Sofia Castro Oliveira

Novel sensor system for leakage current detection on insulator strings of overhead transmission lines

We report the development of a measurement system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. A capacitive sensor connected to the processing module allows recording the relative humidity of the outer environment. At the present stage, six measurement units have been deployed on CHESFs electrical transmission system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings

Novel routing algorithm for transparent optical networks based on noise figure and amplifier saturation

We propose and demonstrate a novel dynamic routing algorithm for transparent optical networks based on physical layer impairments such as amplifier noise accumulation, amplifier gain saturation, wavelength dependent gain and losses along lightpaths. The metrics of our algorithm is based on the calculation of the noise figure using the well known formulation for cascade of elements in lightpaths. We assume no wavelength conversion capabilities in our network and we assign wavelengths using a first fit algorithm. For a given call, our algorithm assigns the first available wavelength and calculates the best route (minimum noise figure). Upon the calculation of the noise figure of the lightpath, we obtain the bit error rate (BER). Our algorithm blocks a call if there is no wavelength available or if the BER for the available wavelength is above a given level, which guarantees a pre-defined quality-of-service for the network operation. We present simulation results of dynamic traffic in a hypothetical meshed network in terms of blocking probabilities as a function of network load and amplifier characteristics. We show that our algorithm outperforms the traditional shortest path routing algorithm.

Fiber-optic sensor system for leakage current detection on insulator strings of overhead transmission lines

In this paper we report the development of an optical system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. At the present stage, six different systems have been deployed on CHESFs electrical distribution system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings.

Preoperative thyroid function and weight loss after bariatric surgery

Thyroid function has an important role on body weight regulation. However, the impact of thyroid function on weight loss after bariatric surgery is still largely unknown. We evaluated the association between preoperative thyroid function and the excess weight loss 1 year after surgery, in 641 patients with morbid obesity who underwent bariatric surgery. Patients with a history of thyroid disease, treatment with thyroid hormone or antithyroid drugs and those with preoperative evaluation consistent with overt hypothyroidism or hyperthyroidism were excluded. The preoperative levels of TSH and FT4 were not associated with weight loss after bariatric surgery. The variation of FT3 within the reference range was also not associated with weight loss. In contrast, the subgroup with FT3 above the reference range (12.3% of patients) had a significantly higher excess weight loss than patients with normal FT3. This difference remained significant after adjustment for age, sex, BMI, type of surgery, TSH and FT4. In conclusion, we observed an association between high FT3 and a greater weight loss after bariatric surgery, highlighting a group of patients with an increased benefit from this intervention. Our results also suggest a novel hypothesis: the pharmacological modulation of thyroid function may be a potential therapeutic target in patients undergoing bariatric surgery.

Cardiovascular risk factors in patients with autoimmune thyroiditis

Introduction: Thyroid dysfunction has been related to an increased cardiovascular risk resulting from alterations in lipid profile, insulin resistance, homocysteine levels and low grade systemic inflammation. The impact of normal TSH levels and subclinical hypothyroidism and autoimmunity in the increased cardiovascular risk remains controversial. Our objective was to evaluate the interrelations between thyroid function, thyroid autoimmunity and cardiovascular risk factors, in patients with autoimmune thyroiditis. Methods: 353 subjects with autoimmune thyroiditis were evaluated. We defined three groups based on TSH levels: TSH 0.5-2.5 μUI/mL, TSH 2.5-5.0 μUI/mL and TSH 5.0-10.0 μUI/mL. We recorded thyroid function tests, thyroid autoimmunity, insulin resistance markers including HOMA-IR (Homeostasis Model Assessment for Insulin Resistance), lipid profile, homocysteine, high-sensitivity C-reactive protein (hs-CRP) and vitamin B12 levels. Statistical analysis was performed using KruskalWallis test and Spearman correlations. Results: Our sample comprised 94% females with a mean age of 47.0 ± 16.3 years. The group TSH 5.0-10.0 μUI/mL presented higher levels of HOMA-IR when compared to the other two groups [2.96 (1.76-4.59) in TSH 5.0-10.0 μUI/mL vs 1.86 (0.97-2.56) in TSH 2.5-5.0 μUI/mL and 1.58 (1.06-2.46) in TSH 0.5-2.5 μUI/mL, p = 0.002]. In the total group we observed positive correlations between free T3 and both HDL (r = 0.118, p = 0.028) and apolipoprotein A-I (Apo A-I) (r = 0.129, p = 0.024); TSH was positively correlated with HOMA-IR (r = 0.146, p = 0.018) while free T4 was negatively correlated with homocysteine (r = -0.119, p = 0.041). In the group TSH 0.5-2.5 μUI/mL, positive correlations were found between TSH and both HDL (r = 0.136, p = 0.031) and homocysteine (r = 0.147, p = 0.028), between free T4 and CRP (r = 0.136, p = 0.037) and between anti-thyroglobulin antibodies and apolipoprotein B (r = 0.165, p = 0.013); anti-thyroglobulin antibodies were negatively correlated with homocysteine (r = -0.186, p = 0.006). Negative correlations between anti-thyroglobulin antibodies, total cholesterol (r = 0.371, p = 0.004), LDL (r = -0.325, p = 0.011), apolipoprotein B (r = -0.342, p = 0.022) and lipoprotein(a) (r = -0.470, p = 0.001) were revealed in the group TSH 2.5-5.0 μUI/mL. Regarding the group TSH 5.0-10.0 μUI/mL, we found positive correlations between free T3 and HDL (r = 0.358, p = 0.030), vitamin B12 (r = 0.398, p = 0.024) and HOMA-IR (r = 0.424, p = 0.031), and between anti-thyroglobulin and homocysteine (r = 0.383, p = 0.033). Conclusion: We observed significant correlations between thyroid function, thyroid autoimmunity, insulin resistance, lipid profile and homocysteine that may contribute to an increased cardiovascular risk in patients with autoimmune thyroiditis.

Novel Sensor System for Leakage Current Detection on Insulator Strings of Overhead Transmission Lines

We report the development of a measurement system capable of monitoring and characterizing the main features of the leakage current flowing on a polluted insulator string of a high-voltage transmission line. The system comprises a fiber-optic sensor, directly connected to one insulator of the string, that emits a sample of the leakage current waveform to a processing module via an optical link. A capacitive sensor connected to the processing module allows recording the relative humidity of the outer environment. At the present stage, six measurement units have been deployed on CHESFs electrical transmission system in the Northeast of Brazil, and studies are underway to further correlate the degree of environmental pollution with humidity and leakage current activities on high-voltage insulator strings