Mechanical Behavior of the Lamellar Structure in Semi-Crystalline Polymers

We have employed molecular dynamics simulations to study the behavior of virtual polymeric materials under an applied uniaxial tensile load. Through computer simulations, one can obtain experimentally inaccessible information about phenomena taking place at the molecular and microscopic levels. Not only can the global material response be monitored and characterized along time, but the response of macromolecular chains can be followed independently if desired. The computer-generated materials were created by emulating the step-wise polymerization, resulting in self-avoiding chains in 3D with controlled degree of orientation along a certain axis. These materials represent a simplified model of the lamellar structure of semi-crystalline polymers,being comprised of an amorphous region surrounded by two crystalline lamellar regions. For the simulations, a series of materials were created, varying i) the lamella thickness, ii) the amorphous region thickness, iii) the preferential chain orientation, and iv) the degree of packing of the amorphous region. Simulation results indicate that the lamella thickness has the strongest influence on the mechanical properties of the lamella-amorphous structure, which is in agreement with experimental data. The other morphological parameters also affect the mechanical response, but to a smaller degree. This research follows previous simulation work on the crack formation and propagation phenomena, deformation mechanisms at the nanoscale, and the influence of the loading conditions on the material response. Computer simulations can improve the fundamental understanding about the phenomena responsible for the behavior of polymeric materials, and will eventually lead to the design of knowledge-based materials with improved properties.

Semi-automatic 3D Segmentation Of Costal Cartilage In CT Data From Pectus Excavatum Patients

One of the current frontiers in the clinical management of Pectus Excavatum (PE) patients is the prediction of the surgical outcome prior to the intervention. This can be done through computerized simulation of the Nuss procedure, which requires an anatomically correct representation of the costal cartilage. To this end, we take advantage of the costal cartilage tubular structure to detect it through multi-scale vesselness filtering. This information is then used in an interactive 2D initialization procedure which uses anatomical maximum intensity projections of 3D vesselness feature images to efficiently initialize the 3D segmentation process. We identify the cartilage tissue centerlines in these projected 2D images using a livewire approach. We finally refine the 3D cartilage surface through region-based sparse field level-sets. We have tested the proposed algorithm in 6 noncontrast CT datasets from PE patients. A good segmentation performance was found against reference manual contouring, with an average Dice coefficient of 0.75±0.04 and an average mean surface distance of 1.69±0.30mm. The proposed method requires roughly 1 minute for the interactive initialization step, which can positively contribute to an extended use of this tool in clinical practice, since current manual delineation of the costal cartilage can take up to an hour.

The tourist potential of the Minho-Lima region (Portugal)

Visions for Global Tourism Industry: Creating and Sustaining Competitive Strategies

Planning Considerations for Tourism in the Minho-Lima Region (Northwest Portugal)

In administering their territories, most local municipalities aim to preserve their natural, historical and ethnographical resources while simultaneously using them to increase revenue and employment. In order to efficiently promote the products and services available and attract tourists, decision makers, private and public, need to know and incorporate tourists’ preferences in their marketing strategies. In this chapter we illustrate the use of stated preferences as an instrument to identify national and foreign tourists’ preferences regarding the products and services that the touristic destination of the Minho-Lima region (Northwest Portugal) should offer. As a starting point, we have taken the three general groups of touristic resources mentioned above as attributes. We take Ponte de Lima, a municipality in this region that has a strong cultural tourism potential as an example to identify possible future tourism scenarios for this territory. We believe the previously identified methodology can be a valuable instrument in the identification of the strengths and weaknesses of the selected territory and, thus, support the decision making process behind its future tourist development and marketing strategies.

Portugal’s Minho-Lima region as a tourist destination: tourism operators’ attitudes towards its management and promotion

The success of tourism development depends on the capacity of a region’s tourism agents to establish and sustain networks, involving both private-sector companies and the public sector. Creating an attractive destination able to compete with others that are better positioned and consolidated requires cooperative behaviour among the various agents involved. This behaviour will facilitate both external and internal competition, which in turn will assure better product quality, continuous product renewal, a strong offer of unique experiences and the efficient use of endogenous resources. In this paper, the authors discuss the results of a survey of restaurant owners and of interviews conducted with the main institutional agents concerned with tourism promotion and the economic development of the Minho–Lima region. Such an approach, the authors argue, can be valuable in identifying the strengths and weaknesses of the area in question with regard to future tourism development. The authors work from the premise that the commitment of tourism agents constitutes a precondition for the success of the strategy to be defined. This is especially applicable to Minho–Lima, which to date has suffered from an absence of commitment and coordination on the part of those agents.