Formation Mechanisms of Cracks Formed during Hot Rolling of Free-machining Steel Billets

In this study, cracks formed in the edge side of Bi-S-based free-machining steel billets during hot rolling were analyzed in detail, and their formation mechanisms were clarified in relation with microstructure. Particular emphasis was placed on roles of bands of pearlites or C- and Mn-rich regions and complex iron oxides present in the edge side. Pearlite bands in the cracked region were considerably bent to the surface, while those in the noncracked region were parallel to the surface. This was because the alignment direction of pearlite bands was irregularly deviated up to 45 deg from the normal direction parallel to the surface, while the billet was rolled and rotated at 90 deg in the same direction between rolling passes. On the edge side, where pearlite bands were bent, iron oxides intruded deeply into the interior along pearlite bands, which worked as stress concentration sites during hot rolling and, consequently, main causes of the crack initiation in the rolled billet. On the surface of the wire rod rolled from the cracked billet, a few scabs were found when some protrusions were folded during hot rolling. In order to prevent the cracking in billets and scab formation in wire rods, (1) the increase of rolling passes and the decrease of reduction ratio for homogeneous rolling of billets and (2) the reduction in sulfur content for minimizing the formation and intrusion of complex iron oxides were suggested.X113sciescopu

Cracking Phenomenon Occurring durin Hot Rolling of Bi-containing Free-Cutting steel Rods

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Thermal irritation of teeth during dental treatment procedures

While it is reasonably well known that certain dental procedures increase the temperature of the tooth's surface, of greater interest is their potential damaging effect on the pulp and tooth-supporting tissues. Previous studies have investigated the responses of the pulp, periodontal ligament, and alveolar bone to thermal irritation and the temperature at which thermal damage is initiated. There are also many in vitro studies that have measured the temperature increase of the pulp and tooth-supporting tissues during restorative and endodontic procedures. This review article provides an overview of studies measuring temperature increases in tooth structures during several restorative and endodontic procedures, and proposes clinical guidelines for reducing potential thermal hazards to the pulp and supporting tissues

Liver transplantation from a non–heart-beating donor

Interest in utilizing organs from non–heart-beating donors (NHBDs) has increased because of the organ shortage. However, liver transplantation (LT) from NHBDs has been scarcely performed in Korea because only Maastricht category IV is legally permitted. We present one case of LT from an NHBD with extracorporeal membrane oxygenation (ECMO) support. The case was a 42-year-old male patient with alcoholic liver cirrhosis. The model for end-stage liver disease score was 28. The donor was a 47-year-old female who was diagnosed with brain death due to cerebral infarct, but cardiac arrest occurred before brain death was finally confirmed. Thus, venous-arterial type ECMO was initiated for circulatory support. In the operating room, asystole developed just after ECMO was stopped. After waiting for 5 minutes, cardiac death was declared. It took 6 minutes from skin incision to aorta perfusion. The recipient hepatectomy and graft implantation were performed according to the standard procedures of adult whole LT. The patient recovered from LT uneventfully and has been doing well for 9 years after LT. The use of NHBDs is a method to increase the potential pool of organ donors, thus changes toward enhanced public awareness and acceptance of donating organs, and legal support at the government level are necessary

Institutional standard framework and experience of living donor liver transplantation for overseas non-Korean patients at Asan Medical Center

Background : Liver transplantation (LT) for foreign patients is a sensitive issue because of possibility of transplant tourism and difficulty in posttransplant follow-up. This study describes the institutional standard framework and experience of living donor LT (LDLT) for overseas non-Korean patients in a Korean high-volume LDLT center. Methods : The framework and experience of LDLT for 105 non-Korean patients from 2010 to 2019 were retrospectively investigated. Results : Only 3.1% of patients who underwent LDLT were overseas non-Koreans; of these, 83.8% were from the United Arab Emirates and Mongolia. Selection criteria for recipients and donors were the same as for Korean citizens. Of the 105 recipients, 95 (90.5%) were adults. The most common reasons for transplantation were hepatitis B or C virus-associated liver cirrhosis. Of the 95 adults, 78 (82.1%) received right liver grafts, and 16 (16.8%) received dual grafts. The most frequent donors for adult recipients were sons and daughters, whereas the most frequent donors for pediatric recipients were parents. Of the 10 pediatric patients, eight were from the United Arab Emirates; their common primary diseases were biliary atresia, acute liver failure, hepatoblastoma, and genetic metabolic diseases. The 1-, 3-, and 5-year posttransplant overall patient survival rates in all patients were 96.2%, 92.4%, and 92.4%, respectively. The 5-year overall patient survival rates were 91.8% in adult recipients and 100% in pediatric recipients (P=0.47). Conclusions: LDLT at Korean high-volume LT centers including our institution is safe and effective for non-Korean patients with end-stage liver disease seeking alternatives not available in their own countries

Prolonged hepatic inflow occlusion to reduce bleeding during recipient hepatectomy in living donor liver transplantation

Background : Living donor liver transplantation (LDLT) causes bleeding in recipients during the careful preservation of most perihilar structures during this surgery. This case-control study aimed to analyze the effect of prolonged hepatic inflow occlusion (PHIO) when applied during recipient hepatectomy in LDLT. Methods : The study group comprised patients who underwent PHIO with Model for End-Stage Liver Disease (MELD) scores ranging from 26 to 35 (n=20). The following two control groups were selected according to their MELD scores: the low-MELD score group (MELD scores of 15-20, n=40) and the high-MELD score group (MELD scores of 26-35, n=40). Total dissection time for hepatic mobilization and dissection and blood loss during these procedures were compared between the two groups. Results : In the PHIO study group, mean total dissection time and mean PHIO duration were 226.3±59.4 and 68.2±19.1 minutes, respectively. Twelve patients underwent PHIO twice, and the other eight patients underwent PHIO once. The low-MELD score control group and the PHIO study group showed similar dissection duration (216.0±43.9 vs. 226.3±59.4 minutes, P=0.82) and similar blood loss volume during dissection (2,112.5±1,614.9 vs. 2,350.0±951.9 mL, P=0.17). The high-MELD score control group and the PHIO study group showed similar dissection duration (241.0±41.9 vs. 226.3±59.4 minutes, P=0.71), but the PHIO group showed a significantly lower blood loss during dissection than the high-MELD score group (2,350.0±951.9 vs. 2,815.0±1,813.9 mL, P=0.002). During and after PHIO, no adverse complication was observed, except for transient splanchnic congestion. Conclusions: Our findings suggest that PHIO is a simple effective method to reduce intraoperative bleeding during hepatic mobilization and dissection during LDLT operation requiring difficult dissection

Outcomes of deceased donor liver transplantation from elderly donors

Background : Favorable outcomes achieved after deceased donor liver transplantation (DDLT) suggest that use of elderly donors may be an effective way to expand donor pool. Methods : This was a retrospective analysis of adult DDLT using elderly donors. It was a double-arm study that compared posttransplant outcomes to ascertain whether use of elderly donors (aged ≥76 years) has adverse effects on outcome of DDLT. Elderly donor study group included 14 donors aged ≥76 years and elderly donor control group comprised 39 donors aged 66–75 years. Results : Mean donor age of the study and control groups was 78.2±3.1 years and 68.9±2.7 years, respectively (P<0.001). Other clinical parameters were comparable between these two donor groups. The 1-, 3-, and 5-year graft survival rates in the elderly study group were 83.6%, 59.7%, and 59.7%, respectively, and those in the elderly control group were 79.4%, 68.1%, and 59.6%, respectively (P=0.97). The overall 1-, 3-, and 5-year survival rates after donation from elderly study group were 83.6%, 59.7%, and 59.7%, respectively, and those after donation from control group were 79.3%, 72.1%, and 64.1%, respectively (P=0.74). Regarding overall patient survival, univariate analysis identified pretransplant requirement for ventilator support (P=0.021) and pretransplant renal replacement therapy (P=0.025) as statistically significant risk factors; however, neither was significant on multivariate analysis. Conclusions: The results of this study suggest that using an elderly donor graft might not worsen the posttransplant outcomes significantly; thus, advanced age per se may not be an exclusion criterion for organ donation

Prognosis of hepatic epithelioid hemangioendothelioma after living donor liver transplantation

Background : Epithelioid hemangioendothelioma (EHE) is a rare borderline vascular tumor. Due to its rarity and protean behavior, the optimal treatment of hepatic EHE has not yet been standardized. This single-center study describes outcomes in patients with hepatic EHE who underwent living donor liver transplantation (LDLT). Methods : The medical records of patients who underwent LDLT for hepatic EHE from 2007 to 2016 were reviewed. Results : During 10-year period, four patients, one man and three women, of mean age 41.3±11.1 years, underwent LDLT for hepatic EHE. Based on imaging modalities, these patients were preoperatively diagnosed with EHE or hepatocellular carcinoma, with percutaneous liver biopsy confirming that all four had hepatic EHE. The tumors were multiple and scattered over entire liver, precluding liver resection. Blood tumor markers were not elevated, except that CA19-9 and des-γ-carboxy prothrombin was slightly elevated in one patient. Mean model for end-stage liver disease score was 10.8±5.7. All patients underwent LDLT using modified right liver grafts, with graft-recipient weight ratio of 1.11±0.19, and all recovered uneventfully after LDLT. One patient died due to tumor recurrence at 9 months, whereas the other three have done well without tumor recurrence, resulting in 5-year disease-free and overall patient survival rates of 75% each. The patient with tumor recurrence was classified as a high-risk patient based on the original and modified hepatic EHE-LT scoring systems. Conclusions: LDLT can be an effective treatment for patients with unresectable hepatic EHEs that are confined within the liver and absence of macrovascular invasion and lymph node metastasis

Cross-sectional analysis of immunosuppressive regimens focused on everolimus after liver transplantation in a Korean high-volume transplantation center

Background : The mammalian target of the rapamycin inhibitor has dual inhibitory effects on cell growth and angiogenesis. This study aimed to analyze the usage of everolimus on actual immunosuppression (IS) regimens through a cross-sectional study in a high-volume liver transplantation (LT) center. Methods : Our institutional LT database was searched for adult patients who underwent primary LT surgery between January 2010 and December 2016. We identified 2,093 LT recipients with observation periods of 1 to 8 years.Results : We divided the 2,093 recipients into three groups according to the posttransplant follow-up period as follows: group A (12-36 months; n=680), group B (37-60 months; n=560), and group C (>60 months; n=853). The individual IS agents were tacrolimus in 1,807 patients (86.3%), cyclosporine in 169 patients (8.1%), mycophenolate mofetil (MMF) in 1,310 patients (62.6%), and everolimus in 115 patients (5.5%). The most common IS regimens were tacrolimus-MMF combination and tacrolimus monotherapy, regardless of the posttransplant period. Patients with pretransplant malignancies were administered everolimus more frequently than those without pretransplant malignancies (P<0.001). In 102 patients with hepatocellular carcinoma recurrence or de novo malignancies, IS regimens included everolimus-tacrolimus in 41 patients (40.2%), tacrolimus-MMF in 27 patients (26.4%), tacrolimus in 20 patients (19.6%), MMF in 10 patients (9.8%), cyclosporine in three patients (2.9%), and cyclosporine-MMF in one patient (1.0%).Conclusion : s: Administration of everolimus after LT has been gradually increasing with the expansion of indications in our institutional practice. Currently, the role of everolimus is minimal and not comparable to that of tacrolimus, but it has a unique position in the field of IS after LT