Structural Driving Factors for the Coupled Electron and Proton Transfer Reactions in Mitochondrial Cytochrome BC1 Complex: Binding Geometries of Substrates and Protonation States of Ionizable Amino Acid Side Chains Near Qi and Qo Sites

Coupled electron and proton transfer (CEPT) events are fundamental for many bioenergetic conversions that involve redox reactions. Understanding the details underlying CEPT processes will advance our knowledge of (1) how nature regulates energy conversion; (2) our strategies for achieving renewable energy sources; (3) how to cope with CEPT dysfunction diseases. Studies of the detailed mechanism(s) of CEPT in biological systems is challenging due to their complex nature. Consequently, controversies between the concerted and sequential mechanism of CEPT for many systems remain. This dissertation focuses on the bovine mitochondrial cytochrome bc1 complex. CEPT in the bc1 complex operates by a modified Q-cycle (1) and catalyzes electron transfer from ubiquinol (QH2), to cyt c via an iron sulfur cluster (ISC) and to the low potential hemes of cyt b, where it reduces ubiquinone (UQ). The electron transfer is coupled to the translocation of protons across the mitochondrial inner membrane, generating a proton gradient that drives ATP synthesis. Although the Q-cycle is widely accepted as the model that best describes how electrons and protons flow in bc1, detailed binding geometries at the Qo site (QH2 oxidation site) and Qi site (UQ reduction site) remain controversial. The binding geometries play critical roles in the thermodynamic and/or kinetic control of the reaction and protonatable amino acid side chains can participate in the proton transfer. The central focuses of this dissertation are molecular dynamics simulations of cofactor binding geometries near the Qo and Qi sites, calculations of the pKa values of ionizable amino acid side chains implicated in cofactor binding, especially the ISC-coordinated histidines, and implications for the proposed mechanism(s) of CEPT. For the first time, pKa values of the ISC-coordinated histidines are differentiated. The computed pKa values of 7.8±0.5 for His141 and 9.1±0.6 for His161 agree well with experiment (7.63±0.15 and 9.16±0.28). Thus, His161 should be protonated at physiological pH and cannot be the first proton acceptor in the QH2 oxidation. Water mediated hydrogen bonds between substrate models and the protein and water accessibility to the Qo and Qi sites were maintained in simulations, implying that water molecules are likely the proton donors and acceptors

FACTORS INFLUENCING THE USE OF PHYPHOX SOFTWARE IN PHYSICS TEACHING AT HIGH SCHOOLS IN VIETNAM

In the context of contemporary digital education, the use of Phyphox software to turn smartphones into physics experiment equipment opens new opportunities for physics education in Vietnam, yet there are many challenges and opportunities to be explored. This study aims to evaluate the factors influencing the integration of this technology into teaching through a survey of 48 physics teachers nationwide using an online questionnaire with a 5-point Likert scale. Results show that teachers are confident and willing to adopt new technology, recognizing the positive impact of the software on educational quality and student engagement. However, they face difficulties integrating the software into lessons and lack support from resources and school leadership. The study emphasizes the importance of integrating technology into education and provides a basis for developing more effective teacher support strategies. This research contributes to the theoretical foundation on software use in education and aids policy makers, educational managers, and software developers in shaping strategies to optimize technology use in education, enhancing educational quality and preparing students with the necessary skills for the digital era

Evaluating factors affecting attitudes of IT-intensive and non-IT-intensive students towards e-assessment

Despite the significant shift to distance computer-based test as an inevitable outcome of Industry 4.0 and the public lockdown of COVID-19, little effort has been made to research this new testing mode. To address this issue, this study targets two groups of information technology (IT)-intensive and non-IT-intensive students with an aim of investigating factors that effectively encourage each group to adopt online assessment and whether their majors cause any differences in the students’ attitudes. Based on the student perception of e-assessment questionnaire (SPEAQ) with some slight modifications, a final 28-item survey was formed and distributed to 400 students. Results have shown that the factors of security, and affective factors were the top factors to impact both groups of students, while the impact of validity and practicality varied among the two groups and reliability and teaching-learning were at the bottom. Besides, there were no noticeable differences in the attitudes of students coming from different majors

Application of the Empirical Mode Decomposition On the Characterization and Forecasting of the Arrival Data of an Enterprise Cluster

Characterization and forecasting are two important processes in capacity planning. While they are closely related, their approaches have been different. In this research, a decomposition method called Empirical Mode Decomposition (EMD) has been applied as a preprocessing tool in order to bridge the input of both characterization and forecasting processes of the job arrivals of an enterprise cluster. Based on the facts that an enterprise cluster follows a standard preset working schedule and that EMD has the capability to extract hidden patterns within a data stream, we have developed a set of procedures that can preprocess the data for characterization as well as for forecasting. This comprehensive empirical study demonstrates that the addition of the preprocessing step is an improvement over the standard approaches in both characterization and forecasting. In addition, it is also shown that EMD is better than the popular wavelet-based decomposition in term of extracting different patterns from within a data stream

Students' Views of Art Education as Their Future Career

Art has long been an important subject of the education system. In Vietnam, teaching arts is taken a solid position as a subject of the education system from primary to tertiary education level. However, little is known about the situation and the need for transformation in the way students are trained to become art teachers. To clarify the view and attitudes of the to-be-an-art-teacher students, we conducted an online survey to collect data from students who enrolled in the bachelor course, majoring in art teaching at a university in Vietnam. A total of 57 students participated in the survey, most of them are females in the second year of the on-the-job B.A. course. The results showed that the respondents reported needing more diversified learning content such as applied arts, installation, and multimedia. They showed a need to have more practice sessions and fieldwork such as visiting museums and exhibitions. The respondents specified that they chose this major because they love the subject and love teaching, as well as to address the social need of learning arts, as arts seem to be a more important subject for elementary education. They shared a positive attitude toward the internationalization of local art education, however, none of them plan to study abroad. These findings imply the need for improving the quality of teaching and internationalization of art teacher education to meet international standards in the context of a developing country

How to Support Poor Vietnamese Consumers to Deal with Food Price Volatility and Food Safety Issues

With 66 per cent of the population living in rural areas, over half depending on farm activities, food security and food safety are now two sides of the government effort to ensure food accessibility for the poor in Vietnam. While people living on low incomes may have to choose cheaper food over safer food, they are now more aware of food safety issues, and need more support to access safe food. After a long time of focusing on increasing food security in terms of quantities, new efforts are now needed to change the practice and awareness of stakeholders to move to quality?oriented production and consumption, including creating reasonable incentives for food producers, socialising of food safety monitoring and improving food safety inspection in Vietnam

EFFICACY OF Ageratum LEAF EXTRACT ON POSTHARVEST ROT CAUSED BY Aspergillus niger AND Colletotrichum sp. ON CHILLI FRUITS

Abstract: The damage of chilli, an important spice fruit, comes from fungal diseases caused mainly by Aspergillus niger and Colletotrichum sp. The fungi on chilli fruits would directly harm consumers’ health. Plant extracts containing bio-active compounds with antimicrobial properties could be a good possible solution to deal with the fungi. This study aims to evaluate the in vitro and in vivo efficacy of aqueous extracts from the leaves of Ageratum plants against A. niger and Colletotrichum sp. The results show that the optimal efficacy of the treatment of Ageratum leaf extract is at a concentration of 6%, with the efficacy of Ageratum leaf extract on colonial diameter at approximately 43–44% for the two fungi at 96 hours after inoculation. The 6% Ageratum leaf extract has a high efficacy (~54.23%) on limiting the development of Aspergillus rot lesions on chilli fruits 4 days after inoculation. Meanwhile, the efficacy of the extract on Colletotrichum lesions is 11.34%, lower than that of Aspergillus rot.Keywords: Ageratum leaf extract, chilli fruit, rot lesio

Modified Dijkstra's Routing Algorithm for Security with Different Trust Degrees

A great number of efficient methods to improve the performance of the networks have been proposed in physical-layer security for wireless communications. So far, the security and privacy in wireless communications is optimized based on a fixed assumption about the trustworthiness or trust degrees (TD) of certain wireless nodes. The nodes are often classified into different types such as eavesdroppers, untrusted relays, and trusted cooperative nodes. Wireless nodes in different networks do not completely trust each other when cooperating or relaying information for each other. Optimizing the network based on trust degrees plays an important role in improving the security and privacy for the modern wireless network. We proposed a novel algorithm to find the route with the smallest total transmission time from the source to the destination and still guarantee that the accumulated TD is larger than a trust degree threshold. Simulation results are presented to analyze the affects of the transmit SNR, node density, and TD threshold on different network performance elements

Multihop Decode-and-Forward Relay Networks: Secrecy Analysis and Relay Position Optimization

Relay communication has advantages over direct transmission in terms of secrecy capacity. In this paper, the performance of secrecy, offered by multihop decode-and-forward relaying, is investigated and compared to its counterpart in direct transmission. Three key performance measures are derived over Rayleigh fading channels: probability of non-zero secrecy capacity, secure outage probability and secrecy capacity, which are valid for an arbitrary number of hops. Based on the tractable form of the probability of non-zero secrecy capacity, the optimization problem of trusty relay replacement is also studied. Numerical results indicate that a proper relay replacement can increase the network security without extra network resources. The correctness of analytical results is confirmed by using a MATLAB-based independent simulation model