Risk-based decision making method for maintenance policy selection of thermal power plant equipment

This study presents a decision-making method for maintenance policy selection of power plants equipment. The method is based on risk analysis concepts. The method first step consists in identifying critical equipment both for power plant operational performance and availability based on risk concepts. The second step involves the proposal of a potential maintenance policy that could be applied to critical equipment in order to increase its availability. The costs associated with each potential maintenance policy must be estimated, including the maintenance costs and the cost of failure that measures the critical equipment failure consequences for the power plant operation. Once the failure probabilities and the costs of failures are estimated, a decision-making procedure is applied to select the best maintenance policy. The decision criterion is to minimize the equipment cost of failure, considering the costs and likelihood of occurrence of failure scenarios. The method is applied to the analysis of a lubrication oil system used in gas turbines journal bearings. The turbine has more than 150 MW nominal output, installed in an open cycle thermoelectric power plant. A design modification with the installation of a redundant oil pump is proposed for lubricating oil system availability improvement. (C) 2009 Elsevier Ltd. All rights reserved.

ECONOMICAL OCCUPATION OF AGRICULTURAL AREA OF PIRACICABA (SAO PAULO STATE, BRAZIL), INCLUDING RISK THROUGH LINEAR PROGRAMMING

The economic occupation of an area of 500 ha for Piracicaba was studied with the irrigated cultures of maize, tomato, sugarcane and beans, having used models of deterministic linear programming and linear programming including risk for the Target-Motad model, where two situations had been analyzed. In the deterministic model the area was the restrictive factor and the water was not restrictive for none of the tested situations. For the first situation the gotten maximum income was of R$ 1,883,372.87 and for the second situation it was of R$ 1,821,772.40. In the model including risk a producer that accepts risk can in the first situation get the maximum income of R$ 1,883,372. 87 with a minimum risk of R$ 350 year(-1), and in the second situation R$ 1,821,772.40 with a minimum risk of R$ 40 year(-1). Already a producer averse to the risk can get in the first situation a maximum income of R$ 1,775,974.81 with null risk and for the second situation R$ 1.707.706, 26 with null risk, both without water restriction. These results stand out the importance of the inclusion of the risk in supplying alternative occupations to the producer, allowing to a producer taking of decision considered the risk aversion and the pretension of income.

Auto-anticorpos anti-LDLox e sua correlação com o perfil lipídico e o estado nutricional de adolescentes

OBJETIVO: Avaliar se o conteúdo de auto-anticorpos anti-LDL oxidada (anti-LDLox) no plasma de adolescentes correlaciona-se com suas medidas antropométricas e com o perfil lipídico. MÉTODOS: O estudo incluiu 150 adolescentes com idade entre 10 e 15 anos, recrutados do ambulatório de obesidade da Universidade Federal de São Paulo (SP) e de escolas públicas de Piracicaba (SP). Foram avaliadas medidas antropométricas, como índice de massa corporal, circunferência de cintura e do braço, classificando os adolescentes em eutrófico, sobrepeso e obeso. Para as análises bioquímicas, foi realizado o perfil lipídico através de métodos enzimáticos colorimétricos, e para detecção do conteúdo de auto-anticorpos anti-LDLox, utilizou-se o método de ELISA. RESULTADOS: Segundo análises das variáveis antropométricas, o grupo obeso apresentou perfil alterado em relação aos grupos eutrófico e sobrepeso (p < 0,01), indicando risco cardiovascular. Quando o perfil lipídico foi avaliado, observaram-se diferenças estatisticamente significativas para as concentrações de colesterol total (p = 0,011), HDL-colesterol (p = 0,001) e LDL-colesterol (p < 0,042) nos grupos eutrófico e obeso. Para as análises de auto-anticorpos anti-LDLox plasmática, os grupos sobrepeso (p = 0,012) e obeso (p < 0,001) apresentaram valores superiores ao grupo eutrófico. Também houve correlações entre os auto-anticorpos anti-LDLox e variáveis antropométricas. CONCLUSÃO: A presença de auto-anticorpos anti-LDLox em adolescentes e as alterações metabólicas no perfil lipídico variaram de modo proporcional com parâmetros antropométricos, o que torna o conteúdo de anti-LDLox um potencial indicador bioquímico de risco para síndrome metabólica.

Notificação imprecisa da ingestão energética na dieta de adolescentes

Objetivos: Examinar a prevalência da sub e supernotificação da ingestão energética em adolescentes e seus fatores associados. Métodos: Estudo transversal com 96 adolescentes na pós-puberdade (47 com peso normal e 49 obesos), com idade média de 16,6±1,3 anos. Peso e altura foram medidos e o índice de massa corporal foi calculado. A composição corporal foi avaliada através de absorciometria por raios X de dupla energia. A ingestão de alimentos foi avaliada por meio de um registro alimentar de 3 dias. Realizou-se uma avaliação bioquímica (níveis séricos de colesterol total, LDL, HDL, glicose plasmática e insulina). Os subnotificadores relataram uma ingestão energética < 1,35 x taxa metabólica basal (TMB), enquanto os supernotificadores relataram uma ingestão energética > 2,4 x TMB. Resultados: Notificação imprecisa (sub ou supernotificação) da ingestão energética foi identificada em 65,6 por cento dos adolescentes (64,6 e 1 por cento de sub e supernotificação, respectivamente). Os adolescentes obesos apresentaram 5.0 vezes mais chances de subnotificar a ingestão energética (IC95 por cento 2,0-12,7) do que os participantes com peso normal. Os subnotificadores apresentaram taxas mais altas de ingestão insuficiente de carboidratos (19,3 versus 12,1 por cento, p = 0,046) e de lipídios (11,3 versus 0 por cento, p < 0,001) do que os notificadores plausíveis. A ingestão de colesterol também foi mais baixa entre os subnotificadores (p = 0,017). Não houve diferenças significativas na composição corporal e nos parâmetros bioquímicos em relação à notificação imprecisa. Conclusões: Os resultados obtidos demonstraram alta porcentagem de notificação imprecisa da ingestão energética entre adolescentes, principalmente entre os obesos, o que sugere que os valores de consumo de nutrientes ajustado para o consumo de energia deveriam ser empregados na análise de risco da relação dieta-doença a fim de contribuir para a redução de erros associados à notificação imprecisa

Timoshenko versus Euler beam theory: Pitfalls of a deterministic approach

The selection criteria for Euler-Bernoulli or Timoshenko beam theories are generally given by means of some deterministic rule involving beam dimensions. The Euler-Bernoulli beam theory is used to model the behavior of flexure-dominated (or ""long"") beams. The Timoshenko theory applies for shear-dominated (or ""short"") beams. In the mid-length range, both theories should be equivalent, and some agreement between them would be expected. Indeed, it is shown in the paper that, for some mid-length beams, the deterministic displacement responses for the two theories agrees very well. However, the article points out that the behavior of the two beam models is radically different in terms of uncertainty propagation. In the paper, some beam parameters are modeled as parameterized stochastic processes. The two formulations are implemented and solved via a Monte Carlo-Galerkin scheme. It is shown that, for uncertain elasticity modulus, propagation of uncertainty to the displacement response is much larger for Timoshenko beams than for Euler-Bernoulli beams. On the other hand, propagation of the uncertainty for random beam height is much larger for Euler beam displacements. Hence, any reliability or risk analysis becomes completely dependent on the beam theory employed. The authors believe this is not widely acknowledged by the structural safety or stochastic mechanics communities. (C) 2010 Elsevier Ltd. All rights reserved.

Human Error Contribution in Collision and Grounding of Oil Tankers

The purpose of this article is to present a quantitative analysis of the human failure contribution in the collision and/or grounding of oil tankers, considering the recommendation of the ""Guidelines for Formal Safety Assessment"" of the International Maritime Organization. Initially, the employed methodology is presented, emphasizing the use of the technique for human error prediction to reach the desired objective. Later, this methodology is applied to a ship operating on the Brazilian coast and, thereafter, the procedure to isolate the human actions with the greatest potential to reduce the risk of an accident is described. Finally, the management and organizational factors presented in the ""International Safety Management Code"" are associated with these selected actions. Therefore, an operator will be able to decide where to work in order to obtain an effective reduction in the probability of accidents. Even though this study does not present a new methodology, it can be considered as a reference in the human reliability analysis for the maritime industry, which, in spite of having some guides for risk analysis, has few studies related to human reliability effectively applied to the sector.

Cost risk benefit analysis to support chemoprophylaxis policy for travellers to malaria endemic countries

Background: In a number of malaria endemic regions, tourists and travellers face a declining risk of travel associated malaria, in part due to successful malaria control. Many millions of visitors to these regions are recommended, via national and international policy, to use chemoprophylaxis which has a well recognized morbidity profile. To evaluate whether current malaria chemo-prophylactic policy for travellers is cost effective when adjusted for endemic transmission risk and duration of exposure. a framework, based on partial cost-benefit analysis was used Methods: Using a three component model combining a probability component, a cost component and a malaria risk component, the study estimated health costs avoided through use of chemoprophylaxis and costs of disease prevention (including adverse events and pre-travel advice for visits to five popular high and low malaria endemic regions) and malaria transmission risk using imported malaria cases and numbers of travellers to malarious countries. By calculating the minimal threshold malaria risk below which the economic costs of chemoprophylaxis are greater than the avoided health costs we were able to identify the point at which chemoprophylaxis would be economically rational. Results: The threshold incidence at which malaria chemoprophylaxis policy becomes cost effective for UK travellers is an accumulated risk of 1.13% assuming a given set of cost parameters. The period a travellers need to remain exposed to achieve this accumulated risk varied from 30 to more than 365 days, depending on the regions intensity of malaria transmission. Conclusions: The cost-benefit analysis identified that chemoprophylaxis use was not a cost-effective policy for travellers to Thailand or the Amazon region of Brazil, but was cost-effective for travel to West Africa and for those staying longer than 45 days in India and Indonesia.

Prostate cryoablation: Prospective analysis comparing high- and low-risk prostate cancer outcomes

Aim: To evaluate percutaneous cryotherapy as a primary treatment option for prostate cancer, comparing different risk groups. Patients and Methods: Forty-seven prostate cryoablation procedures were performed on 44 patients. Patients median age was 70.9, and average pretreatment PSA of 13.8 ng/dl. Patients were divided into low-risk (13 patients), high-risk (24 patients) and radiation failure patients (7 patients). The follow-up period ranged from 18 to 60 months (median 41 months). Results: In the low-risk group, we found after 12 and 24 months of follow-up, 92 and 86% of patients free of PSA relapse (PSA < 1 ng/ml), respectively. In the high-risk group, the PSA failure was 39 and 52.9%. For the radiation failure group, 86 and 71.4% of patients had PSA below 1 ng/dl. At 48 months of follow-up, 80% of the low-risk patients, 42.8% of the high-risk group and 71.4% of the radiation failure group were free of PSA relapse. The complication rates were low, with 13% of urinary incontinence and no cases of rectal injury. Conclusion: Prostate cryoablation is a viable and promising minimally invasive alternative for localized or locally advanced prostate cancer patients. Copyright (c) 2008 S. Karger AG, Basel.

Body mass index and risk of head and neck cancer in a pooled analysis of case-control studies in the International Head and Neck Cancer Epidemiology (INHANCE) Consortium

Methods We pooled data from 17 case-control studies including 12 716 cases and the 17 438 controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated for associations between body mass index (BMI) at different ages and HNC risk, adjusted for age, sex, centre, race, education, tobacco smoking and alcohol consumption. Results Adjusted ORs (95% CIs) were elevated for people with BMI at reference (date of diagnosis for cases and date of selection for controls) < 18.5 kg/m(2) (2.13, 1.75-2.58) and reduced for BMI > 25.0-30.0 kg/m(2) (0.52, 0.44-0.60) and BMI >= 30 kg/m(2) (0.43, 0.33-0.57), compared with BMI > 18.5-25.0 kg/m(2). These associations did not differ by age, sex, tumour site or control source. Although the increased risk among people with BMI < 18.5 kg/m(2) was not modified by tobacco smoking or alcohol drinking, the inverse association for people with BMI > 25 kg/m(2) was present only in smokers and drinkers. Conclusions In our large pooled analysis, leanness was associated with increased HNC risk regardless of smoking and drinking status, although reverse causality cannot be excluded. The reduced risk among overweight or obese people may indicate body size is a modifier of the risk associated with smoking and drinking. Further clarification may be provided by analyses of prospective cohort and mechanistic studies.

Sexual behaviours and the risk of head and neck cancers: a pooled analysis in the International Head and Neck Cancer Epidemiology (INHANCE) consortium

Background Sexual contact may be the means by which head and neck cancer patients are exposed to human papillomavirus (HPV). Methods We undertook a pooled analysis of four population-based and four hospital-based case-control studies from the International Head and Neck Cancer Epidemiology (INHANCE) consortium, with participants from Argentina, Australia, Brazil, Canada, Cuba, India, Italy, Spain, Poland, Puerto Rico, Russia and the USA. The study included 5642 head and neck cancer cases and 6069 controls. We calculated odds ratios (ORs) of associations between cancer and specific sexual behaviours, including practice of oral sex, number of lifetime sexual partners and oral sex partners, age at sexual debut, a history of same-sex contact and a history of oral-anal contact. Findings were stratified by sex and disease subsite. Results Cancer of the oropharynx was associated with having a history of six or more lifetime sexual partners [OR = 1.25, 95% confidence interval (CI) 1.01, 1.54] and four or more lifetime oral sex partners (OR = 2.25, 95% CI 1.42, 3.58). Cancer of the tonsil was associated with four or more lifetime oral sex partners (OR = 3.36, 95 % CI 1.32, 8.53), and, among men, with ever having oral sex (OR = 1.59, 95% CI 1.09, 2.33) and with an earlier age at sexual debut (OR = 2.36, 95% CI 1.37, 5.05). Cancer of the base of the tongue was associated with ever having oral sex among women (OR = 4.32, 95% CI 1.06, 17.6), having two sexual partners in comparison with only one (OR = 2.02, 95% CI 1.19, 3.46) and, among men, with a history of same-sex sexual contact (OR = 8.89, 95% CI 2.14, 36.8). Conclusions Sexual behaviours are associated with cancer risk at the head and neck cancer subsites that have previously been associated with HPV infection.

Total Exposure and Exposure Rate Effects for Alcohol and Smoking and Risk of Head and Neck Cancer: A Pooled Analysis of Case-Control Studies

Although cigarette smoking and alcohol consumption increase risk for head and neck cancers, there have been few attempts to model risks quantitatively and to formally evaluate cancer site-specific risks. The authors pooled data from 15 case-control studies and modeled the excess odds ratio (EOR) to assess risk by total exposure (pack-years and drink-years) and its modification by exposure rate (cigarettes/day and drinks/day). The smoking analysis included 1,761 laryngeal, 2,453 pharyngeal, and 1,990 oral cavity cancers, and the alcohol analysis included 2,551 laryngeal, 3,693 pharyngeal, and 3,116 oval cavity cancers, with over 8,000 controls. Above 15 cigarettes/day, the EOR/pack-year decreased with increasing cigarettes/day, suggesting that greater cigarettes/day for a shorter duration was less deleterious than fewer cigarettes/day for a longer duration. Estimates of EOR/pack-year were homogeneous across sites, while the effects of cigarettes/day varied, indicating that the greater laryngeal cancer risk derived from differential cigarettes/day effects and not pack-years. EOR/drink-year estimates increased through 10 drinks/day, suggesting that greater drinks/day for a shorter duration was more deleterious than fewer drinks/day for a longer duration. Above 10 drinks/day, data were limited. EOR/drink-year estimates varied by site, while drinks/day effects were homogeneous, indicating that the greater pharyngeal/oral cavity cancer risk with alcohol consumption derived from the differential effects of drink-years and not drinks/day.

Marijuana Smoking and the Risk of Head and Neck Cancer: Pooled Analysis in the INHANCE Consortium

Background: Marijuana contains carcinogens similar to tobacco smoke and has been suggested by relatively small studies to increase the risk of head and neck cancer (HNC). Because tobacco is a major risk factor for HNC, large studies with substantial numbers of never tobacco users could help to clarify whether marijuana smoking is independently associated with HNC risk. Methods: We pooled self-reported interview data on marijuana smoking and known HNC risk factors on 4,029 HNC cases and 5,015 controls from five case-control studies within the INHANCE Consortium. Subanalyses were conducted among never tobacco users (493 cases and 1,813 controls) and among individuals who did not consume alcohol or smoke tobacco (237 cases and 887 controls). Results: The risk of HNC was not elevated by ever marijuana smoking [odds ratio (OR), 0.88; 95% confidence intervals (95% Cl), 0.67-1.16], and there was no increasing risk associated with increasing frequency, duration, or cumulative consumption of marijuana smoking. An increased risk of HNC associated with marijuana use was not detected among never tobacco users (OR, 0.93; 95% Cl, 0.63-1.37; three studies) nor among individuals who did not drink alcohol and smoke tobacco (OR, 1.06; 95% Cl, 0.47-2.38; two studies). Conclusion: Our results are consistent with the notion that infrequent marijuana smoking does not confer a risk of these malignancies. Nonetheless, because the prevalence of frequent marijuana smoking was low in most of the contributing studies, we could not rule out a moderately increased risk, particularly among subgroups without exposure to tobacco and alcohol. (Cancer Epidemiol Biomarkers Prev 2009;18(5):1544-51)

Interaction between Tobacco and Alcohol Use and the Risk of Head and Neck Cancer: Pooled Analysis in the International Head and Neck Cancer Epidemiology Consortium

Background: The magnitude of risk conferred by the interaction between tobacco and alcohol use on the risk of head and neck cancers is not clear because studies have used various methods to quantify the excess head and neck cancer burden. Methods: We analyzed individual-level pooled data from 17 European and American case-control studies (11,221 cases and 16,168 controls) participating in the International Head and Neck Cancer Epidemiology consortium. We estimated the multiplicative interaction parameter (psi) and population attributable risks (PAR). Results: A greater than multiplicative joint effect between ever tobacco and alcohol use was observed for head and neck cancer risk (psi = 2.15; 95% confidence interval, 1.53-3.04). The PAR for tobacco or alcohol was 72% (95% confidence interval, 61-79%) for head and neck cancer, of which 4% was due to alcohol alone, 33% was due to tobacco alone, and 35% was due to tobacco and alcohol combined. The total PAR differed by subsite (64% for oral cavity cancer, 72% for pharyngeal cancer, 89% for laryngeal cancer), by sex (74% for men, 57% for women), by age (33% for cases < 45 years, 73% for cases > 60 years), and by region (84% in Europe, 51% in North America, 83% in Latin America). Conclusions: Our results confirm that the joint effect between tobacco and alcohol use is greater than multiplicative on head and neck cancer risk. However, a substantial proportion of head and neck cancers cannot be attributed to tobacco or alcohol use, particularly for oral cavity cancer and for head and neck cancer among women and among young-onset cases. (Cancer Epidemiol Biomarkers Prev 2009;18(2):541-50)

Type of Alcoholic Beverage and Risk of Head and Neck Cancer-025EFA Pooled Analysis Within the INHANCE Consortium

The authors pooled data from 15 case-control studies of head and neck cancer (9,107 cases, 14,219 controls) to investigate the independent associations with consumption of beer, wine, and liquor. In particular, they calculated associations with different measures of beverage consumption separately for subjects who drank beer only (858 cases, 986 controls), for liquor-only drinkers (499 cases, 527 controls), and for wine-only drinkers (1,021 cases, 2,460 controls), with alcohol never drinkers (1,124 cases, 3,487 controls) used as a common reference group. The authors observed similar associations with ethanol-standardized consumption frequency for beer-only drinkers (odds ratios (ORs) = 1.6, 1.9, 2.2, and 5.4 for <= 5, 6-15, 16-30, and > 30 drinks per week, respectively; P(trend) < 0.0001) and liquor-only drinkers (ORs = 1.6, 1.5, 2.3, and 3.6; P < 0.0001). Among wine-only drinkers, the odds ratios for moderate levels of consumption frequency approached the null, whereas those for higher consumption levels were comparable to those of drinkers of other beverage types (ORs = 1.1, 1.2, 1.9, and 6.3; P < 0.0001). Study findings suggest that the relative risks of head and neck cancer for beer and liquor are comparable. The authors observed weaker associations with moderate wine consumption, although they cannot rule out confounding from diet and other lifestyle factors as an explanation for this finding. Given the presence of heterogeneity in study-specific results, their findings should be interpreted with caution.

Involuntary smoking and head and neck cancer risk: Pooled analysis in the International Head and Neck Cancer Epidemiology Consortium

Although active tobacco smoking has been identified as a major risk factor for head and neck cancer, involuntary smoking has not been adequately evaluated because of the relatively low statistical power in previous studies. We took advantage of data pooled in the International Head and Neck Cancer Epidemiology Consortium to evaluate the role of involuntary smoking in head and neck carcinogenesis. Involuntary smoking exposure data were pooled across six case-control studies in Central Europe, Latin America, and the United States. Adjusted odds ratios (OR) and 95% confidence interval (95% CI) were estimated for 542 cases and 2,197 controls who reported never using tobacco, and the heterogeneity among the study-specific ORs was assessed. In addition, stratified analyses were done by subsite. No effect of ever involuntary smoking exposure either at home or at work was observed for head and neck cancer overall. However, long duration of involuntary smoking exposure at home and at work was associated with an increased risk (OR for >15 years at home, 1.60; 95% CI, 1.12-2.28; P(trend) <0-01; OR for >15 years at work, 1.55; 95% CI, 1.04-2.30; P(trend) = 0.13). The effect of duration of involuntary smoking exposure at home was stronger for pharyngeal and laryngeal cancers than for other subsites. An association between involuntary smoking exposure and the risk of head and neck cancer, particularly pharyngeal and laryngeal cancers, was observed for long duration of exposure. These results are consistent with those for active smoking and suggest that elimination of involuntary smoking exposure might reduce head and neck cancer risk among never smokers.