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We present algorithms for constructing and resolving spectral problems for novel photonic crystal surface-emitting lasers with large emission areas, given by first-order PDEs with two spatial dimensions. These algorithms include methods to overcome computer-arithmetic-related challenges when dealing with huge and small numbers. We show that the finite difference schemes constructed using relatively coarse numerical meshes enable accurate estimation of several major optical modes, which are essential in practical applications. [ABSTRACT FROM AUTHOR]

The cochlea forms a key element of the human auditory system in the temporal bone. Damage to the cochlea continues to produce significant impairment for sensory reception of environmental stimuli. To improve this impairment, the optical cochlear implant forms a new research approach. A prerequisite for this method is to understand how light propagation, as well as scattering, reflection, and absorption, takes place within the cochlea. We offer a method to study the light distribution in the human cochlea through phantom materials which have the objective to mimic the optical behavior of bone and Monte‐Carlo simulations. The calculation of an angular distribution after scattering requires a phase function. Often approximate functions like Henyey–Greenstein, two‐term Henyey–Greenstein or Legendre polynomial decompositions are used as phase function. An alternative is to exactly calculate a Mie distribution for each scattering event. This method provides a better fit to the data measured in this work. [ABSTRACT FROM AUTHOR]

Finite‐difference time‐domain (FDTD) simulations of the transmission spectra of planar small‐footprint photonic components with up to four types of morphological disorder as a materials parameter are performed with the aim to identify the individual contributions of the type of disorder to the spectral features. We concentrate on optical components that have a small footprint, that is, their extensions in two dimensions are roughly one order of magnitude higher than the wavelength. They are modeled by a regular pattern of cylinders in a 7 × 10 square lattice, modified by the introduction of a disorder parameter varying either presence, radius, position, distance, or dielectric properties of the cylinders and the surrounding medium. Although the observation that an increasing amount of disorder results in a decreasing transmission intensity of an optical component is well known, quantitative studies of the particular spectral changes and a clear correlation especially with multiple types and amounts of disorder are rare. From these findings, we propose a model component that can incur a compensation of disorder‐induced spectral effects of geometric type with such effects of dielectric type. Our work shows that several types of disorder as well as the mixing two types of disorder can be used for an intentional adaptation of the spectral transmission characteristics and may be considered in the design of small‐footprint photonic components such as scatterers, diffusers, and waveguides. [ABSTRACT FROM AUTHOR]

Carbon nanotube-reinforced polymers belong to a class of composite materials, which have been largely investigated due to their special electrical, thermal and mechanical properties. In the case of electrical conductivity of carbon nanotube-reinforced polymer, a critical amount of carbon nanotubes as a filler material enables a sharp increase of electrical conductivity. At this certain volume fraction of carbon nanotubes, the material turns into a conductor because of the percolation effect. This effect occurs due to the formation of a closed pathway of filler material through the system. Mesoscopic simulation models of these materials were carried out to predict their electrical conductivity. In this paper, the effects of carbon nanotube curvature and their alignment parallel or perpendicular to the electrical flow direction inside a representative volume element were analysed and an optimized carbon nanotube distribution is presented. A network with a longest average path length per (rigid) carbon nanotube but also cross-linking (only nearly isotropic alignment) shows the best conductivity in the preferred direction. [ABSTRACT FROM AUTHOR]

Carbon nanotube reinforced polymers belong to a class of composite materials, which have been largely investigated due to their specific electrical, thermal and mechanical properties. In the case of electrical conductivity of carbon nanotube reinforced polymers, a critical amount of filler material ensures a sharp increase of conductivity. The material forms a percolation pathway and instantly turns the composite into a conductor. Mesoscopic simulations of these materials were carried out to predict electrical conductivity of carbon nanotube reinforced polymers and their critical amounts. This research work deals with percolation thresholds, converging representative volume elements and the effect of the discontinuous behaviour of conductivity considering tunnelling effects found in atomistic approaches on mesoscopic simulation models. [ABSTRACT FROM AUTHOR]

CRH is known as the main stimulator of ACTH release. In representatives of all nonmammalian vertebrates, CRH has also been shown to induce TSH secretion, acting directly at the level of the pituitary. We have investigated which cell types and receptors are involved in CRH-induced TSH release in the chicken (Gallus gallus). Because a lack of CRH type 1 receptors (CRH-R1) on the chicken thyrotropes has been previously reported, two hypotheses were tested using in situ hybridization and perifusion studies: 1) TSH secretion might be induced in a paracrine way involving melanocortins from the corticotropes; and 2) thyrotropes might express another type of CRH-R. For the latter, we have cloned a partial cDNA encoding the chicken CRH-R2. Neither alpha-melanotropin (alpha-MSH) nor its powerful analog Nle4,d-Phe7-MSH could mimic the in vitro TSH-releasing effect of ovine CRH. The nonselective melanocortin receptor blocker SHU91199 did not influence CRH- or TRH-induced TSH secretion. On the other hand, we have found that thyrotropes express CRH-R2 mRNA. The involvement of this CRH receptor in the response of thyrotropes to CRH was further confirmed by the fact that TSH release was stimulated by human urocortin III, a CRH-R2-specific agonist, whereas the TSH response to CRH was completely blocked by the CRH-R blocker astressin and the CRH-R2-specific antagonist antisauvagine-30. We conclude that CRH-induced TSH secretion is mediated by CRH-R2 expressed on thyrotropes.