Semi-intensive production of Penaeus vannamei in Guatemala

SUMMARY Because marine shrimp species convenient for aquacultural purposes live mainly in warm-water environments, commercial shrimp farms are located principally along tropical and sub-tropical marine coastlines. Other than the South-East Asiatic countries, the Latin America countries are important shrimp producers that contribute in satisfying the international demand of marine shrimp. Part of the imported shrimp in Italy come from Guatemala, where the shrimp aquaculture (representing around the 88% of the total aquaculture production) is based mainly on the Pacific white shrimp (Penaeus vannamei). Common rearing procedures of one of the biggest marine shrimp farms operating in Guatemala are described. Some productive parameters of Penaeus vannamei brought out by semi-intensive system in earthen ponds are quantified. Productive data result in a uniform distribution of weight classes at different days after stocking, besides the growth trend and feed conversion ratio agree with the growth performance of Penaeus vannamei. Growth data, fitted on the von Bertalanffy model, present the maximum weight gain (0.13 g/day) 28 days after stocking. Shrimp survival after a grow-out period of 80 days in a 2.44-ha pond is around 56% and the gross yield turns out to be more than one ton per hectare. In conclusion, semi-intensive shrimp farming performed in Guatemala allows to have high productivities as well as a good quality product. On the other hand it must be highlighted that this kind of cultivation represents a risk for the environmental equilibrium along the coasts of tropical countries. RIASSUNTO Poiché le specie di gambero marino utilizzate a fini produttivi sono originarie principalmente degli ambienti con acqua a temperatura elevata, le aziende che producono questi gamberi sono situate maggiormente lungo le coste dei Paesi tropicali e sub-tropi- cali. Oltre ai Paesi del Sud-Est Asiatico, i Paesi dell’America Latina sono importanti produttori, che contribuiscono a soddisfare la domanda internazionale di gamberi marini. Parte dei gamberi importati in Italia proviene dal Guatemala, dove la produzione di gamberi, che rappresenta l’88% della produzione nazionale di acquacoltura, è basata principalmente sul gambero bianco del Pacifico (Penaeus vannamei). Vengono descritte le comuni procedure produttive di una delle più grandi aziende di gamberi marini operanti in Guatemala. Vengono inoltre valutati alcuni parametri produttivi del Penaeus vannamei, allevato con un sistema semi-intensivo all’interno dei bacini di questa azienda. I dati di peso risultano distribuiti uniformemente alle diverse epoche dopo la semina, inoltre l’andamento dei pesi e l’indice di conversione alimentare concordano con i parametri di crescita del Penaeus vannamei. I dati di crescita, stimati con il modello proposto da von Bertalanffy, evidenziano il massimo incremento di peso (0,13 g al giorno) al 28° giorno dalla semina. La sopravvivenza dei gamberi dopo un periodo di accrescimento di 80 giorni in un bacino di 2,44 ettari è di circa il 56% e la resa supera il quantitativo di una tonnellata per ettaro. Nel complesso l’allevamento di gamberi con sistema semiintensivo, condotto in Guatemala, sembra fornire un’alta produttività combinata con una buona qualità del prodotto finale. D’altronde deve essere considerato che questo sistema d’allevamento rappresenta un serio rischio per l’equilibrio ambientale lungo le coste dei paesi tropicali

Aplicación de elementos finitos en la predicción del factor de intensidad de esfuerzos para fisuras en modo abertura

Se expone la importancia del criterio KIC en Fractomecánica y su campo de aplicabilidad. Se indican Las Limitaciones de la formulación analítica. Se proponen dos criterios de evaluación de K1 en base al Método de Elementos Finitos: el Criterio del Promedio de Valores y el Criterio del Intercepto. Se entregan resultados para ambos criterios aplicados a tres especímenes finitos, incluyendo una evaluación de cada criterio

Generalized immersion and nonlinear robust output regulation problem

summary:The problem of output regulation of the system affected by unknown constant parameters is considered here. Under certain assumptions, such a problem is known to be solvable using error feedback via the so-called immersion to an observable linear system with outputs. Nevertheless, for many interesting cases this kind of finite dimensional immersion is difficult or even impossible to find. In order to achieve constructive procedures for wider classes, this paper investigates a more general type of immersion. Such a generalized immersion enables to solve robust output regulation problem via dynamic feedback compensator using error and exosystem state measurement. When the exosystem states are not completely measurable, a modified observed-based generalized immersion is then presented. The main result obtained here is that under reasonable assumptions both the full and partial exosystem measurement problems are equivalently solvable. Examples together with computer simulation are included to clarify the suggested approach

A Sampled-data Regulator using Sliding Modes and Exponential Holder for Linear Systems

In a general command tracking and disturbance rejection problem, it is known that a sampled-data controller using zero-order hold may only guarantee asymptotic tracking at the sampling instances, but in general cannot guarantee the absence of ripples between the sampling instants. In this paper, a discrete robust regulator and a sampled-data robust regulator using slide modes techniques and exponential holder are presented. In particular, it is shown that the controller proposed for the sampled-data system ensures asymptotic tracking when applied to the continuous-time system

In vivo characterisation of a therapeutically relevant self-assembling 18 F-labelled β-sheet forming peptide and its hydrogel using positron emission tomography

Positron emission tomography (PET) and fluorescence labelling have been used to assess the pharmacokinetics, biodistribution and eventual fate of a hydrogel-forming nonapeptide, FEFKFEFKK (F9) in healthy mice, using 18F-labelled and fluoresceinisothiocyanate (FITC) - labelled F9 analogues. F9 was site-specifically radiolabelled with 2-[18F]fluoro-3-pyridinecarboxaldehyde ([18F]FPCA) via oxime bond formation. [18F]FPCA-F9 in vivo fate was evaluated both as a solution, following intravenous administration, and as a hydrogel when subcutaneously injected. The behaviour of FITC-F9 hydrogel was assessed following subcutaneous injection. [18F]FPCA-F9 demonstrated high plasma stability and primarily renal excretion; [18F]FPCA-F9 when in solution and injected into the bloodstream displayed prompt bladder uptake (53.4 ± 16.6 SUV at 20 minutes post injection) and rapid renal excretion, whereas [18F]FPCA-F9 hydrogel, formed by co-assembly of [18F]FPCA-F9 monomer with unfunctionalised F9 peptide and injected subcutaneously, showed gradual bladder accumulation of hydrogel fragments (3.8 ± 0.4 SUV at 20 minutes post injection), resulting in slower renal excretion. Gradual disaggregation of the F9 hydrogel from the site of injection was monitored using FITC-F9 hydrogel in healthy mice (60 ± 3 over 96 hours), indicating a biological half-life between 1-4 days. The in vivo characterisation of F9, both as a gel and a solution highlights its potential as a biomaterial

Host-parasite relationships in root-knot disease of white mulberry

Severe infections of white mulberry feeder roots and heavy soil infestations by Meloidogyne arenaria race 2 were found in southern Spain. This is the first record of M. arenaria on white mulberry in Europe. Morphometric observations, analysis of the esterase electrophoretic pattern, and artificial inoculations of race differentials were used to characterize nematodes. Nematode-induced mature galls were spherical and usually contained one or more females, males, and egg masses with eggs. Feeding sites were characterized by the development of giant cells that contained granular cytoplasm and many hypertrophied nuclei. Giant cell cytoplasm was aggregated along a thickened cell wall. Vascular tissues within galls appeared disorganized. The relationship between the initial nematode population density (Pi) in a series from 0 to 1,024 eggs and juveniles/cm3 soil and growth of white mulberry seedlings was tested in the greenhouse. A Seinhorst model was fitted to plant height and top fresh weight. Tolerance limits of white mulberry to M. arenaria race 2 for plant height and top fresh weight were, respectively, 1.1 and 1.38 eggs and juveniles/cm3 soil. The minimum relative values for plant height and top fresh weight were 0 at Pi > 64 and Pi > 128 eggs and juveniles/cm3 soil, respectively. Maximum nematode reproduction rate was 435-fold at the lowest Pi. Additional keywords: histopathology, Morus alba, pathogenicity, threshold limitPeer reviewe

Dynamic Control Applied to a Laboratory Antilock Braking System

The control of an antilock braking system is a difficult problem due to the existence of nonlinear dynamics and uncertainties of its characteristics. To overcome these issues, in this work, a dynamic nonlinear controller is proposed, based on a nonlinear observer. To evaluate its performance, this controller has been implemented on an ABS Laboratory setup, representing a quarter car model. The nonlinear observer reconstructs some of the state variables of the setup, assumed not measurable, to establish a fair benchmark for an ABS system of a real automobile. The dynamic controller ensures exponential convergence of the state estimation, as well as robustness with respect to parameter variations