Hypotension associated with spinal anesthesia for cesarean section is still a clinical problem. The role of crystalloid preLOADING to prevent hypotension associated with spinal anesthesia in parturients during cesarean section has been challenged. However, studies with crystalloids predict that fluid LOADING should be more efficacious if administered immediately after induction of spinal anesthesia. The effects of colloid LOADING after spinal anesthesia in cesarean section have not been studied enough. The aim of this study was to compare pre and co-LOADING of hetastarch for the prevention of hypotension following spinal anesthesia for cesarean delivery.Materials and Methods: This randomized clinical trial study was performed in 112 parturients (ASA I or II) undergoing elective cesarean section. Patients were randomly allocated to one of the two groups to receive rapid infusion of 500 ml of 6% hydroxyethylstarch (HES) before spinal anesthesia (preLOADING group, n=56), or rapid infusion of 500 ml of HES after induction of spinal anesthesia (co-LOADING group, n=56). The incidence of hypotension and the amount of vasopressor, (ephedrine 5 mg/mL+phenylephrine 25 micg/mL) were compared in the treatment of hypotension.Results: There was no significant difference in hypotension between the two groups (P=0.58). The preLOADING group used 2.2±1 ml of vasopressor mixture compared with 1.7±0.7 ml in the co-LOADING group (P=0.04) and the difference was significant.Conclusion: Colloid LOADING after induction of spinal anesthesia is as effective as preLOADING in reducing hypotension in cesarean section.

Nowadays, natural gas is used as a reliable energy resource around the world. Usually, natural gas requires sweetening processes before consumption and AMINE units are widely employed for this purpose. AMINE unit is used for the separation of acid gases, such as H2S and CO2, from natural gas by means of AMINE solutions. Energy consumption of AMINE units is significantly high, due to considerable heating and cooling requirements, and practical methods that reduce energy demand are of interest. In this manuscript, a real AMINE unit of a gas refinery in Iran has been simulated and simulation results have been compared to actual data, available from the real unit and engineering documents. Simulation results have been found in good agreement with actual industrial data. After simulation validation, the application of multiple inlet AMINE lines to the absorption column has been exAMINEd by several simulations and the optimum location of AMINE entrance to AMINE contactor has been investigated. Research results have revealed that by the correct application of multiple lean AMINE streams, AMINE circulation rate can be reduced and 11% energy consumption reduction can be achieved. This study has been performed based on actual plant conditions without the usual simplifications used in similar studies.

This paper includes the significant onsite experience of the authors related to problems faced in AMINE systems with fresh AMINE and their possible solutions in phases #2&3 of South Pars gas complex. The AMINE system was designed as a closed circuit system with the primary objective of removing H2S, CO2, and other acidic components from gaseous hydrocarbon streams. AMINE plant operational problems such as excessive foaming, intense corrosion and capacity reduction are observed in gas sweetening unit. Heat stable salt (HSS) accumulations were found to be one of the main reasons for corrosions. Since there are no MDEA purification facilities in phase #2&3, it was decided to replace old MDEA solution with fresh MDEA. However, there are some problems that many plants have experienced after AMINE replacing or construction. In this paper, practical strategies with experimental data were proposed to overcome these problems.

The use of mixed AMINE system in gas treating processes is increasing today. For natural gas sweetening purposes, mixed AMINEs are typically mixtures of MDEA and DEA or MEA that enhance CO2 removal while retaining desirable characteristics of MDEA such as reduced corrosion problems and low heats of reaction. In this work, a process simulator was used to predict the performance of an Iranian gas sweetening plant with a sour gas feed containing 6.41% CO2 and 3.85% H2S on molar basis. Various mixtures of diethanolAMINE (DEA) and Methyl diethanolAMINE (MDEA) were used to investigate the potential for an increase in plant capacity. It was noticed that the process simulator is quite capable in predicting the existing plant performance and can potentially guide in selecting the optimum blend composition. It was also noticed that a substantial increase in plant capacity is quite possible by just adding MDEA to the existing solvent and keeping the solvent flow rate and stripper rebuilder heat duty. In another word, it is possible to increase the plant capacity from 293 to 357 MMSCFD using a mixed AMINE system.

Background and Aim: A key factor in restoring the endodontically treated teeth is ferrule preparation. When the ferrule is absent, occlusal loads may cause the post or root to fracture. The purpose of this in vitro study was to evaluate the effect of ferrule preparation on fatigue resistance of teeth restored with quartz-fiber posts.Materials and Methods: Twenty single-rooted lower premolars having similar dimentions were randomly devided into two groups of 10. In control group the teeth were prepared with 3-mm of remaining coronal tooth structure and in test group teeth were prepared with 1-mm of remaining coronal tooth structure. The teeth were endodontically treated. 9-mm long Post holes were prepared, and D.T. light quartz-fiber(RTD,France) posts were cemented with Panavia F2(Kuraray,Japan).Then the core build up was done with Bisco core build up composite(Bisco,USA) and full metal crowns were cemented with Zinc phosphate(Harvard cement, Germany). All specimens were mounted in acrylic resin blocks and intermittently loaded (180 N) at an angulation of 45- degree to the long axis of the teeth at a frequency of 4 loads per second, until failure occurred.Results: There was significant difference between the loads cycles of two groups studied. (p<0.0001).Conclusion: The results of this study showed that an increased amount of coronal dentin significantly increases the fracture resistance of teeth restored with quartz-fiber posts.