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Metallic fillers play a significant role in the brake friction material formulation due to its high thermal conductivity, tribo-load bearing ability against the rotor, friction stability and wear resistance. Brass powder is widely used in the formulation because of good thermal conductivity, fade and wear resistance. The commercial brass composed of 70 wt.% copper and 30 wt.% zinc. In this work, the brass powders with identical morphology and different weight percentage (wt.%) copper and zinc content is evaluated for its tribological and physico-mechanical performance in the brake friction material formulation. Three set of brake friction pads were fabricated with three different brass powders of varying copper and zinc content, 60% Cu-40% Zn, 70% Cu-30% Zn, and 80% Cu-20% Zn, respectively. The objectives of this study were to find the physico-mechanical properties based on Indian Standard IS 2742 and tribological performance of the brake pads based on ASTM G99-95 using pin-on-disc tribometer. The wear mechanism of the brake composite of worn surface was studied using scanning electron microscope. The brake friction composites were ranked based on extension evaluation method by considering the tribo-mechanical performance parameters. It is observed that brass with 80% Cu and 20% Zn proved to be the best performer based on the weighted average dependent degree of extension evaluation.

Background:Spinal anesthesia for cesarean section is associated with a high incidence of hypotension. The synergism between intrathecal opioids and local anesthetics may make it possible to achieve reliable spinal anesthesia with minimal hypotension using a minidose of local anesthetic. Methods: Forty-four preeclamptic parturients undergoing cesarean section were randomized in two groups of 22 patients. Group A received a spinal anesthetic of bupivacaine 6 mg plus fentanyl 20 µg , and group B received 12 mg bupivacaine. Hypotension was defined as a 30% decrease in systolic and diastolic pressure from baseline. Hypotension was treated with intravenous ephedrine boluses 2.5-5 mg up to maximum 50 mg. Results: All patients had satisfactory anesthesia. Five of 22 patients in group A required ephedrine, a single dose of 5 mg. Seventeen of 22 patients in group B required vasopressor support of blood pressure.The lowest recorded systolic,diastolic and mean blood pressures as fractions of the baseline pressures were 71.2%, 64.5% and 70.3% versus 59.9%, 53.5% and 60.2% respectively for group A versus group B. Conclusion: A “minidose” of 6 mg bupivacaine in combination with 20 µg fentanyl may provide satisfactory spinal anesthesia for cesarean section in the preeclamptic patient. The minidose combination caused dramatically less hypotension than 12 mg bupivacaine and nearly eliminated the need for vasopressor support of blood pressure.

Nitroglycerin has a relaxing effect on the smooth muscles of organs including uterus. This study investigates the effect of intravenous nitroglycerin in emergency cesarean sections in which rapid and transient uterine relaxation for rapid and nontraumatic extraction of the fetus is necessary. Sixty pregnant women who were been candidates for emergency cesarean and needed rapid uterine relaxation for different reasons were selected. These subjects underwent spinal anesthesia and at the time of uterine incision, 100 micrograms of nitroglycerin was injected to them intravenously. The time lapse between nitroglycerin administration and fetal extraction, the degree of uterine relaxation, the amount of intraoperative hemorrhage, uterine tone after fetal delivery and APGAR scores of the infants were all controlled and recorded. The results showed that in 53 (88.3%) of patients the uterus was acceptably relaxed and the fetus was delivered very easily. Only in 7 patients (11.7%) uterine relaxation was not acceptable. The mean decrease in systolic and diastolic blood pressures after nitroglycerin administration compared with before injection BP was 12.96 mmHg and 7.86 mmHg, respectively. There was not any prolonged effect of the drug such as uterus relaxation tone or abnormal bleeding. Also none of the delivered infants had low APGAR scores. Besides, in patients with acceptable uterine relaxation the first and fifth minute APGAR score of infants were higher (P = 0.008 and P = 0.000), respectively. This study shows that nitroglycerin can relax uterine smooth muscles very rapidly and transiently and in emergencies it can be an appropriate alternative to other tocolytic agents with prolonged effect or onset time.

This article deals with the laminar flow of a viscous fluid and heat transfer analysis due to a porous stretching/shrinking cylinder with partial slip condition. The flow equations corresponding to momentum and energy equations are transformed into a set of highly nonlinear ordinary differential equations by means of similarity transformations, which are then, solved numerically using Runge–Kutta–Fehlberg method. The physical significance of the various involved parameters on the flow velocity and temperature distribution is discussed through graphs and tables in detail. It is found that the dual solutions exist for the shrinking cylinder, while a unique solution exists for stretching cylinder. Comparison of the present results with the existing previous results is given and found to be in good agreement.

هدف اصلی این پژوهش بررسی رابطه بین انگیزش تحصیلی و تفکر انتقادی دانش آموزان و مقایسه آن در مدارسهوشمند و عادی بود. روش تحقیق، علی مقایسه ای )پس رویدادی( بوده که جامعه آماری آن را کلیه دانش آموزانپسر کلاس هشتم در سال تحصیلی 1393 تش یکل دادند. با استفاده از نمون هگیری خوشه ای مرحله ای و بر اساس فرمولکوکران تعداد 156 نفر ) 113 نفر از مدارس عادی و 43 نفر از مدارس هوشمند( انتخاب شدند. جهت گردآوری داده هایمورد نیاز از پرسشنامه های استاندارد انگیزش تحصیلی هارتر و مهارت های تفکر انتقادی واتسون و گلیزر استفاده شد کهپنج خرده مقیاس عمده استنباط، شناسایی مفروضات، استنتاج، تعبیر و تفسیر وارزشیابی استدلال های منطقی را میسنجد. برای بدست آوردن روایی پرسشنام هها از روایی محتوایی و صوری استفاده شد. ضریب پایایی نیز از طریق آلفایکرونباخ به ترتیب 94 / 0 و 79 / 0 برآورد گردید. جهت تجزیه و تحلیل داد هها از روش های آمار توصیفی و آمار استنباطیهمچون کالموگروف-اسمیرونوف، ضریب همبستگی پیرسون، آزمون t برای گروه های مستقل استفاده شد. نتایج نشانداد که بین تفکر انتقادی و مولف ههای آن با انگیزش تحصیلی رابطه وجود ندارد، همچنین یافته ها نشان داد که میانگینانگیزش تحصیلی و تفکر انتقادی دانش آموزان مدارس هوشمند بیشتر از مدارس عادی می باشد.