Separation of Tröger's Base Enantiomers Through a Combination of Simulated Moving Bed Chromatography and Crystallization

This paper studies the coupling of simulated moving bed (SMB) chromatography with crystallization for the separation of Tröger's base enantiomers. SMB is used to achieve a certain level of enrichment and then evaporative crystallization of the extract and raffinate streams leads to the final product with the specified purity. The optimization of the combined process is based on thermodynamic data about adsorption isotherms of the two enantiomers in ethanol on microcrystalline cellulose triacetate (CTA) and about solubility of the two enantiomers in ethanol. The results, obtained using a genetic algorithm, prove that there is an optimal value of the purity achieved in the SMB that maximizes the productivity of the combined proces

Transatrial access for left atrial pressure (LAP) monitoring line placement in arterial switch operation (ASO) in neonates

Left Atrial pressure monitoring is a useful and accurate method to guide Left ventricle filling in the patients who undergo Arterial switch operation for transposition of great arteries. We have used a different technique in three TGA patients for LA pressure monitoring line placement. After cleaning and draping,right internal jugular vein (rt IJV) located through 22G venous cannula, guide wire was put in followed by sliding the 22Gx8cm vygon arterial catheter over the guide wire into the right atrium that was directed transatrially into LA by the operating surgeon during atrial septum repair. The catheter was secured by silk on the neck and dressed with transparent dressing and was kept for a period of 48-72hrs. LA pressure monitoring is helpful in anticipating LV dysfunction in ASO

Single lung ventilation in a young child for repair of coarctation of aorta

Single lung ventilation in small children is extremely challenging. In this case, a paediatric bronchial blocker was successfully inserted in a 19-month-old child to provide single lung ventilation using a modified insertion technique. It provided excellent working conditions during thoracotomy and our method of insertion may help in reducing the cost

Investigation of energy storage systems, its advantage and requirement in various locations in Australia

Storage minimizes the intermittent nature of renewable sources. Solar and wind are the two fostered source of renewable energy. However, the availability of useful solar radiation and wind speed varies with geographical locations, and also the duration of this energy sources varies with seasonal variation. With the available vast open land and geographical position, Australia has great potential for both solar and wind energies. However, both these sources require energy buffering to support load demand to ensure required power quality. Electricity demand is increasing gradually, and also Australia has target to achieve 20% electricity from renewable sources by 2020. For effective utilization of solar and wind energy potential location of these sources needs to be identified, and effective size of storage needs to be estimated for best utilization according to the load demand. Therefore this paper investigated wind speed and solar radiation data of 210 locations in Australia, identified the potential locations, and estimated required storage in various potential locations to support residential load demand. Advantages of storage were analyzed in terms of loading on distribution transformer and storage support during energy fluctuation from renewable energy. Further analysis showed that storage greatly reduces greenhouse gas emission and reduces overall cost of energy by maximizing the use of solar and wind energies

Optimizing control of simulated moving bed separations ofmixtures subject to the generalized Langmuir isotherm

Simulated moving bed (SMB) is a cost-efficient separation technique that offers high productivity and low solvent consumption. SMB has gained importance in the pharmaceutical and fine chemical industry to perform complex separation tasks. However, an open and challenging problem is the optimal, robust operation of the SMB process. We have developed a control scheme that integrates the optimization and control of the SMB unit. A significant feature of the controller is that only minimal information of the system has to be provided, i.e. the linear adsorption behavior of the mixture to be separated and the average void fraction of the columns. Therefore, a full characterization of the adsorption behavior of the mixture and the columns is no longer required. In this ‘cycle to cycle' control scheme, the measurements, optimization and control actions are performed once in every cycle. This paper presents simulation results of the control scheme applied to the separation of binary mixtures characterized by generalized Langmuir isotherms. The results are presented and analyzed in the frame of the triangle theory that has been recently extended to encompass these types of isotherms. Besides, online optimum performance of the SMB unit is compared with off-line optimization carried out using genetic algorithm. The results show that the controller fulfills the product and process specifications while operating the SMB unit optimally, regardless of the different types of Langmuir isotherms that the systems exhibi

Comparison between intravenous boluses versus infusion of tranexamic acid (TXA) to reduce bleeding in paediatric cyanotic congenital heart disease (CHD) surgeries

Objective: To compare the intravenous boluses and intravenous continuous infusion of tranexamic acid (TXA) to reduce postoperative bleeding in cyanotic congenital heart disease surgeries. Study Design: Single-blinded randomised clinical trial. Place and Duration of Study: Anaesthesia Department, The Aga Khan University Hospital, Karachi, from July 2016 to April 2017.Methodology: Sixty patients of cyanotic congenital heart disease, undergoing either palliative or corrective surgery involving cardiopulmonary bypass (CPB), were recruited. These 60 patients were divided randomly into two groups. The infusion group received intravenous infusion of TXA at 5 mg/kg/hour while the bolus group received three intravenous boluses of 10 mg/kg after induction, after going to bypass and after protamine reversal. Data was collected through predesigned proforma. There were two primary outcomes: postoperative bleeding in the first 24 hours, and chest closure time.Results: Postoperative bleeding was 13.94 (10.27-20.18) ml/kg in the first 24 hours in infusion group and 15.05 (9.04- 23.50) ml/kg in the bolus group. Chest closure time was 38.5 (25-45) in infusion group and 30 (20-46.25) minutes in the bolus group. There was no statistically significant and clinical difference between both groups regarding postoperative bleeding in the first 24 hours and chest closure time.Conclusion: These infusion and bolus groups had comparable postoperative bleeding and chest closure time

Contegra valved conduit in the paediatric population: an exciting prospect for right ventricle to pulmonary artery reconstruction; experience and outcomes at Aga Khan University

Objective: The focus of this study is to share the experience and outcomes of Contegra graft implantation in the paediatric and adult population in Pakistan. Methods: Between May 2007 and July 2011, 16 patients, underwent implantation of a Contegra valved conduit. All operations were performed through a median sternotomy with cardiopulmonary bypass. Indications included: Pulmonary atresia with ventricular septal defect (n=11), Tetralogy of Fallot with absent Pulmonary Valve (PV) syndrome (n=2), double outlet right ventricle, transposition of great arteries and pulmonary stenosis (n=1), isolated aortic valve disease (n=1) and a pseudo-aneurysm with infective endocarditis (n=1).Conduit sizes varied between 16-22 mm. Results: The three in hospital deaths were unrelated to the Contegra valved conduit. One patient was lost to follow up. Of the 12 survivors, 10 are currently free from re-operation or complications related to the conduit while one needed distal pulmonary artery dilatation owing to critical stenosis and another had severe Valvular regurgitation. Echocardiographic evaluation of the Contegra valved conduit demonstrated no haemodynamically significant valve regurgitation in 10 patients. Conclusion: In this small review of 16 operations using the Contegra valved conduit for Right Venticular Outflow Tract (RVOT) reconstruction in the paediatric population, we observed good post operative results concerning conduit function. The Contegra conduit provides an excellent substitute to the homograft with satisfactory early and mid-term results though long term results are awaited in Pakista

Role of serum angiotensin converting enzyme in sarcoidosis

This study was conducted to determine the role of Serum Angiotensin Converting Enzyme (SACE) as a marker in the differential diagnosis of pulmonary diseases and prognosis of sarcoidosis, A retrospective analysis of 113 medical records of patients at The Aga Khan University Hospital, with laboratory investigation for SACE was performed. Among 113 patients, 51 cases were found to have sarcoidosis, 44 of them had SACE levels greater than 52 lU/L (mean ACE 104.44). SACE levels were also found elevated in other clinical conditions like tuberculosis (mean 58.64 lUlL), but the enzyme level were less (p0.04) than those found in sarcoidosis (mean (92-97 lUlL). SACE activity was found to be considerably lower in other chronic lung diseases such as, fibrosing alveolitis (mean 43.98 lUlL), interstitial lung disease (mean 42.11 lU/L) and chronic obstructive lung disease (mean 40.85 lUlL). Twenty patients of sarcoidosis, who received steroid tretalment subsequently showed a decline in the SACE levels. SACE is a useful marker in differential diagnosis as 37.2% cases of sarcoidosis compared to only 9.09% of tuberculosis had SACE levels greater than 100 lUlL. In addition, our data also suggest that serum ACE is useful for the diagnosis as well as monitoring prognosis in sarcoidosis (JPMA 48:131,1998)

Integration of renewable energy resources into the distribution network : a review on required power quality

Power quality is the critical element of modern power system network where more and more distributed energy resources (DER) can be found. Distributed generation, generates electricity from many small DER particularly from renewable sources. Distributed generator (DG) within the network from renewable energy resources (RER) like solar and wind, bring significant challenges to maintain acceptable power quality (PQ) at the consumer end. This paper investigates PQ issues associated with RER. It reviews existing PQ standards for distribution network (DN) and also summarized the experiences of several Distributed Network Service Provider (DNSP) while integrating DGs into the grid. It was found that few PQ parameter ranges varies in different standards due to lack of harmonization and that may hinder to accept bulk renewable energy into the grid