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Energetics and thermodynamic stability of potential Fe (II) -hexa-aza-active sites for O_(2) reduction in PEM fuel cells

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SusMat 2022年第6期2卷 731-748页

作者： vassili P.Glibin Jean-Pol Dodelet Gaixia Zhang Department of Chemical and Biochemical Engineering University of Western OntarioLondon OntarioCanada Institut National de la Recherche Scientifique(INRS) Energie Materiaux Telecommunications Research CentreVarennesQuebecCanada Department of Electrical Engineering Ecole de Technologie Superieure(ETS)1100rue Notre-Dame OuestMontrealQuebec H3C 1K3Canada

We present here a thermodynamic assessment of the stability behavior in acid environment at 298 and 353 K(80◦C)of two iron(II)hexa-aza-macrocyclic complexes and of an hexa-aza-iron-based site(Fe^(II)N_((4+2))/C)that should potentially be active for the oxygen reduction reaction in proton exchange membrane(PEM)fuel cells.The calculations of the equilibrium constant(K c)for the demetallation reaction indicate that the iron(II)-hexa-aza-macrocyclic complexes and Fe^(II)N_((4+2))/C are chemically stable in an acid medium at 298 and 353 K.Compared with two other potential model sites(Fe^(II)N_((4+2))/C and Fe II N(2+2)/C)that were thought to be present in the same Fe-based catalysts,K c of Fe^(II)N_((4+2))/C is two to three orders of magnitude smaller at 353 K,and three to four orders of magnitude smaller at 298 K,than K c for Fe^(II)N_((4+2))/C or Fe II N(2+2)/C,revealing the great chemical stability of Fe^(II)N_((4+2))/C.In this work,we discuss about a novel proposition that the two catalytic sites active in these Fe-based catalysts are Fe II N_(4)/C and Fe^(II)N_((4+2))/C.This proposition is in agreement with the durability behavior of these catalysts in PEM fuel cells and also with their known physico-chemical characterizations.The origin of the fast and slow decay behaviors of the different sites,which are active at the Fe–N–C-based cathode of PEM fuel cells,is also discussed.

关键词： active site fuel cell oxygen reduction reaction thermodynamic stability

Martensitic twinning transformation mechanism in a metastable IVB element-based body-centered cubic high-entropy alloy with high strength and high work hardening rate

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Journal of Materials Science & Technology 2022年第29期124卷 217-231页

作者： Yuhe Huang Junheng Gao vassili Vorontsov Dikai Guan Russell Goodall David Dye Shuize Wang Qiang Zhu W.Mark Rainforth Iain Todd Department of Materials Science and Engineering University of SheffieldSheffield S13JDUnited Kingdom Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen518055China Beijing Advanced Innovation Center for Materials Genome Engineering University of Science and Technology BeijingBeijing 100083China Department of Materials Royal School of MinesImperial College LondonLondon SW72BPUnited Kingdom

Realizing high work hardening and thus elevated strength–ductility synergy are prerequisites for the practical usage of body-centered-cubic high entropy alloys(BCC-HEAs).In this study,we report a novel dynamic strengthening mechanism,martensitic twinning transformation mechanism in a metastable refractory element-based BCC-HEA(TiZrHf)Ta(at.%)that can profoundly enhance the work hardening capability,leading to a large uniform ductility and high strength simultaneously.Different from conventional transformation induced plasticity(TRIP)and twinning induced plasticity(TWIP)strengthening mechanisms,the martensitic twinning transformation strengthening mechanism combines the best characteristics of both TRIP and TWIP strengthening mechanisms,which greatly alleviates the strengthductility trade-off that ubiquitously observed in BCC structural alloys.Microstructure characterization,carried out using X-ray diffraction(XRD)and electron back-scatter diffraction(EBSD)shows that,upon straining,α”(orthorhombic)martensite transformation,self-accommodation(SA)α”twinning and mechanicalα”twinning were activated sequentially.Transmission electron microscopy(TEM)analyses reveal that continuous twinning activation is inherited from nucleating mechanical{351}type I twins within SA“{351}”typeⅡtwinnedα”variants on{351}twinning plane by twinning transformation through simple shear,thereby accommodating the excessive plastic strain through the twinning shear while concurrently refining the grain structure.Consequently,consistent high work hardening rates of 2–12.5 GPa were achieved during the entire plastic deformation,leading to a high tensile strength of 1.3 GPa and uniform elongation of 24%.Alloy development guidelines for activating such martensitic twinning transformation strengthening mechanism were proposed,which could be important in developing new BCC-HEAs with optimal mechanical performance.

关键词： Metastable high entropy alloy Work hardening rate Martensitic transformation Self-accommodating martensite Twinning transformation

标准元素分析方法的变更及其性能的改进(英文)

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光谱学与光谱分析 2003年第1期23卷 104-114页

作者： vassili Karanassion Department of Chemistry

本文详细地论述了标准元素分析方法的变更及其性能的改进。

关键词：标准元素分析方法电感耦合等离子体微型化仪器光谱分析

Wavevector Selective Metasurfaces and Tunnel Vision Filters

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Light(Science & Applications) 2015年第1期4卷 301-305页

作者： vassili A Fedotov Jan Wallauer Markus Walther Mauro Perino Nikitas Papasimakis Nikolay I Zheludev Optoelectronics Research Centre and Centre for Photonic Metamaterials University of SouthamptonSouthamptonSO171BJUK Department of Molecular and Optical Physics University of FreiburgD-79104 FreiburgGermany Department of Information Engineering University of PadovaPadovaItaly Centre for Disruptive Photonic Technologies TPINanyang Technological University637371 SingaporeSingapore

Metasurfaces offer unprecedented flexibility in the design and control of light propagation,replacing bulk optical components and exhibiting exotic optical effects.One of the basic properties of the metasurfaces,which renders them as frequency selective surfaces,is the ability to transmit or reflect radiation within a narrow frequency band that can be engineered on demand.Here we introduce and demonstrate experimentally in the THz domain the concept of wavevector selective surfaces–metasurfaces transparent only within a narrow range of light propagation directions operating effectively as tunnel vision filters.Practical implementations of the new concept include applications in wavefront manipulation,observational instruments,vision and free-space communication in light-scattering environments.

关键词： flat optics metafilms metasurfaces planar metamaterials wavefront manipulation

Existence of Solutions to Path-Dependent Kinetic Equations and Related Forward-Backward Systems

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Open Journal of Optimization 2013年第2期2卷 39-44页

作者： vassili Kolokoltsov Wei Yang Department of Mathematics and Statistics University of Strathclyde Glasgow UK Department of Statistics University of Warwick Coventry UK

This paper is devoted to path-dependent kinetics equations arising, in particular, from the analysis of the coupled backward-forward systems of equations of mean field games. We present local well-posedness, global ex... 详细信息

关键词： Kinetic Equation Mean Field Control Global Existence Path Dependence Nonlinear Markov Process Coupled Backward-Forward Systems

Iron Metabolism Abnormalities in Children with Homozygous Sickle Cell Disease in Brazzaville

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Open Journal of Pediatrics 2023年第3期13卷 394-407页

作者： Lucie Charlotte Ollandzobo Ikobo Hardy Maryse Ibovi Gataud Steve vassili Missambou Mandilou Olivia Firmine Galiba Atipo-Tsiba Rolf Iwandza Jean Robert Mabiala Babela Faculty of Health Sciences Marien Ngouabi University Brazzaville Congo Department of Infant Pediatrics CHU of Brazzaville Brazzaville Congo Department of Clinical Haematology CHU Brazzaville Brazzaville Congo Antoinette-Sassou-Nguesso National Reference Centre for Sickle Cell Disease in Brazzaville Brazzaville Congo

Introduction: Sickle cell disease is the most common genetic disease in the world, particularly in sub-Saharan Africa. It is a protean condition with multiple complications including disturbed iron metabolism. Objectives: To determine the prevalence of iron metabolism abnormalities in children with homozygous sickle cell disease, to describe the epidemiological, clinical and paraclinical characteristics of children with these abnormalities and to identify associated factors. Patients and Methods: This was a cross-sectional analytical study conducted over 9 months in the mother-child consultation unit of the Brazzaville University Hospital, the National Reference Centre for Sickle Cell Disease and the paediatric department of the Blanche Gomes mother-child hospital. It concerned children aged between 3 months and 15 years followed up for homozygous sickle cell disease. The study was based on a haemogram, iron metabolism test, LDH, transaminases and CRP. Results: The overall prevalence of iron metabolism abnomalities was 40.7%. Of the 145 children included, 35.9% had iron overload and 4.8% iron deficiency. Iron overload was associated with infections, undernutrition, iron supplementation and number of blood transfusions. Iron deficiency was not significantly associated with any factor but recurrent infections were relatively more frequent. Conclusion: Abnormalities of iron metabolism in sickle cell patients are relatively frequent, which justifies monitoring during follow-up for early detection and better management. .

关键词： Anomalies Metabolism Iron Child Homozygous Sickle Cell Disease Brazzaville

Mathematical Modeling of Peat Self-ignition at Ambient Temperature Oscillations

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Journal of Energy and Power Engineering 2013年第3期7卷 491-495页

作者： vassili Gorelski Konstantin Zhiltsov Aleksei Yashchuk Alexander Shteinberg Alexander Berlin Research Institute of Applied Mathematics and Mechanics Tomsk State University Tomsk 634050 Russia ALOFT Corporation Berkeley 94708 California USA Nikolay Nikolaevich Semenov Institute of Chemical Physics of the Russian Academy of Sciences Moscow 117977 Russia

In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the oscillation periods, commensurate with the adiabatic induction period of thermal explosion, implement a kind of resonance which corresponding with average ambient temperature. At both high and very low frequencies oscillations at ambient temperature, their influence on the critical condition and on the induction period of thermal explosion is negligible. However, at low-frequencies influence of ambient temperature oscillations, even a relatively low amplitude, on critical condition and especially on induction period of thermal explosion, can be very strong.

关键词：温度振荡数学建模环境温度自燃泥炭热爆炸诱导期谐波振荡

Biological Markers of Undernutrition and Risk of Complications in Children Hospitalized at the Teaching Hospital of Brazzaville

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Journal of Biosciences and Medicines 2022年第2期10卷 1-9页

作者： Christel Mikolélé-Bilombo Lucie Charlotte Atipo-Ibara Ollandzobo Steve vassili Missambou Mandilou Thibaut Ocko Gokaba Lethso Clausina Mikolélé-Bilomb Ahoui Josué Simo Louokdom Martial Landry Miguel Etienne Mokondjimobe Donatien Moukassa Jean Robert Mabiala-Babela Ange Antoine Abena Jean-Rosaire Ibara Faculty of Health Sciences Marien Ngouabi University Brazzaville Congo Department of Pediatrics Teaching Hospital of Brazzaville Brazzaville Congo Department of Gastroenterology and Hepatology Teaching Hospital of Brazzaville Brazzaville Congo Cameroon Mountain University Douala Cameroon Denis Sassou Nguesso University Brazzaville Congo

Introduction: Undernutrition is a condition frequently encountered in pediatrics. It leads to an increased morbidity and mortality regardless of the underlying condition or other risk factors such as age. In countries with limited resources such as ours, the diagnosis of undernutrition is often limited to the clinical presentation, and the contribution of biology is not often taken into account. Objectives: To establish the relationship between anthropometric parameters and biological markers in the diagnosis and classification of undernutrition and to assess the risk of infectious complications during undernutrition in children. Materials and Methods: A cross-sectional study conducted in Brazzaville among undernourished children aged 1 - 59 months between October 2018 and April 2019. Clinical diagnosis was based on WHO growth charts. The CRP, orosomucoid, albumin and transthyretin were obtained using the Cobas c311 analyzer, which enabled the calculation of Prognostic Inflammatory and Nutritional Index (PINI). The comparison of the means of the biological markers used the Student’s t-test, the risk of infectious complications the chi-square. The correlation of the diagnostic value of Z-score weight/height and PINI was also investigated. The significance level was set at 0.05. Results: Of the 95 children enrolled 63 (66.3%) were clinically severely malnourished, including 26 acute (41.3%) and 37 chronic (58.7%). The PINI revealed severe undernutrition in 85 children (89.4%) including 50 acute (58.8%) and 35 chronic (41.2%). CRP and orosomucoid were statistically higher in severe acute undernutrition (p Conclusion: Anthropometric parameters have a front-line advantage for assessing and classifying undernutrition. However, biological markers of undernutrition with PINI should be systematized in the diagnosis and management of undernutrition.

关键词： Undernutrition Nutritional Marker Inflammatory Marker PINI Child Congo

Sexual Behaviour of Congolese Teenagers

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Open Journal of Pediatrics 2021年第4期11卷 656-668页

作者： Lucie Charlotte Ollandzobo Ikobo Steve vassili Missambou Mandilou Messie Josias Matsielo Lynda Tchidjo Ngamo Evrard Romaric Nika Jean Robert Mabiala Babela Faculté des Sciences de la Santé Université Marien Ngouabi Brazzaville Congo Service de pédiatrie nourrisson CHU de Brazzaville Brazzaville Congo

Introduction: Sexual risk behaviour among adolescents is a public health problem worldwide. Widely studied in the Western countries, this problem has only been addressed partially in Brazzaville. Thus, 12 years later, we conducted this study with the aim of analysing the sexual behaviour of adolescents in Congo. Patients and Methods: This was a cross-sectional and analytical study from January to August 2019 (8 months). It involved 2000 adolescents residing in the departments of Brazzaville and Pointe-Noire constituting the urban population, and those of Cuvette and Bouenza, the rural population. Results: A total of 1167 adolescents reported being sexually active. The mean age at first sexual intercourse differed between the two sexes (p 0.0005). Of the adolescents surveyed 96.1% (n = 1122) claimed to have ever heard of HIV/AIDS infection and 8.7% (n = 101) to have ever contracted sexually transmitted infections. The main channel of information was school in 57.7%. Condoms were the only means of protection (85.5%). The factors associated with risky sexual behaviour were, on the one hand, those related to the adolescent (lack of schooling, orphan status, alcohol and tobacco consumption, paid employment and possession of a mobile phone). On the other hand, those related to parents (low level of education, mother’s employment status and single-parent household structure). The frequency of sexually active adolescents was similar in both settings (p < 0.05). The rates of adolescents having ever heard of HIV/AIDS were almost similar with a slight predominance in urban areas (p < 0.09). Early sexual int

关键词： Adolescent Risky Sexual Behaviour Congo