with a sustain voltage of 225 V.     

High‐Xe‐content high‐efficacy PDPs

Abstract— The trade‐off between PDP efficacy improvement and driving voltages was investigated for several design factors. It was found that for a proper combination of an increased Xe content, cell design, and the use of a TiO₂ layer combined with “non‐saturating” phosphors, a large increase in both efficacy and luminance can be realized at moderately increased drive voltages. In a 4‐in. color test panel, a white efficacy of 5 lm/W and a luminance of 5000 cd/m² was obtained for sustaining at 260 V in addressed condition.     

Onset of virus systemic infection in plants is determined by speed of cell-to-cell movement and number of primary infection foci

The cornerstone of today''s plant virology consists of deciphering the molecular and mechanistic basis of host–pathogen interactions. Among these interactions, the onset of systemic infection is a fundamental variable in studying both within- and between-host infection dynamics, with implications in epidemiology. Here, we developed a mechanistic model using probabilistic and spatio-temporal concepts to explain dynamic signatures of virus systemic infection. The model dealt with the inherent characteristic of plant viruses to use two different and sequential stages for their within-host propagation: cell-to-cell movement from the initial infected cell and systemic spread by reaching the vascular system. We identified the speed of cell-to-cell movement and the number of primary infection foci in the inoculated leaf as the key factors governing this dynamic process. Our results allowed us to quantitatively understand the timing of the onset of systemic infection, describing this global process as a consequence of local spread of viral populations. Finally, we considered the significance of our predictions for the evolution of plant RNA viruses.     

A representation of all solutions of the control algebraic Riccati equation for infinite-dimensional systems

We obtain a representation of all self-adjoint solutions of the control algebraic Riccati equation associated to the infinite-dimensional state linear system Σ(A,B,C) under the following assumptions: A generates a C ₀-group, the system is output stabilizable, strongly detectable and the dual Riccati equation has an invertible self-adjoint non-negative solution.     

Modelling and controller design for distributed parameter systems via residence time distribution

For chemical reactors with non-linear fluid dynamics, a linear model realisation is proposed. The inputs are the ingoing concentration of a certain component in the fluid, and the reaction rate. The output is the outgoing concentration. The realisation makes use of a first-order reaction equation, and the residence time distribution of the fluid particles inside the reactor. Also dead time is incorporated in the modelling. The method is tested on two non-linear models for which the residence time distributions are known analytically. The first model is a series of mixed tanks, and it is shown by simulation that the method gives an accurate approximation of the original model. The second model is a UV disinfection reactor, which has a dead time. For this model, the residence time distribution is first fitted by a form that is suitable for our realisation method. Simulations show that for realistic disturbances a high-performance linear controller can be designed. After that, the residence time distribution of a real life UV reactor (for which we have no model) is fitted by a suitable form. The fit is of the same quality as for the UV reactor model. This indicates that also for the real life UV reactor a high-performance controller can be designed.     

Exact observability of diagonal systems with a finite-dimensional output operator

In this paper equivalent conditions for exact observability of diagonal systems with a finite-dimensional output operator are given. One of these equivalent conditions is the conjecture of Russell and Weiss (SIAM J. Control Opt. 32(1) (1994) 1–23). The other conditions are in terms of the eigenvalues and the Lyapunov solutions of finite-dimensional subsystems.