Partial discharge behavior under operational and anomalous conditions in HVDC systems

Power cables undergo various types of overstressing conditions during their operation that influence the integrity of their insulation systems. This causes accelerated ageing and might lead to their premature failure in severe cases. This paper presents an investigation of the impacts of various dynamic electric fields produced by ripples, polarity reversal and transient switching impulses on partial discharge (PD) activity within solid dielectrics with the aim of considering such phenomena in high voltage direct current (HVDC) cable systems. Appropriate terminal voltages of a generic HVDC converter were reproduced - with different harmonic contaminations - and applied to the test samples. The effects of systematic operational polarity reversal and superimposed switching impulses with the possibility of transient polarity reversal were also studied in this investigation. The experimental results show that the PD is greatly affected by the dynamic changes of electric field represented by polarity reversal, ripples and switching. The findings of this study will assist in understanding the behaviour of PDs under HVDC conditions and would be of interest to asset managers considering the effects of such conditions on the insulation diagnostics

The effects of ranitidine and hydrocortisone on the complications of femoral artery obstruction treated by streptokinase following cardiac catheterization in pediatric patients with congenital heart diseases

Background: The most important complication following cardiac catheterization required urgent therapeutic management is vessel obstruction and arterial thrombosis. The morbidity following this complication can be decreased by surgery intervention and/or thrombolytic drugs. Objectives: In this study we evaluated the effects of ranitidine and hydrocortisone in pediatric patients with congenital heart diseases who suffered from femoral artery obstruction following cardiac catheterization on decreasing the events after streptokinase administration. Materials and Methods: This semi experimental study was conducted on 47 patients among 600 cases who underwent cardiac catheterization from April 2002 to December 2011.The patients suffered from distal vessel obstruction following cardiac catheterization with no response to surgery intervention, were enrolled and divided in two groups. Streptokinase was administrated in both groups. Patients in group 2 (25 cases) received ranitidine and hydrocortisone before streptokinase administration. In first group (22 patients), the loading dose of streptokinase was 2000IU/kg/ in 20-30 minutes/ infusion and thereafter streptokinase was administrated 1000 IU /kg/hour. In group 2, the loading dose was 3000IU/kg in 20-30 minutes /infusion and 1500 IU/kg/hour as maintenance dose. The infusion dose of streptokinase was decreased and then terminated in 2-3 hours by the time arterial pulse was detected by pulse oximetry. Results: There were 13 (59, 1) male and 9 (40.9) female patients in group 1. In group 2, there were 15 (60) male and 10 (40) female cases (P = 0.949). Patients in both groups were matched well regarding age, body weight, height and the duration of streptokinase infusion (P < 0.05). The incidence of hematoma was higher in group 1 than group 2 (P = 0.032). Group 1 patients required more blood transfusion than group 2 because the incidence of bleeding was more in the first group (P = 0.042). Twelve patients in group 1 required fresh frozen plasma transfusion versus 4 patients in group 2 (P = 0.049). Local oozing was detected more in group 1 (P = 0.042). Significant bleeding was occurred in 6 cases in group 1; however this event was not occurred in any patients in group 2 (P = 0.007). Four patients in group 1 suffered from anaphylactic shock after streptokinase administration, no patients in group 2 suffered from this complication though (P = 0.041). Conclusions: Based on the results of this study, we concluded that streptokinase was able to remove the vessel thrombosis at the site of cardiac catheterization and ranitidine and hydrocortisone administration before streptokinase may be effective in order to reduce the complications related to thrombolytic drugs; however the experience of the performer is an issue of concern in this matter

The first experience of ex-vivo lung perfusion (EVLP) in Iran: An effective method to increase suitable lung for transplantation

Background: Although lung transplantation is a well-accepted treatment for end-stage lung diseases patients, only 15-20 of the brain-dead donors' lungs are usable for transplantation. This results in high mortality of candidates on waiting lists. Ex-vivo lung perfusion (EVLP) is a novel method for better evaluation of a potential lung for transplantation. Objective: To report the first experience of EVLP in Iran. Methods: The study included a pig in Vienna Medical University, Vienna, Austria, and 4 humans in Masih Daneshvari Hospital, Tehran, Iran. All brain-dead donors from 2013 to 2015 in Tehran were evaluated for EVLP. Donors without signs of severe chest trauma or pneumonia, with poor oxygenation were included. Results: An increasing trend in difference between the pulmonary arterial pO2 and left atrial pO2, an increasing pattern in dynamic lung compliance, and a decreasing trend in the pulmonary vascular resistance, were observed. Conclusion: The initial experience of EVLP in Iran was successful in terms of important/critical parameters. The results emphasize on some important considerations such as precisely following standard lung harvesting and monitoring temperature and pressure. EVLP technique may not be a cost-effective option for low-income countries at first glance. However, because this is the only therapeutic treatment for end-stage lung disease, it is advisable to continue working on this method to find alternatives with lesser costs

Testing one-body density functionals on a solvable model

There are several physically motivated density matrix functionals in the literature, built from the knowledge of the natural orbitals and the occupation numbers of the one-body reduced density matrix. With the help of the equivalent phase-space formalism, we thoroughly test some of the most popular of those functionals on a completely solvable model.Comment: Latex, 16 pages, 4 figure

The first experience of ex-vivo lung perfusion (EVLP) in Iran: An effective method to increase suitable lung for transplantation

Background: Although lung transplantation is a well-accepted treatment for end-stage lung diseases patients, only 15-20 of the brain-dead donors' lungs are usable for transplantation. This results in high mortality of candidates on waiting lists. Ex-vivo lung perfusion (EVLP) is a novel method for better evaluation of a potential lung for transplantation. Objective: To report the first experience of EVLP in Iran. Methods: The study included a pig in Vienna Medical University, Vienna, Austria, and 4 humans in Masih Daneshvari Hospital, Tehran, Iran. All brain-dead donors from 2013 to 2015 in Tehran were evaluated for EVLP. Donors without signs of severe chest trauma or pneumonia, with poor oxygenation were included. Results: An increasing trend in difference between the pulmonary arterial pO2 and left atrial pO2, an increasing pattern in dynamic lung compliance, and a decreasing trend in the pulmonary vascular resistance, were observed. Conclusion: The initial experience of EVLP in Iran was successful in terms of important/critical parameters. The results emphasize on some important considerations such as precisely following standard lung harvesting and monitoring temperature and pressure. EVLP technique may not be a cost-effective option for low-income countries at first glance. However, because this is the only therapeutic treatment for end-stage lung disease, it is advisable to continue working on this method to find alternatives with lesser costs

Postoperative complications after procedure for prolapsed hemorrhoids (PPH) and stapled transanal rectal resection (STARR) procedures

Procedure for prolapsing hemorrhoids (PPH) and stapled transanal rectal resection for obstructed defecation (STARR) carry low postoperative pain, but may be followed by unusual and severe postoperative complications. This review deals with the pathogenesis, prevention and treatment of adverse events that may occasionally be life threatening. PPH and STARR carry the expected morbidity following anorectal surgery, such as bleeding, strictures and fecal incontinence. Complications that are particular to these stapled procedures are rectovaginal fistula, chronic proctalgia, total rectal obliteration, rectal wall hematoma and perforation with pelvic sepsis often requiring a diverting stoma. A higher complication rate and worse results are expected after PPH for fourth-degree piles. Enterocele and anismus are contraindications to PPH and STARR and both operations should be used with caution in patients with weak sphincters. In conclusion, complications after PPH and STARR are not infrequent and may be difficult to manage. However, if performed in selected cases by skilled specialists aware of the risks and associated diseases, some complications may be prevented

Depositional environment of the Bagh-e-Vang Formation – the only occurrence of upper Lower Permian in Iran

A transgression of the Tethys Ocean occurred in east central Iran, like in other areas of the Tethys Ocean, around the Yakhtashian/Bolorian (regional chronostratigraphical units corresponding with the Artinskian/Kungurian of the Early Permian) transition. This led to the development of a carbonate platform that is represented in the Shirgesht area on the northern part of the Tabas Block by the Bagh-e-Vang Formation, which constitutes the only known sedimentary unit from the late Early Permian in Iran. Field data and thin-section analysis indicate deposition on a carbonate ramp with barriers separating a lagoonal area with intertidal mud flats from the open-marine environment. The overall transgres-sive development is indicated by the presence of open-marine sediments on top of the barrier and lagoonal sediments