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  • richardmitnick 4:16 pm on April 8, 2021 Permalink | Reply
    Tags: , , , City University of Hong Kong [香港城市大學] (HK), , Diamonds as prime candidates for advanced functional devices in microelectronics; photonics; and quantum information technologies, Microfabricated diamonds, , Next-generation microelectronics, , The first time showing the extremely large uniform elasticity of diamond by tensile experiments.   

    From City University of Hong Kong [香港城市大學] (HK): “Stretching diamond for next-generation microelectronics” 

    From City University of Hong Kong [香港城市大學] (HK)

    01 Jan 2021 [Just now in social media. What woke them up?]

    Office of the Vice-President (Research & Technology)
    City University of Hong Kong
    Tel +852 3442-6847
    Fax +852 3442-0322
    vprt@cityu.edu.hk

    1
    Stretching of microfabricated diamonds pave ways for applications in next-generation microelectronics. Credit: Dang Chaoqun / City University of Hong Kong.

    Diamond is the hardest material in nature. But out of many expectations it also has great potential as an excellent electronic material. A joint research team led by City University of Hong Kong (CityU) has demonstrated for the first time the large, uniform tensile elastic straining of microfabricated diamond arrays through the nanomechanical approach. Their findings have shown the potential of strained diamonds as prime candidates for advanced functional devices in microelectronics; photonics; and quantum information technologies.

    The research was co-led by Dr Lu Yang, Associate Professor in the Department of Mechanical Engineering (MNE) at CityU and researchers from Massachusetts Institute of Technology(US) and Harbin Institute of Technology [哈尔滨工业大学] (CN). Their findings have been recently published in the prestigious scientific journal Science, titled “Achieving large uniform tensile elasticity in microfabricated diamond”.

    “This is the first time showing the extremely large uniform elasticity of diamond by tensile experiments. Our findings demonstrate the possibility of developing electronic devices through ‘deep elastic strain engineering’ of microfabricated diamond structures,” said Dr Lu.

    2
    Diamond: “Mount Everest” of electronic materials.

    Well known for its hardness, industrial applications of diamonds are usually cutting, drilling, or grinding. But diamond is also considered as a high-performance electronic and photonic material due to its ultra-high thermal conductivity, exceptional electric charge carrier mobility, high breakdown strength and ultra-wide bandgap. Bandgap is a key property in semi-conductor, and wide bandgap allows operation of high-power or high-frequency devices. “That’s why diamond can be considered as ‘Mount Everest’ of electronic materials, possessing all these excellent properties,” Dr Lu said.

    However, the large bandgap and tight crystal structure of diamond make it difficult to “dope”, a common way to modulate the semi-conductors’ electronic properties during production, hence hampering the diamond’s industrial application in electronic and optoelectronic devices. A potential alternative is by “strain engineering”, that is to apply very large lattice strain, to change the electronic band structure and associated functional properties. But it was considered as “impossible” for diamond due to its extremely high hardness.

    Then in 2018, Dr Lu and his collaborators discovered that, surprisingly, nanoscale diamond can be elastically bent with unexpected large local strain. This discovery suggests the change of physical properties in diamond through elastic strain engineering can be possible. Based on this, the latest study showed how this phenomenon can be utilized for developing functional diamond devices.

    Uniform tensile straining across the sample

    3
    Fig2: Illustration of tensile straining of microfabricated diamond bridge samples. Credit: Dang Chaoqun / City University of Hong Kong.

    The team firstly microfabricated single-crystalline diamond samples from a solid diamond single crystals. The samples were in bridge-like shape – about one micrometre long and 300 nanometres wide, with both ends wider for gripping (see Fig. 2).

    The diamond bridges were then uniaxially stretched in a well-controlled manner within an electron microscope. Under cycles of continuous and controllable loading-unloading of quantitative tensile tests, the diamond bridges demonstrated a highly uniform, large elastic deformation of about 7.5% strain across the whole gauge section of the specimen, rather than deforming at a localized area in bending. And they recovered their original shape after unloading.

    By further optimizing the sample geometry using the American Society for Testing and Materials (ASTM) standard, they achieved a maximum uniform tensile strain of up to 9.7%, which even surpassed the maximum local value in the 2018 study, and was close to the theoretical elastic limit of diamond. More importantly, to demonstrate the strained diamond device concept, the team also realized elastic straining of microfabricated diamond arrays.

    Tuning the bandgap by elastic strains

    The team then performed density functional theory (DFT) calculations to estimate the impact of elastic straining from 0 to 12% on the diamond’s electronic properties. The simulation results indicated that the bandgap of diamond generally decreased as the tensile strain increased, with the largest bandgap reduction rate down from about 5 eV to 3 eV at around 9% strain along a specific crystalline orientation. The team performed an electron energy-loss spectroscopy analysis on a pre-strained diamond sample and verified this bandgap decreasing trend.

    Their calculation results also showed that, interestingly, the bandgap could change from indirect to direct with the tensile strains larger than 9% along another crystalline orientation. Direct bandgap in semi-conductor means an electron can directly emit a photon, allowing many optoelectronic applications with higher efficiency.

    These findings are an early step in achieving deep elastic strain engineering of microfabricated diamonds. By nanomechanical approach, the team demonstrated that the diamond’s band structure can be changed, and more importantly, these changes can be continuous and reversible, allowing different applications, from micro/nanoelectromechanical systems (MEMS/NEMS), strain-engineered transistors, to novel optoelectronic and quantum technologies. “I believe a new era for diamond is ahead of us,” said Dr Lu.

    Dr Lu, Dr Alice Hu, who is also from MNE at CityU, Professor Li Ju from Massachusetts Institute of Technology(US) and Professor Zhu Jiaqi from HIT are the corresponding authors of the paper. The co-first authors are Dang Chaoqun, PhD graduate, and Dr Chou Jyh-Pin, former postdoctoral fellow from MNE at CityU, Dr Dai Bing from HIT, and Chou Chang-Ti from National Chiao Tung University [國立交通大學] (CN). Dr Fan Rong and Lin Weitong from CityU are also part of the team. Other collaborating researchers are from the DOE’s Lawrence Berkeley National Laboratory (US), University of California, Berkeley (US), and Southern University of Science and Technology [南方科技大學](CN).

    The research at CityU was funded by the Hong Kong Research Grants Council and the National Natural Science Foundation of China.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    City University of Hong Kong [香港城市大學](HK)(CityU) is a public research university in Kowloon, Hong Kong. It was founded in 1984 as City Polytechnic of Hong Kong and became a fully accredited university in 1994.

    The university has nine main schools offering courses in business, science, engineering, liberal art, social sciences, law and Veterinary Medicine, along with Chow Yei Ching School of Graduate Studies, CityU Shenzhen Research Institute, and Hong Kong Institute for Advanced Study.

    City University’s origins lie in the calls for a “second polytechnic” in the years following the 1972 establishment of the Hong Kong Polytechnic. In 1982, Executive Council member Chung Sze-yuen spoke of a general consensus that “a second polytechnic of similar size to the first should be built as soon as possible.” District administrators from Tuen Mun and Tsuen Wan lobbied the government to build the new institution in their respective new towns. The government instead purchased temporary premises at the new Argyle Centre Tower II in Mong Kok, a property developed by the Mass Transit Railway Corporation in concert with the then-Argyle Station. The new school was called City Polytechnic of Hong Kong, a name chosen among nearly 300 suggestions made by members of the public.

    The new polytechnic opened on 8 October 1984, welcoming 480 full-time and 680 part-time students. The provision for part-time students contributed to high enrolment, with the quota being filled almost immediately.

    The architectural contract to design the new campus was won by Percy Thomas Partnership in association with Alan Fitch and W.N. Chung. It was originally slated to open by October 1988. The first phase was officially opened by Governor Wilson on 15 January 1990, and boasted 14 lecture theatres and 1,500 computers. By 1991, the school had over 8,000 full-time students and approximately 3,000 part-time students. The second phase of the permanent campus opened 1993. The school achieved university status in 1994 and the name was changed accordingly.

    In April 2015 the university abruptly and controversially shut down its MFA programme in creative writing. Students and alumni launched a petition against the decision, while the faculty and noted international writers issued an open letter questioning the reasoning behind the closure. Acclaimed Canadian novelist and faculty member Madeleine Thien, writing in The Guardian, was among those who attributed the decision to censorship and diminishing freedom of expression in Hong Kong.

     
  • richardmitnick 2:33 pm on December 31, 2020 Permalink | Reply
    Tags: , , , City University of Hong Kong [香港城市大學] (HK), Deep elastic strain engineering, , , Nanoscale diamond can be elastically bent with unexpected large local strain., , , Strained diamonds as prime candidates for advanced functional devices in microelectronics; photonics; and quantum information technologies.   

    From City University of Hong Kong [香港城市大學] (HK): “Stretching diamond for next-generation microelectronics” 

    From City University of Hong Kong [香港城市大學] (HK)

    01 Jan 2021
    Office of the Vice-President (Research & Technology)
    5107, 5/F, Cheng Yick-chi Building, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Kowloon, Hong Kong SAR
    Tel:+852 3442-6847
    Fax: +852 3442-0322
    vprt@cityu.edu.hk

    1
    Fig: Stretching of microfabricated diamonds pave ways for applications in next-generation microelectronics. (Credit: Dang Chaoqun / City University of Hong Kong.

    Diamond is the hardest material in nature. But out of many expectations, it also has great potential as an excellent electronic material. A joint research team led by City University of Hong Kong (CityU) has demonstrated for the first time the large, uniform tensile elastic straining of microfabricated diamond arrays through the nanomechanical approach. Their findings have shown the potential of strained diamonds as prime candidates for advanced functional devices in microelectronics, photonics, and quantum information technologies.

    The research was co-led by Dr Lu Yang, Associate Professor in the Department of Mechanical Engineering (MNE) at CityU and researchers from Massachusetts Institute of Technology (MIT) and Harbin Institute of Technology (HIT). Their findings have been recently published in the prestigious scientific journal Science, titled Achieving large uniform tensile elasticity in microfabricated diamond.

    “This is the first time showing the extremely large, uniform elasticity of diamond by tensile experiments. Our findings demonstrate the possibility of developing electronic devices through ‘deep elastic strain engineering’ of microfabricated diamond structures,” said Dr Lu.

    Diamond: “Mount Everest” of electronic materials

    Well known for its hardness, industrial applications of diamonds are usually cutting, drilling, or grinding. But diamond is also considered as a high-performance electronic and photonic material due to its ultra-high thermal conductivity, exceptional electric charge carrier mobility, high breakdown strength and ultra-wide bandgap. Bandgap is a key property in semi-conductor, and wide bandgap allows operation of high-power or high-frequency devices. “That’s why diamond can be considered as ‘Mount Everest’ of electronic materials, possessing all these excellent properties,” Dr Lu said.

    However, the large bandgap and tight crystal structure of diamond make it difficult to “dope”, a common way to modulate the semi-conductors’ electronic properties during production, hence hampering the diamond’s industrial application in electronic and optoelectronic devices. A potential alternative is by “strain engineering”, that is to apply very large lattice strain, to change the electronic band structure and associated functional properties. But it was considered as “impossible” for diamond due to its extremely high hardness.

    Then in 2018, Dr Lu and his collaborators discovered that, surprisingly, nanoscale diamond can be elastically bent with unexpected large local strain. This discovery suggests the change of physical properties in diamond through elastic strain engineering can be possible. Based on this, the latest study showed how this phenomenon can be utilized for developing functional diamond devices.

    2
    Fig2: Illustration of tensile straining of microfabricated diamond bridge samples. Credit: Dang Chaoqun / City University of Hong Kong.

    Uniform tensile straining across the sample

    The team firstly microfabricated single-crystalline diamond samples from a solid diamond single crystals. The samples were in bridge-like shape – about one micrometre long and 300 nanometres wide, with both ends wider for gripping (see Fig. 2). The diamond bridges were then uniaxially stretched in a well-controlled manner within an electron microscope. Under cycles of continuous and controllable loading-unloading of quantitative tensile tests, the diamond bridges demonstrated a highly uniform, large elastic deformation of about 7.5% strain across the whole gauge section of the specimen, rather than deforming at a localized area in bending. And they recovered their original shape after unloading.

    By further optimizing the sample geometry using the American Society for Testing and Materials (ASTM) standard, they achieved a maximum uniform tensile strain of up to 9.7%, which even surpassed the maximum local value in the 2018 study, and was close to the theoretical elastic limit of diamond. More importantly, to demonstrate the strained diamond device concept, the team also realized elastic straining of microfabricated diamond arrays.

    Tuning the bandgap by elastic strains

    The team then performed density functional theory (DFT) calculations to estimate the impact of elastic straining from 0 to 12% on the diamond’s electronic properties. The simulation results indicated that the bandgap of diamond generally decreased as the tensile strain increased, with the largest bandgap reduction rate down from about 5 eV to 3 eV at around 9% strain along a specific crystalline orientation. The team performed an electron energy-loss spectroscopy analysis on a pre-strained diamond sample and verified this bandgap decreasing trend.

    Their calculation results also showed that, interestingly, the bandgap could change from indirect to direct with the tensile strains larger than 9% along another crystalline orientation. Direct bandgap in semi-conductor means an electron can directly emit a photon, allowing many optoelectronic applications with higher efficiency.

    These findings are an early step in achieving deep elastic strain engineering of microfabricated diamonds. By nanomechanical approach, the team demonstrated that the diamond’s band structure can be changed, and more importantly, these changes can be continuous and reversible, allowing different applications, from micro/nanoelectromechanical systems (MEMS/NEMS), strain-engineered transistors, to novel optoelectronic and quantum technologies. “I believe a new era for diamond is ahead of us,” said Dr Lu.

    Dr Lu, Dr Alice Hu, who is also from MNE at CityU, Professor Li Ju from MIT and Professor Zhu Jiaqi from HIT are the corresponding authors of the paper. The co-first authors are Dang Chaoqun, PhD graduate, and Dr Chou Jyh-Pin, former postdoctoral fellow from MNE at CityU, Dr Dai Bing from HIT, and Chou Chang-Ti from National Chiao Tung University. Dr Fan Rong and Lin Weitong from CityU are also part of the team. Other collaborating researchers are from the Lawrence Berkeley National Laboratory, University of California, Berkeley, and Southern University of Science and Technology.

    The research at CityU was funded by the Hong Kong Research Grants Council and the National Natural Science Foundation of China.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    City University of Hong Kong [香港城市大學](HK)(CityU) is a public research university in Kowloon, Hong Kong. It was founded in 1984 as City Polytechnic of Hong Kong and became a fully accredited university in 1994.

    The university has nine main schools offering courses in business, science, engineering, liberal art, social sciences, law and Veterinary Medicine, along with Chow Yei Ching School of Graduate Studies, CityU Shenzhen Research Institute, and Hong Kong Institute for Advanced Study.

    City University’s origins lie in the calls for a “second polytechnic” in the years following the 1972 establishment of the Hong Kong Polytechnic. In 1982, Executive Council member Chung Sze-yuen spoke of a general consensus that “a second polytechnic of similar size to the first should be built as soon as possible.” District administrators from Tuen Mun and Tsuen Wan lobbied the government to build the new institution in their respective new towns. The government instead purchased temporary premises at the new Argyle Centre Tower II in Mong Kok, a property developed by the Mass Transit Railway Corporation in concert with the then-Argyle Station. The new school was called City Polytechnic of Hong Kong, a name chosen among nearly 300 suggestions made by members of the public.

    The new polytechnic opened on 8 October 1984, welcoming 480 full-time and 680 part-time students. The provision for part-time students contributed to high enrolment, with the quota being filled almost immediately.

    The architectural contract to design the new campus was won by Percy Thomas Partnership in association with Alan Fitch and W.N. Chung. It was originally slated to open by October 1988. The first phase was officially opened by Governor Wilson on 15 January 1990, and boasted 14 lecture theatres and 1,500 computers. By 1991, the school had over 8,000 full-time students and approximately 3,000 part-time students. The second phase of the permanent campus opened 1993. The school achieved university status in 1994 and the name was changed accordingly.

    In April 2015 the university abruptly and controversially shut down its MFA programme in creative writing. Students and alumni launched a petition against the decision, while the faculty and noted international writers issued an open letter questioning the reasoning behind the closure. Acclaimed Canadian novelist and faculty member Madeleine Thien, writing in The Guardian, was among those who attributed the decision to censorship and diminishing freedom of expression in Hong Kong.

     
  • richardmitnick 12:03 pm on December 23, 2020 Permalink | Reply
    Tags: "A powerful computational tool for efficient analysis of cell division 4D image data", Advancing further studies in tumor growth., , , Bottleneck in analysing massive amount of cell division data., Breakthrough in segmenting cell images automatically., City University of Hong Kong [香港城市大學] (HK), , The tool developed by the team is called “CShaper”.   

    From City University of Hong Kong [香港城市大學] (HK): “A powerful computational tool for efficient analysis of cell division 4D image data” 

    From City University of Hong Kong [香港城市大學] (HK)

    22 Dec 2020

    Office of the Vice-President (Research & Technology)
    5107, 5/F, Cheng Yick-chi Building, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Kowloon, Hong Kong SAR
    Tel: +852 3442-6847
    Fax: +852 3442-0322
    vprt@cityu.edu.hk

    A joint research team co-led by City University of Hong Kong (CityU) has developed a novel computational tool that can reconstruct and visualise three-dimensional (3D) shapes and temporal changes of cells, speeding up the analysing process from hundreds of hours by hand to a few hours by computer. Revolutionising the way biologists analyse image data, this tool can advance further studies in developmental and cell biology, such as the growth of cancer cells.

    The interdisciplinary study was co-led by Professor Yan Hong, Chair Professor of Computer Engineering and Wong Chung Hong Professor of Data Engineering in the Department of Electrical Engineering (EE) at CityU, together with biologists from Hong Kong Baptist University (HKBU) and Peking University. Their findings have been published in the scientific journal Nature Communications.

    The tool developed by the team is called “CShaper”. “It is a powerful computational tool that can segment and analyse cell images systematically at the single-cell level, which is much needed for the study of cell division, and cell and gene functions,” described Professor Yan.

    1
    Morphological dynamics of cell division of C. elegans embryo cell at single-cell resolution. (Photo source: DOI number: 10.1038/s41467-020-19863-x).

    Bottleneck in analysing massive amount of cell division data

    Biologists have been investigating how animals grow from a single cell, a fertilised egg, into organs and the whole body through countless cell divisions. In particular, they want to know the gene functions, such as the specific genes involved in cell divisions for forming different organs, or what causes the abnormal cell divisions leading to tumourous growth.

    A way to find the answer is to use the gene knockout technique. With all genes present, researchers first obtain cell images and the lineage tree. Then they “knock out” (remove) a gene from the DNA sequence, and compare the two lineage trees to analyse changes in the cells and infer gene functions. Then they repeat the experiment with other genes being knocked out.

    In the study, the collaborating biologist team used Caenorhabditis elegans (C. elegans) embryos to produce terabytes of data for Professor Yan’s team to perform computational analysis. C. elegans is a type of worm which share many essential biological characteristics with humans and provide a valuable model for studying the tumour growth process in humans.

    “With estimated 20,000 genes in C. elegans, it means nearly 20,000 experiments would be needed if knocking out one gene at a time. And there would be an enormous amount of data. So it is essential to use an automated image analysis system. And this drives us to develop a more efficient one,” he said.

    Breakthrough in segmenting cell images automatically

    Cell images are usually obtained by laser beam scanning. The existing image analysis systems can only detect cell nucleus well with a poor cell membrane image quality, hampering reconstruction of cell shapes. Also, there is a lack of reliable algorithm for the segmentation of time-lapsed 3D images (i.e. 4D images) of cell division. Image segmentation is a critical process in computer vision that involves dividing a visual input into segments to simplify image analysis. But researchers have to spend hundreds of hours labelling many cell images manually.

    The breakthrough in CShaper is that it can detect cell membranes, build up cell shapes in 3D, and more importantly, automatically segment the cell images at the cell level. “Using CShaper, biologists can decipher the contents of these images within a few hours. It can characterise cell shapes and surface structures, and provide 3D views of cells at different time points,” said Cao Jianfeng, a PhD student in Professor Yan’s group, and a co-first author of the paper.

    To achieve this, the deep-learning-based model DMapNet developed by the team plays a key role in the CShaper system. “By learning to capture multiple discrete distances between image pixels, DMapNet extracts the membrane contour while considering shape information, rather than just intensity features. Therefore CShaper achieved a 95.95% accuracy of identifying the cells, which outperformed other methods substantially,” he explained.

    2
    The framework of CShaper. With deep-learning-based DMapNet, time-lapse 3D cell shapes across the development with defined cell identity are generated (shown in the right green box). (Photo source: DOI number: 10.1038/s41467-020-19863-x).

    With CShaper, the team generated a time-lapse 3D atlas of cell morphology for the C. elegans embryo from the 4- to 350-cell stages, including cell shape, volume, surface area, migration, nucleus position and cell-cell contact with confirmed cell identities.

    3
    3D projections of images of nuclei (green and white dots) and membranes (red lines) at different time points. (Photo source: DOI number: 10.1038/s41467-020-19863-x).

    Advancing further studies in tumor growth

    “To the best of our knowledge, CShaper is the first computational system for segmenting and analysing the images of C. elegans embryo systematically at the single-cell level,” said Mr Cao. “Through close collaborations with biologists, we proudly developed a useful computer tool for automated analysis of a massive amount of cell image data. We believe it can promote further studies in developmental and cell biology, in particular in understanding the origination and growth of cancer cells,” Professor Yan added.

    They also tested CShaper on plant tissue cells, showing promising results. They believe the computer tool can be adopted to other biological studies.

    Professor Yan, Professor Tang Chao from Peking University, and Professor Zhao Zhongying from HKBU are the corresponding authors of the paper. The co-first authors are Cao Jianfeng, PhD student from EE at CityU, Guan Guoye from Peking University, and Ho Vincy Wing Sze from HKBU.

    The funding support for the study included the National Institutes of Health, Hong Kong Research Grants Council, the Ministry of Science and Technology of China, and the National Natural Science Foundation of China.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    City University of Hong Kong [香港城市大學](HK)(CityU) is a public research university in Kowloon, Hong Kong. It was founded in 1984 as City Polytechnic of Hong Kong and became a fully accredited university in 1994.

    The university has nine main schools offering courses in business, science, engineering, liberal art, social sciences, law and Veterinary Medicine, along with Chow Yei Ching School of Graduate Studies, CityU Shenzhen Research Institute, and Hong Kong Institute for Advanced Study.

    City University’s origins lie in the calls for a “second polytechnic” in the years following the 1972 establishment of the Hong Kong Polytechnic. In 1982, Executive Council member Chung Sze-yuen spoke of a general consensus that “a second polytechnic of similar size to the first should be built as soon as possible.” District administrators from Tuen Mun and Tsuen Wan lobbied the government to build the new institution in their respective new towns. The government instead purchased temporary premises at the new Argyle Centre Tower II in Mong Kok, a property developed by the Mass Transit Railway Corporation in concert with the then-Argyle Station. The new school was called City Polytechnic of Hong Kong, a name chosen among nearly 300 suggestions made by members of the public.

    The new polytechnic opened on 8 October 1984, welcoming 480 full-time and 680 part-time students. The provision for part-time students contributed to high enrolment, with the quota being filled almost immediately.

    The architectural contract to design the new campus was won by Percy Thomas Partnership in association with Alan Fitch and W.N. Chung. It was originally slated to open by October 1988. The first phase was officially opened by Governor Wilson on 15 January 1990, and boasted 14 lecture theatres and 1,500 computers. By 1991, the school had over 8,000 full-time students and approximately 3,000 part-time students. The second phase of the permanent campus opened 1993. The school achieved university status in 1994 and the name was changed accordingly.

    In April 2015 the university abruptly and controversially shut down its MFA programme in creative writing. Students and alumni launched a petition against the decision, while the faculty and noted international writers issued an open letter questioning the reasoning behind the closure. Acclaimed Canadian novelist and faculty member Madeleine Thien, writing in The Guardian, was among those who attributed the decision to censorship and diminishing freedom of expression in Hong Kong.

     
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