Nonsingular potentials from excited state factorization of a quantum system with position dependent mass

The modified factorization technique of a quantum system characterized by position-dependent mass Hamiltonian is presented. It has been shown that the singular superpotential defined in terms of a mass function and a excited state wave function of a given position-dependent mass Hamiltonian can be used to construct non-singular isospectral Hamiltonians. The method has been illustrated with the help of a few examples.Comment: Improved version accepted in J. Phys.

Double trouble at high density::Cross-level test of ressource-related adaptive plasticity and crowding-related fitness.

Population size is often regulated by negative feedback between population density and individual fitness. At high population densities, animals run into double trouble: they might concurrently suffer from overexploitation of resources and also from negative interference among individuals regardless of resource availability, referred to as crowding. Animals are able to adapt to resource shortages by exhibiting a repertoire of life history and physiological plasticities. In addition to resource-related plasticity, crowding might lead to reduced fitness, with consequences for individual life history. We explored how different mechanisms behind resource-related plasticity and crowding-related fitness act independently or together, using the water flea Daphnia magna as a case study. For testing hypotheses related to mechanisms of plasticity and crowding stress across different biological levels, we used an individual-based population model that is based on dynamic energy budget theory. Each of the hypotheses, represented by a sub-model, is based on specific assumptions on how the uptake and allocation of energy are altered under conditions of resource shortage or crowding. For cross-level testing of different hypotheses, we explored how well the sub-models fit individual level data and also how well they predict population dynamics under different conditions of resource availability. Only operating resource-related and crowding-related hypotheses together enabled accurate model predictions of D. magna population dynamics and size structure. Whereas this study showed that various mechanisms might play a role in the negative feedback between population density and individual life history, it also indicated that different density levels might instigate the onset of the different mechanisms. This study provides an example of how the integration of dynamic energy budget theory and individual-based modelling can facilitate the exploration of mechanisms behind the regulation of population size. Such understanding is important for assessment, management and the conservation of populations and thereby biodiversity in ecosystems

Neural Networks for Defect Recognition on Masks and Integrated Circuits: First Result

Surmann H, Kiziloglu B, Rückert U, Goser K. Neural Networks for Defect Recognition on Masks and Integrated Circuits: First Result. In: Proceedings of Neuro-Nimes: Neural Networks and their Applications. 1991: 581-591

Response of Daphnia to substances released from crowded congeners and conspecifics

The effects of chemicals released from crowded congeners and conspecifics on life history parameters of the freshwater zooplankters Daphnia cucullata and Daphnia pulex were examined. Length and age at maturity of D. pulex were affected by crowding chemicals. Reproduction was lower in crowded medium, and ephippia were produced. Newborn D. pulex in crowded medium were significantly longer than the controls. The intrinsic rate of population increase of D. pulex was 14 and 25% lower than the control when exposed to crowded medium from D. cucullata and D. pulex, respectively. Neither urea nor ammonia (at 1 mg l-1) seemed to be responsible for these effects in D. pulex. In D. cucullata, no significant effect of crowding infochemicals on length and age at maturity was found. However, crowding chemicals reduced reproduction. No ephippia were produced in crowded medium, but up to 83% non-developing eggs were observed in D. cucullata. Newborns were similarly sized in crowded and standard medium. The intrinsic rate of population increase of D. cucullata was 44 and 96% lower than the control when exposed to crowded medium from D. cucullata and D. pulex, respectively. Clearance rates of D. pulex were significantly reduced in crowded media compared with standard medium, which could partly explain why the animals exposed to crowding chemicals reacted as if they were food limited

Implementation of a Biologically Inspired Neuron-Model in FPGA

This paper presents the implementation of a biologically inspired neuron-model. Learning is performed on-line in special synapses based on the biologically proved hebbian learning algorithm. This algorithm is implemented on-chip allowing an architecture of autonomous neural units. The algorithm is transparent so connections between the neurons can easily be engineered. Due to their functionality and their flexibility only few neurons are needed to fulfill basic tasks. A parallel and a serial concept for an implementation in an FPGA (Field Programmable Gate-Array) are discussed. A prototype of the serial approach is developed in a XILINX FPGA series 3090. This solution has one excitatory, one inhibitory, two hebbian synapses and one output operating with 8 bit resolution. The internal computation is performed at higher resolution to eliminate errors due to overflow. The hebbian weights are stored at a precision of 19 bit for multiplication. The prototype works at a clock frequency of 5 ..

Response of Daphnia to substances released from crowded congeners and conspecifics

The effects of chemicals released from crowded congeners and conspecifics on life history parameters of the freshwater zooplankters Daphnia cucullata and Daphnia pulex were examined. Length and age at maturity of D. pulex were affected by crowding chemicals. Reproduction was lower in crowded medium, and ephippia were produced. Newborn D. pulex in crowded medium were significantly longer than the controls. The intrinsic rate of population increase of D. pulex was 14 and 25% lower than the control when exposed to crowded medium from D. cucullata and D. pulex, respectively. Neither urea nor ammonia (at 1 mg l(-1)) seemed to be responsible for these effects in D. pulex. In D. cucullata, no significant effect of crowding infochemicals on length and age at maturity was found. However, crowding chemicals reduced reproduction. No ephippia were produced in crowded medium, but up to 83% non-developing eggs were observed in D. cucullata. Newborns were similarly sized in crowded and standard medium. The intrinsic rate of population increase of D. cucullata was 44 and 96% lower than the control when exposed to crowded medium from D. cucullata and D. pulex, respectively. Clearance rates of D. pulex were significantly reduced in crowded media compared with standard medium, which could partly explain why the animals exposed to crowding chemicals reacted as if they were food limited