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5. Boron Doping of Silicon Quantum Dots via Hydrogen Silsesquioxane-Capped Diffusion for Photovoltaics and Medical Imaging

Author

Milliken, Sarah, Cheong, I. Teng, Cui, Kai, and Veinot, Jonathan G. C.

Subjects
solution processability, tailoring composition, silicon quantum dots, photoluminescence, General Materials Science, doping, surface functionalization
Abstract

Doped silicon quantum dots (SiQDs) with defined size, dopant distribution, and surface chemistry are highly sought after as a scientific curiosity because their unique properties offer a wide array of potential applications including multimodal medical imaging and photovoltaic devices. This report describes a diffusion-based postsynthesis doping method for incorporating high concentrations of B (2.5–5.0 at. %) into preformed SiQDs of predefined sizes while simultaneously maintaining their structure and morphology. The processing temperature, atmosphere, and QD size all strongly influence the resulting B-doped SiQDs. The as-synthesized doped SiQDs exhibit size-dependent photoluminescence spanning the visible to near-infrared spectral regions, are compatible with aqueous environments, and are readily rendered compatible with organic solvents upon functionalization with appropriate alkoxide surface groups. Being able to effectively tune the size and surface chemistry of the present B-doped SiQDs make them excellent candidates for use in targeted applications such as multimodal imaging and photovoltaic devices.

Published
2022

7. Imágenes Doppler de arterias intrapulmonares dentro de la atelectasia y su impacto en la poscarga del ventrículo derecho con ecocardiografía transesofágica

Author

Longo, S., Cheong, I., Siri, J.E., Tamagnone, F., and Acosta, C.

Abstract

La cirugía cardíaca por toracoscopia videoasistida (VATS) requiere ventilación unipulmonar (VUP) y monitorización con ecografía transesofágica (ETE). Utilizando Doppler color y espectral es posible estudiar el patrón de flujo sanguíneo en los vasos pulmonares dentro del pulmón atelectasiado. El objetivo de este reporte de casos es evidenciar la habilidad de la ETE para detectar el flujo sanguíneo dentro del pulmón atelectásico, así como también valorar la resistencia vascular pulmonar (RVP) y poscarga del ventrículo derecho, utilizando esta misma herramienta.

Published
2024
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13. P1019: A PREDICTION RULE TO GUIDE JAK2 MUTATION TESTING IN PATIENTS WITH SUSPECTED POLYCYTHEMIA VERA: RESULTS FROM THE JAK2 PREDICTION COHORT (JAKPOT) STUDY

Author

Chin-Yee, B., primary, Bhai, P., additional, Cheong, I., additional, Matyashin, M., additional, Hsia, C., additional, Kawata, E., additional, Ho, J., additional, Levy, M., additional, Stuart, A., additional, Lin, H., additional, Chin-Yee, I., additional, Kadour, M., additional, Sadikovic, B., additional, and Lazo-Langner, A., additional

Published
2022
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14. Educating Pre-Service Teachers for a Sustainable Environment

Author

Cheong, I. P.-A

Abstract

The paper reports on an initiative to develop the knowledge, skills and attitudes needed for a sustainable environment. The initiative involved the training of pre-service teachers to not only be aware of, or know about environmental problems and want to act for the environment, but also to be able to act for the environment. Small group community problem solving projects illustrate the nature of environmental community problems that could be acted upon. The process of the projects, including how the pre-service teachers identified the community problems and conducted the projects, is described. Outcomes of the projects including reflections about what the pre-service teachers have learnt in being involved with the projects show the nature of capacity building efforts possible to work towards a sustainable environment. Lessons learnt from the involvement in community problem solving projects are also highlighted.

Published
2005

15. A Teacher's Personal Journey in Using Science Projects

Author

Petra, Dk Hjh Siti Fatimah binti Pg Hj and Cheong, I. P.-A

Abstract

This paper will reflect on the experiences of an educator who had supervised students in a number of science projects entered for competitions organised regionally and internationally. Personal experiences and difficulties faced are shared and possible solutions are discussed. Various factors that affected the progress of the science projects and hence influenced their success are also discussed. The perceived benefits of science projects with students and those involved directly and indirectly are shared. Lastly, an attempt is made to discuss ways to make the science project teaching and learning strategy more viable, meaningful and useful in school-based lessons.

Published
2004

18. Colloidal Silicon Quantum Dot‐Based Cavity Light‐Emitting Diodes with Narrowed and Tunable Electroluminescence.

Author

Cheong, I Teng, Mock, Josef, Kallergi, Maria, Groß, Elisabeth, Meldrum, Alkiviathes, Rieger, Bernhard, Becherer, Markus, and Veinot, Jonathan G. C.

Subjects
*LIGHT emitting diodes, *QUANTUM dots, *ELECTROLUMINESCENCE, *SEMICONDUCTOR nanocrystals, *SILICON, *HIGH voltages
Abstract

Luminescent colloidal silicon quantum dots (SiQDs) are explored as alternatives to metal‐based quantum dots for light‐emitting diodes (LEDs) because of the abundance and biocompatibility of silicon. To date, the broad electroluminescence (EL) bandwidth (>100 nm) and blueshifting of EL at high applied voltages of SiQD‐LEDs are outstanding challenges that limit a competitive spectral purity and device stability. Herein, the fabrication and testing of SiQD‐LEDs that incorporate a Fabry–Pérot cavity are reported which exhibit a narrow spectral linewidth as low as ≈23 nm. The presented devices also provide wavelength and visual stability from +4 to +8 V, as well as spectral tunability. [ABSTRACT FROM AUTHOR]

Published
2023
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24. Primary Human Derived Blood Outgrowth Endothelial Cells: An Appropriate In Vitro Model to Study Shiga Toxin Mediated Damage of Endothelial Cells

Author

Feitz, W.J.C., Kar, N.C.A.J. van de, Cheong, I., Velden, T.J.A.M. van der, Ortiz-Sandoval, C.G., Orth-Höller, D., Heuvel, L.P.W.J. van den, Licht, C., Feitz, W.J.C., Kar, N.C.A.J. van de, Cheong, I., Velden, T.J.A.M. van der, Ortiz-Sandoval, C.G., Orth-Höller, D., Heuvel, L.P.W.J. van den, and Licht, C.

Abstract

Contains fulltext : 225063.pdf (publisher's version ) (Open Access), Hemolytic uremic syndrome (HUS) is a rare disease primarily characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. Endothelial damage is the hallmark of the pathogenesis of HUS with an infection with the Shiga toxin (Stx) producing Escherichia coli (STEC-HUS) as the main underlying cause in childhood. In this study, blood outgrowth endothelial cells (BOECs) were isolated from healthy donors serving as controls and patients recovered from STEC-HUS. We hypothesized that Stx is more cytotoxic for STEC-HUS BOECs compared to healthy donor control BOECs explained via a higher amount of Stx bound to the cell surface. Binding of Shiga toxin-2a (Stx2a) was investigated and the effect on cytotoxicity, protein synthesis, wound healing, and cell proliferation was studied in static conditions. Results show that BOECs are highly susceptible for Stx2a. Stx2a is able to bind to the cell surface of BOECs with cytotoxicity in a dose-dependent manner as a result. Pre-treatment with tumor necrosis factor alpha (TNF-α) results in enhanced Stx binding with 20-30% increased lactate dehydrogenase (LDH) release. Endothelial wound healing is delayed in a Stx2a-rich environment; however, this is not caused by an effect on the proliferation rate of BOECs. No significant differences were found between control BOECs and BOECs from recovered STEC-HUS patients in terms of Stx2a binding and inhibition of protein synthesis.

Published
2020

25. Analysis of Research Trends on Climate Change Mitigation and Adaptation for Climate Change Policy

Author

Oh， Yoon-kyung and Cheong-I Kim

Subjects
Climate change mitigation, Climate change, Forestry, Psychology
Abstract

기후변화 문제는 더 이상 특정 지역이나 국가만의 문제가 아닌 전 세계가 함께 대응해야 할 글로벌 공공재 관리 문제이다. 본 연구에서는 대표적인 기후변화 대응 전략인 완화(mitigation)와 적응(adaptation)에 관한 논문들의 동향을 분석함으로써 학술 차원에서 국내 연구 방향을 설정하고, 나아가 정책 차원에서 향후 우리나라 기후변화 대응정책의 시사점을 제시하고자 하였다. 정부 정책을 채택 · 시행하는 과정에서 연구 투자 및 참여, 연구자의 관심 변화 등이 동반되는 경향이 나타나는 점을 반영하여 연구의 흐름을 통해 정책변화를 파악하였다. 기후변화 완화와 적응에 관한 연구동향을 살펴보기 위하여 유엔기후변화협약(UNFCCC)과 파리협약(Paris Agreement)이 채택 · 이행된 시점인 1992년과 2015년을 고려해 1990년부터 2017년까지 SCI/SCIE, SSCI에 등재된 논문들의 연구동향을 분석하였다. 기후변화 완화와 적응 간 연구동향의 차이 분석에 중점을 두었으며, 아울러 키워드 네트워크 분석을 통해 좀 더 구체적인 완화 전략과 적응 전략의 특성차이를 파악하고자 하였다. 먼저, Web of Science(WoS)를 활용하여 국제기후협약이 채택 · 이행되는 동안 연구동향이 어떻게 변화하였는지를 시기 · 국가 · 연구 분야 · 피인용횟수 등의 측면에서 분석한 후, Textom을 통해 완화 전략과 적응 전략 관련 키워드를 추출하여 키워드 간 네트워크를 분석하였다.

Published
2018

29. Redox‐Active Heteroatom‐Functionalized Polyacetylenes.

Author

Luppi, Bruno T., Muralidharan, Abhishek V., Ostermann, Nils, Cheong, I T., Ferguson, Michael J., Siewert, Inke, and Rivard, Eric

Subjects
POLYACETYLENES, CHEMICAL reduction, RING-opening polymerization, AMINO group, LIGHT absorption, ELECTROLYTIC oxidation, CLICK chemistry
Abstract

The discovery of metallic conductivity in polyacetylene [‐HC=CH‐]n upon doping represents a landmark achievement. However, the insolubility of polyacetylene and a dearth of methods for its chemical modification have limited its widespread use. Here, we employ a ring‐opening metathesis polymerization (ROMP) protocol to prepare functionalized polyacetylenes (fPAs) bearing: (1) electron‐deficient boryl (‐BR2) and phosphoryl (‐P(O)R2) side chains; (2) electron‐donating amino (‐NR2) groups, and (3) ring‐fused 1,2,3‐triazolium units via strain‐promoted Click chemistry. These functional groups render most of the fPAs soluble and can lead to intense light absorption across the visible to near‐IR region. Also, the presence of redox‐active boryl and amino groups leads to opposing near‐IR optical responses upon (electro)chemical reduction or oxidation. Some of the resulting fPAs show greatly enhanced air stability when compared to known polyacetylenes. Lastly, these fPAs can be cross‐linked to yield network materials with the full retention of optical properties. [ABSTRACT FROM AUTHOR]

Published
2022
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41. What Do You Know about Alternative Energy? Development and Use of a Diagnostic Instrument for Upper Secondary School Science

Author

Cheong, I., Johari, M., Said, H., Treagust, David, Cheong, I., Johari, M., Said, H., and Treagust, David

Abstract

The need for renewable and non-fossil fuels is now recognised by nations throughout the world. Consequently, an understanding of alternative energy is needed both in schools and in everyday life-long learning situations. This study developed a two-tier instrument to diagnose students’ understanding and alternative conceptions about alternative energy in terms of: sources of alternative energy, greenhouse gas emission, as well as advantages, and disadvantages. Results obtained with Years 10 and 11 students (n = 491) using the 12-item two-tier instrument (α = 0.61) showed that students’ understanding of alternative energy was low (M = 7.03; SD = 3.90).The 23 alternative conceptions about alternative energy sources that could be identified from the instrument are reported. The implications for teaching and learning about alternative energy and suggestions for further development and improvement of the instrument are presented.

Published
2015

42. Evaluating Students' Understanding of Kinetic Particle Theory Concepts Relating to the States of Matter, Changes of State and Diffusion: A Cross-National Study

Author

Treagust, David, Chandrasegaran, Arulsingam, Crowley, Julianne, Yung, B., Cheong, I., Othman, J., Treagust, David, Chandrasegaran, Arulsingam, Crowley, Julianne, Yung, B., Cheong, I., and Othman, J.

Abstract

This paper reports on the understanding of three key conceptual categories relating to the kinetic particle theory: (1) intermolecular spacing in solids, liquids and gases, (2) changes of state and intermolecular forces and (3) diffusion in liquids and gases, amongst 148 high school students from Brunei, Australia, Hong Kong and Singapore using 11 multiple-choice items that required students to provide explanations for their selection of particular responses to the items. Students’ responses to the items revealed limited understanding of the particle theory concepts, with nine alternative conceptions held by more than 10% of various samples of students. Also, 40.5–78.4%of all students indicated consistent understanding relating to the three conceptual categories based on their responses to the 11 items. However, when their explanations were taken into account, very few students displayed consistent understanding of the related concepts.

Published
2010

43. Evaluation of Students' Conceptual Understanding of Malaria

Author

Cheong, I., Treagust, David, Kyeleve, I., Oh, P., Cheong, I., Treagust, David, Kyeleve, I., and Oh, P.

Abstract

In this study, a two‐tier diagnostic test for understanding malaria was developed and administered to 314 Bruneian students in Year 12 and in a nursing diploma course. The validity, reliability, difficulty level, discriminant indices, and reading ability of the test were examined and found to be acceptable in terms of measuring students' understanding and identifying alternative conceptions with respect to malaria. Results showed that students' understanding of malaria was high for content, low for reasons, and limited and superficial for both content and reasons. The instrument revealed several common alternative conceptual understandings students' hold about malaria. The MalariaTT2 instrument developed could be used in classroom lessons for challenging alternative conceptions and enhancing conceptions of malaria.

Published
2010

45. Can Science Education Help to Reduce Global Warming?: An International Study of the Links between Students’ Beliefs and their Willingness to Act

Author

Rodríguez, Manuel, primary, Dua, Shweta, additional, Ambusaidi, Abdullah, additional, Cheong, I. Poh-Ai, additional, Yoon, Hye-Gyoung, additional, Kim, Mijung, additional, Boyes, Eddie, additional, Stanisstreet, Martin, additional, Skamp, Keith, additional, Malandrakis, Georgios, additional, Fortner, Rosanne, additional, Kilinc, Ahmet, additional, Taylor, Neil, additional, and Chhokar, Kiran, additional

Published
2011
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