Impact of Inverter Based Resources on System Stability in Low Inertia Power System Network

Inverter-based resources (IBRs), such as solar and wind power are gaining popularity because of their increasing acceptance, environmental benefits and decreasing costs. However, their integration into power systems can lead to significant impacts on system inertia and frequency stability, which are crucial for maintaining the reliability of the power grid. In traditional power systems, the synchronous generators provide inertia, which helps to stabilize the frequency of the system. However, IBRs do not have this inherent inertia, and their integration can result in a decrease in system inertia, leading to frequency instability. This is because IBRs are typically connected to the grid through power electronics, which can introduce additional control and communication delays that affect the system's response to disturbances. To address this issue, various techniques have been proposed, such as virtual and synthetic inertia, to increase the effective inertia of IBRs. This thesis will cover the modeling of Battery Energy Storage Systems (BESS) and Static Synchronous Condenser (STATCOM) into power systems using PSS/E software to improve the effective inertia of the system and voltage profile respectively, ensuring that the power grid operates with reliability and stability

Paucity of trauma literature from a highly burdened developing country

Abstract Introduction: Trauma is the leading cause of death among a younger population not only in USA but in Pakistan as well. The high prevalence of disease should result in a larger amount of data and a larger number of publications resulting in the ability to explore improvements in the field. This study aimed to review the trauma literature generated from Pakistan. Methods: Journals indexed with PubMed from January 2010 to December 2014 were searched using the search term ‘‘Trauma AND Pakistan’’ filtering for relevant dates and human reports only. The abstracts and articles were reviewed by the authors to collect data on a proforma. Results: 114 articles were published from Pakistan during these five years; 64% of articles were published in international journals; 63% of articles were published in journals with an Impact Factor less than 1; 54% of articles were published from one of four provinces of Pakistan; 64% of articles provided Level 4 evidence whilst another 14% of articles provided Level 5 evidence on the topic; 55% of articles discussed epidemiology in non-representative populations. Conclusions: Trauma literature from Pakistan is not only lacking significantly in quantity but is also of poor quality and is unable to offer conclusions on a particular trauma subject. There is huge room for improvement in the upcoming years

Improving outcomes of emergency bowel surgery using NELA model

Objective: To find outcomes of emergency bowel surgery and review the processes involved in the care of these patients on the same template used in National Emergency Laparotomy Audit (NELA).Study Design: An audit.Place & Duration of Study: Surgery Department, The Aga Khan University Hospital, Karachi, from December 2013 to November 2014.Methodology: Patients undergone emergency bowel surgery during the review period were included. Demographic data, type of admission, ASA grade, urgency of surgery, P-POSSUM score, indication of surgery, length of stay and outcome was recorded. Data was then compared with the data published by NELA team in their first report. P-value for categorical variables was calculated using Chi-square tests.Results: Although the patients were younger with nearly same spectrum of disease, the mortality rate was significantly more than reported in NELA (24% versus 11%, p=0.004). Comparison showed that care at AKUH was significantly lacking in terms of proper preoperative risk assessment and documentation, case booking to operating room timing, intraoperative goal directed fluid therapy using cardiac output monitoring, postoperative intensive care for highest risk patients and review of elderly patients by MCOP specialist. Conclusion: This study helped in understanding the deficiencies in the care of patients undergoing emergency bowel surgery and alarmingly poor outcomes in a very systematic manner. In view of results of this study, it is planned to do interventions in the deficient areas to improve care given to these patients and their outcomes with the limited resources of a developing country

Changes in patterns and outcomes of trauma patients after betterment in law and order situation of the city

Objective: To assess the impact of the law and order situation of a city on the pattern of traumatic injuries and the overall outcomes of trauma victims. Methods: The retrospective study of prospective trauma surgery data was done at Aga Khan University Hospital, Karachi, and comprised data of patients with torso injuries before the improvement of law and order situation from January 2012 to March 2013 in Group A, and of those with similar injuries after the law and order situation improved in the city from January 2018 to March 2019 in Group B. The required data was collected by a single researcher using a predesigned questionnaire. Inter-group comparison was done to see the difference in patterns of injuries and outcomes. Data were analysed using SPSS 22. Results: Of the 676 cases reviewed, Group A had 416(61.5%); 363(87%) males and 53(13%) females with overall mean age of 37±13 years. Group B had 260(38.5%); 219(84%) males and 41(16%) females with overall mean age of 36±13 years (p\u3e0.05). Penetrating trauma alone or combined with blunt force was the most common mechanism in Group A i.e. 245 (59%) patients, while in group B blunt trauma was the commonest cause 209 (80.4%) patients. There was an overall 156 (37.5%) cases reduction in torso trauma cases. Mortality in Group A was 22(5.3%) and in Group B it was 7(2.7%). Conclusions: With the improvement in the law and order situation, there was reduction in overall trauma cases and the pattern of trauma shifted from penetrating to blunt injuries

Generalized Exponentiated Moment Exponential Distribution

Moment distributions have a vital role in mathematics and statistics, in particular in probability theory, in the perspective research related to ecology, reliability, biomedical field, econometrics, survey sampling and in life-testing. Hasnain (2013) developed an exponentiated moment exponential (EME) distribution and discussed some of its important properties. In the present work, we propose a generalization of EME distribution which we call it generalized EME (GEME) distribution and develop various properties of the distribution. We also present characterizations of the distribution in terms of conditional expectation as well as based on hazard function of the GEME random variable

Management of early rectal cancer: Current practice and future

Early rectal cancer management includes tumour stages TiS, T1 and some selected T2 lesions that undergo appropriate clinical pre-operatie evaluation. Local excision of these lesions with acceptable recurrence rate can be achieved through various transanal endoscopic techniques like transanal endoscopic microsurgery (TEM) and transanal minimal invasive surgery (TAMIS) that are superior to simple transanal excision (TAE). The current literature review was planned to present the oncological evaluation of local excision in the context of available evidence. An overview of perioperative adjuvant therapies employed along with local excision is presented, with an update on the latest trials

Better outcome of splenectomy in younger patients suffering from chronic immune thrombocytopenia

Abstract Immune thrombocytopenia purpura (ITP) may need splenectomy after failure of medical treatment. The aim of this study was to explore the outcome of splenectomy in chronic ITP and to point out factors which can predict better response to splenectomy. This retrospective chart review was conducted at the Aga Khan University Hospital, Karachi, and comprised adult patients who underwent splenectomy for ITP from October 2005 to December 2015. Of the 51 patients, 37(72.5%) were females and 14(27.5%) were males. The overall median age was 32 years (interquartile range: 18-65 years). Complete response was seen in 43(84.3%) patients, 2(4%) had response and 6(11.7%) had no response. Relapse rate of ITP at 1 year was 4(8.8%). Multivariate analysis showed that failure rate of splenectomy in the 41(80.4%) patients aged \u3c50 years was 3(7%) as opposed to 3(30%) in the 10(19.6%) patients aged \u3e50 years (p=0.04). Splenectomy was found to be a safe and effective option for treatment of ITP. Young age at the time of surgery was associated with good response to surgery

A six-month retrospective study of resources burden by trauma victims in the surgical intensive care unit of a university hospital in Pakistan

Introduction: Trauma is the fourth leading cause of death globally and constitutes a huge burden on limited critical care resources. Aim This study aimed to identify the trauma patient burden in terms of resources used in the surgical intensive care unit (SICU) of Aga Khan University Hospital in Pakistan which also included characteristics and outcomes of trauma and non-trauma patients.Methods: We retrospectively reviewed all patient data for adult patients (\u3e16 years old) admitted to the SICU from July through December 2014.Results: Of 141 SICU cases included in our study period, 32 (22.7%) trauma patients were identified. On further stratification of trauma patients, road traffic injuries (43.8%), gunshot injuries (43.8%), and blast injuries (6.3%) were the most common, and about 73% of all trauma patients underwent emergency surgical interventions, comprising a huge burden on all resources. The average age of the trauma patients was significantly lower than non-trauma patients (36 years ± 13 vs. 49 years ± 19; p \u3c 0.01). The male-to-female ratio was 7:1 in trauma cases and 2:1 in non-trauma cases (p = 0.019). There was no statistically significant difference in mortality (31.3% vs. 42.2% p \u3e 0.05) and median length of stay [Median (interquartile range), 5(8) vs. 4(7); p \u3e 0.05] between trauma and non-trauma patients.Conclusions: Trauma constitutes a significant burden in terms of resources used for the SICU of the Aga Khan University, Pakistan. Trauma victims are predominantly young men in whom gunshot injuries are as common as road traffic injuries. Emergency surgical interventions comprise the largest draw on resources, followed by use of blood products, radiological, and laboratory investigations

Gastric stromal tumors: clinical presentations, diagnosis and outcome

Objective: To determine the clinical presentations, of gastric stromal tumors with diagnostic methods, pathology and outcome after surgery. Study Design: A case series. Duration and Setting: From January 1988 to December 2002 at The Aga Khan University Hospital, Karachi. Patients and Methods: All patients of age 14 years and above, diagnosed histopathologically to have gastric stromal tumors were included. The data of these patients was collected retrospectively from January 1988 to December 1998, and prospectively from January 1999 to December 2002. All the patients were studied as a single group. Results: There were 11 patients. Their mean age was 54 years, with 8 males and 3 females. Five patients presented with upper gastrointestinal bleeding, and 4 with lower gastrointestinal bleeding. Eight patients had pain in epigastrium and 2 had vomiting. Upper gastrointestinal endoscopy was done in all patients, and ultrasound was done in 4 patients. CT scan was done in 7 patients. Preoperative diagnosis could be made in 6 patients. Only one patient had liver metastasis. Wedge resection was performed in 5 proximal gastrectomy with gastroesophageal anastomosis in 3, and partial gastrectomy with gastrojejunostomy in another 3 patients. The mean tumor size was 8.0 centimeters. Two patients had benign, 2 had intermediate and 7 had malignant tumors. The mean duration of followup was 41 months. Follow-up was completed in 8 patients, out of whom 6 were alive, and 2 patients expired due to other causes at the time of completion of this study.Conclusion: Gastric stromal tumors are uncommon. Larger gastric stromal tumors are usually symptomatic with gastrointestinal bleeding as a common presentation. Immunohistochemical techniques are required for the diagnosis. Complete surgical resection is the curative therapy