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Electrocatalytic hydrogen peroxide formation on mesoporous non-metal nitrogen-doped carbon catalyst

Journal of Energy Chemistry 2016年第2期25卷 249-255页

作者： Frédéric Hasché Mehtap Oezaslan Peter Strasser Tim-patrick Fellinger Technische Universitat Berlin Department of Chemistry10623 BerlinGermany Max Planck Institut fur Kolloid-und Grenzfliichenforschung Department of Colloids14424 PoadamGermany Carl von Ossietzky University of Oldenburg Department of ChemistryElectrocatalysis26111 OldenburgGermany

direct electrochemical formation of hydrogen peroxide（H2O2） from pure O2 and H2on cheap metal-free earth abundant catalysts has emerged as the highest atom-efficient and environmentally friendly reaction pathway and is therefore of great interest from an academic and industrial point of view. Very recently,novel metal-free mesoporous nitrogen-doped carbon catalysts have attracted large attention due to the unique reactivity and selectivity for the electrochemical hydrogen peroxide formation [1–3]. In this work,we provide deeper insights into the electrocatalytic activity, selectivity and durability of novel metal-free mesoporous nitrogen-doped carbon catalyst for the peroxide formation with a particular emphasis on the influence of experimental reaction parameters such as p H value and electrode potential for three different electrolytes. We used two independent approaches for the investigation of electrochemical hydrogen peroxide formation, namely rotating ring-disk electrode（RRdE） technique and photometric UV–VIS technique. Our electrochemical and photometric results clearly revealed a considerable peroxide formation activity as well as high catalyst durability for the metal-free nitrogen-doped carbon catalyst material in both acidic as well as neutral medium at the same electrode potential under ambient temperature and pressure. In addition, the obtained electrochemical reactivity and selectivity indicate that the mechanisms for the electrochemical formation and decomposition of peroxide are strongly dependent on the p H value and electrode potential.

关键词： Electrochemical hydrogen peroxide formation Selectivity Mesoporous nitrogen-doped carbon Green synthesis Electrocatalysis Metal-free catalysis

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变母线电压的LLC高压电容充电电源设计

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强激光与粒子束 2024年第2期36卷 93-99页

作者：曾宇轩菲华•帕兰斯于克训谢贤飞华中科技大学电气与电子工程学院武汉430074

提出了一种两级式可变母线电压的高压电容充电电源技术方案,该拓扑在半桥LLC谐振电路的基础上增加了一级图腾柱无桥功率因数校正(PFC)电路,通过改变母线电压来解决传统LLC谐振电源在输出更高电压时,工作频率变化范围过大带来的充电效率... 详细信息

提出了一种两级式可变母线电压的高压电容充电电源技术方案,该拓扑在半桥LLC谐振电路的基础上增加了一级图腾柱无桥功率因数校正(PFC)电路,通过改变母线电压来解决传统LLC谐振电源在输出更高电压时,工作频率变化范围过大带来的充电效率下滑的问题。由于图腾柱电路本身具备功率因数校正的功能,该电源设计还拥有能够直接从电网取电而不影响电网电能质量的优势。首先介绍了本电源设计中两部分的电路拓扑和工作原理,采用等效电阻法分析了电容负载下的电源输出特性。针对前级图腾柱电路设计了双环控制器以实现对母线电压和功率因数的控制,针对后级LLC电路提出了比例积分(PI)加低通滤波的恒流控制器以降低高频噪声带来的不利影响。最后通过模型构建与仿真分析,研究了高压电容充电电源3000 V/1 A时的充电特性,验证了本电源技术方案、设计和控制策略的可行性。

关键词：图腾柱无桥功率因数校正变母线电压 LLC谐振变换器双闭环控制恒流控制高压电容充电

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Management and Outcome of Urethral Strictures at Two Tertiary Health Facilities in Cameroon

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Open Journal of Urology 2024年第8期14卷 435-446页

作者： Martin divine Mokake divine Enoru Eyongeta Ekani Mahamat Ekani diana Nunga Theophile Chunteng Nana Ntungwetape Ngwane Mwambo Nalova Elroy patrick Weledji Chichom Alain Mefire Marcellin Ngowe Ngowe department of Surgery and Specialties Faculty of Health Sciences University of Buea Buea Cameroon department of Surgery Regional Hospital Buea Buea Cameroon department of Surgery Regional Hospital Limbe Limbe Cameroon department of Surgery Douala General Hospital Douala Cameroon

Introduction and Objectives: Urethral stricture is a reduction in the caliber of the urethral lumen impeding the outflow of urine. It predominantly affects males. The disease burden is severe in our milieu where access to specialized care is limited. Our goal was therefore to assess the management and outcome of male urethral stricture at two tertiary hospitals in douala, Cameroon. Materials and Methods: This was a hospital-based retrospective study of patients managed for urethral stricture over 5 years (January 1st, 2017 to december 31st, 2021) at the douala General and Laquintinie Hospitals. data on sociodemographic, clinical, paraclinical, and treatment options were extracted using pre-structured forms. data was analyzed using Statistical Package for Social Sciences (SPSS) version 28. Statistical significance was set at p-value Results: We exploited 130 medical records. The mean age of patients was 46.5 years. dysuria and weak urine stream were the major presenting complaints (63.8% and 23.8% respectively). The etiology of urethral stricture was iatrogenic in 42.3% of cases. The strictures were mostly single (89.8%), and the bulbar urethra was most affected (46.9%). 28 patients had urinary tract infections and the most frequently isolated germ was E. coli in 29.6%. direct visual internal urethrotomy (dVIU) was performed in 42.3% of cases. Surgery, especially excision and primary anastomosis (EPA) was done in 28.5% of cases. Major complications were wound infection, acute kidney injury (AKI), and urethrocutaneous fistulae affecting 3.1, 2.3, and 1.5% of cases respectively. The recurrence rate was 17% with a mortality rate of 0.08%. Conclusion: Urethral stricture is common in our adult male population. The cause is mainly iatrogenic and the bulbar urethra is most affected. Minimally invasive and open reconstruction are frequently used treatment options with significant recurrence rates in the long term.

关键词： Urethral Stricture Management Outcomes

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Assessment of the Vaccination Status of Children Aged 6 to 30 Months in a Tertiary Level Health Care Center in Côte d’Ivoire

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Open Journal of Pediatrics 2024年第3期14卷 536-546页

作者： Yenan John patrick Kpangni Jean Bertrand Yao Kouassi Christian Yeboua Yao Kossonou Roland Aka-Tanoh Koko Aude Hélène Avi-Siallou Christelle Honorine Asse Kouadio Vincent department of Pediatrics University Teaching Hospital of Bouake Bouake Ivory Coast Unit Pediatric Surgery University Teaching Hospital of Bouake Bouake Ivory Coast

Introduction: Vaccination coverage in Côte d’Ivoire over the period 2011 to 2015 was below the target of 95% for all antigens. The objective of this study was to analyze the vaccination status of children aged 6 to 30 months with a view to improving vaccination coverage. Patients and Methods: This was a descriptive cross-sectional study which took place from June to September 2018 in a tertiary health center, focusing on children aged 6 to 30 months with a correctly completed health record. The parameters studied were sex, age, educational level of mothers, dates of vaccine administration and reason for missed vaccination opportunities. Results: We retained 212 children. The sex ratio was 1.21 and 93% had received the BCG vaccine before the age of 1 month. The average ages of combined and co-administered vaccines for the 1st and 2nd doses were 7.66 ± 3.81 and 12.88 ± 3.95 weeks, respectively. The median was 16.57 weeks for the 3rd dose. The proportion of vaccinated subjects was greater than 90% for the BCG vaccine and the 3 doses of combined vaccines, and 77% for the yellow fever and measles vaccines. The reasons for non-vaccination were attributable to the children’s parents and health facilities. Conclusion: Improving vaccination coverage requires regular supply of vaccines to centers, and the involvement of all health professionals, community and religious leaders in the vaccination awareness process.

关键词： Children Vaccination Coverage Missed Opportunities

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Investigation of Acoustomagnetoelectric Effect in Bandgap Graphene by the Boltzmann Transport Equation

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World Journal of Condensed Matter Physics 2024年第1期14卷 10-20页

作者： Raymond Edziah Samuel S. Bentsiefi Kwadwo dompreh Anthony Twum Emmanuel Kofi Amewode patrick Mensah-Amoah Ebenezer T. Tatchie Cynthia Jebuni-Adanu Samuel Y. Mensah department of Physics University of Cape Coast Cape Coast Ghana department of Physics Education University of Education Winneba Ghana

We study the acoustomagnetoelectric (AME) effect in two-dimensional graphene with an energy bandgap using the semiclassical Boltzmann transport equation within the hypersound regime, (where represents the acoustic wavenumber and is the mean free path of the electron). The Boltzmann transport equation and other relevant equations were solved analytically to obtain an expression for the AME current density, consisting of longitudinal and Hall components. Our numerical results indicate that both components of the AME current densities display oscillatory behaviour. Furthermore, geometric resonances and Weiss oscillations were each defined using the relationship between the current density and Surface Acoustic Wave (SAW) frequency and the inverse of the applied magnetic field, respectively. Our results show that the AME current density of bandgap graphene, which can be controlled to suit a particular electronic device application, is smaller than that of (gapless) graphene and is therefore, more suited for nanophotonic device applications.

关键词： Boltzmann Transport Equation Acoustomagnetoelctric Effect Surface Acoustic Wave Gapless Graphene Weiss Oscillations

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基于ddQN强化学习的沥青路面养护决策

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粉煤灰综合利用 2024年第4期 147-153页

作者：石文康徐勋倩康峰沂顾钰雯 GANHOUEGNON Eric patrick 南通大学交通与土木工程学院南通市公路事业发展中心

通过ddQN强化学习的方法开展路面养护决策分析，以路面长期效益费用比的最大化为目标构建养护决策模型，计算出效益费用比更优的养护方案。模型以道路条数和使用年限为状态特征，以四种养护措施为动作空间，以路面养护效益与资金比值作... 详细信息

通过ddQN强化学习的方法开展路面养护决策分析，以路面长期效益费用比的最大化为目标构建养护决策模型，计算出效益费用比更优的养护方案。模型以道路条数和使用年限为状态特征，以四种养护措施为动作空间，以路面养护效益与资金比值作为奖励，构建了一种动作选择策略，使养护方案满足最低使用要求。结果表明：基于ddQN养护决策模型的收敛速度比dQN模型快1倍，计算出的养护方案具有较高效益费用比，路面处于优良状态。

关键词：沥青路面路面养护决策深度强化学习养护方案

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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

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Streamlined CFd simulation framework to generate wind-pressure coefficients on building facades for airflow network simulations

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Building Simulation 2021年第4期14卷 1189-1200页

作者： Timur dogan patrick Kastner Cornell University Department of ArchitectureEnvironmental Systems LaboratoryEast Sibley HallIthacaNY14850USA

Building energy modeling software generally comes with capable airflow network solvers for natural ventilation evaluation in multi-zone building energy models. These approaches rely on arrays of pressure coefficients representing different wind directions derived from simple box-shaped buildings without contextual obstructions. For urban or obstructed sites, or more complex building shapes, however, further evaluation is needed to avoid geometric oversimplification. In this study, we present an automated and easy-to-use simulation workflow for OpenFOAM-based exterior airflow simulations to generate arrays of pressure coefficients for arbitrary building shapes and contextual situations. The workflow is compared to other methods commonly used to obtain pressure coefficients for natural ventilation analysis. Finally, we assess for which climate zones and building types modelers should rely on more accurate CFd-based pressure coefficients and where it may be justifiable to rely on easier and readily available analytical approaches to determine pressure coefficients. Results suggest that existing workflows lead to significant error in predicted comfort hours for climates in the Global South and modelers should consider CFd-based facade pressure coeficients.

关键词： natural ventilation airflow networks EnergyPlus pressure coefficients computational fluid dynamics

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Cardiac Surgery at Yaoundé General Hospital by a Local Team: Activity Report from September 2022 to January 2024

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World Journal of Cardiovascular Surgery 2024年第6期14卷 87-94页

作者： Laurence Carole Ngo Yon Charles Mve Mvondo Hermann Nestor Tsague Kengni Zephanie Kobe Fokalbo Sépolin Lowe Mireille dakleu Alain patrick Menanga William Ngatchou djomo Vincent de Paul djientcheu department of Cardiothoracic and Vascular Surgery Yaound General Hospital Yaound Cameroon department of Surgery and Specialities Faculty of Medicine and Pharmaceutical Sciences University of Douala Douala Cameroon department of Clinical Sciences Faculty of Medicine and Pharmaceutical Sciences University of Douala Douala Cameroon department of Clinical Sciences Faculty of Medicine and Biomedical Sciences University of Yaound Yaound Cameroon department of Surgery and Specialities Faculty of Medicine and Biomedical Sciences University of Yaound Yaound Cameroon

Introduction: The practice of cardiac surgery (CS) in sub-Saharan Africa faces a number of challenges. We report on the surgical activities of the first 17 months of the program launched at the Yaoundé General Hospital (YGH), describing the types of interventions and the early results. Patients and Methods: This was a descriptive cross-sectional study including patients who underwent CS from September 2022 to January 2024 at the YGH. Clinical, operative and postoperative data were collected and analysed retrospectively by R software. Results: A total of 37 patients underwent CS during the study period, divided into 23 (62.2%) open-heart and 14 (37.8%) closed-heart cases. Males predominated (sex ratio 1.17). The median age and interquartile range (IQR) were 36 years (9 - 51). Isolated valve surgery, in 15 (40.5%) cases, was the most common procedure in open-heart surgery cases. Closed-heart surgery involved closure of the patent ductus arteriosus in 9 (24.3%) cases, coronary artery bypass grafting in 3 (8.1%) cases, and pericardectomy in 2 (5.4%) cases. The median duration of extracorporeal circulation and aortic cross-clamping was 101 min (IQR 84 - 143) and 74 min (IQR 54 - 112) respectively. The median duration of mechanical ventilation was 2 hours (IQR 2 - 3). The median intensive care unit stay and median hospital stay were 2 days (IQR 2 - 3) and 7 days (IQR 5 - 8) respectively. Operative mortality was 2 (5.4%). Conclusion: Cardiac surgery remains a major challenge for African populations. The early results achieved by the local team are satisfactory. An increase in surgical activity should be strongly encouraged to facilitate local training and ensure the sustainability of the activity.

关键词： Cardiac Surgery Sub-Saharan Africa Cameroon

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Laparoscopic Surgery of Incisional Hernia: Technique and Short-Term Results in Three Surgical Units in Cameroon

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Surgical Science 2024年第4期15卷 232-243页

作者： Guy Aristide Bang Eric patrick Savom Achille Aimé Bekolo Otiti Fred dikongue dikongue Mahamat Yannick Ekani Boukar Richard II Mbele Cédric Paterson Atangana daniel Biwole Biwole Arthur Essomba Yaoundé Teaching Hospital Yaound&#233 Cameroon Faculty of Medicine and Biomedical Sciences of the University of Yaoundé I Yaound&#233 Cameroon Yaoundé General Hospital Yaound&#233 Cameroon Faculty of Medicine and Biomedical Sciences of the University of dschang Dschang Cameroon Faculty of Health Sciences University of Buea Buea Cameroon Yaoundé Central Hospital Yaound&#233 Cameroon

Introduction: Incisional hernia is a common medical situation and its treatment has always been a challenge for general surgeons. If laparoscopic repair has become a gold standard elsewhere, it is increasingly done in our milieu, but no data has been found. The aim of this study was to review this surgery done in our country so far, to describe the operative technique and to evaluate the postoperative outcomes. Patients and Methods: We conducted an observational descriptive study with retrospective collection of data from the 1st of July 2018 to 30th of June 2022, in three hospitals in Cameroon. data on socio-demographic and clinical characteristics, surgical technique and postoperative outcomes of patients who had a laparoscopic repair of their incisional hernia were collected. Results: We reviewed 20 files. There were 14 women with an average age of 54.6 years. The average BMI was 32.8 kg/m2. Thirteen patients had a moderate size hernia and the hernia was localized at the midline in 18 cases. Only composite biface meshes were used with dimensions chosen to obtain at least 5 cm overlap. Spiral tacks were the only fixation means used. We registered 3 complications. One case of generalized peritonitis secondary to missed digestive perforation, one case of seroma and one case of postoperative ileus. We registered no death. Conclusion: Laparoscopic repair of incisional hernias is feasible in a resource-limited setting like ours. Compliance with the operative technique and recommendations is important to obtain short-term results closed to that put forward by literature.

关键词： Incisional Hernia Laparoscopy Repair Composite Biface Mesh Postoperative Outcomes

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