Simulation du Comportement sous Irradiation aux Ions Lourds du Nanocomposite Au-SiO2

Metal-glass nanocomposites are interesting owing to their particular optical-properties. Ion irradiation can be used as a tool to fabricate nanocomposites. The aim of this thesis was to study, from a fundamental point of view, the behavior of gold nanoparticles (NPs) embedded in an amorphous silica matrix under irradiation. My contribution consists in the interpretation, by modeling and numerical simulation, of experimental results previously obtained by researchers of the Laboratoire des Solides Irradiés. In a first type of experiments, the system was irradiated with 4 MeV gold ions while in a second type the irradiation was performed by using 74 MeV krypton ions.For the study of the first type of experiments, the simulation by kinetic Monte Carlo (KMC) on rigid lattice was chosen and developed specifically to study the behavior of NPs irradiated at different temperatures. The simulations allows us to reproduce qualitatively the experimental results at any temperature. We found that the system evolves within a direct coarsening regime at high temperature (T>900 K) whereas at low temperatures (T60 nm) by the incident ions. We imagined a scenario for the mechanism of deformation which is based on the thermal expansion of the melted NP into the track produced by the incident ion in the matrix. Its implementation using a new simulation technique helped to refine certain elements of the scenario and to improve the overall understanding of the process. The qualitative agreement between the experimental data and the results obtained by the simulation validate the proposed mechanism.Les matériaux nanocomposites de type métal-verre sont intéressants en raison de leurs propriétés optiques particulières. La technique de fabrication utilisant les faisceaux d’ions est un outil prometteur pour les nanocomposites. L’objectif de cette thèse était d’étudier d’un point de vue fondamental le comportement sous irradiation de nanoparticules (NPs) d’or enfouies dans une matrice de silice amorphe. Ma contribution réside dans l’interprétation par modélisation et simulation numérique des résultats expérimentaux obtenus auparavant par des chercheurs du Laboratoire des Solides Irradiés. Dans le premier type d’expériences, le système a été irradié par des ions d’or de 4 MeV alors que dans le second type l’irradiation est effectuée avec des ions de krypton de 74 MeV.Dans la première partie, la simulation par Monte Carlo cinétique (KMC) sur réseau rigide a été choisie et développée spécifiquement pour étudier le comportement de NPs sous irradiation à différentes températures. Les simulations ont permis de reproduire qualitativement les résultats expérimentaux à toute température. Nous avons retrouvé en particulier le mûrissement d’Ostwald qui se produit à haute température (T>900 K) et la dissolution des NPs qui se produit à basse température (T60 nm) selon l’axe de l’ion incident. Nous avons imaginé un scénario du mécanisme de la déformation qui repose sur la dilatation thermique de la NP métallique fondue dans la région de la trace de l’ion incident. Sa mise en œuvre, grâce à une nouvelle technique de simulation développée spécialement, a permis d’affiner certains éléments du scénario et d’améliorer la compréhension globale du processus. L’accord qualitatif entre les données expérimentales et les résultats obtenus par simulation valide le mécanisme proposé

Effect of deposition time on gold nanodendrite porous structure and on signals of Hg(II) in environment

The influences of deposition time (tdep) for Au nanodendrite preparation on carbon cloth electrodes on the surface structure, electrochemical behavior and voltammetric signal for Hg(II) detection have been studied. The obtained results showed that from 60 s to 300 s, the longer deposition time, the larger dendrite length as well as the more increased density of dendrite structure became. Calculated from data showed that the electroactive surface area approached to the maximum value of 3.686 cm2 with tdep = 300 s. The typical electrochemical behaviour of the prepared electrodes was mass transfer diffusion to the electrode surface and being considered as planar diffusion. Using DPASV technique, the peak height of Hg(II) could appoach to 52 µA with tdep = 60 s. Keywords. Gold nanodendrite, deposition time, surface structure, electrochemical properties, mercury

DEWATS dissemination in Vietnam: achievements and lessons learnt

The speedy economic development and rapid growth of population and urbanization in Vietnam have created great pressure on the environment by its manufacturing process and human activities. Thus, it is necessary to protect the environment through policies and appropriate technology for the sustainable development of the country. The DEcentralized WAstewater Treatment Solutions (DEWATS) dissemination in Vietnam is one of the measures contributing to address this issue

Screening of a Small Spherical Macroion by Oppositely Charged Flexible Polyelectrolyte

Electrostatic interactions play important roles in the assembly, the structureand the functions of many biological as well as soft matter systems. In the presence of a macro-ion in aqueous solution, oppositely charged molecules mobilize around it to screen out its electrostatic potential. In this paper, we focus on screening of small macroion by a flexible polyelectrolyteusing Monte-Carlo simulation. It is shown that the condensation of the polyelectrolyte around the macroion shows a first order phase transition from a dense to a dilute concentration of monomers. The width of the condensed region increases with stronger screening or with smaller macro-ion charges. For small macro-ion charge, or when the Coulomb interactions are strongly screened, no complexation between the polyelectrolyte and the macro-ion happens.Additionally, long polyelectrolyte protrudes both tails and loops from the macroion. This is quite different from the case of large macroions where only tails appear. Our results can be used to explain various experimental trends

SCREENING ANTIBACTERIAL ACTIVITY OF VIETNAMESE PLANT EXTRACTS AGAINST HUMAN PATHOGENIC BACTERIA

Objectives: Infectious diseases caused by bacteria are a leading cause of death worldwide. Hence, the objectives of the study are aimed to evaluate the antibacterial activity against five human pathogenic bacteria of methanolic extracts from 66 plants collected from Vietnam. Methods: The broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of methanol extracts of 66 plant species against five bacterial strains. Results: In this study, all the plant extracts were active against at least one train with MIC values ranging from 24 to 2048 μg/mL. Twenty-five plant extracts were active against all three Gram-positive bacteria (Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus). Of these, the extracts of Macaranga trichocarpa (Rchb. f. and Zoll.) Mull. Arg. (Euphorbiaceae), Calophyllum inophyllum L. (Clusiaceae) and Caryodaphnopsis baviensis (Lecomte) Airy Shaw (Lauraceae) exhibited the highest antibacterial activity (MIC =24–128 μg/mL), followed by extracts of Betula alnoides Buch.- Ham. e × . D. Don (Betulaceae), Acronychia pedunculata (L.) Miq. (Rutaceae), Croton alpinus A. Chev. ex Gagnep. (Euphorbiaceae) (MIC =64–256 μg/mL). Furthermore, the extract of Rhus chinensis Mill. (Anacardiaceae) and Annona reticulata L. (Annonaceae) exhibited potent antibacterial activity against the two Bacillus species (MIC =32–64 μg/mL). Conclusion: Results of this study reveal that plant extracts from Vietnam have highly antibacterial activity against Gram-positive bacteria. These results suggest that Vietnamese plant extracts may be a rich source of antibacterial drugs

GEOTOURISM CURRENT STATE AND FUTURE PROSPECTS: A CASE STUDY IN THE CAO BANG UNESCO GLOBAL GEOPARK, VIETNAM

Cao Bang Geopark is one of three UNESCO heritage sites in Vietnam, with unique geological, landscape and cultural properties of high value to tourism. This study aims to provide a better understanding of the potential for geotourism development in Cao Bang Global Geopark, thereby proposing reasonable development strategies in the future. The research using the multicriteria assessment and SWOT analysis tool found that Cao Bang Global Geopark has a high ability to attract tourists and exploit large tourism resources globally. However, the infrastructure, technical facilities, human resources and investment capital for geotourism are still limited and need to be improved. The research results can be considered useful references for academia and managers in finding strategies and solutions for sustainable geotourism development at Cao Bang Geopark in the future

PERSPECTIVES ON PERCEPTIONS AND PRACTICE THROUGH LEARNING CULTURES OF ENGLISH-SPEAKING COUNTRIES OF HIGH-QUALITY ENGLISH STUDIES PROGRAM STUDENTS, SCHOOL OF FOREIGN LANGUAGES, CAN THO UNIVERSITY, VIETNAM

The overall goal of the project is to understand the awareness or perceptions and practice of students of the High-quality English Studies program, School of Foreign Languages (SFL), Can Tho University (CTU), Vietnam when studying cultures of English-speaking countries (CESCs) to improve intercultural competence. The research on the perspectives or opinions of 200 High-quality English Studies students, 12 of them joining the semi-structured interview, about their awareness and practice through learning CESCs. The analysis would help the researcher understand the difficulties of students when studying cultural modules from English-speaking countries at SFL, CTU. The research results would suggest solutions to overcome the difficulties that students encounter, and at the same time provide factors that contribute to improving the intercultural competence of language students. Also, through the research results, despite many obstacles in the process of absorbing culture from cultural modules, students still retain their interest and love for the course-CESCs. However, it can be seen that the difficulty that many students often encounter is still cultural differences, thereby raising awareness of the need to learn cultures for students. Next is to design teaching materials to become more attractive and attractive, proactively find opportunities to communicate with foreigners.  Article visualizations

Pencil lead graphite electrochemically modified with polyglutamic acid as a sensor for detection of enrofloxacin in aqueous media

This study investigates the modification of pencil lead graphite electrodes with polyglutamic acid using an effective and fast static method to develop a sensor for the detection of enrofloxacin (ENR). The successful fabrication of pGA on the electrode surface was confirmed by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier-transform infrared spectroscopy. The conditions of electrochemical modification, including the applied potentials and number of cycles in the potentiostatic process, were systematically investigated to determine their effects on the ENR electrochemical response. The pH of the electrolyte media was also explored to elucidate the electrochemical reaction mechanism of ENR. The developed electrochemical sensor was evaluated using square wave stripping voltammetry for ENR detection. Under optimal conditions, the sensor demonstrated good reproducibility with a relative standard deviation of 4.3% (from five measurements) for ENR signal detection. A linear relationship between ENR concentration and its peak current was observed in the concentration range of 0.1 to 5 µM, with a high correlation coefficient of 0.9988. The limit of detection for ENR using the sensor was 0.12 µM. Our findings provide valuable insights into the design and optimisation of pencil lead graphite electrode-based sensors for ENR detection in aqueous media

Dry Eyes Status on Des Scale and Related Factors in Outpatients at Vietnam National Institute of Ophthalmology

BACKGROUND: Dry eye (DE) can effect on quality of life by pain, inability to perform certain activities that require prolonged attention (driving, reading,…) and productivity at work and finally effect to Q0L associated with DE. OSDI is scale questionnaire is created team to measure the quality of life related to ocular surface disease. AIM: To describe the dry eye disease according to OSDI scale and related factors of this disease. METHODS: A cross-sectional descriptive study was carried out on outpatients (≥ 16-year-old) who were examined and diagnosed with dry eyes at Vietnam National Institute Of Ophthalmology from April to July 2018. Data was collected using the OSDI questionnaire. RESULTS: The average age of participants was 44.6 years; 80.9% of patients were female; 39.9% were identified having mild dry eye. The related factors have been identified that associated with severe dry eye, including age OR = 1.03 (95%CI: 1.01-1.05, p = 0.005), binocular good vision OR = 0.11 (95%CI: 0.05-0.23; p < 0.0001), medical history OR = 17.09 (95%CI: 2.24-130.25; p < 0.0001), chronic conjunctivitis OR = 0.36 (95%CI: 0.14-0.91; p = 0.027), refractive errors OR = 0.14 (95%CI: 0.04-0.48; p < 0.0001), Sjogren's syndrome OR = 31.13 (95%CI: 7.08-136.76; p < 0.0001). CONCLUSION: Several related factors have been identified associated with severe dry eye, including: age, binocular good vision, medical history, chronic conjunctivitis, refractive errors, Sjogren's syndrome

Determinants of antibiotic prescribing in primary care in Vietnam: a qualitative study using the Theoretical Domains Framework

Background: To formulate effective strategies for antimicrobial stewardship (AMS) in primary care, it is crucial to gain a thorough understanding of factors influencing prescribers' behavior within the context. This qualitative study utilizes the Theoretical Domains Framework (TDF) to uncover these influential factors. Methods: We conducted a qualitative study using in-depth interviews and focus group discussions with primary care workers in two provinces in rural Vietnam. Data analysis employed a combined inductive and deductive approach, with the deductive aspect grounded in the TDF. Results: Thirty-eight doctors, doctor associates, and pharmacists participated in twenty-two interviews and two focus group discussions. We identified sixteen themes, directly mapping onto seven TDF domains: knowledge, skills, behavioral regulation, environmental context and resources, social influences, social/professional role and identity, and optimism. Factors driving unnecessary prescription of antibiotics include low awareness of antimicrobial resistance (AMR), diagnostic uncertainty, prescription-based reimbursement policy, inadequate medication supplies, insufficient financing, patients’ perception of health insurance medication as an entitlement, and maintaining doctor-patient relationships. Potential factors facilitating AMS activities include time availability for in-person patient consultation, experience in health communication, and willingness to take action against AMR. Conclusion: Utilizing the TDF to systematically analyze and present behavioral determinants offers a structured foundation for designing impactful AMS interventions in primary care. The findings underscore the importance of not only enhancing knowledge and skills but also implementing environmental restructuring, regulation, and enablement measures to effectively tackle unnecessary antibiotic prescribing in this context