A steady-state genetic algorithm with resampling for noisy inventory control

Noisy fitness functions occur in many practical applications of evolutionary computation. A standard technique for solving these problems is fitness resampling but this may be inefficient or need a large population, and combined with elitism it may overvalue chromosomes or reduce genetic diversity. We describe a simple new resampling technique called Greedy Average Sampling for steady-state genetic algorithms such as GENITOR. It requires an extra runtime parameter to be tuned, but does not need a large population or assumptions on noise distributions. In experiments on a well-known Inventory Control problem it performed a large number of samples on the best chromosomes yet only a small number on average, and was more effective than four other tested technique

Método de determinação e avaliação da depleção de oxitetraciclina em camarão marinho Method for the determination and evaluation of oxytetracycline depletion in marine shrimp

O objetivo deste trabalho foi validar um método para determinação de resíduos de oxitetraciclina (OTC) em camarões, por meio de cromatografia líquida de alta eficiência, e avaliar, pelo método validado, a depleção de resíduos de OTC em camarões in vivo. Para a validação, foram utilizados camarões isentos de OTC e camarões adicionados de OTC in vitro. Foram estabelecidos: seletividade, tempo de retenção, linearidade (coeficiente de correlação), faixa de trabalho, recuperação relativa, limites de detecção e quantificação do método (LDM e LQM, respectivamente) e repetibilidade. Para o experimento in vivo, rações com 200, 400 e 500 &#956;g g-1 de OTC foram administradas aos camarões durante 14 dias. Foi avaliada a concentração do resíduo desse antibiótico no músculo e na carapaça até 22 dias após a suspensão da droga. O coeficiente de correlação linear foi de 0,9997 para o extrato fortificado da matriz, na faixa de trabalho de 0,02 a 0,4 &#956;g g-1; a recuperação foi de 106±17,1% e os LDM e LQM foram de 0,006 e 0,019 &#956;g g-1, respectivamente. O tempo de residência da droga na carapaça dos animais (de 10 a 13 dias) foi maior em comparação ao tempo de residência no músculo (5 dias).<br>This work aimed at validating a method for the determination of oxytetracycline (OTC) residues in shrimp by means of high performance liquid chromatography (HPLC), and at evaluating the OTC residue depletion in shrimps in vivo using the validated method. The shrimp used for validation were either not submitted or submitted to in vitro OTC addition. Selectivity, retention time, linearity (correlation coefficient), work range, relative recovery, detection and method quantification limits and repeatability were determined. For the in vivo experiment, shrimp were fed with feed medicated with OTC at 200, 400 and 500 &#956;g g-1 for 14 days. Oxytetracycline residue concentration in the animals' muscle and carapace was assessed for up to 22 days after stopping medication. The results obtained were: 0.9997 linear correlation coefficient for the fortified matrix extract within a work range of 0.02-0.4 &#956;g g-1, 106±17.1% recovery and 0.006 and 0.019 &#956;g g-1 detection and quantification limits, respectively. A greater OTC residence time was observed in the carapace (10 to 13 days) when compared to the muscle (5 days)

Cooperative Jahn-Teller effect in a 2D mesoscopic C

Fullerene molecules adsorbed on surfaces often show macroscopic average distortions. As charged ions C60n- are known to be Jahn-Teller (JT) active, it is suggested that these distortions could be a manifestation of cooperative JT effects (CJTE) due to interactions between neighbouring fullerene ions. In order to understand the distortion properties it is necessary to take correlations between different distortions into account. However, this can’t easily be done in the mean field approximation usually used to describe the CJTE. We therefore propose an alternative procedure to describe 2D mesoscopic islands of C60 ions in which a pseudo vector spin \hbox{$\overrightarrow{S}$} is evoked to represent degenerate JT-distorted states when the quadratic JT coupling is considered. This approach is analogous to methods used for 2D magnetic systems. We then use the differential operator technique in effective field theory within the Ising approach. We include the effects of weak surface interactions and dynamic motion between equivalent distortions via terms equivalent to anisotropy and a transverse field in magnetism respectively. For distortions to D5d symmetry, we determine single site correlations as a function of temperature, the macroscopic average distortion describing a structural phase transition, and the isothermal response function. Phase diagrams are presented for relevant cases of the system parameters