Fluorescent biosensor using whole cells in an inorganic translucent matrix

8 pagesInternational audienceAn optical biosensor based on vegetal cells entrapped in an inorganic translucent matrix and fluorescence detection has been developed. The biosensor uses Chlorella vulgaris immobilized in a translucent support produced from sol-gel technology. The translucence of the structure enables the algal active layer to be placed directly in contact with the optical fibers for fluorescence detection. This configuration has many advantages over the use of an opaque support because no space between the optical fibers and the active layer is required to collect fluorescence. This reagentless biosensor allows determination of diuron as an anti-PSII herbicide and its long term activity is assessed

Sol-gel process for vegetal-cells encapsulation

International audienceA sol-gel process was carried out at room temperature to obtain porous silica matrixes for entrapment of vegetal cells. The process uses sodium silicate as a precursor rather than alkoxides to avoid generation of by-products that is detrimental to Chlorella vulgaris cells. The influence of several factors influencing the gelification was explored to optimize the encapsulation process. The technique produces a transparent matrix and is then very suitable for vegetal cells entrapment since they require light for their photosynthetic activity. Activity of the algal cells was determined by measurement of the intensity of fluorescence emission at 682 nm. This measurement also allowed to evaluate the efficiency of the immobilization technique and assess the long term activity of the encapsulated whole-cells

Synchronous-scan fluorescence of algal cells for toxicity assessment of heavy metals and herbicides.

International audienceSynchronous-scan spectrofluorometry was applied to Chlorella vulgaris cells to assess the toxicity of heavy metals and herbicides in water. Simultaneous scan of both the excitation and emission spectra was done at a constant wavelength difference Deltalambda (20-140 nm) between the emission and excitation wavelengths in the range of 420-700 nm emission, where a peak of fluorescence was observed. Its position depends on Deltalambda. Fluorescence measurements were conducted with algal cells in suspension in water and immobilized in a translucent silica matrix. The influence of toxic chemicals was tested with cadmium as a heavy metal and with atrazine, diuron, DNOC and paraquat as herbicides. The toxic effect of those chemicals mainly results in a quenching of algal cells fluorescence by reducing their photosynthetic activity

Enhancing light scattering effect of white LEDs with ZnO nanostructures

Pc-LEDs, the lighting method that blends blue LED light with yellow light from phosphor to discharge white radiation, is one of the most advance known for high lumen output. However, pc-LEDs has inferior due to angular CCT deviation, which prevent pc-LEDs from reaching better performance. As a result, this research is conducted to address the need of pc-LEDs development by introducing a configuration doped with ZnO nanoparticles. The finite-difference time-domain (FDTD) method and the phosphor layer containing ZnO were applied in the experiments. The effect of ZnO-filled on the performance of color quality pc-LEDs is confirmed through calculated results. In particular, the uniformity of scattered light is improved with the presence of ZnO. In addition, ZnO particles also minimize the deviation of color temperature and enhance the color quality. Although there is a small decline in lumen output to achieve better color temperature uniformity, however, with suitable concentrations such as 0.25% N-ZnO, 0.25% S-ZnO, and 0. 75% R-ZnO, the decline is acceptable. The research on ZnO pc-LEDs demonstrates that this affordable and simple configuration can improve lighting properties and create other directions to enhance white ligh

DOES DEMOGRAPHICS MATTER IN LIFELONG LEARNING? A RESEARCH CONTEXT OF VIETNAM

Objective: Lifelong learning (LLL) has lately attracted significant attention from the society in general, universities and corporations in particular. For the case of Vietnam, the Government has pledged to create a Lifelong Learning Society. A number of initiatives have been launched to help achieve this goal, including the Southeast Asian Ministers of Education Organization Centre for Lifelong Learning (SEAMEO CELLL) and "Book Day", a day dedicated to encouraging reading and raising awareness of its importance in the development of knowledge and skills. Lifelong learning (LLL) programs are also being adopted at libraries, museums, cultural centers, and clubs in Vietnam. In addition to the effort done by the Vietnamese government, a number of non-governmental, non-profit organizations and educational institutions have started to take action to encourage literacy and lifelong learning. It can be said that education and educational reforms are always the top concern of each country. This study is to investigate about lifelong learning of community with 4 aspects: (1) Learning Competencies; (2) Learning Contexts; (3) Learning Contents and (4) Learning Goals as well as examining the differences in the opinion about lifelong learning between categorical variables. The second purpose of the study is to examine the relationship between an individual's perspective on lifelong learning and their actual learning capacity, as well as learning motive. Methods: The paper deploys primary data collecting from 270 people in different sectors and different occupations. Standard statistical techniques such as mean analysis, OLS multivariable analysis are used to find the answer for proposed hypotheses. Results: Using a sample of 270 respondents varying in age, gender, and employment status, the authors found that there are differences on the attitudes towards lifelong learning, the motivations and skills needed for this “journey”. Conclusion: From the findings, researchers proposed recommendations to promoting and fostering lifelong learning of community with the case of Vietnam

Investigation on the application of ZnO nanostructures to improve the optical performance of white light-emitting diodes

Though combining blue LED chips with yellow phosphor has been the most common method in white light-emitting diode (WLED) production, the attained angular correlated color temperature (CCT) uniformity is still poor. Thus, this article proposes to add ZnO nanostructures to WLED packages to promote the color uniformity of the WLEDs. The outcomes of the research demonstrate that utilizing ZnO at different amount can affect the scattering energy and the CCT deviations in WLEDs packages in different extents. Particularly, adding the node-like (N-ZnO), sheet-like (S-ZnO), and rod-like (R-ZnO) leads to the corresponding decreases of CCT deviations from 3455.49 K to 96.30 K, 40.03 K, and 60.09 K, respectively. Meanwhile, with 0.25% N-ZnO, 0.75% S-ZnO, and 0.25 % R-ZnO, WLED devices can achieve both better CCT homogeneity and lower reduction in luminous flux. The results of this article can be a valuable document for the manufacturer to use as reference in improving their WLED products

The application of dual-layer remote phosphor geometry in achieving higher color quality of WLEDs

If remote phosphor structures are put into comparison with conformal phosphor or in-cup phosphor, their luminous flux are better, but the color quality is not as elevated. This leads to an obvious need of a practical solution to enhance color quality. Therefore, many studies were carried out to achieve this purpose, and so is ours. We proposed using two layers of phosphor in WLEDs to achieve better rendering ability and chromatic performance. The identical WLEDs with different color temperatures, 5600 K-8500 K, were used and reported in this paper. Our research consists of two parts, which are placing a layer of red phosphor SrwFxByOz:Eu2+,Sm2+on the yellow YAG:Ce3+ phosphor layer at first, and then specifying an appropriate SrwFxByOz:Eu2+,Sm2+ concentration to reach the highest color performance. It is shown that with the contribution of SrwFxByOz:Eu2+,Sm2+,the color rendering index (CRI) and color quality scale (CQS) are increased. This can be explained by the increased amount of red light components in the WLEDs when the concentration of SrwFxByOz:Eu2+,Sm2+ was greater. However, excessive SrwFxByOz:Eu2+,Sm2+ will cause the reduction in the flux, which has been proven by the application of Mie scattering and the Lambert-Beer law. Therefore, the conclusion will present an optimal amount of SrwFxByOz:Eu2+,Sm2+ to obtain high color quality while minimizing the light loss

Clustering lifestyle risk behaviors among Vietnamese adolescents and roles of school : a Bayesian multilevel analysis of global school-based student health survey 2019

Background: Adolescence is a vulnerable period for many lifestyle risk behaviors. In this study, we aimed to 1) examine a clustering pattern of lifestyle risk behaviors; 2) investigate roles of the school health promotion programs on this pattern among adolescents in Vietnam. Methods: We analyzed data of 7,541 adolescents aged 13–17 years from the 2019 nationally representative Global School-based Student Health Survey, conducted in 20 provinces and cities in Vietnam. We applied the latent class analysis to identify groups of clustering and used Bayesian 2-level logistic regressions to evaluate the correlation of school health promotion programs on these clusters. We reassessed the school effect size by incorporating different informative priors to the Bayesian models. Findings: The most frequent lifestyle risk behavior among Vietnamese adolescents was physical inactivity, followed by unhealthy diet, and sedentary behavior. Most of students had a cluster of at least two risk factors and nearly a half with at least three risk factors. Latent class analysis detected 23% males and 18% females being at higher risk of lifestyle behaviors. Consistent through different priors, high quality of health promotion programs associated with lower the odds of lifestyle risk behaviors (highest quality schools vs. lowest quality schools; males: Odds ratio (OR) = 0·67, 95% Highest Density Interval (HDI): 0·46 – 0·93; females: OR = 0·69, 95% HDI: 0·47 – 0·98). Interpretation: Our findings demonstrated the clustering of specific lifestyle risk behaviors among Vietnamese in-school adolescents. School-based interventions separated for males and females might reduce multiple health risk behaviors in adolescence. Funding: The 2019 Global School-based Student Health Survey was conducted with financial support from the World Health Organization. The authors received no funding for the data analysis, data interpretation, manuscript writing, authorship, and/or publication of this article. © 2021 The Author(s

Using CaCO3-doped package to improve correlated color temperature uniformity of white light-emitting diodes

The white light-emitting diode (WLED) has been the most advance lighting method currently, however, the fabrication process of this configuration still has drawbacks which negatively affect its color quality. This research was conducted to provide a method for WLED’s lighting output enhancement. Since CaCO3 particles are excellent for thermal stability enhancement, especially when being combined with an adhesive substance, we decided to integrate CO3 particles into resin matrix such as melamine formaldehyde (MF) and investigate their influences on the optical properties, including color uniformity and lumen output, of the WLED. The results showed that CaCO3 and MF resin are beneficial to the light scattering efficiency, which results in higher luminous flux and chromatic quality for WLED packages. In addition to that, the appropriate amounts of MF resin and CaCO3 for reaching the best lumen efficiency and color quality are figured out at 1% and 10%, respectively. Moreover, another advantage of using MF resin and CaCO3 for fabricating WLEDs is cost effectiveness. Hence, it has turned out that CaCO3 and MF resins can be potential materials for next high-quality WLED generations

Towards Green Tourism Development: Customers’ Perception of Using Plastic Products in the 5-star Hotels in Ho Chi Minh City

In recent years, green tourism has become a development trend, attracting the attention of the community, tourism businesses and tourists in many countries around the world. However, the approach of green tourism development in Vietnam is still limited in terms of scale and participants. This article examines the situation of using plastic products and the plastic waste treatment in the 5-star hotels in Ho Chi Minh City. Specifically, this study aims to explore the perception of customers of the use of plastic products. By doing so, the study contributes to clarifying the current situation of green tourism development in the hotel sector in the study area. The authors used the research methods of questionnaire, semi-structured interview and non-participant observation to conduct this study. Research results show that although the use of plastic products in hotels is still high, the plastic waste treatment is not thorough because of high treatment costs. But, the hotels tend to change policy on the treatment of plastic waste in an environmentally friendly manner. Besides, customers’ perception of plastic products is completely positive related to their attitudes when using, the willingness to pay and the desire to access more environmentally friendly services and products in the hotel sector. Based on the results, the article also discusses and suggests implications and approaches to developing products and services in hotels towards the development of green tourism and sustainable tourism in the future