156 research outputs found
Machining of 2D material by ultrasonic embossing
No full textAs popularity of 2D material has increased over the years since the discovery of Graphene in 2004, their usage in the field was also characterised by their properties. Graphene for its mechanical properties like high strength, stiffness, toughness, and conductivity. Hexagonal Boron Nitride for its chemical inertness and electrical insulation properties. By working with 2D materials in the nanoscale, the author hopes to understand and gauge their properties in
the quantum scale. Hence, in this report the author will share the process of creating nanostructures and nanodots from Graphene and Hexagonal Boron Nitride with the use of ultrasonic embossing on substrate materials like silver and copper whilst exploring the
parameters used to obtain the highest yield of nanostructures. From previous studies and research on similar topics, the fundamental method of choice for sample preparation will be the top-down mechanical exfoliation. More commonly known as the “Scotch-tape” method.
The author will also be testing out other methods of sample preparation for bulk materials that are already in the powdered form. With existing studies of ultrasonic embossing on other types of 2D materials, the author started off with a familiarisation process with the
type and characteristics of the materials and equipment. On the other hand, skill sets employed during the experiment such as delicate handling of samples and skilful usage of the scanning electron microscope needs to be gained through repeated practices. The
results obtained from the ultrasonic embossing confirms that the greatest yield of nanostructures falls within the range of 1300N – 1400N for welding and holding forces and embossing amplitude ranging from 17% - 22%.Bachelor of Engineering (Mechanical Engineering
Nanostructured materials for electrochemical carbon dioxide reduction and biosensing
No full textThe work included in this thesis aims to investigate a new metal nanostructure fabrication method and its unique applications. Strategies of nanostructure synthesis can be diverse, but a fast, scalable, and cost-effective method for 1D material fabrication in one step has not been reported yet. In this thesis, a room temperature ultrasonic nanoimprinting technique for 1D metal nanostructure fabrication has been developed. Working at room temperature, ultrasonic nanoimprinting rapidly fabricates multi-compositional nanostructures made of virtually all solid materials regardless of their ductility, hardness, reactivity, and melting points. As proof-of-concept, the applications of the fabricated nanostructures for electrochemical CO2 reduction and quorum sensing have been demonstrated.
First, the ultrasonic nanoimprinting method is introduced for complex 1D nanostructure fabrication, including pure metal nanowires, bimetallic nanorods, and metal nanorods with built-in nanogaps. The working principle of ultrasonic nanoimprinting is investigated by atomic resolution characterization and molecular dynamics simulation.
Second, Ag and Au based 1D nanostructure as catalysts for electrochemical CO2 reduction reaction are presented. The Ag@AgClx CSNWs offer high catalytic activity and selectivity towards CO, owing to the high conductivity of Ag core and abundant active sites on AgClx shell. Then electric field effect on ordered Au nanowires is investigated and (semi)quantified. At the same time, we show that high index facets play a crucial role in electrochemical CO2RR on Au nanowire catalyst, which works synergistically with concentrated electric field to optimize the CO2RR activity.
Third, Ag nanorods with build-in nanogaps are fabricated by using our ultrasonic nanoimprinting after depositing alumina sacrificial layer and Ag layer on the substrate by e-beam evaporation. As a biosensing platform, this substrate shows strong Raman signals for quorum sensing.
In summary, a fast, scalable, energy-efficient, and cost-effective 1D metal nanostructure fabrication method has been developed. The fabricated nanowires and complex 1D nanostructure show high potential for various engineering applications, including electrochemical CO2 reduction to fuel and quorum sensing.Doctor of Philosoph
Mid-infrared group IV nanowire laser
No full textSemiconductor nanowires have shown great potential for enabling ultracompact lasers for integrated photonics platforms. Despite the impressive progress in developing nanowire lasers, their integration into Si photonics platforms remains challenging largely because of the use of III-V and II-VI semiconductors as gain media. Recently, group IV nanowires, particularly direct bandgap GeSn nanowires capable of emitting above 2 μm, have emerged as promising cost-effective gain media for Si-compatible nanowire lasers, but there has been no successful demonstration of lasing from this seemingly promising nanowire platform. Herein, we report the experimental observation of lasing above 2 μm from a single bottom-up grown GeSn nanowire. By harnessing strain engineering and optimized cavity designs simultaneously, the single GeSn nanowire achieves an amplified material gain that can sufficiently overcome minimized optical losses, resulting in single-mode lasing with an ultralow threshold of ~5.3 kilowatts per square centimeter. Our finding paves the way for all–group IV mid-infrared photonic-integrated circuits with Si-compatible lasers for on-chip classical and quantum applications
Autism Spectrum Disorder: New Insights into Molecular Pathophysiology and Therapeutic Development
No full textThis eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contac
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Tourism Gamification and Immersive Experience: A Perspective of Arousal Theory
No full textNing Zhang ([email protected]) is a master’s student in the School of Tourism Management at Sun Yat-sen University, China. Ning obtained her bachelor’s degree in Tourism Management at Zhengzhou University. Her research focuses mainly on tourist experience.
Yueyin Zhou ([email protected]) is an undergraduate student in the School of Tourism Management at Sun Yat-sen University, China. Yueyin’s major is Event Economic and Management. Her research mainly focuses on tourist experience.
Yingsha Zhang, Ph.D. ([email protected]), is an associate professor of tourism in the School of Tourism Management at Sun Yat-sen University, China. Yingsha’s research mainly focuses on destination marketing and management, tourist behavior and decision-making, and tourism geography, with special emphasis on theme parks. Yingsha Zhang is the corresponding author.
Junyu Zhou ([email protected]) is an undergraduate student in the School of Tourism Management at Sun Yat-sen University, China. Yueyin’s major is Event Economic and Management. His research mainly focuses on tourist experience.By viewing all tourism as activities with different gamification levels and collecting 1088 valid questionnaires, this study examines the relationship between the tourism gamification index and immersive tourism experience, with travel experience and arousal demand as moderators suggested by the arousal theory. The scale of gamification index was determined first, based on which a scale and a calculation formula for tourism gamification index were then developed. Comparisons were conducted between leisure sports tourism, Han-Chinese-costume photo-shooting tourism, and traditional sightseeing tourism. Findings suggest that overall, immersive tourism experience is positively influenced by tourism gamification index and the square of arousal demand, and negatively affected by travel experience. The influence of tourism gamification index on immersive tourism experience is moderated by arousal demand. These relationships vary significantly between different types of tourism. The tourism gamification index for leisure sports tourism and Han-Chinese-costume photo-shooting tourism is significantly higher than that for sightseeing tourism
Three-dimensional surface texture synthesis
No full textThis copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that the copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the prior consent of the author or the University (as may be appropiate) Texture synthesis has been extensively investigated by both computer vision and computer graphics communities during the past twenty years. However, the input and output are normally 2D intensity texture images. If the subjects are 3D surface textures (such as brick, woven or knitted textiles, embossed wallpapers etc.), these 2D synthesis techniques cannot provide the information required for rendering under other than the original illumination and viewpoint conditions. The aim of this thesis therefore is to develop inexpensive approaches for the synthesis of 3D surface textures. Few publications are available in this research area. We first introduce an overall framework for the synthesis of 3D surface textures. The framework essentially combines surface representation methods wit
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No full textAlthough numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation
Enhanced Dendrite Resistance in Reversible Electrochemical Pneumatic Batteries with Nanoimprinted Nanowire Anodes for Jamming Robots
No full textTraditional electric robots often rely on heavy gear units or expensive force–torque sensors, whereas pneumatic robots offer a cost-effective and simple alternative. However, their dependence on noisy and bulky pneumatic systems, such as compressed air technology, limits their portability and adaptability. To overcome these challenges, we have developed a reversible electrochemical pneumatic battery (REPB) that is compact, noise-free, energy-efficient, and portable. This innovative REPB, principled by the electrochemical redox reactions of zinc–air batteries, can simultaneously supply both electric and pneumatic power, either positive or negative pressure. Its modular, multi-stack structure allows for the easy customization of power output and capacity to suit various applications. We demonstrate the utility of REPB through its application in jamming robots, such as a novel soft yet robust gripper that merges the strengths of hard and soft grippers, enabling universal robotic gripping. This work presents a groundbreaking approach to powering devices that require pneumatic support
Single-crystalline Ge₁₋ₓSnₓ/Si p–n heterojunction photodiodes with Sn compositions up to 10%
No full textGeSn/Si heterojunction photodiodes are attractive because they can extend light detection wavelength range. However, the development of such photodiodes via epitaxial growth faces great challenges due to unavoidable issues such as lattice and thermal mismatches between Si and GeSn. Here, print Si nanomembranes are transferred on GeSn/Ge/Si substrates to form the GeSn/Si heterojunction photodiodes. The p-Ge0.977Sn0.023/n-Si heterojunction photodiodes exhibit a good rectifying behavior with a low dark current density of 40 mA cm−2 and responsivity of 0.41 A W−1 at 1550 nm under a reverse bias of −2 V. In addition, the detection wavelength range of p-Ge0.9Sn0.1/n-Si is extended to 2100 nm because of the increased Sn composition. The bandgap calculation of as-grown GeSn with various Sn compositions is carried out. It confirms that the enhanced responsivity and extended detection wavelength ranges are attributed to the reduced bandgap from 750 to 601 meV when the Sn composition is increased from 2.3% to 10%. The result shows that the transfer printing of a freestanding single-crystalline Si nanomembrane to a bulk GeSn/Ge/Si substrate can provide an excellent alternative route for realizing GeSn/Si heterojunction photodiodes.Agency for Science, Technology and Research (A*STAR)Ministry of Education (MOE)Submitted/Accepted versionThis work was supported by the A*STAR, Singapore, Advanced Manufacturing and Engineering (AME) Young Individual Research Grant (YIRG) under the Project A2084c0066 and Ministry of Education, Singapore, under the Grant Academic Research Fund Tier 2 grant (T2EP50120-0001) and Tier 1-2020-T1-002-020 (RG136/20)
PRC2 ba xiang yao wu zai bi yan ai zhi liao li mian de zuo yong ji xiang guan ji zhi yan jiu
No full textAberrant hypermethylation enriched in regulatory regions of polycomb repressive complex-2 (PCR2)-related genes were frequently found in nasopharyngeal carcinoma (NPC). PRC2 has three core subunits: enhancer of Zeste 2 (EZH2), embryonic ectoderm development (EED) and suppressor of Zeste 12 (SUZ12), which can mediate gene silencing. The main aim of this study is to investigate if PRC2 protein subunits maybe exploited as potential therapeutic targets for NPC.Firstly, the prognostic significance of EZH2, EED, SUZ12 expression and H3K27me3 level was investigated in 93 NPC samples. These proteins were overexpressed in over 70% of NPC tumors and EZH2 expression was correlated with more advanced T-stage. EZH2 and EED expression were positively correlated with H3K27me3 level in NPC tissues. EZH2 and EED were strongly expressed in Epstein-Barr virus (EBV)-positive NPC cell lines (C666-1, C17C and NPC43), but weakly in EBV-negative cell line HK1 and NP69.Secondly, this study investigated some novel combinational strategies against NPC in vitro, using PRC2-targeting agents as a backbone. The preclinical effect of an EED inhibitor (EED226) and an EZH2 inhibitor (EPZ-6438) was investigated in four NPC cell lines (C666-1, C17C, NPC43 and HK1) and an immortalized normal nasopharyngeal epithelial cell line (NP69), either alone or concomitantly with chemotherapy or other epigenetic modulators. Treatment with EED226 led to reduced level of H3K27me3, but with minimal inhibitory effect on cell growth. The combination of EPZ-6438 and trichostatin-A (TSA) yielded the highest synergy score in vitro.Thirdly, we investigate the effect of downregulating Switch/Sucrose Non-Fermentable (SWI/SNF) chromatin remodeling complex components on cellular response to PRC2-targeting agents. Since AT-Rich interaction domain 1A (ARID1A) and BRCA1-associated protein-1 (BAP1) have high expression levels in C666-1 cells, we used small interfering RNA (siRNA) to knockdown those genes in it. Cytotoxicity effect was detected after treatment with PRC2-targeting agents in knockdown clones. Downregulating ARID1A and BAP1 had no significant influence on cellular response to PRC2-targeting agents in vitro.Finally, considering that EED226 alone can significantly downregulate H3K27me3 expression at low concentration, we speculated that EED226 might induce transcriptional re-programming of NPC cells. Therefore, we investigated the effect of EED226 on global gene expression in C666-1 cells using RNA sequencing analysis. Gene ontology (GO) and KEGG pathway enrichment analysis found that EED226 (5 M) predominantly affected the expression of major histocompatibility complex class I (MHC-I) genes and cell cycle-related genes. Furthermore, treatment with EED226 resulted in increased MHC-I proteins in vitro. Since artificial neural network (ANN) predicted potential synergistic effect of combining EED226 and cyclin-dependent kinase 4/6 (CDK4/6) inhibitor (LEE011), subsequent experiments were performed, demonstrating a synergistic inhibitory effect on cell growth in vitro. Mechanistic studies revealed that EED226 decreased the expression of CDK4/6 and pCDK4/6, resulted in synergistic effect with LEE011. The co-treatment induced up-regulation of p21 and down-regulation of pRb.In summary, this study found that PRC2-targeting agents could exert synergistic effect on growth inhibition of NPC cells when combined with TSA or LEE011. Since MHC-I gene alterations were found in a third of NPC tumors, the effect of EED226 on MHC-I expression on response to immunotherapy in NPC warrants further investigations.PCR2複合物相關基因異常高甲基化富集在鼻咽癌（NPC）中常發。 PRC2具有三個核心亞基： EZH2， EED 和 SUZ12。PRC2抑製劑可以介導基因沉默。這項研究的主要目的是研究PRC2蛋白亞基是否可被用作NPC的潛在治療靶標。首先，我們在93個NPC樣本中檢測了EZH2，EED，SUZ12和H3K27me蛋白質表達水平及其與NPC預後的關係。這些蛋白質在超過70％的NPC腫瘤中過度表達，EZH2表達與NPC的T分期相关，EZH2和EED表達與NPC組織中的H3K27me3水平相关。 EZH2和EED在EBV陽性的NPC細胞系（C666-1，C17C和NPC43）中高表達，但在EBV陰性細胞系HK1和NP69中低表達。其次，本研究驗證了一些使用PRC2靶向抑製劑作為基礎的針對NPC的新型治療組合在體外的效果。我們對EED靶向抑製劑（EED226）和EZH2靶向抑製劑（EPZ-6438）進行了單獨或組合化學療法藥物或其他表觀遺傳調節藥物的研究，研究在NPC細胞系（C666-1，C17C，NPC43和HK1）和永生的正常鼻咽上皮細胞系（NP69）中進行。研究顯示，用EED226進行治療可減少H3K27me3的表達水平，但對NPC細胞生長的抑製作用小。EPZ-6438和TSA的組合在體外研究中獲得了最高的協同作用評分。第三，我們研究SWI/SNF複合物對PRC2靶向抑製劑細胞水平治療效果的影響。ARID1A和BAP1在C666-1細胞中具有高表達水平，我們使用siRNA沉默NPC細胞中的有關基因，随後用PRC2靶向劑處理細胞， 檢測它的細胞毒性作用。下調ARID1A和BAP1在體外沒有明顯影響PRC2靶向抑製劑的治療效果。最後，考慮到EED226在低濃度就能顯著下調H3K27me3的表達，我們使用RNA測序分析研究了EED226對C666-1細胞系中基因表達的影響。GO和KEGG富集分析發現EED226 （5 M）主要影響MHC複合物的和細胞週期相關基因的表達。體外實驗證實，EED226能夠上調鼻咽癌細胞內MHC-I蛋白的表達量。ANN預測EED226和CDK4/6抑製劑（LEE011）具有潛在協同作用。後續實驗證明他們確實在體外對細胞生長具有協同抑製作用。EED226能夠降低CDK4/6和pCDK4/6的表達，與LEE011產生協同作用。總之，這項研究發現PRC2靶向抑製劑可以與TSA或LEE011聯合使用，發揮協同作用，對NPC細胞生長產生抑製作用。EED靶向抑製劑在對NPC免疫治療反應中MHC-I表達的影響值得進一步研究調查。Zhu, Junyu.Ph.D. Chinese University of Hong Kong 2020.Includes bibliographical references (leaves 89-99).Abstracts also in Chinese.Title from PDF title page (viewed on November 07, 2022).Zhu, Junyu
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