Vitality is a fundamental trait for the development of a plant. It is known to depend on various factors, such as climate, soil, and the plant’s genetics, but the progressive depletion of soil nutrients make it a priority for the industry to pinpoint which of the controllable qualities of a seed have the biggest impact on vitality. This work describes techniques applied in a high-throughput phenotyping project, the first of this magnitude for a complex plant, the potato (solanum tuberosum). We also present the results of an analysis of associations between the chemical composition of the seed potatoes and field performance, solving the arising underdetermined linear systems by means of PLS regression. We show that some but not all of the chemical data is strongly associated to vitality.

@en

This paper presents a modified self-consistent drift-diffusion-reaction model suitable for the analysis of electron-beam irradiated insulators at both short and long time scales. A novel boundary condition is employed that takes into account the reverse electron current and a fully dynamic trap-assisted generation-recombination mechanism is implemented. Sensitivity of the model with respect to material parameters is investigated and a calibration procedure is developed that reproduces experimental yield-energy curves for uncharged insulators. Long-time charging and yield variations are analyzed for stationary defocused and focused beams as well as moving beams dynamically scanning composite insulators.

@en

By placing, in vacuum, a stack of transmission dynodes (tynodes) on top of a CMOS pixel chip, a single free electron detector could be made with outstanding performance in terms of spatial and time resolution. The essential object is the tynode: an ultra thin membrane, which emits, at the impact of an energetic electron on one side, a multiple of electrons at the other side. The electron yields of tynodes have been calculated by means of GEANT-4 Monte Carlo simulations, applying special low-energy extensions. The results are in line with another simulation based on a continuous charge-diffusion model. By means of Micro Electro Mechanical System (MEMS) technology, tynodes and test samples have been realized. The secondary electron yield of several samples has been measured in three different setups. Finally, several possibilities to improve the yield are presented.

@en

Analytical solutions are presented for the electromagnetic radiation by an arbitrary pulsed source into a homogeneous time-varying background medium. In the constant-impedance case an explicit radiation formula is obtained for the synchronous permittivity and permeability described by any positive function of time. As might be expected, such a medium introduces significant spectral shifts and spatiotemporal modulation, which are analyzed here for the linear and exponential time variations of the medium parameters. In the varying-impedance case the solution is obtained for the fourth-order polynomial time dependence of the permittivity. In addition to the spectral shifts and modulation this spatially homogeneous medium scatters the field introducing causal echoes at the receiver location.@en

Previously we have shown that apart from discrete spectrum (eigenvalues), the threedimensional volume integral operator of electromagnetic scattering has a conitnuous essential spectrum as well. Here we derive the corresponding essential modes. We use the Weyl definition of essential spectrum, where such modes are described in terms of singular sequences. A closed form expression for the required sequence is obtained and its properties are analyzed. We also discuss the physical meaning and the conditions on the excitation of the essential resonances.@en

We show that the mode corresponding to a point of the essential spectrum of the electromagnetic scattering operator is a vector-valued distribution representing the square root fo the three-dimensional Dirac's delta function. An explicit expression for this singular mode in terms of the Weyl sequence is provided and analysed. The essential resonance occurs if the permittivity of an object gets close to zero, which is often the case in plasmas and negative-permittivity metamaterials. Such resonance would lead to a perfect localization (confinement) of the electromagnetic field. Simultaneously, however, a portion of electromagnetic energy is removed from the Hilbert spcae and therefore the whole process may be viewed as absorption.@en

The notion of effective permittivity originates from the effective medium theory (EMT), where a medium randomly inhomgeneous on a micro-scale is represented as a homogeneous bulk material. There exist many different formulas that give the effective permitivity in terms of the permettivities, sizes and shapes of the microscopic constituents. Normally one tries to find an expression which would suit all possible illumination and measurement conditions. The problem is, in fact, an inverse scattering problem, and as such can be investigated using the standard inversion methodology. In particular, we have looked at it in the context of effective inversion, i.e. inversion with very limited scattered field data where it is impossible to reconstruct an inhomgeneous subsurface target, by may be possible to recover its effective permittivit having an approximate knowledge of the outer shape of the object. That latter shape is often the result of simple linearizedimaging algorithms, such as the travel-time tomography and the sampling method. The difference with the EMT is that, strictly speaking, the reconstructed effective permittivity suits only some particular illumination and measurement configuration. Yet our results indicate that the reconstructed effective permittivities are closely related to the permittivities of the constituents. On the other hand, the inverse scattering approach is much more rigorous as far as the reconstruction of the effective permittivity is concerned, than the general but approximate techniques of the EMT. For example, no statistical assumptions are needed and the onhomogeneities do not have to be electrically small. This time we shall talk about a very fast and efficient numerical method specifically designed for the effective inversion problem. As common in inverse scattering, the problem is nonlinear and therefore requires repetitive solution of the associated forward scattering problem. In its turn the forward problem has to be solved by one or another iterative algorithm. Hence, the solution of the inverse problem requires multiple runs of an iterative scheme. Most of the work in such a scheme is done at the stage of construction of the so-called Kryloc subspace. In the effective inversion case, however, the once constructed Krylov subspace can be re-used, thereby significantly reducing the computational order of the inverse problem. With the help of this reduced-order algorithm various inhomogeneous targets can be analyzed with little computational effort. Special attention will be paid to the disperion of the reconstructed effective permittivity.@en