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Strengthening mechanisms analysis and tailoring of bimodal grain structures for enhanced strength in CoCrFeMnNi high-entropy alloys

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Rare Metals 2024年第8期43卷 3893-3903页

作者： Jaesoung Lee Seulgi Kim Taehyun Kwon Young ii Kim Suyeon Kim Sung Ho Song Bin Lee Dongju Lee Department of Urban Energyand Environmental EngineeringChungbuk National UniversityCheongju 28644Republic of Korea Division of Advanced Materials Engineering Kongju National UniversityChungnam 330-717Republic of Korea Department of Advanced Materials Engineering for Information and Electronics Integrated-Education Institute for Frontier Science and Technology(BK21 Four)Kyung Hee UniversityYongin17104Republic of Korea

The CoCrFeMnNi high-entropy alloys(HEAs)with a(face-centered cubic) FCC structure has garnered considerable attention for its exceptional ductility and strain hardening ***,its yield strength is insufficient for structural *** this study,strengthening mechanisms in these HEAs were investigated to gain insight into the mechanical properties according to alloy powder ***,we present a novel approach to achieve both high strength and high ductility through the creation of a bimodal structure consisting of both coarse and fine grains via gas atomization and spark plasma sintering processes.A bimodally structured HEA prepared with a mass ratio of 2:8 between coarse particles(75-106 μm) and fine particles(≤25 μm)yielded optimal results,with a strength of 491.95 MPa and elongation of 19.64%.This strength value represents an~41% increase compared with the sample that displayed a fine single microstructure(347.08 MPa for yield strength).The strength enhancement was attributed to the prevention of plastic deformation initiation from the fine particles during *** innovative approach to the creation of HEAs with bimodal structures shows promise for various applications,such as structural components that require a combination of high strength and high ductility.

关键词： High-entropy alloys CrCoFeMoNi Bimodal Gas atomization Mechanical properties

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BMPRⅡ^(+)neural precursor cells isolated and characterized from organotypic neurospheres:an in vitro model of human fetal spinal cord development

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Neural Regeneration Research 2024年第2期19卷 447-457页

作者： Michael W.Weible ii Michael D.Lovelace Hamish D.Mundell Tsz Wai Rosita Pang Tailoi Chan-Ling Bosch Institute Discipline of Anatomy and Histology(F13)University of SydneySydneyNSWAustralia School of Environment and Science Griffith UniversityNathanQLDAustralia Discipline of Medicine Nepean Clinical SchoolFaculty of Medicine and HealthUniversity of SydneyKingswoodNSWAustralia New South Wales Brain Tissue Resource Centre School of Medical SciencesFaculty of Medicine and HealthUniversity of SydneyCharles Perkins Centre(D17)SydneyNSWAustralia

Roof plate secretion of bone morphogenetic proteins(BMPs)directs the cellular fate of sensory neurons during spinal cord development,including the formation of the ascending sensory columns,though their biology is not well ***-ⅡBMP receptor(BMPRⅡ),the cognate receptor,is expressed by neural precursor cells during embryogenesis;however,an in vitro method of enriching BMPRⅡ^(+)human neural precursor cells(hNPCs)from the fetal spinal cord is *** was undertaken on intact second-trimester human fetal spinal cord using antibodies to BMPRⅡand leukemia inhibitory factor(LIF).Regions of highest BMPRⅡ^(+)immunofluorescence localized to sensory *** and meningeal-associated BMPRⅡ^(+)vascular cells were identified in both intact fetal spinal cord and cortex by co-positivity with vascular lineage markers,CD34/*** immunostaining identified a population of somas concentrated in dorsal and ventral horn interneurons,mirroring the expression of LIF receptor/CD118.A combination of LIF supplementation and high-density culture maintained culture growth beyond 10 passages,while synergistically increasing the proportion of neurospheres with a stratified,*** neurospheres were characterized by BMPRⅡ^(+)/MAP2ab^(+/–)/βⅢ-tubulin^(+)/nestin^(–)/vimentin^(–)/GFAP^(–)/NeuN^(–)surface hNPCs surrounding a heterogeneous core ofβⅢ-tubulin^(+)/nestin^(+)/vimentin^(+)/GFAP^(+)/MAP2ab^(–)/NeuN^(–)multipotent *** cultures from tripotential neurospheres contained neuronal(βⅢ-tubulin^(+)),astrocytic(GFAP+),and oligodendrocytic(O4+)lineage ***-activated cell sorting-sorted BMPRⅡ^(+)hNPCs were MAP2ab^(+/–)/βⅢ-tubulin^(+)/GFAP^(–)/O4^(–)in *** is the first isolation of BMPRⅡ^(+)hNPCs identified and characterized in human fetal spinal *** data show that LIF combines synergistically with high-density reaggregate cultures to support the organotypic reorganization of neurospheres,characterize

关键词： BMPRⅡ bone morphogenetic protein histotypic human spinal cord development leukemia inhibitory factor neurosphere organotypic reaggregate sensory columns

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Birds’Diversity in Kalfou Forest Reserve and Its Peripheral Zone, Far North, Cameroon

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Open Journal of Animal Sciences 2024年第2期14卷 137-155页

作者： Ghislain Noé Kougoum Piebeng Simon A. Tamungang Daksala Wansang Jean Tonleu Laurentine Soufo Muhammad Bilal Awa ii Taku Alexis Teguia Department of Biological Sciences Faculty of Science University of Maroua Maroua Cameroon Department of Animal Biology Faculty of Science University of Dschang Dschang Cameroon Department of Forestry and Wildlife Technology College of Technology University of Bamenda Bamenda Cameroon Department of Environmental Sciences Higher Polytechnical Training School University of Maroua Maroua Cameroon Department of Biology Virtual University of Pakistan Rawalpindi Campus Punjab Pakistan Department of Animal Production Faculty of Agronomy and Agricultural Science University of Dschang Dschang Cameroon

The Far North Region of Cameroon is home to a great diversity of bird species, which unfortunately remains very little explored. This work was initiated to establish an inventory of birds and the factors affecting their diversity and distribution for sustainable management in the Kalfou Forest Reserve (KFR) and its periphery. Two methods were used for sampling, linear strip transects from which direct counts and indirect observations were made and the mist netting to complement the first. In total, 2525 birds were observed, including 149 species, belonging to 20 orders and 55 families. Accipitridae had the greatest number of species (11). The species richness was greater in the KFR (117 species) compared to the periphery (95 species). The specific richness was higher in wooded savannah compared to other habitats. Shannon index was significantly higher in the KFR (3.99) compared to that obtained in the periphery (3.80). The value of the Simpson index was higher on the outskirts of the KFR than on the periphery. The indices of species diversity were greater in the wooded savannah compared to other vegetation types. The seasons had no influence on bird diversity. Among the human activities encountered, the pressure indices were more important for grazing (7.3 contacts/km). Human activities have resulted in a significant decrease in specific richness. Six endangered species were encountered, four belonging to the Accipitridae family. The greater bird diversity in the reserve compared to the periphery shows that protected areas are a long-term solution for biodiversity conservation.

关键词： Bird Diversity Habitats Bird Species Human Activities Conservation Kalfou

Thoracoscopy in Cameroon: Indications, Technics and Short Term Results

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Surgical Science 2024年第4期15卷 278-288页

作者： Guy Aristide Bang Richard ii Mbele Fabrice Stephane Arroye Betou Arlette Joelle Moukitek Banaken Amos Bella Ela Charles Mve Mvondo Arthur Essomba Department of Surgery and Specialities Faculty of Medicine and Biomedical Sciences Yaound&#233 I University Yaound&#233 Cameroon Department of Surgery and Specialities Yaound&#233 Teaching Hospital Yaound&#233 Cameroon General Surgery Service Mvog-Ada District Hospital Yaound&#233 Cameroon Department of Cardiothoracic and Vascular Surgery Laquintinie Hospital Douala Cameroon Department of Cardiothoracic and Vascular Surgery Yaound&#233 General Hospital Yaound&#233 Cameroon Cardiac Center Shisong St. Elizabeth Catholic General Hospital Shisong Kumbo Cameroon

Introduction: Thoracoscopy is a video-assisted surgical approach that mirrors the techniques used in thoracotomy. Our aim is to map the current state of thoracoscopy practice in Cameroon’s hospitals. Methods: This was a descriptive study that collected both retrospective and prospective data over 57 months across four hospitals in Cameroon. It included 13 patients and focused on variables such as socio-demographic factors, clinical profiles, surgical procedures, and postoperative follow-up. Results: Thirteen patients, predominantly male (84.6%, n = 11), with a mean age of 37.5 ± 16 years, were enrolled. Alcohol use (61.5%) and smoking (38.5%) were the most common past histories. The major complaints were dyspnea (84.6%) and chest pain (58.3%). The primary surgical procedure was clot-free thoracoscopy in 30.8% of cases, mainly for persistent hemothorax (41.8%). Most surgeries were elective (76.9%) and performed under general anesthesia with selective intubation (61.5%). The most common approach was single-port thoracoscopy (U-VATS) (76.9%), with no reported difficulties;however, one intraoperative incident occurred and was successfully treated. Drainage was performed systematically in all patients, and one case required conversion to open surgery. Postoperative complications were minor (Clavien-Dindo grade I) and mainly consisted of pain, with a mortality rate of 15.4%. No significant association was found between risk factors and the occurrence of complications or postoperative mortality. Conclusion: Thoracoscopy, a novel approach in our context, primarily focuses on minor thoracic surgeries.

关键词： Thoracoscopy Single-Port Hemothorax Cameroon

Clinical Epidemiology and Surgical Treatment of Spontaneous Perforations of the Terminal Ileum: A Multicentre Study in Cameroon

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Surgical Science 2024年第5期15卷 311-320页

作者： Eric Patrick Savom Richard ii Mbele Mahamat Yannick Ekani Boukar Abdal Deudeu Cédric Paterson Atangana Fred Dikongue Dikongue Guy Aristide Bang Marc Leroy Guifo Yaoundé General Hospital Yaound&#233 Cameroon Faculty of Medicine and Biomedical Sciences of the University of Yaoundé I Yaoundé Cameroon Faculty of Health Sciences University of Buea Buea Cameroon Faculty of Medicine and Biomedical Sciences of the University of Dschang Dschang Cameroon Yaoundé Teaching Hospital Yaoundé Cameroon

Background: Perforations of the terminal ileum are a frequent clinical situation and a therapeutic challenge. Surgical treatment is controversial. Several surgical modalities have been proposed and postoperative morbidity and mortality remain high. The aim of this study was to review our experience in the surgical management of perforations of the terminal ileum. Patients and methods: This is a descriptive cross-sectional study with retrospective data collection from January 1, 2017 to December 31, 2021, in five hospitals in Cameroon. Patients’ demographic, clinical presentation, surgical findings and 30-days postoperative outcomes data were collected. Results: We collected 34 files. The sex ratio was 1.4 and the average age was 20.28 years. The average consultation time was 9.1 days. Abdominal pain was present in all our patients. Peritoneal irritation was present in 46 cases (88.5%). The mean time to treatment after admission was 17.5 hours. The perforation was unique in 40 cases (76.9%) and located between 6 and 10 cm from the ileocecal valve in 29 cases (55.8%). Typhoid was the most suspected etiology intraoperatively in 38 cases (73.1%). A simple suture was performed in 18 patients (34.6%), resection with anastomosis in 11 patients (21.2%) and an ileostomy in 5 patients (9.6%). The average length of hospitalization was 21.74 days. Postoperative morbidity and mortality were 32.7% and 17.3% respectively. Conclusion: Perforations of the terminal ileum are common and affect young people. Surgical procedures are varied. Reducing consultation and care times and respecting treatment principles could improve postoperative morbidity and mortality, which remain high.

关键词： Perforation of the Terminal Ileum Simple Suture Resection Morbidity Mortality

Results of Surgical Management of Malignant Obstruction of the Common Bile Duct in Yaoundé

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Surgical Science 2024年第4期15卷 265-277页

作者： Eric Patrick Savom Gaël Tsanga Nomo Richard ii Mbele Mahamat Yannick Ekani Boukar Cédric Paterson Atangana Fred Dikongue Dikongue Guy Aristide Bang Arthur Essomba Yaoundé General Hospital Yaound&#233 Cameroon Faculty of Medicine and Biomedical Sciences of the Universityof Yaoundé I Yaound&#233 Cameroon Faculty of Health Sciences University of Buea Buea Cameroon Faculty of Medicine and Biomedical Sciences of the University of Dschang Dschang Cameroon Yaoundé Teaching Hospital Yaound&#233 Cameroon

Introduction: In Cameroon, surgery remains the only approach in malignant obstructions of the common bile duct (MOCBD) even in palliative situations. The aim of this work was to describe the modalities of surgical treatment of MOCBD, evaluate the results and detect the factors associated with postoperative morbidity and mortality. Patients and Methods: We conducted an analytical observational study, with retrospective data collection from the files of patients operated upon for MOCBD. This was done in four referral hospitals in the city of Yaoundé for a 42-month period spanning from January 1, 2020 to June 30, 2023. Demographic data, clinical presentation, surgical data, and 30-day postoperative outcomes were collected. Results: We collected 71 files. The sex ratio was 1.4 and the mean age was 56 ± 11 years. Fifty-three (53) patients (74.6%) were overweight or obese and 10 patients (14.1%) were hypertensive. A clinical cholestasis syndrome was present in 69 patients (97.2%). Fifty-five (55) patients (77.5%) had a cancer of the head of the pancreas, 8 patients (11.3%) had an extra-hepatic cholangiocarcinoma and 8 patients (11.3%) had an ampullary adenocarcinoma. Eight (8) resections (11.3%) with curative intent had been carried out and in 63 cases (88.7%), surgery was palliative. Postoperative morbidity was 55.7%, influenced by advanced WHO stage (p = 0.02). Postoperative mortality was 25.7%, associated with a high ASA score (p = 0.01). Conclusion: Pancreatic head cancer is the main etiology of malignant obstructions of the common bile duct in Cameroon. Surgical treatment is most often palliative. Postoperative morbidity and mortality are high, influenced by high WHO and ASA scores.

关键词： Malignant Obstruction Common Bile Duct Palliative Treatment Morbidity Mortality

生鲜农产品零售商的区块链技术投资决策与订货策略

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工程管理科技前沿 2024年第5期43卷 9-16页

作者：向泽华王明征李永刚浙江大学管理学院浙江杭州310058 大连理工大学经济管理学院辽宁大连116024

区块链技术在生鲜农产品供应链中已经得到广泛应用。本文以报童模型为基础,研究了零售商在生鲜农产品市场中订货决策以及区块链投资策略问题。在模型中考虑了需求和农产品新鲜度的随机性、区块链的投资成本以及区块链技术的预测精度水... 详细信息

区块链技术在生鲜农产品供应链中已经得到广泛应用。本文以报童模型为基础,研究了零售商在生鲜农产品市场中订货决策以及区块链投资策略问题。在模型中考虑了需求和农产品新鲜度的随机性、区块链的投资成本以及区块链技术的预测精度水平等特征的基础上,比较零售商在使用区块链前后的订货策略和绩效水平,分析区块链为农产品供应链带来的商业价值以及零售商对于区块链的投资策略。研究表明:零售商利用区块链技术可以及时预测到农产品的新鲜度状态,优化了零售商的订货策略,从而在减少食品浪费和提高供应链绩效水平方面发挥重要作用。然而在一些特定情况下,零售商投入过多资源以实现高精度的区块链预测并不是一个最优选择,此时零售商采用低精度的区块链技术也能实现收益的增长。而当区块链投资成本超过特定阈值时,零售商将不会采用区块链技术。

关键词：区块链生鲜农产品供应链报童模型新鲜度投资策略

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海南热带雨林国家公园尖峰岭片区山铜材种群空间分布格局

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林草资源研究 2024年第2期 17-25页

作者：张顺卫李婧涵杨小波李东海黄耀杜春雁商乃演海南大学生态与环境学院海口570228

山铜材(Chunia bucklandioides)为国家二级重点保护野生植物,数量稀少、分布范围狭窄,研究山铜材的种群现状及分布格局对其种群的保护和可持续发展具有重要意义。以海南热带雨林国家公园尖峰岭片区内的山铜材种群为研究对象,采用径级结... 详细信息

山铜材(Chunia bucklandioides)为国家二级重点保护野生植物,数量稀少、分布范围狭窄,研究山铜材的种群现状及分布格局对其种群的保护和可持续发展具有重要意义。以海南热带雨林国家公园尖峰岭片区内的山铜材种群为研究对象,采用径级结构代替年龄结构的方法,将山铜材划分为4个龄级(Ⅰ级、Ⅱ级、Ⅲ级、Ⅳ级),运用成对相关函数g(r)对山铜材种群及其各龄级的空间分布格局及关联性进行分析。研究表明:1)山铜材种群存在假性稳定增长的现象,只能在该生境中繁衍,很难扩大其种群规模;2)山铜材种群在小尺度下呈聚集分布,随着尺度的增加,大部分种群向均匀分布发展,少部分种群呈随机分布和聚集分布趋势;3)不同龄级的个体皆在小尺度下为聚集分布,其中Ⅰ级和Ⅱ级个体聚集程度较大,随着尺度的增加,部分龄级存在均匀分布,最终皆演变为随机分布;4)不同龄级间的空间关联性表明了山铜材主要靠Ⅲ级和Ⅳ级个体扩萌更新,其萌生个体对母树的依赖性强弱为Ⅱ级>Ⅰ级>Ⅲ级>Ⅳ级。因此,未来在山铜材种群的保护中,应以保护母树为主,适当间伐母树周边的萌生苗和清除倒伏枝条萌生苗附近的小型植物,将实生苗进行迁地保护,以此来扩大和保护山铜材野生种群。

关键词：山铜材萌生种群结构空间分布格局空间关联性

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Surgical Management of Perforated Colon Tumours in Yaoundé: A Multicentre Retrospective Review of 30-Day Postoperative Outcome

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Surgical Science 2024年第5期15卷 330-341页

作者： Eric Patrick Savom Richard ii Mbele Colman Tamboh Tankou Mahamat Yannick Ekani Boukar Cédric Paterson Atangana Fred Dikongue Dikongue Daniel Biwole Biwole Guy Aristide Bang Arthur Essomba Yaoundé General Hospital Yaound&#233 Cameroon Faculty of Medicine and Biomedical Sciences University of Yaound&#233 I Yaound&#233 Cameroon Faculty of Health Sciences University of Buea Buea Cameroon Faculty of Medicine and Biomedical Sciences University of Dschang Dschang Cameroon Yaoundé Central Hospital Yaound&#233 Cameroon Yaoundé University Teaching Hospital Yaound&#233 Cameroon

Introduction: Colon cancer is often diagnosed late in our context and there is a high prevalence of complicated forms, this including perforation. The optimal surgical treatment remains controversial. The aim of this study was to improve the short-term postoperative outcomes of patients operated upon for perforated colon cancer, by identifying factors associated with complications occurring within 30 days after surgery. Patients and methods: We carried out an analytical observational study, with a retrospective collection of data from the files of patients operated upon for an in situ tumoral colon perforation. This was done in four referral hospitals in the city of Yaoundé. The period was from the 1st of January, 2012 to the 31st of December, 2021. Cox regression identified the factors associated with postoperative morbidity and mortality. Results: We collected files of 46 patients. The mean age was 54.7 ± 19.9 years with a sex ratio of 1.4. The clinical presentation on admission was dominated by the presence of signs of peritoneal irritation (91.3%) and bowel obstruction (28.3%). The diagnosis was made preoperatively in 16 cases (34.8%). The surgical procedures consisted of colectomy with anastomosis in 28 cases (60.9%) and without anastomosis in 14 cases (30.4%). Postoperative morbidity was 60.9% dominated by surgical site infection (37%). Postoperative mortality was 39.1%. The existence of generalized peritonitis was associated with the occurrence of postoperative complications (p = 0.019). The main factors associated with postoperative mortality were resection with primary anastomosis (p = 0.027), enterocutaneous fistula (p = 0.005). Conclusion: Colic resection with primary anastomosis or ideal colectomy is associated with an increased risk of mortality and should therefore not be performed in this setting.

关键词： Perforated Colon Cancer Postoperative Morbidity and Mortality Colectomy Acute Generalized Peritonitis