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Background To evaluate the stress distribution of three-element prostheses on two different implant systems (External Hexagon (EH) or Morse Taper (MT)) and with two different retention mechanisms (screw-retained or cemented), by photoelastic analysis and strain gauge analyses. Material and Methods Four photoelastic and 24 strain gauge models of a partially edentulous maxilla were made and were divided in four groups according to connection and retention system: Group I (EH-C) – external hexagon+cement-retained prosthesis; Group II (EH-S) external hexagon+screw-retained prosthesis; Group III (MT-C) – morse taper+cement-retained prosthesis; Group IV (MT-S) – morse taper+screw-retained prosthesis. The implants were installed in the axial position, the first in the region of element 15 and the distal implant in the region of element 17. Loads of 100 N were applied on the occlusal surface of the prosthesis for 10 seconds. For the photoelasticity analysis, photographic images were taken and were evaluated according to the number of high-intensity fringes. For the strain gauge analysis, the strain gauges were positioned on the marginal crest of the implants and on the apical region, being numbered for analysis of the stress distribution in each region. The electrical signals were captured and processed by specific software. Results Higher concentration of tension was observed in the apical region of the implants and mainly in the distal implant, where the formation of fringes was higher. The microstrain values obtained for each group were similar: EH-C (454±18,3 µɛ); EH-S (469±94 µɛ); MT-C (466±49,8 µɛ); MT-S (460±36,6 µɛ). It was observed that apical position had higher stress concentrations for all analyzed groups. Conclusions The different connections and fixation mode did not interfere in the amount of tension generated in the tissue adjacent to the implant, also the region that generated the greatest amount of tension was in the apical region of the anterior implant. Key words: Dental implants, biomechanics, fixed prosthodontics.

On a competitive market gas transportation rates must be as low as possible while recovering capital expenses — Capex and operating and maintenance expenses — Opex at a return rate expected by the project sponsors to recover their investment. To guarantee project feasibility, designers must be concerned not only with technical and direct economic aspects but should also incorporate availability and economic risk analysis to make sure that under operating conditions along the economic life of a project the cash flow will be kept inside predicted values and therefore will not expose project sponsors to undesirable negative Net Present Values — NPV. This paper will present a methodology to address these important aspects with focus on pipeline economics. Pipeline availability study associated with compressor stations failure analysis will be evaluated under Monte Carlo simulation and consequently their impacts on gas pipeline capacity will be economically evaluated. Quantitative economic risk analysis using Monte Carlo simulation is part of the methodology. The adoption of this methodology allows committing more pipeline transmission capacity to a level close to maximum without exposing the Transporter to losses of revenue and contractual penalties. Also prevents designing an oversized and less competitive system with unused spare capacity and consequently higher transportation rates.

The energy shortage in Brazil prompted for the need of alternative and reliable energy sources that could be put into operation in a short period of time while being environmentally friendly and with flexibility to be installed around the country, taking advantage of the existing electric grid and therefore minimizing overall investments. Gas fired power plants proved to be the best selection, which covered all the requirements. The Ministry of Mines and Energy of Brazil set a program addressing initially 55 thermo power plants totaling about 20,402 MW. From this total 18,263 MW of installed power was from 49 gas fired power plants demanding gas volumes in the range of 88 MMm3/d most of this power to be available from 2001 to 2003. With this challenge, Petrobras has started to design a gas pipeline network expansion plan with investments of more than 1 billion US$ for its system alone, including new gas pipelines, new compressor and custody transfer stations and loop lines. In line with this expansion project more investments are required for the Bolivia-Brazil Gas Pipeline in Bolivia (0.2 billion US$) and Brazil (0.35 billion US$), and the new gas pipeline from Argentina to Brazil (0.25 billion US$) totaling 1.8 billion US$ of additional investments in gas pipeline expansion. All of this expansion design was based on technical and economic analysis that took into consideration the availability of gas supply from Brazil, Bolivia and Argentina. This paper presents the scope of the expansion, the technical and economical assumptions and the hydraulic simulation that was used to allow an investment decision.

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