Multi-Objective Optimization of the Process Parameters in Electric Discharge Machining of 316L Porous Stainless Steel Using Metaheuristic Techniques.

Electric discharge machining is an essential modern manufacturing process employed to machine porous sintered metals. The sintered 316L porous stainless steel (PSS) components are widely used in diverse engineering domains, as interconnected pores are present. The PSS material has excellent lightweight and damping properties and superior mechanical and metallurgical properties. However, conventional machining techniques are not suitable for porous metals machining. Such techniques tend to block the micro-pores, resulting in a decrease in porous materials' breathability. Thus, the EDM process is an effective technique for porous metal machining. The input process parameters selected in this study are peak current (Ip), pulse on time (Ton), voltage (V), flushing pressure (fp), and porosity. The response parameters selected are material removal rate (MRR) and tool wear rate (TWR). The present work aims to obtain optimum machining process parameters in the EDM of porous sintered SS316L using two meta-heuristic optimization techniques, i.e., Teaching Learning-Based Optimization (TLBO) and Particle Swarm Optimization (PSO) algorithms, to maximize the MRR and minimize the TWR values. In the case of PSS having a 12.60% porosity value, PSO and TLBO algorithms give same optimum machining parameters. However, for PSS having an 18.85% porosity value, the PSO algorithm improves by about 5.25% in MRR and by 5.63% in TWR over the TLBO. In the case of PSS having a 31.11% porosity value, the PSO algorithm improves about 3.73% in MRR and 6.46% in TWR over the TLBO. The PSO algorithm is found to be consistent and to converge more quickly, taking minimal computational time and effort compared to the TLBO algorithm. The present study's findings contribute valuable information in regulating the EDM performance in machining porous SS316L.

Pathological, molecular, and clinical characteristics of cholangiocarcinoma: A comprehensive review.

Cholangiocarcinomas are a heterogeneous group of highly aggressive cancers that may arise anywhere within the biliary tree. There is a wide geographical variation with regards to its incidence, and risk-factor associations which may include liver fluke infection, primary sclerosing cholangitis, and hepatolithiasis amongst others. These tumours are classified into intrahepatic, perihilar and distal based on their anatomical location. Morphologically, intrahepatic cholangiocarcinomas are further sub-classified into small and large duct variants. Perihilar and distal cholangiocarcinomas are usually mucin-producing tubular adenocarcinomas. Cholangiocarcinomas develop through a multistep carcinogenesis and are preceded by dysplastic and in situ lesions. While clinical characteristics and management of these tumours have been extensively elucidated in literature, their ultra-structure and tumour biology remain relatively unknown. This review focuses on the current knowledge of pathological characteristics, molecular alterations of cholangiocarcinoma, and its precursor lesions (including biliary intraepithelial neoplasia, intraductal papillary neoplasms of the bile duct, intraductal tubulopapillary neoplasms and mucinous cystic neoplasm).

ABO-Incompatible Living Donor Liver Transplant From a Blood Type A2 Donor to a Type B Recipient: A Note of Caution.

Standardization of immunomodulation protocols has enabled ABO-incompatible liver transplants with outcomes similar to those of ABO-compatible liver transplants. Patients with the A2 blood group are unique because they have a diminished expression of the A antigen. Despite rare immune complications, this phenomenon of diminished expression has led to treatment of type A2 donors according to the regimen for type O blood group donors in ABO-incompatible liver transplants. Additionally, the requirement for pretransplant recipient immunomodulation is consi dered minimal when considering these donors. The transplant of a type A2 donor kidney to a type B recipient is well recognized; however, for liver donation the A2-to-B transplant is rare. Here, we present a case of 48-year-old male patient with blood group type B who underwent ABO-incompatible liver transplant of a right lobe liver graft from a type A2 donor. Postoperatively, despite adequate immunosuppression and initiation of thera - peutic plasma exchange, the patient developed severe and refractory antibody-mediated rejection that ultimately abated with a splenectomy. This report highlights the low but tangible risk of antibody-mediated rejection in ABO-incompatible liver transp lants from type A2 donors and emphasizes the importance of serial monitoring of anti-A isohemag glutinin titers and posttransplant splenectomy to ensure that liver grafts with antibody-mediated rejection can be rescued.

Anatomical Basis for Selective Multiple Arterial Reconstructions in Living Donor Liver Transplantation.

BACKGROUND: Need for routine reconstruction of all arteries in grafts with multiple arterial inflows remains an unsettled debate. The aim of following article is to review an anatomical basis of a decision-making strategy to deal with multiple arteries in living donor liver transplantation (LDLT). METHODS: LDLT performed between August 2009-2019 were included. Grafts were classified into grafts with single artery (group 1); multiple arteries, all reconstructed (group 2); and multiple arteries, one reconstructed (group 3). Frequency of double arteries in relation to graft type, type of reconstruction, incidence of arterial and biliary complications and survival was compared. RESULTS: 1086 LDLT were analysed (adults: 750, paediatric: 336). 1007 grafts (92.2%) had single artery (group 1), and 79 (7.8%) grafts had multiple arteries. All arteries were reconstructed in 19 (24%) patients (group 2), while 60 grafts (75.9%) had only one artery reconstructed (group 3). Left lobe (18.8%) and left lateral segments (10.7%) grafts were more likely to have multiple arteries (p = 0.001). The likelihood of reconstructing multiple arteries was similar in all graft types, 27.3% in right and 25% and 21.4% in left lobe and left lateral segments, respectively (p > 0.05). There was no difference in biliary complications (p = 0.85), hepatic artery thrombosis (p = 0.82), and post-surgical hospital stay (p = 0.38) between the three groups. The presence of multiple arteries or their selective reconstruction did not affect survival (p = 0.73). CONCLUSIONS: Multiple arterial inflows are not an uncommon entity and demonstration of good hilar collateralization helps in avoiding unnecessary arterial reconstruction without adverse outcomes.

Radiological tumor density and lymph node size correlate with survival in resectable adenocarcinoma of the pancreatic head: A retrospective cohort study.

INTRODUCTION: Tumors within the pancreatic head show a variable density and enhancement on computerized tomography (CT). The relationship between the radiological appearance of pancreatic adenocarcinoma on CT and survival remains unclear. The aim of this study was to evaluate the relationship between the tumor density on CT and survival. We also evaluated the correlation between lymph node (LN) size and overall survival in patients undergoing pancreaticoduodenectomy for head of pancreas adenocarcinoma. MATERIALS AND METHODS: Case records of patients undergoing pancreaticoduodenectomy for the adenocarcinoma of pancreas head, between 2005 and 2009, were evaluated. CT was interpreted to document tumor density - Hounsfield unit (HU) and LN size of enlarged LNs. Histology was analyzed to review tumor differentiation and LN status. Survival was correlated with LN size and tumor density (HU). RESULTS: Increasing tumor density was significantly associated with an adverse outcome (P = 0.042, hazard ratio [HR] 1.034, 1.002-1.067 95% confidence interval [95% CI]). Patients with well-differentiated tumors had significantly lower tumor density as compared to moderately differentiated tumors (39.00 ± 26.00 vs. 71.31 ± 21.03 HU, P = 0.005). LN size more than 1 cm irrespective of LN status strongly correlated with the survival and was found to be an important prognostic factor (19.37 ± 2.71 months vs. 27.44 ± 2.74 months; P = 0.025; HR 2.70; 1.09-6.68 95% CI). CONCLUSION: Increasing pancreatic tumor density and the lymph nodal size of more than 1 cm are strong predictors of unfavorable overall survival for resectable adenocarcinoma of the pancreatic head. Further studies are required to identify the value of these proposed prognostic factors.

Rare presentation of self-resolving multifocal inflammatory pseudo-tumour of liver.

Inflammatory pseudo-tumour (IPT) of the liver is a rare condition with the appearance of a tumour-like space occupying lesion. Aetiology and natural history is not known for these benign lesions, as they are commonly diagnosed as malignant lesions and frequently undergo surgical resection since spontaneous resolution is very rare. Multifocal IPT involving both lobes of liver are rarely reported. Here we report a unique case of multifocal IPT of the liver which resolved spontaneously within 5 wk period.

Successful management of gastrointestinal haemorrhage associated with ischaemic colonic ulceration in acute pancreatitis with video assisted retroperitoneal debridement.

CONTEXT: Colonic involvement is an uncommon but potentially lethal complication of severe acute pancreatitis and has received little attention in the surgical literature. Such complications can range from localized colonic pathology to widespread ischaemic pancolitis. Treatment options have historically been limited to resection of the affected segment. CASE REPORT: We describe the successful role of video assisted retroperitoneal pancreatic debridement in the management of two cases presenting with major gastrointestinal haemorrhage due to localised colonic ulceration on the background of acute necrotising pancreatitis. CONCLUSION: Video assisted retroperitoneal debridement should be considered early in the management of local colonic complications associated with severe acute necrotising pancreatitis.