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ANALYZING THE DURATION OF SUCCESS AND FAILURE IN MARKOV-MODULATED BERNOULLI PROCESSES
No full textA Markov-modulated Bernoulli process is a generalization ofa Bernoulli process in which the success probability evolves over time according to a Markov chain. It has been widely applied in various disciplines for modeling and analysis of systems in random environments. This paper focuses on providing analytical characterizations of the Markov-modulated Bernoulli process by introducing key metrics, including success period, failure period, and cycle. We derive expressions for the distributions and the moments of these metrics in terms of the model parameters
Clathrate hydrate formation in the presence of sodium lignin sulfonate
No full textIn this communication, the prediction of gas hydrate formation conditions in the presence of sodium lignin sulfonate is predicted using two thermodynamic models. The first model employs the Peng-Robinson equation of state for the vapor phase, the UNIQUAC model for the activity coefficient of water, and Henry’s law constants for predicting gas solubility. In this model, sodium lignin sulfonate is treated as a molecule. The second model introduces an extended Peng-Robinson equation of state, tailored for electrolyte solutions, to calculate gas solubility and fugacity of components, with the activity coefficient of water set to unity. In this model, it is assumed that sodium lignin sulfonate and water undergo a reaction, resulting in the production of lignin sulfonic acid, sodium, and hydroxide ions. Both models are integrated with the van der Waals-Platteeuw theory to determine the conditions for gas hydrate formation. The results from the first model reveal that, for a given gas at different temperatures and sodium lignin sulfonate concentrations, the surfactant can exhibit inhibitory or promoting effects. Conversely, the second model suggests that, across all studied gases, an increase in sodium lignin sulfonate concentration corresponds to an elevation in hydrate formation pressure, signifying an improvement in inhibitory impact
The Impact of Elevated Anal Sphincteric Tone on Anastomotic Leakage in Robotic Rectal Resection
No full textSince the introduction of total mesorectal excision (TME) in 1982, surgical approaches for low rectal cancer have evolved, leading to reduced recurrence rates and improved survival. However, despite these advancements, anastomosis leakage remains a significant postoperative complication with incidence rates ranging from 2.5% to 21%. This study aims to explore the correlation between preoperative manometry results and surgical outcomes, particularly focusing on anastomosis leakage in robotic surgery. Clinical data of patients who underwent robot-assisted low anterior resection or ultra-low anterior resection for rectal cancer at Asan Medical Center from April 2014 to July 2022 were reviewed. Patient demographics, postoperative outcomes, including anastomosis leakage, and preoperative anorectal manometry, focusing on maximum resting pressure (MRP) and maximum squeezing pressure (MSP) data, was analyzed. Of the 248 patients analyzed, complications were observed in 42 patients (16.9%), with anastomosis stricture being the most common. Anastomosis leakage occurred in 10 cases, necessitating additional surgical interventions. The MRP in patients with and without leakage had shown no significant differences (p=0.297), while MSP showed significant differences (p=0.036). MRP exceeding the upper limit of 70 mmHg showed significant differences in anastomosis leakage(p=0.045). Rectal compliance (RC) in patients with and without leakage also showed significant differences (p=0.030). MRP over the upper limit of 70 mmHg, MSP over 224 mmHg, or RC over 2.25 mL/mmHg may have an impact on anastomosis leakage based on receiver operating characteristic (ROC) curve analysis. In planning robotic surgery for rectal tumor, the results of anorectal manometry may help operator to decide whether to create ileostomy to reduce the risks regarding anastomosis leakage.|1982년 전직장간막절제술(TME)이 소개된 이후로 저위부 직장암의 수술방법은 진화해 왔 으며, 이로 인해 재발률이 감소하고, 생존률이 향상되었다. 그러나 발전에도 불구하고, 문합 부 누출은 2.5%에서 21%까지 다양한 발생률로 중대한 수술 후 합병증 중 하나로 남아 있 다. 본 연구는 수술 전 직장 항문 내압 검사의 결과와 수술 결과 간의 상관관계를 탐구하고, 특히 로봇 수술에서의 문합부 누출에 중점을 두었다. 본 연구에서는 2014년 4월부터 2022년 12월까지 직장암으로 진단되어 로봇 저위전방 절 제술 및 초저위전방 절제술을 시행한 환자의 임상자료를 토대로 연구를 진행하였다. 환자의 인구 통계학적 정보, 수술 후 결과 (문합부 누출 포함), 그리고 수술 전 직장 항문 내압 검 사 결과, 특히 최대 안정 압력 (MRP) 및 최대 압축 압력 (MSP) 데이터를 중점적으로 분석 하였다. 분석한 248명의 환자 중 42 (16.9%)에서 합병증이 발생하였으며, 그 중에서 가장 흔한 것 은 문합부 협착이었다. 문합부 누출은 10건에서 발생하여 추가적인 수술적 개입이 필요했다. 누출이 발생한 환자와 그렇지 않은 환자 사이에서 MRP 값에서는 유의한 차이를 보이지 않 았으나, MRP가 정상 값의 최고 값인 70 mmHg 이상인 경우 누출이 유의하게 증가하는 현상 을 확인하였다. MSP의 경우 문합부 누출과 연관성을 보였으나, 정상 값을 대입하였을 때에 는 유의한 차이를 찾을 수 없었고, 직장 유연도 (RC)의 경우 유의한 차이를 보였다. ROC curve를 분석하였을 때, MRP 70 mmHg 이상이거나 MSP 224 mmHg 이상, RS 2.25 mL/mmHg 이상인 경우 문합부 누출과 연관이 있을 수 있음을 알게 되었다. 직장암의 로봇 절제술을 계획할 때 직장 항문 내압 검사의 결과는 수술자가 문합부 누출 의 위험을 낮추기 위해 장루를 만들지 여부를 결정하는 데 도움을 줄 수 있을 것으로 보인 다. 본 연구 결과 수술 전 항암 방사선 치료에 완전 관해를 보인 직장암에서 국소 절제의 시행은 타당한 치료가 될 수 있음을 확인할 수 있었다.Maste
Risk Factors for the Mortality of Patients With Coronavirus Disease 2019 Requiring Extracorporeal Membrane Oxygenation in a Non-Centralized Setting: A Nationwide Study
No full textBackground: Limited data are available on the mortality rates of patients receiving extracorporeal membrane oxygenation (ECMO) support for coronavirus disease 2019 (COVID-19). We aimed to analyze the relationship between COVID-19 and clinical outcomes for patients receiving ECMO.
Methods: We retrospectively investigated patients with COVID-19 pneumonia requiring ECMO in 19 hospitals across Korea from January 1, 2020 to August 31, 2021. The primary outcome was the 90-day mortality after ECMO initiation. We performed multivariate analysis using a logistic regression model to estimate the odds ratio (OR) of 90-day mortality. Survival differences were analyzed using the Kaplan-Meier (KM) method.
Results: Of 127 patients with COVID-19 pneumonia who received ECMO, 70 patients (55.1%) died within 90 days of ECMO initiation. The median age was 64 years, and 63% of patients were male. The incidence of ECMO was increased with age but was decreased after 70 years of age. However, the survival rate was decreased linearly with age. In multivariate analysis, age (OR, 1.048; 95% confidence interval [CI], 1.010-1.089; P = 0.014) and receipt of continuous renal replacement therapy (CRRT) (OR, 3.069; 95% CI, 1.312-7.180; P = 0.010) were significantly associated with an increased risk of 90-day mortality. KM curves showed significant differences in survival between groups according to age (65 years) (log-rank P = 0.021) and receipt of CRRT (log-rank P = 0.004).
Conclusion: Older age and receipt of CRRT were associated with higher mortality rates among patients with COVID-19 who received ECMO
New anti-mesenteric delta-shaped stapled anastomosis: Technical report with short-term postoperative outcomes in patients with Crohn's disease
No full textBackground: Medical treatment for Crohn's disease (CD) has continuously improved, which has led to a decrease in surgical recurrence rates. Despite these advancements, 25% of patients will undergo repeat intestinal surgery. Recurrence of CD commonly occurs on the mesentery side of the anastomosis site.
Aim: To compare the new anti-mesenteric side-to-side delta-shaped stapled anastomosis (DSA) with the conventional stapled functional end-to-end anastomosis (CSA).
Methods: This retrospective study included CD patients who underwent ileo-ileal or ileo-colic anastomosis between January 2020 and December 2023. The DSA technique employed a stapler to maintain the concept of anti-mesentery side-to-side anastomosis by performing a 90° vertical closure of the open window compared with the CSA technique. At the corner where the open window is closed, the DSA avoids forming a pouch and creates an anastomosis resembling a delta shape within the intestinal lumen. We compared demographics, preoperative condition, operative findings, and operative outcomes for the two techniques.
Results: The study included 175 patients, including 92 in the DSA group and 83 in the CSA group. The two groups were similar in baseline characteristics, preoperative medical treatment, and operative findings except for the Montreal classification location. The 30-days postoperative complication rate was significantly lower in the DSA group compared with the CSA group (16.3% vs 32.5%, P = 0.009). Ileus incidence was significantly lower in the DSA group than in the CSA group (4.3% vs 14.5%, P = 0.033), and the hospital stay was shorter in the DSA group than in the CSA group (5.67 ± 1.53 days vs 7.39 ± 3.68 days, P = 0.001).
Conclusion: The DSA technique was feasible and showed comparable postoperative outcomes with lower short-term complications compared with the CSA technique. Further studies on CD recurrence and long-term complications are warranted
STUDY ON LATTICE STRUCTURES USING ADDITIVE MANUFACTURING AND ITS APPLICATION ON CONFORMAL COOLING CHANNEL FOR HOT STAMPING
No full textThis study investigates the design, manufacturing, and application of lattice structures produced via additive manufacturing, focusing on their integration into conformal cooling channels for hot stamping dies. Lattice structures, known for their high strength-to-weight ratio, enhanced load distribution, and superior thermal management, present a promising solution for optimizing the performance of hot stamping molds. Additive manufacturing techniques were employed to fabricate the lattice structures with high precision.
The mechanical properties of an additively manufactured (AMed) FCCXYZ lattice structure were experimentally investigated across various materials. Lattice structures with relative densities (RD) ranging from 0.11 to 0.36 exhibited different compressive failure modes depending on the RD. A layer-by-layer collapse mode is observed at low relative density (RD), whereas a bulk failure mode is observed at high RD. The study observed a layer-by-layer collapse mode at low relative density (RD) and a bulk failure mode at high RD. These findings will be a valuable reference for designing energy-absorbing components in metal additive manufacturing (AM).
The investigation aims to explore the design principles of additively manufactured (AMed) lattice structural conformal cooling channels for hot stamping applications. These structures offer structural stiffness, serve as thermal fins, and facilitate the occurrence of turbulent flow in the channel. To evaluate heat transfer and cooling performance, three different surface area densities with the same relative density were examined. Computational fluid dynamics was employed to analyze the coolant flow within the lattice structures with varying surface area densities. Both experimental and computational findings demonstrate that selecting the appropriate surface density for the lattice structure can enhance cooling performance while upholding a constant relative density. This directly influences the weight reduction and stiffness of the cooling die.Docto
Impact of Interactional Justice on Long-Term Orientation and Logistics Performance in the Supply Chain
No full textThe aim of this study is to empirically analyze the impact of justice on long-term orientation and logistics performance in the relationships between firms within the supply chain. Specifically, justice is categorized into distributive justice, procedural justice, and interactional justice. This study particularly concentrates on interactional justice, which pertains to the quality of interpersonal treatment. To investigate their correlation, a survey was conducted among employees working in departments related to supply chains in South Korea, resulting in a total of 350 valid questionnaire responses. Subsequently, the hypotheses were assessed using structural equation modeling with SPSS 18.0 and AMOS 18.0. The findings of the study are as follows: The subfactors of interactional justice, such as interpersonal justice and informational justice, both had a positive impact on long-term orientation. Furthermore, long-term orientation positively influenced logistics performance. Based on the aforementioned results, the following conclusions can be drawn: Long-term orientation among firms in the supply chain plays a pivotal role in enhancing logistics performance. Given that the perception of justice heightens the likelihood of such long-term orientation, firms in the supply chain must take this relationship into careful consideration
Development and characterization of orthotopic xenograft humanized mouse models for ovarian cancer to evaluate the efficacy of immuno-oncology drugs and explore resistance mechanisms
No full textBackground: Although immunotherapy has not yet been as successful in ovarian cancer (OC), it holds promise as a therapeutic approach. Preclinical models of OC are necessary to evaluate the efficacy of immuno-oncology (IO) drugs targeting human immune components but have been currently underexploited. Developing mouse models with a humanized (Hu) immune system could enhance our understanding of the human immune response to IO drugs, which have so far shown limited effectiveness in OC. This study aimed to establish a Hu mouse model of OC that mimics the OC tumor microenvironment (TME) with a human immune system. Methods: OC xenograft models were established in CD34+ Hu-mice by intraperitoneal injection with luciferase-expressing SKOV-3 Luc and OVCAR-3 Luc OC cells. Tumor growth was monitored using bioluminescence imaging (BLI), and the efficacy of PD-1 blockade with pembrolizumab was assessed in the SKOV-3 Luc Hu-mouse model. The immune profiles of the tumors were examined using colorimetric immunostaining and flow cytometry. RNA-seq data were also analyzed to explore the gene expression signature of pembrolizumab non- responsive tumors. Results: Tumor formation and growth were confirmed by increased BLI in both OC orthotopic xenograft Hu-mice models. Human lymphocyte and myeloid cell subsets were detected in the tumors, draining lymph nodes, blood, and spleens of these models. The SKOV-3 Luc tumor- bearing Hu-mice did not respond to pembrolizumab monotherapy. These tumors in this model exhibited a high prevalence of tumor-infiltrating macrophages. The tumors within intraperitoneal cavity of Hu-mice treated pembrolizumab showed lower levels of CD8+ T cells, memory B cells, and plasma cells, and higher levels of naïve M0 macrophages and activated mast cells compared to tumors in the PBS control group. Moreover, increased expression of Histone deacetylases (HDAC) class I target genes, genes associated with epithelial- mesenchymal transition (EMT), and fibroblasts were identified in tumors of pembrolizumab- treated Hu-mice. Conclusion: This study confirmed the successful growth of SKOV-3 Luc and OVCAR-3 Luc OC cells in the peritoneal cavity of Hu-mice. The two OC xenograft Hu-mouse models established in this study serves as a valuable resources for investigating the efficacy of IO drugs.Docto
Visible-Light Photoredox Catalyzed Alkylation of Imine Using Alcohol as a Radical Precursor
No full text이민은 아민 합성에서 중요한 중간체이다. 아민은 농약 및 의약품에서 생물학적 활성 화합물의 합성을 위한 공급원료 화학물질 및 빌딩 블록으로 널리 사용된다. 전통적으로 아민은 친핵체로서 유기금속을 사용하여 이민 부가 반응에 의해 합성된다. 지난 10년 동안 알킬 트리플루오로보레이트 및 실리케이트와 같은 다양한 라디칼 전구체를 사용하여 아민을 제조하기 위해 가시광선 광촉매 반응이 개발되었다. 여기서 우리는 가시광선 광촉매 하에서 PCET 메커니즘을 통해 벤질 알코올을 알킬 라디칼 전구체로 사용하는 아민 합성에 대한 새로운 전략을 보고한다. 광범위한 알킬 아민이 양호한 수율에서 우수한 수율로 수득되었다. 이 전략은 또한 금속이 없는 광촉매를 사용하여 온화한 조건에서 수행되었다.|Imines are important intermediates in the synthesis of amine scaffolds. The amines are widely used as feedstock chemicals and building blocks for synthesis of biologically active compounds in agrochemicals and pharmaceuticals. Traditionally, amines are synthesized by imine addition reactions using organometallics as nucleophiles. In the past decade, visible light photoredox-catalyzed imine addition reactions have been developed to prepare amines using various radical precursors, such as alkyl trifluoroborates and silicates. Herein, we report a new strategy for the synthesis of amines using benzyl alcohols as alkyl radical precursors via the PCET mechanism under photoredox catalysis. A wide range of alkyl amines were obtained in good to excellent yields. This strategy was also conducted under mild conditions using a metal-free photocatalyst.Maste
Economic Order Quantity Model Under Conditions of Accounts Payables
No full textIn this paper, we study an EOQ model that a retailer can utilize when a supplier offers a certain level of annual accounts payable to a retailer as a trade credit policy. The accounts payable method is based on a one-year calendar year, and allows retailers to purchase products on credit without interest up to a certain level of accounts payable. At the end of the year, the retailer must pay off the accounts payable. However, almost all inventory management studies incorporate delay in payment as a trade credit policy into their inventory models. We develop an EOQ model that reflects the accounts payable. Numerical examples are used to verify the validity of the model, and it is found that similar results are obtained compared to the EOQ model reflecting the delay in payment. Furthermore, we present managerial insights from the in-depth analysis: (1) The accounts payable provided by supplier proportionally affects the retailer"s cost savings, but does not significantly affect the retailer"s economic order quantity; (2) Some supply contracts between the supplier and retailer are required for them to benefit jointly