A stratified compartmental model for the transmission of Sparicotyle chrysophrii (Platyhelminthes: Monogenea) in gilthead seabream (Sparus aurata) fish farms †

The rapid development of intensive fish farming has been associated with the spreading of infectious diseases, pathogens and parasites. One such parasite is Sparicotyle chrysophrii (Platyhelminthes: Monogenea), which commonly infects cultured gilthead seabream (Sparus aurata)-a vital species in Mediterranean aquaculture. The parasite attaches to fish gills and can cause epizootics in sea cages with relevant consequences for fish health and associated economic losses for fish farmers. In this study, a novel stratified compartmental epidemiological model of S. chrysophrii transmission was developed and analysed. The model accounts for the temporal progression of the number of juvenile and adult parasites attached to each fish, as well as the abundance of eggs and oncomiracidia. We applied the model to data collected in a seabream farm, where the fish population and the number of adult parasites attached to fish gills were closely monitored in six different cages for 10 months. The model successfully replicated the temporal dynamics of the distribution of the parasite abundance within fish hosts and simulated the effects of environmental factors, such as water temperature, on the transmission dynamics. The findings highlight the potential of modelling tools for farming management, aiding in the prevention and control of S. chrysophrii infections in Mediterranean aquaculture

An algorithm for solving the distributed termination detection problem

In this paper we present an algorithm for solving the distributed termination detection problem. In particular, a strategy based on message counting is used to detect the termination of a distributed computation consisting of a set of processes asynchronously communicating over communication links. The proposed algorithm does not require the FIFO property for the communication links. The assumptions regarding the connectivity of the processes are very simple. For the proposed algorithm we demonstrate the correctness, we evaluate the message and the bit complexity and we give a detailed description of a MPI implementation

Scheduling in dial-indexed production lines

An innovative approach to maximize throughput in dial indexes flow lines provided by an automatic and synchronous part transfer mechanism is outlined. In this class of production systems, the performance measures are directly related to the control operating method, defined as the schedule of activities performed by the part transport mechanism and the workstations during each dial cycle. Usually, a unique operating method (i.e. the main operating method) is adopted to control the production flow and is designed to process any part type workable in the system, independently by the required part program. In order to design higher-performance systems, current industrial research is focused on the implementation of more efficient hardware technologies. However, technological and economical aspects sometimes limit greatly the possibility to have remarkable results. The goal of the proposed solution was to improve system performance by optimizing the control and management methods and without any expensive change in the system hardware. The approach was based on the definition of new operating methods characterized by a throughput value higher than the one of the main operating method. In a second step, an integer linear mathematical programming model was formulated to sequence the parts at the loading station in order to maximize the system throughput. An actual application was analysed to assess the validity of the proposed approach. Computational experiments have shown a remarkable increase in system performance

Epidemiology of infections caused by multiresistant Gram-negatives: ESBLs, MBLs, panresistant strains

Microbial drug resistance is a growing problem of global magnitude. In gram-negative pathogens, the most important resistance problems are encountered in Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter, with increasing trends observed for all major anti-gram-negative agents (β-lactams, fluoroquinolones and aminoglycosides). A matter of major concern is the emergence of new β-lactamases capable of degrading the expanded-spectrum cephalosporins and/or carbapenems, such as the extended-spectrum β-lactamases (ESBLs) and the carbapenemases. These β-lactamase genes are often associated with resistance determinants to non-β-lactam agents (e. g. aminoglycosides and fluoroquinolones), and strains producing ESBLs or carbapenemases often exhibit complex multidrug resistant phenotypes and sometimes are panresistant. The problem is worsened by the dearth of new agents active on multidrug-resistant Gram-negatives in the pipeline. The importance to develop better strategies to control resistance is underscored

Host-vector system for integration of recombinant DNA into chromosomes of transformable and nontransformable streptococci.

We describe a genetic system in which transformation of Streptococcus pneumoniae and Streptococcus sanguis was used to insert recombinant DNA into the conjugative chromosomal element omega (cat tetM) 6001 (omega 6001). The element containing the recombinant DNA was then transferred by conjugation to the chromosome of transformable and nontransformable streptococci. When Escherichia coli plasmid pDP36 was used as donor in transformation, it was capable of inserting 5.9 kilobases of heterologous DNA into the chromosome of competent streptococcal strains carrying omega 6001; the transformants were scored for erythromycin resistance. Genetic analysis showed that in a fraction of the erythromycin-resistant transformants the integration via flanking homology of the heterologous DNA caused inactivation of the tetM gene of omega 6001. By analyzing the stability of the resistance markers, we found that stable integration of heterologous DNA was achieved only in the erythromycin-resistant, tetracycline-sensitive transformants. It was possible to detect conjugal transfer of the heterologous sequences from stable transformants to strains of S. pneumoniae, S. sanguis, Streptococcus pyogenes, and Streptococcus faecalis. The omega 6001-pDP36 host-vector system opens new possibilities for gene transfer in streptococci. By this method cloned streptococcal DNA (possibly mutagenized in vitro) can be returned to the original host, greatly facilitating complementation tests and fine physiological studies

A Web3d application for the bin-packing problem

This paper describes a web application for supporting the user in the assessment of the optimal loading configuration for several carriers (i.e. trucks, containers, ship, etc.). The application has a standard form-based user-interface to insert data of the available carriers and items have to be loaded. The solution of this problem (known as Bin-Packing Problem (BPP)) is found by a specific algorithm and visualized by a 3D graphics representation inside the web page. Although some commercial applications already exist, ours runs directly on the web and offers, at the same time, an efficient and robust solver and a 3D visualization allowing the user to better understand the localization of the items inside the carrier and to interactively change some of the problem constraints directly on the 3D representation