Antibiotic Resistance Profile of Salmonella Strains Isolated at the National Clinical Biology and Public Health Laboratory in Bangui, Central African Republic

In Africa, each year, there are estimated to be more than 91 million cases of salmonellosis and 137,000 cases of death. The problem of antibiotic resistance in Salmonella strains is a threat to public health. The objective of this study is to evaluate the antibiotic resistance profile of Salmonella strains isolated in biological products analyzed at the National Laboratory of Clinical Biology and Public Health (NLCBPH) in Bangui. This is, therefore, a cross-sectional study with a descriptive aim, running from January to December 2022. It focused on the strains of Salmonella isolated and identified in stools, urines, and blood samples. For each strain of Salmonella isolated, an antibiogram was carried out following the recommendations of the French Society of Microbiology (CASFM, 2022). A total of 93 strains of Salmonella have been recorded. The age group 0 - 9 years was 29% and that of >50 years was 11%. The median age of patients was 30 years with a minimum of 1 and a maximum of 78 years. The female gender was more represented at 52.69% than the male gender at 47.31%, i.e. a sex ratio of 0.89 (M/F). Salmonella strains were much more isolated in stools at 62% followed by urines at 29% and blood at 6%. Salmonella arizonae strains were more represented with 52%. Salmonella strains have a resistance rate to Tetracycline of 62.37% followed by Penicillins of 50%. The rate of multi-antibiotic resistance of the Salmonella strains isolated represented 48.38%. Salmonella spp. strains were multi-resistant at 58.69% followed by Salmonella arizonae strains at 47.91%. There is a significant association between the different families of antibiotics and Salmonella strains (p < 0.05). According to the results obtained, Penicillins, Phenicoles, and Cyclins had a high rate of resistance on Salmonella strains. No strain-producing Broad Spectrum Beta-lactamase has been isolated. Salmonella strains represent a zoonotic health danger, constitute a public health problem and remain a current subject. This germ is resistant to the antibiotics used. It is, therefore, essential to emphasize monitoring the resistance of these germs in the Central African Republic (CAR) to improve the health of the population.

Epidemiological and Clinical Aspects of Male Infertility in Patients Consulting at the Urology Department of the Yaounde Central Hospital

Introduction: About 10 to 15% of couples in the world and 20 to 30% in Cameroon consult for infertility problems. Infertility is of male origin in 40% of cases. Our objective was to evaluate the epidemiological and clinical aspects of male infertility in our setting. Methods: This was a cross-sectional and descriptive study, with retrospective data collection from the files of patients received for male infertility, over 5 years and 6 months (from January 1st, 2016 to April 30th, 2021) at the Urology Department of the Yaounde Central Hospital. Phone calls were made to patients with incomplete records for completion following a verbal consent. Data reported on data collection forms were entered into a data entry form designed on CSPro software version 7.2. The database was later exported for descriptive statistics using the IBM SPSS software version 23. Qualitative variables were summarized in frequencies and percentages while quantitative variables were summarized in means with their standard deviations for normally distributed data, or medians and interquartile ranges otherwise. Results: Out of 110 patients whose records were analyzed, the median age was 37.0 years, with an interquartile range of 8.3, with 55.5% in the age group 30 to 39 years. Of these 95 (86.4%) were married, 58 (52.7%) were from the West region, 76 (69.1%) were employed. Past history was dominated by mumps 40 (36.4%), varicocele surgery 25 (22.7%), alcoholism 87 (79.1%) and smoking 15 (13.6%). A disorder of spermatogenesis was found in all our patients: 37 (33.6%) azoospermia, 27 (24.6%) asthenospermia and 26 (23.7%) oligospermia patients. Paraclinical evidence of chlamydia and gonococcal infections were found respectively in 38 (34.5%) and 14 (12.7%) patients, varicocele and testicular dystrophy respectively in 95 (86.4%) and 38 (34.5%) patients. Infertility was primary in 67 (60.9%) patients. Conclusion: Most patients with infertility were in their thirties, had risky social habits and comorbidities. An early start of health promotion activities, comorbidities prevention and early detection of spermogram abnormalities would make it possible to reduce the frequency of male infertility.

Contribution to the Study of Fungal Strains Contaminating Peanut Pastes in Bangui (Central African Republic)

Introduction: Peanut pastes are food products resulting from artisanal or industrial processing, used in cooking in Africa in general and in Central African Republic in particular. These peanut pastes are often contaminated by molds and filamentous fungi involved in the degradation of hygienic and organoleptic or even toxicological quality. This study aims to determine the epidemiological profile of molds contaminating peanut pastes sold on the Central African market. Methodology: This was a cross-sectional study carried out from June to September 2023. Samples of peanut pastes sold on Central African market were taken and analyzed at the National Laboratory of Clinical Biology and Public Health using the conventional microbiology method according to ISO 7954 standards. The data obtained were collected in the ODK 2023.3.1 application and analyzed with the Epi Info 7 software. A multivariate analysis by logistic regression, Ficher’s exact test, and chi2 at the 5% threshold (p Penicillium sp.;11.25% of Mucor sp.;10.63% of Aspergillus terrei;3.13% of Aspergillus niger;1.25% of Aspergillus medullans;28.13% of Aspergillus flavus;2.50% of Aspergillus fumigatus. Peanut pastes stored beyond three days were more contaminated (94.19%). Conclusion: The results of this study made it possible to highlight strains of mold that impact the hygienic and organoleptic quality of peanut pastes sold at the Central African market. Most of the isolated strains were the Aspergillus flavus species which is recognized by its toxigenic effects. This species is much more incriminated in the contamination of foodstuffs with the production of the toxin which causes underlying pulmonary pathologies in humans.

Contribution to the Study of the Incidence of Post-Streptococcal Complications in Republic Central African Republic from 2015 to 2018

Introduction: Acute rheumatic fever (AAR) is a non-suppurative complication of late infection by group A. Infections due to streptococci remain a public health problem in the Central African Republic. The present study aims to determine the incidence rate of AAR cases and its complications. Methodology: This was a retrospective and analytical study over a period of 4 years (from January 2015 to December 2018) at the National Laboratory of Clinical Biology and Public Health (LNBCSP) in Bangui. It focused on samples concerning the diagnosis of AAR and patient files seen in consultation in the capital’s reference health establishments. Laboratory registers and patient consultation files were used to collect data. They were entered into Excel 2010 to be analyzed with Epi Info 7. A univariate analysis by logistic regression, Ficher’s exact test, and chi2 at the 5% threshold (p Results: We analyzed 94 cases meeting Jones’s criteria. The ages of the patients ranged from 18 to 85 years (mean age 52 years and mode 45 years). The incidence rate of AAR for the female sex was higher than that of the male sex during the study period (p > 0.05). It went from 166.6 in 2015 to 200 in 2016 and 2018 cases of AAR per 1000 people per year. The average incidence rate was 296.18 cases of AAR per 1000 people per year. The average incidence rate was 223.5 cases of AAR per 1000 people per year for joint damage. Joint damage represented 80.85% (RR = 0.62;Chi2 = 4.88;95% CI [0.39-0.97];p Conclusion: The study allowed data on the impact rate and complications of the AAR in Bangui. Special attention to data management will help produce a complete result on the problem. Joint complications predominated. Sustaining an effective surveillance system and preventing infection would help reduce the risk of AAR occurrence.

Contribution of Genomic Surveillance in the Detection and Monitoring of SARS-CoV-2 Variants during the 6 Pandemic Waves in the Central African Republic from 2020 to 2023

Objective: The COVID-19 pandemic has highlighted the need to strengthen diagnosis and genomic surveillance capacities. In 2021, Central African managed five waves of COVID-19 by integrating genomic surveillance into their health monitoring system. This study sought to report surveillance data from the National Laboratory of Clinical Biology and Public Health and describe the circulation of SARS-CoV-2 variants. Materials and Methods: This retrospective, descriptive observational study spans three years, from April 2020 to November 2023. It was conducted on a population of consenting volunteers from across the Central African Republic, who were tested using RT-PCR on nasopharyngeal samples. Data with sufficient information were obtained from the National Laboratory of Clinical Biology and Public Health (LNBCSP) databases. Sequencing was largely carried out at the National Institute of Biomedical Research (INRB) in Kinshasa until May 2023, and subsequently at the LNBCSP. Results and Discussion: Out of 97,864 RT-PCR tests performed, 9,764 were positive, resulting in a prevalence of 9.98%. The average age of the patients was 39.97 years ± 13.76, and the male-to-female sex ratio was 2.12. RT-PCR test positivity was significantly associated with age (p = 0.001), sex (p = 0.013) and clinical manifestations. Ten variants circulated during the five recorded waves, with Omicron (B.1.1.529), Delta (B.1.617.2) variants being predominant. Notably, the B.1.620 and B.640 variants were prominent during the second wave. Conclusion: This retrospective study provides key insights into the COVID-19 pandemic in the CAR. It identifies risk factors and details the circulation of various SARS-CoV-2 variants. Enhancing national genomic surveillance capacities would enable the country to better respond to future pandemic challenges.

Prevalence of Gender-Based Violence among Sex Workers in Bangui, Central African Republic (CAR)

Background: Violence against women has become an international public health and human rights issue in recent decades. The violence suffered by sex workers is of little interest for research, yet it constitutes a major health and safety problem. We propose to assess the extent of the phenomenon of gender-based violence (GBV) among sex workers (SWs) in the city of Bangui in the CAR. Methodology: This is a descriptive cross-sectional epidemiological study covering the period from July to October 2021 carried out among SWs in Bangui, the capital of the CAR. Given that the SWs association had only 159 members in Bangui, an exhaustive sampling was retained. Were included in the study, any SW present during the data collection period and having given their written consent. The parameters studied were socio-demographic characteristics: age, sex, residence, level of education, marital status, and characteristics linked to violence: the notion of violence during their professional activity, the type of violence, the declaration and the declaration if necessary, the response and management of this violence. The data collected was analyzed using Epi info version 7 software. Results: Of the 159 SWs that counted the association, 108 had been included. The average age was 27.0 years with extremes of 14 and 46 years. The age groups of 25 to 34 years were the most represented (43.5%). Fifty-six SWs (51.9%) had reached the secondary level. Unemployed SWs were in the majority at 74.1%;Sixty-six (66) SWs in our sample (61.1%) had already been victims of violence during the exercise of their activity Sexual violence was the most represented (28.5%) followed by verbal violence (22.4%). Sixty-eight (62.9%) wanted to stop the professional activity of SWs and 93.1% would accept another income-generating activity in place of sex work. Conclusion: It is necessary to supervise SWs and protect them within the framework of respect for human rights, rather than criminalizing them and the exploiters flouting their human dignity and putting their lives in danger. .

Epidemiological Profile of Men Who Have Sex with Men: First Data about Male Sex Workers in Central African Republic (CAR)

Objectives: Sex work is not well documented among African men. The aim of this study was to describe the epidemiological profile of men who have sex with men (MSM) and eventually to determine the proportion of sex workers (SW) among them, as well as the proportion of MSM who have been victims of gender-based violence (GBV). Material and Methods: A cross-sectional study coordinated by the Direction de la Médecine du Travail was carried out at the headquarters of the association ALTERNATIVES in Bangui Bangui from July 1 to October 31, 2021. Consenting MSM present during the study period were systematically included. Sociodemographic variables, those relating to the future vision of the activity and to GBV were collected and analyzed using Epi-Info version 7 software. Results: Forty MSM with an average age of 23 years and mainly secondary education (75.0%) were included. The vast majority of MSM were unemployed (85.0%). 45.0% had been victims of GBV and wanted to stop working as an MSM (47.5%), and almost 2/3 (65.0%) would accept another income-generating activity in exchange for the MSM. Violence was sexual (32.5%), economic (22.5%), physical (20.0%), verbal (12.5%) and psychological (12.5%). Conclusion: The MSM were mainly young, poorly educated, unemployed, and almost half were victims of GBV. The desire to change MSM activity to another income-generating activity alongside that of MSM shows that many of them are SW, workers in the informal sector. This must be taken into account in prevention activities, even if the data needs to be confirmed on a much larger sample.

Designing a Protection Scheme in Micro-Grid Systems with DG Using Central Protection Unite and Multiple Setting Group Protection Relays

Distributed generators now is widely used in electrical power networks, in some cases it works seasonally, and some types works at special weather conditions like photo voltaic systems and wind energy, and due to this continuous changes in generation condition, the fault current level in network will be affected, this changes in fault current level will affect in the coordination between protection relays and to keep the coordination at right way, an adaptive protection system is required that can adaptive its setting according to generation changes, the fault current level in each case is evaluated using ETAP software, and the required relay setting in each case is also evaluated using Grey Wolf Optimizer (GWO) algorithm, and to select suitable setting which required in each condition, to select the active setting group of protection relay according to generation capacity, central protection unite can be used, and to improve protection stability and minimizing relays tripping time, a proposed method for selecting suitable backup relay is used, which leads to decrease relays tripping time and increase system stability, output settings for relays in all cases achieved our constrains.

Class Central慕课课程How to Write an Essay教学设计分析

调研了美国Class Central网站发布的“2023年250门全球最受欢迎在线课程榜”19门英语写作类MOOC课程。How to Write an Essay被列为250门全球最受欢迎MOOC课程之一,源于其优质的教学设计:世界顶尖大学及其丰富的在线课程经验、优秀师资,教学目标注重培养学习者技能、终身学习理念以及抛锚式教学模式,这对于在线课程建设和教学具有借鉴意义。

肉苁蓉的药理作用及其在中枢神经系统疾病中的研究进展

肉苁蓉(Cistanches)是列当科植物肉苁蓉的肉质茎,又名金笋、地精、大芸。肉苁蓉的提取物主要包括肉苁蓉总苷、苯乙醇苷类、环烯醚萜类、挥发性成分、木脂素类、多糖、生物碱等。肉苁蓉的传统中药作用有补肾壮阳、润肠通便、女子不孕、滋补强身等;现代药理作用包括抗氧化、抗凋亡、调控自噬、增强体力和抗疲劳、改善学习认知功能。相关研究表明肉苁蓉对中枢神经系统疾病具有良好的治疗效果。脑缺血再灌注损伤(Cerebral ischemia reperfusion injury,CIRI)发生常伴随着脑水肿、血脑屏障的破坏、神经炎症、神经元凋亡,肉苁蓉提取物肉苁蓉总苷可抑制神经细胞炎症及凋亡,减少脑梗死面积,对CIRI模型大鼠具有神经保护作用。肉苁蓉通过减少自由基堆积、抑制氧化应激和炎症反应,提高阿尔茨海默病(Alzheimer’s disease,AD)和血管性痴呆(Vascular dementia,Va D)模型大鼠的学习记忆能力。肉苁蓉可以改善帕金森病(Parkinson’s disease,PD)小鼠运动行为异常,发挥神经保护作用。肉苁蓉能够抑制肌萎缩侧索硬化症(Amyotrophic lateral sclerosis,ALS)兴奋性氨基酸的水平,减轻神经毒性作用,改变星形胶质细胞功能,提高神经细胞存活率。目前肉苁蓉对于中枢神经系统疾病的应用越来越广泛,就其药理作用及其在中枢神经系统疾病中的研究进展进行综述,以期为肉苁蓉的开发和利用提供新的思路。

滇中地区主要森林凋落物有效截留量及其影响因素

[目的]研究滇中地区主要森林类型凋落物有效截留量差异及其影响因素,为该地未来植被恢复和森林管理提供科学支撑。[方法]利用样方调查法、烘干法和浸泡法分析了昆明市双河—磨南德水源林自然保护区内的地带性次生常绿阔叶林(SF)、针阔混交林(TF)、旱冬瓜林(ACF)、华山松林(PA)、成熟云南松林(OPY)、幼龄云南松林(YPY)、银荆林(AD)7种主要森林类型凋落物未分解层(OL)和半分解层(OF)的有效截留量及其影响因素。[结果](1) 7种森林类型凋落物厚度为2.06~7.57 cm,其中OL层1.10~4.30 cm, OF层0.83~3.93 cm,凋落物层厚度排序为TF>ACF>PA>OPY>SF>AD>YPY,凋落物蓄积量为4.75~17.45 t/hm^(2),其中OL层占比为32.02%~62.48%,OF层占比为37.52%~67.98%,凋落物层蓄积量排序为TF>PA>SF>OPY>ACF>AD>YPY。(2)凋落物最大持水率为115.3%~170.7%,初始吸水速率为3.65~5.62 g/(g·h),凋落物持水率和浸水时间的关系可用对数函数y=aln(x)+b表示,吸水速率与浸水时间可用幂函数y=kt~n表示。(3)凋落物最大持水量为7.05~32.19 t/hm^(2),排序为PA>TF>SF>OPY>ACF>AD>YPY,有效截留量为5.45~25.34 t/hm^(2),以TF最高(25.34t/hm^(2)),PA(24.99 t/hm^(2))和SF(24.62 t/hm^(2))次之,YPY最低(5.45t/hm^(2)),影响有效截留量的场地特征主要为蓄积量、自然含水率、分解强度以及厚度,影响有效截留量的水动力过程主要是最大失水量、前6.0 h平均吸水速率和前2.0 h平均吸水速率。[结论]滇中地区未来植树造林应以针阔混交林为主,注重对地带性次生常绿阔叶林的保育,采取辅助自然更新的措施促进人工纯林向混交林演化,同时减少踩踏、收集凋落物等人类活动的干扰,从而增加森林生态系统凋落物的水源涵养能力。

三部配穴法针刺治疗慢性中心性浆液性脉络膜视网膜病变的临床效果

目的 观察三部配穴法针刺治疗慢性中心性浆液性脉络膜视网膜病变(CSC)的临床效果。方法 将2022年1月至12月于上海市第一人民医院就诊的84例慢性CSC患者按随机数字表法分为对照组(42例)与治疗组(42例),对照组予维生素B1片、肌苷片、三磷酸腺苷二钠片的基础治疗(40 d),治疗组在对照组的基础上联合三部配穴法针刺,隔天针刺1次,共20次(40 d)。比较两组临床疗效,比较两组治疗前后美国国立眼科研究院视功能问卷-25(NEI-VFQ-25)、中医症状证候量表、最佳矫正视力(BCVA)变化。结果 对照组脱落3例,治疗组脱落4例。治疗组临床疗效优于对照组,差异有统计学意义(P<0.05)。治疗后,两组NEI-VFQ-25评分、BCVA均高于治疗前,且治疗组高于对照组,差异有统计学意义(P<0.05)。治疗后,治疗组中医症状证候量表评分低于本组治疗前及对照组,差异有统计学意义(P<0.05)。结论 三部配穴法针刺联合基础治疗慢性CSC效果显著,具有较高的临床推广及应用价值。

临床淋巴结阴性甲状腺微小乳头状癌患者中央区淋巴结转移危险因素分析

目的 探讨临床淋巴结阴性(cN0)甲状腺微小乳头状癌(PTMC)患者颈中央区淋巴结转移(CLNM)预测模型。方法 本研究纳入2015—2020年在西安交通大学第一附属医院耳鼻咽喉头颈外科手术确诊的cN0-PTMC患者共1271例,根据手术记录和术后病理结果统计年龄、性别、肿瘤最大径、肿瘤位置、侧别、BRAFV600E基因突变、伴结节性甲状腺肿(NG)和桥本氏甲状腺炎(HT)情况、腺外侵犯、被膜侵犯、颈淋巴结转移等临床病理资料,分析CLNM与各临床病理参数的相关性。结果 采用年龄45岁作为分类标准进行单因素分析。结果显示男性患者、年龄、肿瘤直径、是否伴HT、是否多灶性均与cN0-PTMC发生CLNM相关(P<0.05)。伴NG、BRAFV600E基因突变、肿瘤位置、腺外侵犯、肿瘤侧、被膜侵犯均与cN0-PTMC发生CLNM无相关性(P>0.05)。继续进行非条件Logistic回归分析,结果显示男性患者(OR=1.929,95%CI:1.465~2.541),年龄≤45岁(OR=2.581,95%CI:2.004~3.324),多灶性(OR=1.675,95%CI:1.276~2.197)是cN0-PTMC患者发生CLNM的独立危险因素;直径≤5 mm(OR=0.603,95%CI:0.463~0.785)和伴HT(OR=0.642,95%CI:0.452~0.913)是cN0-PTMC患者发生CLNM的保护因素。伴HT是cN0-PTMC患者BRAFV600E基因野生型的危险因素(OR=3.454,95%CI:1.865~6.397)。结论 男性患者、年龄≤45岁、肿瘤直径>5 mm、不伴HT、多灶性是cN0-PTMC患者发生CLNM的独立危险因素。伴HT是此类患者发生BRAFV600E基因突变的保护因素,与其他临床病理特征无相关性。

准噶尔盆地中央坳陷西部下二叠统风城组天然气勘探潜力与重点领域

基于准噶尔盆地中央坳陷西部下二叠统风城组烃源岩有机地球化学、天然气组分和稳定碳同位素组成等分析数据,结合区域沉积环境与生烃演化模拟实验,评价风城组烃源岩的生气潜力,刻画规模有效源灶分布,厘定天然气成因来源,优选有利勘探领域。结果表明:(1)风城组为1套倾油型烃源岩,但滞留液态烃有利于晚期裂解成气,具有生气潜力大、晚期规模成藏的特点;(2)风城组烃源岩最大厚度可达900 m,盆1井西凹陷和沙湾凹陷已进入规模生气阶段,生气强度大于20×10^(8) m^(3)/km^(2)的面积约6 500 km^(2);(3)环中央坳陷西部发现的碳同位素组成较轻的天然气主要为来自风城组烃源岩的高熟油型气,其他则为来自于石炭系煤系烃源岩的煤成气;(4)中央坳陷西部天然气勘探需重点关注源边构造型、源边地层型、源内页岩气型和源内构造型4种类型的有利勘探领域,其勘探潜力值得期待。

以监护仪、输液泵、注射泵为例对全院级医疗设备集中管理模式的实践与探索

目的 探讨建立全院级生命支持类医疗设备集中管理模式的可行性,提高医疗设备精细化管理水平。方法 以我院为主体,选取监护仪、输液泵、注射泵3类设备,从运行模式、绩效分析两个方面建立运行制度,成立医疗设备集中管理中心,实施全院级集中管理。选取2021年7—10月数据作为对照组,选取2022年7—10月数据作为研究组,比较两组数据中3类设备的使用效率,以及两组数据中监护仪的维修周期。结果 实施集中管理后,输注泵使用效率提升9.37%(P﹤0.05),监护仪使用效率提升15.07%(P﹤0.05),监护仪平均维修周期缩短55.93%(P﹤0.05)。结论 医疗设备的集中管理模式可以提升设备使用效率、降低运行成本、降低管理难度,各医疗机构应不断优化管理措施,促进医疗设备的精细化管理。

基于光储混合配置的级联H桥型光伏逆变器功率平衡策略

级联H桥(cascade H-bridge,CHB)变换器由于其模块化结构,已成为大规模光伏(photovoltaic,PV)并网逆变器的优选方案。然而,在不同光照强度和温度下,不同区域PV组件之间发电功率不同,导致CHB变换器相间输出功率不均衡、不稳定等问题。为此,文中提出一种基于CHB结构的光储混合电能路由,在三相CHB光伏逆变器中配置少量的储能模块,利用光储协同控制,维持CHB内部功率稳定,消除分布式PV在相间产生的不均衡功率,且变换器输出功率能够时刻满足网侧上层功率调度,提高了光伏电站的稳定性。针对系统安全区域,在载波移相调制策略下,全桥子模块传输的功率受到约束,并对光伏和储能模块的配置作详细分析。最后,通过仿真以及实验验证所提拓扑及控制策略的正确性和有效性。

人工关节集采对DRG IC29组病例住院费用的影响分析

[目的]研究集中带量采购对人工关节置换术患者住院费用的影响,为深化高值耗材持续改革提供依据。[方法]收集某三级医院集采前后DRG分组IC29组病例的DRG结算数据和医保信息系统的相关信息,进行倾向得分匹配后,采用描述性分析、非参数检验、结构变动度进行费用变化分析。[结果]集采政策实施后的各项费用中位数显示,IC29组病例次均费用下降了33445元,其中材料费下降了34835元;DRG统筹金额下降了13705元,个人自付金额下降了24550元。集采前后的结构变动度为60.52%,材料费呈负向变动,医疗服务费、检查化验费、药品费及其他费呈正向变动。结构变动贡献率前三位为材料费50.00%、医疗服务费26.04%、检查化验费16.36%。[结论]集采后IC29组病例的次均费用、材料费、医保支付和个人负担费用均明显降低,费用结构得到优化,人工关节集中带量采购成效明显。建议持续进行高值耗材集采工作,并协同推进医疗服务价格和医院薪酬制度等其他医改配套政策。

分布式训练系统及其优化算法综述

人工智能利用各种优化技术从海量训练样本中学习关键特征或知识以提高解的质量,这对训练方法提出了更高要求.然而,传统单机训练无法满足存储与计算性能等方面的需求.因此,利用多个计算节点协同的分布式训练系统成为热点研究方向之一.本文首先阐述了单机训练面临的主要挑战.其次,分析了分布式训练系统亟需解决的三个关键问题.基于上述问题归纳了分布式训练系统的通用框架与四个核心组件.围绕各个组件涉及的技术,梳理了代表性研究成果.在此基础之上,总结了基于并行随机梯度下降算法的中心化与去中心化架构研究分支,并对各研究分支优化算法与应用进行综述.最后,提出了未来可能的研究方向.

Farming Features of African Bonytongue Fish Heterotis niloticus in Cameroon, Central Africa

The characterization of African bonytongue Heterotis niloticus fish farming was conducted in the Bi-modal agro-ecological zone of Cameroon from January to May 2021, Thirty-two fish farmers were interviewed and SPSS 6.2 Version was used to analyse the data. The results showed that the majority of fish farmers (81%) are men above 51 years, all of whom are Christians with more than fifty percent of them married. About 43% of them have university level education, and more than 6% of them considered the farming of Heterotis niloticus as their main income-earning activity. The main objective of Heterotis niloticus farming is sales (50%) and the uses (56%) of waged labour. A majority of the farmers produced reared African bonytongue in a polyculture system and 65% of them raised Heterotis niloticus in derivation ponds.

Synoptic-scale reversal of dipole surface temperature anomalies over East Asia and Central Siberia in November 2021

2021年11月,东亚与中西伯利亚经历了相反的冷暖异常转换,表现为“中西伯利亚偏冷,东亚偏暖”与“中西伯利亚偏暖,东亚偏冷”的交替出现.该偶极型气温异常的天气尺度反转伴随着大尺度大气环流异常的反转.进一步分析表明,东亚与中西伯利亚的偶极型气温异常反转是1979-2021年期间11月欧亚气温日变化的主导模态之一(发生概率超过56%).