Chronological Monte Carlo-based assessment of distribution system reliability

Regulatory authorities in many countries, in order to maintain an acceptable balance between appropriate customer service qualities and costs, are introducing a performance-based regulation. These regulations impose penalties, and in some cases rewards, which introduce a component of financial risk to an electric power utility due to the uncertainty associated with preserving a specific level of system reliability. In Brazil, for instance, one of the reliability indices receiving special attention by the utilities is the Maximum Continuous Interruption Duration per customer (MCID). This paper describes a chronological Monte Carlo simulation approach to evaluate probability distributions of reliability indices, including the MCID, and the corresponding penalties. In order to get the desired efficiency, modern computational techniques are used for modeling (UML -Unified Modeling Language) as well as for programming (Object- Oriented Programming). Case studies on a simple distribution network and on real Brazilian distribution systems are presented and discussed. © Copyright KTH 2006.

Assessment of central venous catheter-associated infections using semi-quantitative or quantitative culture methods

Semiquantitative (Maki) and quantitative (Brun- Buisson) culture techniques were employed in the diagnosis of catheter-related bloodstream infections (CRBSI) in patients who have a short-term central venous catheter (inserted for 30 days). The diagnosis of CRBSI was based on the results of semiquantitative and quantitative culture of material from the removed catheters. Catheter tips (118) from 100 patients were evaluated by both methods. Semiquantitative analysis revealed 34 catheters (28.8%) colonized by ≥15 colonyforming units (cfu), while quantitative cultures (34 catheters, 28.8%) showed the growth of ≥103 cfu/mL. Bacteremia was confirmed in four patients by isolating microorganisms of identical species from both catheters and blood samples. Using the semiquantitative culture technique on short-term central venous catheter tips, we have shown that with a cut-off level of ≥15 cfu, the technique had 100.0% sensitivity, specificity of 68.4%, 25.0% positive predictive value (PPV) and 100.0% negative predictive value (NPV), efficiency of 71.4% and a prevalence of 9.5%. The quantitative method, with a cut-off limit of ≥103 cfu/mL, gave identical values: the sensitivity was 100.0%, specificity 68.4%, positive predictive value (PPV) 25.0%, negative predictive value (NPV) 100.0%, efficiency 71.4% and prevalence 9.5%. We concluded that the semiquantitative and quantitative culture methods, evaluated in parallel, for the first time in Brazil, have similar sensitivity and specificity. Keywords: central venous catheter; semi-quantitative culture; quantitative culture; catheter-related bacteremia.

Comparative study of ultrasonographic methods for assessment of pregnancy age in bitches

Compared with human beings, the application of ultrasound in estimating fetal age in bitches is limited due to the large variation of breed and size in this species. Several formulas were developed to calculate the gestational age and to provide the date of birth in dogs, but the efficacy of these formulas on the different gestational stages and dog breeds is unknown. The aim of this study was to compare sonographic methods for assessment of gestational age and days before parturition in dogs with different body weights and pregnancy stages. Twenty seven bitches of several sizes were examined and divided into three groups according to the initial body weight (A: <10kg; B: 10.1 - 20kg; C: >20.1kg); then each group was divided into three subgroups according to pregnancy stage (1st: 18 to 30 days; 2nd: 31 to 40 days; 3rd: >40 days) estimated according to the first day of copulation. Ultrasonography was performed weekly from the first stage of pregnancy. In the first and second stage the following formulas were applied: GA = (6XGSD) + 20; DBP = 65 - IG; by Nyland & Matton (2002); GA: gestational age; DBP: days before parturition; DSG: gestational sac diameter; in the third stage: DBP = 61,2 - (24,6 X BD); DBP = 43,5 - (10,9 X CD); by Burk & Ackerman (1996); BD: biparietal diameter; CD: body diameter, and: GA = (15 X BD) + 20; GA = (7 X CD) + 29; GA = (6 X BD) + (3 X CD) + 30; DBP = 65 - GA; by Nyland & Matton (2002). Results were compared statistically. The equations proposed by Nyland & Matton (2002), were more accurate in all pregnancy stages, with a margin of error of only three days, regardless of the size of the animal; therefore these methods are the best option in veterinary practice.

Reliability of marginal microleakage assessment by visual and digital methods

The aim of this study was to investigate the reliability of visual and digital methods to assess marginal microleakage in vitro. Materials and Methods: Typical Class V preparations were made in bovine teeth and filled with composite resin. After dye penetration (0.5% basic fuchsin), teeth were sectioned and the 53 obtained fragments were assessed according to visual (stereomicroscope) and digital methods (Image Tool Software ® -ITS) (University of Texas Health Science Center-San Antonio Dental School, USA). Two calibrated examiners (A and B) evaluated dye penetration, by means of a stereomicroscope with ×20 magnification (scores), and by the ITS (millimeters). The intra- and inter-examiner agreement was estimated according to Kappa statistics (κ), and intraclass correlation coefficient (ρ). Results: In relation to the visual method, the intra-examiner agreement was almost perfect (κA = 0.87) and substantial (κB = 0.76), respectively to the examiner A and B. The inter-examiner agreement showed an almost perfect reliability (κ = 0.84). For the digital method, the intra-examiner agreement was almost perfect for both examiners and equal to ρ = 0.99, and so was the inter-examiner agreement value. Conclusion: Visual (stereomicroscope) and digital methods (ITS) showed high levels of intra- and inter-examiner reproducibility when marginal microleakage was assessed.