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Voltage instability in power systems arises due to the shortage of reactive power and may cause abnormally low bus voltages leading to a partial or complete blackout. In order to maintain the system voltages within a safe limit, voltage control techniques such as shunt capacitor banks, Static VAR Compensators (SVCs), load shedding, and transformer tap-changer blocking, are employed. In this paper, a novel receding-horizon Model Predictive Control (MPC)-based voltage controller is proposed, which, by optimally controlling generator reactive power and SVC output, maintains the voltage stability of a power system. For this, a sensitivity-based analysis is performed to design a state-space model of the power system. The frequency and voltage dependency of load and generation are considered in the system equations. The voltage control is done step-wise, and the optimal control action in each step is calculated by minimizing a cost function subject to a set of relevant constraints. Different Voltage Stability Indices (VSIs) are used as a measure of voltage stability and also used in the constraints for the optimization problem. The performance of the proposed controller is evaluated on IEEE 9-, 39- and 118-bus systems, considering different types of loads and contingencies. [ABSTRACT FROM AUTHOR]

A disturbance in a power system causes the frequency to deviate from its nominal value. The load and generation of the system are strategically adjusted to restore the synchronous frequency. This paper introduces novel shrinking-horizon model predictive control (MPC) technique, which employs a centralized controller for managing the load-frequency of a single-area power system and distributed controllers for multi-area systems. The controller optimally changes generation settings and sheds non-critical loads to make the frequency and tie-line power deviation zero. In contrast to existing approaches that use an approximate first-order transfer function model, this paper presents a structure-preserving linear state-space model for power systems. This model takes into account frequency and voltage dependencies of both load and generation, allowing for more accurate representation of power system behavior. During rescheduling, the controller minimizes additional cost associated with changes while satisfying various operational and physical constraints. The paper conducts several case studies using IEEE test systems to devise corrective action plans for both under- and over-frequency scenarios. The proposed controller’s robustness is tested against disturbances originating from renewable energy sources. Furthermore, a performance comparison is drawn between the proposed controller and existing control techniques. The comparative analysis indicates that the proposed approach consistently outperforms other controllers in terms of dynamic performance improvement, measured by parameters such as settling time, overshoot, undershoot, and error reduction. It is observed that the maximum undershoot and the settling time of the frequency is the least for centralized control. Comparative studies indicate that under different circumstances, the proposed approach outperforms other controllers in dynamic performance improvement, measured by settling time, overshoot, undershoot, and error reduction. The net rescheduling cost obtained by the proposed centralized MPC, cooperative distributed MPC, and non-cooperative distributed MPC-based controllers is 38, 25, and 24% lower than the conventional PI controller used for LFC of IEEE 39-bus system. This validates the suggested controllers’ cost-effectiveness. [ABSTRACT FROM AUTHOR]

Objectives: To assess depression and health-related quality of life (HRQOL) in 89 people with refractory urge incontinence, nonobstructive urinary retention, or urgency frequency enrolled at 13 U.S. study centers. The subjects were part of a large international, multicenter, randomized clinical trial on the safety and efficacy of sacral nerve stimulation for the treatment of refractory voiding dysfunction.Methods: The Beck Depression Index and the Medical Outcomes Study Short-Form 36 were used to assess depression and HRQOL at baseline and at two follow-up visits.Results: Detectable levels of depression and reduced quality of life were noted at baseline. Subjects implanted with the stimulation device reported significant improvements in both HRQOL and depression at 3 months after implant that were maintained for the 6-month study period. Subjects assigned to the delayed implant group showed a slight worsening of HRQOL and depression from baseline to 3 months that continued through the 6-month visit.Conclusions: The results demonstrated the serious impact that unresolved voiding symptoms have on the physical, social, and psychological dimensions of quality of life. Treating refractory voiding dysfunction with sacral nerve stimulation resulted in improvement in both depression and HRQOL. [Copyright &y& Elsevier]

We report a case of urinary retention and urethral erosion after placement of tension-free vaginal tape. This procedure is gaining wide popularity in both Europe and the United States. Careful attention is necessary to assure tension-free placement of the sling. [ABSTRACT FROM AUTHOR]

This is a unique case of bilateral metachronous testicular mesothelioma of the tunica vaginalis. Testicular mesothelioma is a rare entity found in patients with or without asbestos occupational exposure. The tumor most commonly presents as a unilateral testicular mass. More rare presentations include bilateral synchronous or metachronous tumors. Treatment is with surgical resection and prognosis is not generally favorable. The benefits of adjuvant therapy with radiation or chemotherapy remain unknown and further studies are needed. [ABSTRACT FROM AUTHOR]

Objective: To assess the patient and perioperative characteristics of urethral diverticulectomy using a large multi-institutional prospectively collected database.Materials and Methods: Female patients were identified using the American College of Surgeons National Surgical Quality Improvement Program participant user files (2007-2012) and current procedural terminology codes for urethral diverticulectomy (53,230). Preoperative variables and 30-day complications were examined.Results: Urethral diverticulectomies were performed on 122 females during the study period. The cohort was relatively healthy; 80% of patients had an American Society of Anesthesiologists score of 1 or 2. The majority of procedures were performed in an outpatient setting (82%). The median procedure length was 77.5 minutes (interquartile range: 50.5-112.5), and the median length of stay was 0 days (interquartile range: 0-1). The overall 30-day complication rate was 3.3% (n = 4): 3 patients developed urinary tract infections (UTIs) and 1 patient developed both a UTI and a superficial wound infection.Conclusion: To our knowledge, our study represents the largest multi-institutional cohort of patients having undergone urethral diverticulectomy. The patients requiring this intervention were relatively healthy, and the procedure itself was short, allowing most patients to be discharged within 24 hours. The 30-day complication rate was very low, with UTI being the most common complication. Thus, patients can continue to be confidently counseled that urethral diverticulectomy is a safe procedure with very few perioperative complications. [ABSTRACT FROM AUTHOR]

The fatty acid composition as well as the volatiles of a lipophilic extract from the marine sponge Fasciospongia cavernosa (Schmidt) was analysed. The fatty acids (FA) were characterized by linear saturated fatty acids (33.05 %), branched saturated fatty acids (9.30 %) and mono-unsaturated fatty acids (18.07 %). A significant amount of polyunsaturated fatty acids (PUFA) (30.79 %) was found in the total lipid, which included linoleic acid (18:2 n-6, 11.14 %), 9,12,15-octadecatrienoic acid/α-linolenic acid (18:3 n-3, 1.99 %), dihomo-γ-linolenic acid (20:3 n-6, 2.03 %) and arachidonic acid (20:4 n-3, 0.51 %). An antibacterial assay of the lipid extract of F. cavernosa showed broad- -spectrum activity against different human and fish pathogens. [ABSTRACT FROM AUTHOR]