Abstract

Abstract

Abstract
The restoration and recovery of a defective skull can be performed through operative techniques to implant a customized prosthesis. Recently, image processing and surface reconstruction methods have been used for digital prosthesis design. In this paper we present a framework for prosthesis modeling. Firstly, we take the computed tomography (CT) of the skull and perform bone segmentation by thresholding. The obtained binary volume is processed by morphological operators, frame-by-frame, to get the inner and outer boundaries of the bone. These curves are used to initialize a 2D deformable model that generates the prosthesis boundary in each CT frame. In this way, we can fill the prosthesis volume which is the input for a marching cubes technique that computes the digital model of the target geometry. In the experimental results we demonstrate the potential of our technique and compare it with a related one.

Abstract
Photodynamic therapy is a very promising approach to inactivate pathogenic microorganisms. The photodamage of cells involves reactive oxygen species (ROS) which are generated in situ by two main mechanisms (type I and/or type II). The mechanism responsible for the photoinactivation (PI) of a bioluminescent recombinant Escherichia coli, induced by three different cationic porphyrins, was identified in this work using a rapid method based on the monitoring of the metabolic activity of this bacterium. The inhibitory effect of the photodynamic process in the presence of a singlet oxygen quencher (sodium azide) or free radical scavengers (D-mannitol and L-cysteine) was evaluated by exposing bacterial suspensions with 0.5 mu M Tri-Py+-Me-PF, 5.0 mu M Tetra-Py+-Me or 5.0 mu M Tri-SPy+-Me-PF to white light. Strong bacterial protection was observed with sodium azide (100 mM) for the three cationic porphyrins. However, in the presence of Tri-Py+-Me-PF and Tetra-Py+-Me and the free radical scavengers (L-cysteine and D-mannitol) the reduction on the bacterial bioluminescence was significantly higher and similar to that obtained in their absence (5.4-6.0 log reduction). In the case of Tri-SPy+-Me-PF two distinct behaviours were observed when L-cysteine and D-mannitol were used as free radical scavengers: while the presence of L-cysteine (100 mM) lead to a bacterial protection similar to the one observed with sodium azide, in the presence of D-mannitol only a small protection was detected. The high inhibition of the PS activity by L-cysteine is not due to its radical scavenger ability but due to the singlet oxygen quenching by the sulfanyl group (-SH). In fact, the photodecomposition of 1,3-diphenylisobenzofuran in the presence of Tri-SPy+-Me-PF is completely suppressed when L-cysteine is present. The results obtained in this study suggest that singlet oxygen (type II mechanism) plays a very important role over free radicals (type I mechanism) on the PI process of the bioluminescent E. coli by Tri-Py+-Me-PF, Tetra-Py+-Me and Tri-SPy+-Me-PF. Although the use of scavengers is an adequate and simple approach to evaluate the relative importance of the two pathways, it is important to choose scavengers which do not interfere in both PI mechanisms. Sodium azide and D-mannitol seem to be good oxygen and free radical quenchers, respectively, to study the PI mechanisms by porphyrinic photosensitizers.

Abstract

Abstract
The performance of a company depends on its strategic decisions but also on the efficiency of how those decisions are implemented by all of its sectors. In any company there are different sectors or groups, probably physically distributed, with different levels of autonomy, each one controlling local resources and interacting with the others. Many companies use simulation software to analyze critical sectors based in a number of scenarios, in order to estimate the efficiency of the different configurations. The process of simulate alternative solutions can be time consuming. Depending on the software used it may be necessary to generate new simulation models for each solution, develop new applications or change existing ones. This paper describes a simulation framework where each element is modelled using the discrete-event approach and interoperability between elements is achieved by the combination of web services and Agent-based modelling and simulation (ABMS). The use of ABMS in this framework provides an easier way to evaluate alternative solutions. Each sector or group is an agent that can be added or removed from the model to build different configurations. A multi-hierarchical simulation executive is proposed in order to enable the use of different time intervals in each level. This increases the autonomy of the simulation agents and promotes the use of parallel or distributed solutions.