Realizing quinary charge states of solitary defects in two-dimensional intermetallic semiconductor

Creating and manipulating multiple charge states of solitary defects in semiconductors is of essential importance for solitary defect electronics, but is fundamentally limited by Coulomb''s law. Achieving this objective is challenging, due to the conflicting requirements of the localization necessary for the sizable band gap and delocalization necessary for a low charging energy. Here, using scanning tunneling microscopy/spectroscopy experiments and first-principles calculations, we realized exotic quinary charge states of solitary defects in two-dimensional intermetallic semiconductor Sn₂Bi. We also observed an ultralow defect charging energy that increases sublinearly with charge number rather than displaying the usual quadratic behavior. Our work suggests a promising route for constructing multiple defect-charge states by designing intermetallic semiconductors, and opens new opportunities for developing quantum devices with charge-based quantum states.     

Challenges in STEM Teaching: Implication for Preservice and Inservice Teacher Education Program

As former and current STEM (science, technology, engineering, and mathematics) school teachers in Singapore, we explore the challenges we both experienced while teaching at different STEM schools. Through this article, we make a case for the teacher preparation programs locally and around the world to give more attention to a changing education landscape with emerging specialized STEM schools. Nonetheless, even though specialized STEM teacher preparation is needed, we also caution that having such a specialized program may limit teachers' horizontal transition to mainstream schools and awareness of the contextualized needs of more diverse learners.     

Experimental verification of Faradaic charging in ac electrokinetics

This paper investigates the phenomenon of Faradaic charging in ac electrokinetics. Faradaic reactions were suggested as a key effect responsible for the reversal of pumping direction in ac micropumps. However, this hypothesis has yet to be proven convincingly and directly. Here we present an ion detection strategy to determine the production of ions through Faradaic hydrolytic reactions originating from direct application of voltage to electrolytic solutions during ac electrokinetics. Experiments were performed with symmetrical planar electrodes aligned along a microfluidic channel. Fluorescein, a pH-dependent dye, was employed as the pH indicator for the detection of ion production. Images were captured for analysis at various voltage levels. From analyzing the fluorescence intensity and its distribution, it can be concluded that the production of ions from hydrolytic reactions takes place and increases with the ac voltage. The coefficient of deviation indicates a significant enhancement at ac voltage above 11 V_pp. Lastly, we demonstrate a strategy using dc-biased ac electrokinetics to achieve controllability in direction and magnitude of the net fluid flow in pumping application.     

The use of weblogs in higher education settings: A review of empirical research

“Weblogs” or “blogs” are increasingly visible in higher education settings. Some scholars suggest that blogs are useful because of their reflective nature. However, as this review indicates the research regarding blogs is largely self-report data (surveys, interviews) or content analyses. This review summarizes results of this existing research on weblogs in higher education settings. Limitations of existing empirical studies are discussed and some directions for future research related to the use of blogs in higher education settings are suggested.     

Discontinuum analyses of openings constructed with side drift and limited rock cover

The design of rock support for a typical horseshoe shaped tunnel with considerations of it being excavated into a twin arch tunnel was studied using the distinct element method (DEM). Two different competent rock covers, i.e. 4 m and 7.5 m above the tunnel crown, were analysed. The results are relevant to the granitic geological unit in Singapore which has a weathering profile with rockhead found at some locations to be only 20–35 m below ground level and undulating, leaving limited rock cover for some sections along tunnels of similar depth. The verification of the adequacy of competent rock cover is important to ensure that the choice of ground support is suitable, particularly when the tunnel is excavated using the drill-and-blast method. In the opening geometry analysed in this study, a side drift is excavated adjacent to the first tunnel to create a twin arch opening. This creates a pillar between the openings during the intermediate construction stage. The influence of excavating the side drift on the support of the first opening was studied. We found that the bolt forces in the pillar approximately doubled during the excavation of the side drift, which may have been due to the rock joint inclinations and adopted strength parameters. This paper shows how DEM analyses may be used to complement conventional empirical rock mass classifications to design rock supports. Limitations of the pressure relaxation approach to model 3D effects in 2D are acknowledged.     

What Primary Students in the Chinese Mainland,Hong Kong and Taiwan Value in Mathematics Learning: A Comparative Analysis

It has become increasingly recognized that what teachers and students value affect teaching and learning in general and in the area of mathematics in particular. Yet, the extent to which this is so varies across cultural regions. In recent years, how the ethnic Chinese teach and learn mathematics has attracted much attention worldwide. It is precisely the purpose of the present study to investigate the value structures of three Chinese regions. Using a recently developed and validated questionnaire, students’ values in mathematics learning in the Chinese Mainland, Hong Kong and Taiwan are delineated. In the first place, the results reveal that there are six dimensions in the students’ value structure, namely achievement, relevance, practice, communication, information and communications technology as well as feedback. However, in each of the six value components derived from the principal components analysis, statistically significant differences between the regions were found.     

Importance of Biology in Environmental Education

One of the aims in the Singapore Green Plan is to maintain a more proactive and environmentally conscious population. This can be met through the education of the people. The Plan recognises that one of the most important target groups is the student population. For this to be achieved, a case can be made for the teaching of biology as a core subject in both the primary and secondary schools. According to the Biological Science Inquiry Model, a teaching model designed for instructing and nurturing the learning process of students, a good foundation in biology will enable students to be more open minded, more inquiring into related issues and apply biological principles to rationalise such issues. A good grounding in biology will therefore help students to have a better understanding of environmental issues as these issues are extensively related to biological principles. This can be illustrated by the ten issues concerning the global environment highlighted at the United Nations Conference on the Environment in June 1992. Through a systematic discussion of each of these issues, this paper illustrates the importance of biological knowledge in understanding the problems, implications and consequences of these issues.     

Effects of an Ancient Chinese Mathematics Enrichment Programme on Secondary School Students’ Achievement in Mathematics

Ancient Chinese mathematics has been the focus of many research studies and scholarly works from a historical perspective. However, no move has been made to investigate its role in the teaching and learning of mathematics. This pilot study examined the effects of an Ancient Chinese Mathematics Enrichment Programme (ACMEP) on the academic achievement of second year students from a secondary school in Singapore—a strand of a principal study which had the intent of investigating possible roles of ancient Chinese mathematics in the Singapore secondary school mathematics curriculum. Analysis of covariance was used to examine the difference in mean scores on a variety of formal assessments in mathematics between students who participated in the ACMEP and those who did not. In addition, scores on formal assessments of other relevant subjects were analyzed to further investigate ACMEP’s scope of influence.