Zeno effect and switching of solitons in nonlinear couplers.

The Zeno effect is investigated for soliton type pulses in a nonlinear directional coupler with dissipation. The effect consists in increase of the coupler transparency with increase of the dissipative losses in one of the arms. It is shown that localized dissipation can lead to switching of solitons between the arms. Power losses accompanying the switching can be fully compensated by using a combination of dissipative and active (in particular, parity-time -symmetric) segments.Comment: 3 pages, 4 figures, to be published in Optics Letter

A Computationally Efficient Tool for Assessing the Depth Resolution in Potential-Field Inversion

In potential-field inversion problems, it can be difficult to obtain reliable information about the source distribution with respect to depth. Moreover, spatial resolution of the solution decreases with depth, and in fact the more ill-posed the problem – and the more noisy the data – the less reliable the depth information. Based on early work in depth resolution, defined in terms of the singular value decomposition, we introduce a tool APPROXDRP which uses an approximation of the singular vectors obtained by the iterative Lanczos bidiagonalization algorithm, making it well suited for large-scale problems. This tool allows a computational/visual analysis of how much the depth resolution in a computational potential-field inversion problem can be obtained from the given data.We show that when used in combination with a plot of the approximate SVD quantities, APPROXDRP may successfully show the limitations of depth resolution resulting from noise in the data. This allows a reliable analysis of the retrievable depth information and effectively guides the user in choosing the optimal number of iterations, for a given problem

Subspace-based Fundamental Frequency Estimation

Publication in the conference proceedings of EUSIPCO, Viena, Austria, 200

Resource use in a low-input organic vegetable food supply system in UK - a case study

Use of local renewable resources in a low-input organic vegetable food supply system in UK is evaluated against the use of imported resources in the same system. Despite much focus by the farmer on low-input, the production and distribution system is only supported by 13% local renewable resources based on an emergy assessment. Future sustainability of such systems are discussed

The essential role of luminal BK channels in distal colonic K+ secretion

Distal colonic K+ excretion is determined by the balance of K+ absorption and K+ secretion of the enterocytes. K+ secretion occurs via active basolateral K+ uptake mostly via the NKCC1 co-transporter followed by K+ exit via a luminal K+ channel. The specific focus here is directed towards the luminal secretory K+ channel (1). Several recent observations highlight the pivotal role of the large conductance, Ca2+-activated KCa1.1 (BK, KCNMA) channel as the only functionally relevant luminal K+ efflux pathway in mouse distal colon (2, 3). This conclusion was based on defining results from BK knock-out mice. The following key observations were made : 1. BK channels mediate the resting distal colonic K+ secretion (2, 4), 2. They are acutely stimulated by activation of luminal nucleotide receptor and elevations of intracellular Ca2+ (2, 4, 5), 3. Colonic BK channels are up-regulated by increases of plasma aldosterone (3), 4. In addition, the cAMP-stimulated distal colonic K+ secretion is apparently mediated via BK channels, 5. Finally, aldosterone was found to up-regulate specifically the ZERO (e.g. cAMP activated) C-terminal splice variant of the BK channel. In summary, we suggest that the sole exit pathway for transcellular K+ secretion in mammalian distal colon is the BK channel, which is the target for short term intracellular Ca2+ and cAMP activation and long term aldosterone regulation