Hierarchical Clustering based optimal PMU placement for power system fault observability.

Optimal number and location of phasor measurement units (PMUs) in the power system networks faces challenges for achieving the full network observability during fault conditions. Achieving fault observability approach requires more constraints than normal system observability and consequently suffers from complex analysis and heavy computational burden for the large-scale networks. A new algorithm for determining the optimal PMU placement considering the network fault observability is introduced. The proposed algorithm is achieved through four stages. The first stage is achieved through the network fault simulation to obtain the post fault change in voltage (ΔV) at each bus. Then, the post fault change in voltage (ΔV) is used to build the network connectivity matrix (CM) and forming a new developed Faulted Connectivity Matrix (FCM) that describes the power system topology during the fault conditions. The correlation between the buses is obtained, in the second stage, by applying Pearson correlation coefficient. Hierarchical Clustering technique is given, in the third stage, to cluster the network into coherent zones to find the most correlated buses. Finally, the optimal location of the PMUs is identified within each zone based on simple proposed placement rules. The proposed algorithm is tested under a variety of fault events applied on different standard test systems. The results show the simplicity and the effectiveness of the proposed algorithm.

The influence of circulating anti-Müllerian hormone on ovarian responsiveness to ovulation induction with gonadotrophins in women with polycystic ovarian syndrome: a pilot study.

BACKGROUND: Women with polycystic ovarian syndrome (PCOS) are known to have elevated circulating Anti-Müllerian hormone (AMH), which has been found to desensitize ovarian follicles to follicle stimulating hormone (FSH). The purpose of this study was to investigate the impact of high circulating AMH on ovarian responsiveness to ovulation induction with gonadotrophins in PCOS women. METHODS: This prospective observational pilot study was conducted in two collaborating Fertility Centres in the UK and Egypt. The study included 20 consecutive anovulatory women with PCOS who underwent 34 cycles of human menopausal gonadotrophin (hMG) ovarian stimulation using chronic low-dose step up protocol. Blood samples were collected for the measurement of serum AMH concentrations in the early follicular (day 2-3) phase in all cycles of hMG treatment. The serum levels of AMH were compared between cycles with good vs. poor response. The good response rates and the total dose and duration of hMG treatment were compared between cycles with high vs. low serum AMH concentrations. RESULTS: Cycles with poor response (no or delayed ovulation requiring >20 days of hMG treatment) had significantly (p = .007) higher median{range} serum AMH concentration (6.5{3.2-13.4}ng/ml) compared to that (4.0{2.2-10.2}ng/ml) of cycles with good response (ovulation within 20 days of hMG treatment). ROC curve showed AMH to be a useful predictor of poor response to hMG stimulation (AUC, 0.772; P = 0.007). Using a cut-off level of 4.7 ng/ml, AMH had a sensitivity of 100% and specificity of 58% in predicting poor response. The good response rate was significantly (p < .001) greater in cycles with lower AMH (<4.7 ng/ml) compared to that in those with AMH > = 4.7 ng/ml (100% vs. 35%, respectively). All cycles with markedly raised serum AMH levels (> 10.2 ng/ml) were associated with poor response. Cycles with high AMH (> = 4.7 ng/ml) required significantly (p < .001) greater amounts (median {range}, 1087{450-1650}IU) and longer duration (20 {12-30}days) of hMG stimulation than cycles with lower AMH (525 {225-900}IU and 8{6-14}days). CONCLUSIONS: PCOS women with markedly raised circulating AMH seem to be resistant to hMG ovulation induction and may require a higher starting dose.

The predictive value of circulating anti-Müllerian hormone in women with polycystic ovarian syndrome receiving clomiphene citrate: a prospective observational study.

CONTEXT: Elevated serum anti-Müllerian hormone (AMH) concentration in women with polycystic ovarian syndrome (PCOS) is known to lower sensitivity of ovarian follicles to circulating FSH. This effect may compromise the outcome of clomiphene citrate (CC) ovulation induction. OBJECTIVE: The objective of the study was to investigate the impact of high circulating AMH on the outcome of CC ovulation induction in women with PCOS. DESIGN: This was a prospective cohort observational study. SETTING: The study was conducted at the Fertility Unit, Derby, United Kingdom. PATIENTS: Sixty anovulatory women with PCOS participated in the study. INTERVENTIONS: Serum AMH concentrations were measured on cycle day 2 during 187 CC cycles. These concentrations were compared between responders and nonresponders. The receiver-operating characteristic curve was used to evaluate the prognostic value of circulating AMH. The success rates of CC were compared between patients with high vs low AMH levels. The dose of CC required to achieve ovulation was correlated with serum AMH concentrations. MAIN OUTCOME MEASURES: Ovulation and pregnancy rates were measured. RESULTS: Serum AMH concentrations were significantly (P < .001) lower in responders (achieving ovulation) vs nonresponders (mean ± SEM, 2.5 ± 0.1 vs 5.8 ± 0.7 ng/mL, respectively). Similarly, serum AMH concentrations were significantly (P = .046) lower in pregnant (3.0 ± 0.4 ng/mL) vs nonpregnant patients (4.4 ± 0.5 ng/mL). There was a significant (P = .02) gradient increase of serum AMH levels with the increasing dose of CC required to achieve ovulation. The receiver-operating characteristic curve showed AMH to be a useful predictor of no ovulation (area under the curve, 0.809; P < .001) with a useful cutoff level of 3.4 ng/mL. Ovulation and pregnancy rates were significantly higher (97%, P < .001, and 46%, P = .034) in patients with low AMH (<3.4 ng/mL) vs women with AMH 3.4 ng/mL or greater (48% and 19%). CONCLUSION: PCOS women with high circulating AMH (≥ 3.4 ng/mL) seem to be resistant to CC and may require a higher starting dose.

Determinants of salt sensitivity in black and white normotensive and hypertensive women.

Salt sensitivity (SS) has been linked to human hypertension. We examined ethnic differences in the relation between SS; erythrocyte sodium (Na+i), calcium (Ca2+i), potassium (K+i), and magnesium (Mg2+i); and sodium pump activity in African-American (AA) and white women. In a crossover protocol, similar numbers of normotensive, hypertensive, AA, and white women were randomized to 7 days of a 20 meq/d and a >200 meq/d salt diet (n=199). After an overnight inpatient stay, group differences in supine blood pressure (BP), heart rate, erythrocyte cations, and sodium pump activity were measured. The prevalence of SS (53.5% vs 51%) and salt resistance (26.3% vs 30.0%) was similar in both races. Greater mean BP increase with salt loading was seen in AA vs white hypertensives but not between the normotensive women. In hypertensives, increase in mean arterial pressure was 12.6 vs 8.2 mm Hg in AAs vs whites, respectively (P<0.01), and for systolic BP, it was 23 vs 14.8 mm Hg (P<0.01). Higher Na+i and Ca2+i were noted in SS and salt-intermediate AA than in the corresponding white subjects. Na+i, Ca2+i, and the ratios of Na+i to K+i and of Ca2+i to Mg2+i were positively correlated with salt responsiveness in AA but not in white women. Sodium pump activity was similar between groups, although the change in maximal activity trended to vary inversely with SS in AA. In closely matched AA and white women, the prevalence of SS is similarly high in both races, although the magnitude of BP increase is greater in AA hypertensives. In AA but not in whites, SS is positively associated with Na+i, Ca2+i, and the ratios of Na+i to K+i and of Ca2+i to Mg2+i.