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HKU Ecologist Contributes to Pioneering Earth BioGenome Project Hong Kong

Professor Juan Diego GAITÁN-ESPITIA from the School of Biological Science has joined forces with researchers from all eight UGC-funded universities in the community to embark on the Earth BioGenome Project Hong Kong. This collaborative initiative addresses geographic and species gaps in the Earth BioGenome Project (EBP), a global ‘moonshot for biology’ that aims to sequence, catalog, and characterise the genomes of the Earth’s non-microbial eukaryotic  biodiversity within a decade. Highlighting Hong Kong's exceptional status as a biodiversity hotspot, the project features thousands of species across various taxa, with a particular focus on the organisms of high concern and great interest to Hong Kong. The local community was invited to nominate animal, plant, and fungi species that captivated their attention. The initial batch of genomes selected for study has been published in a Hong Kong-based journal GigaByte. Among the featured species are the golden birdwing butterfly (Troides aeacus), the common chiton (Liolophura japonic), the long-spined sea urchin (Diadema setosum), the edible jelly fungus Dacryopinax spathularia, and the milky mangrove (Excoecaria agallocha). These species were chosen due to their significant scientific and conservation value in the Asia-Pacific region. The ongoing genome study of other emblematic and well-loved local species, such as the black-faced spoonbill (Platalea minor), is still in progress. Thanks to the contributions of Professor Gaitán-Espitia and other dedicated academics, the Earth BioGenome Project Hong Kong not only enhances our understanding of Hong Kong's unique biodiversity but also provides valuable insights for global conservation efforts.   More about Earth BioGenome Project Hong Kong

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HKU Theoretical Physicists Collaborate alongside CAS Experimentalists Uncovering Novel Quantum State known as “Dirac Spin Liquid”

A collaboration between theoretical physicists Dr Chengkang ZHOU and Professor Zi Yang MENG from the Department of Physics at The University of Hong Kong (HKU), along with experimentalists Zhenyuan ZENG and Professor Shiliang LI at the Institute of Physics (IOP), Chinese Academy of Sciences (CAS), and Professor Kenji NAKAJIMA from J-PARC Center, Japan, has led to a discovery in the realm of quantum physics. Their study, published in a recent issue of Nature Physics, sheds light on the long-anticipated emergence of quasiparticles, akin to the famous Dirac particles obeying the relativistic Dirac equation. These quasiparticles, known as Dirac spinons, were theorised to exist within a novel quantum state called a quantum spin liquid state.   Quasiparticles are intriguing entities that emerge from collective behaviour within materials, which can be treated like a group of particles. The Dirac spinons, specifically, are expected to exhibit unique characteristics similar to Dirac particles in high-energy physics and the Dirac electrons in graphene and quantum moire materials, such as a linear dispersion relation between energy and momentum. But such spin-½ charge neutral quasiparticles have not been seen in quantum magnets till this work.   “To find Dirac spinons in quantum magnets has been the dream of generations of condensed matter physicists; now that we have seen the evidence of them, one can start to think about the countless potential applications of such highly entangled quantum material. Who knows, maybe one day people will build quantum computers with it, just as people have been doing in the past half-century with silicon,” said Professor Meng, HKU physicist and one of the corresponding authors of the paper.   The team's investigation focused on a unique material known as YCu3-Br, characterised by a kagome lattice structure leading to the appearance of these elusive quasiparticles. Previous studies had hinted at the material's potential to exhibit a quantum spin liquid state, making it an ideal candidate for exploration. In order to enable the observation of spinons in YCu3-Br, the research team overcame numerous challenges by assembling approximately 5000 single crystals together, meeting the requirements for conducting experiments such as inelastic neutron scattering (see Fig. 1d). Using advanced techniques like inelastic neutron scattering, the team probed the material's spin excitations and observed intriguing conical spin continuum patterns, reminiscent of the characteristic Dirac cone. While directly detecting single spinon proved challenging due to experimental limitations, the team compared their findings with theoretical predictions, revealing distinct spectral features indicative of the presence of spinons in the material.   Finding spectral evidence of Dirac spinon excitations has always been a challenge. This discovery provides compelling evidence for the existence of a Dirac quantum spin liquid state, which can be akin to a clear cry cutting through the fog of spectral investigation on the quantum spin liquid state. The findings not only advance our fundamental understanding of condensed matter physics but also open doors for further exploration into the properties and applications of YCu3-Br.   Characterised by the presence of fractional spinon excitations, the quantum spin liquid state is potentially relevant to high-temperature superconductivity and quantum information. In this state, the spins are highly entangled and remain disordered even at low temperatures. Therefore, investigating the spectral signals arising from spinons obeying the Dirac equation would provide a broader understanding of the quantum spin liquid state of matter. Such understanding also serves as a guidepost toward its broader applications, including the exploration of high-temperature superconductivity and quantum information.   For a detailed explanation of the research, please visit here: https://www.scifac.hku.hk/page/detail/8595     The journal paper entitled ‘Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet’ can be accessed from here: https://www.nature.com/articles/s41567-024-02495-z   The study was supported by the Ministry of Science and Technology of China, the Chinese Academy of Sciences and grants from Hong Kong Research Grants Council. Neutron scattering measurements were performed on AMATERAS, J-PARC.   The theoretical work of the paper is carried out by Dr Chengkang Zhou, a Postdoctoral Fellow at the Department of Physics, and his supervisor, Professor Zi Yang MENG. They are supported by the Collaborative Research Fund and ANR/RGC Joint Research Scheme of the Hong Kong Research Grants Council, highlighting the forward-looking perspective and support of the Hong Kong government in the research of quantum materials. The theoretical calculations conducted in this study were performed on the High-Performance Computing Platform at the Information Technology Services, HKU, and the ‘Blackbody’ supercomputer at the Department of Physics at HKU, as well as the Beijing PARATERA Tech CO., Ltd. (https://cloud.paratera.com).   Figure 1. Left photo: (From the left) Dr Chengkang Zhou and Professor Zi Yang Meng from the Department of Physics at The University of Hong Kong. Figure 2. Right photo: (From the left) Professor Shiliang Li and Mr Zhenyuan Zeng from the Institute of Physics, Chinese Academy of Sciences.   Figure 3.  a. Schematic diagram of the conical excitations of Dirac spinons and the conical continuum spectrum formed by two spinons. b. Schematic diagram of the conical spin excitations in YCu3(OH)6Br2[Br0.33(OD)0.67]. c. Relationship between the half-width at half-maximum and energy. The solid line represents a linear fit. d. A magnified image of some co-aligned crystals, and the front view of co-aligned samples on two Cu plates.   Figure 4. (On the left): Spin excitations in YCu3(OD)6[Br0.33(OD)0.67] measured via the neutron scattering. e,f, Intensity contour plots of the INS results as a function of E and Q along the [H, 0] direction at 0.3 K (e) and 30 K (f).   Figure 5. (On the right): Linear spin wave prediction on the kagome lattice: a and b show the spin spectra without introducing disorder effects. c and d display the spectra with the same parameters but introduce disordered effects to fit the experimental results. e and f show the spectra with different kinds of disorder.

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A conceptual image illustrating the tidal disruption of a Pop III star and its subsequent feeding of a massive black hole in the early universe. Image credit: Space Telescope Science Institute/Ralf Crawford

HKU Astrophysicists Discover a Novel Method for Hunting the First Stars

A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at The University of Hong Kong (HKU) has discovered a novel method for detecting the first-generations stars, known as Population III (Pop III) stars, which have never been directly detected. The research has been widely acknowledged by the international astronomy community with a highlight from the Space Telescope Science Institute, which operates several NASA telescopes. These potential discoveries about Pop III stars hold the promise of unlocking the secrets of the universe's origin and providing a deeper understanding of the remarkable journey from the primordial cosmos to the world we inhabit today. Their findings have recently been published in The Astrophysical Journal Letters. Shortly after the Universe began with the Big Bang, the first stars, composed mainly of hydrogen and helium, began to form. The properties of these first-generation stars, Pop III, are very different from stars like our own Sun or even the ones that are forming today. They were tremendously hot, gigantic in size and mass, but very short-lived. Pop III stars are the first factories to synthesise most elements heavier than hydrogen and helium around us today. They are also very important for forming later generations of stars and galaxies. However, there have not been convincing direct detections of Pop III stars up to now, as these stars formed in the early universe are very far away and way too faint for any of our telescopes on the ground or in space. For the first time, HKU scientists discovered a novel method for detecting these first stars in the early Universe. A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at HKU proposed that a Pop III star can be torn apart into pieces by tidal force if it wanders into the vicinity of a massive black hole. In such a tidal disruption event (TDE), the black hole feasts on the stellar debris and produces very luminous flares. The researchers investigated the complex physical process involved and demonstrated that these flares can shine across billions of light years to reach us today. Most importantly, they have found that the unique signatures of these TDE flares can be used to identify the existence of Pop III stars and gain insights into their properties. ‘As the energetic photons travel from a very faraway distance, the timescale of the flare will be stretched due to the expansion of the Universe. These TDE flares will rise and decay over a very long period of time, which sets them apart from the TDEs of solar-type stars in the nearby Universe,’ said Professor Jane Dai, principal investigator and the corresponding author of the project. ‘Interestingly, not only are the timescales of the flares are stretched, so is their wavelength. The optical and ultraviolet light emitted by the TDE will be transferred to infrared emissions when reaching the Earth.’ Dr Rudrani KAR CHOWDHURY, Postdoctoral Fellow of the Department of Physics at HKU and the first author of the paper, further added. What makes the discovery more exciting is that two NASA flagship missions, the recently launched James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman), have the capability to observe such infrared emissions from great distances. Professor Priya NATARAJAN of the Department of Astronomy and Physics at Yale University and a co-author of the paper mentioned, ‘Roman’s unique capabilities of simultaneously being able to observe a large area of the sky and peeking deep into early Universe makes it a promising probe for detecting these Pop III TDE flares, which would in turn serve as an indirect discovery of Pop III stars.’ Ms Janet CHANG, a PhD student at the Department of Physics at HKU and co-author of the paper, added, ‘We expect that a few dozens of these events will be detected by Roman every year if the right observation strategy is pursued.’ With these findings in mind, the next decade presents significant potential for identifying these distinct sources, leading to exciting revelations about Pop III stars and unraveling the mysteries of the universe’s inception.   Click here to view the journal paper. Click here to learn more about Professor Jane Lixin Dai and her research group.  Read the news story featured by the Space Telescope Science Institute.

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HKU Ecologist Contributes to Pioneering Earth BioGenome Project Hong Kong

Professor Juan Diego GAITÁN-ESPITIA from the School of Biological Science has joined forces with researchers from all eight UGC-funded universities in the community to embark on the Earth BioGenome Project Hong Kong. This collaborative initiative addresses geographic and species gaps in the Earth BioGenome Project (EBP), a global ‘moonshot for biology’ that aims to sequence, catalog, and characterise the genomes of the Earth’s non-microbial eukaryotic  biodiversity within a decade. Highlighting Hong Kong's exceptional status as a biodiversity hotspot, the project features thousands of species across various taxa, with a particular focus on the organisms of high concern and great interest to Hong Kong. The local community was invited to nominate animal, plant, and fungi species that captivated their attention. The initial batch of genomes selected for study has been published in a Hong Kong-based journal GigaByte. Among the featured species are the golden birdwing butterfly (Troides aeacus), the common chiton (Liolophura japonic), the long-spined sea urchin (Diadema setosum), the edible jelly fungus Dacryopinax spathularia, and the milky mangrove (Excoecaria agallocha). These species were chosen due to their significant scientific and conservation value in the Asia-Pacific region. The ongoing genome study of other emblematic and well-loved local species, such as the black-faced spoonbill (Platalea minor), is still in progress. Thanks to the contributions of Professor Gaitán-Espitia and other dedicated academics, the Earth BioGenome Project Hong Kong not only enhances our understanding of Hong Kong's unique biodiversity but also provides valuable insights for global conservation efforts.   More about Earth BioGenome Project Hong Kong

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HKU Theoretical Physicists Collaborate alongside CAS Experimentalists Uncovering Novel Quantum State known as “Dirac Spin Liquid”

A collaboration between theoretical physicists Dr Chengkang ZHOU and Professor Zi Yang MENG from the Department of Physics at The University of Hong Kong (HKU), along with experimentalists Zhenyuan ZENG and Professor Shiliang LI at the Institute of Physics (IOP), Chinese Academy of Sciences (CAS), and Professor Kenji NAKAJIMA from J-PARC Center, Japan, has led to a discovery in the realm of quantum physics. Their study, published in a recent issue of Nature Physics, sheds light on the long-anticipated emergence of quasiparticles, akin to the famous Dirac particles obeying the relativistic Dirac equation. These quasiparticles, known as Dirac spinons, were theorised to exist within a novel quantum state called a quantum spin liquid state.   Quasiparticles are intriguing entities that emerge from collective behaviour within materials, which can be treated like a group of particles. The Dirac spinons, specifically, are expected to exhibit unique characteristics similar to Dirac particles in high-energy physics and the Dirac electrons in graphene and quantum moire materials, such as a linear dispersion relation between energy and momentum. But such spin-½ charge neutral quasiparticles have not been seen in quantum magnets till this work.   “To find Dirac spinons in quantum magnets has been the dream of generations of condensed matter physicists; now that we have seen the evidence of them, one can start to think about the countless potential applications of such highly entangled quantum material. Who knows, maybe one day people will build quantum computers with it, just as people have been doing in the past half-century with silicon,” said Professor Meng, HKU physicist and one of the corresponding authors of the paper.   The team's investigation focused on a unique material known as YCu3-Br, characterised by a kagome lattice structure leading to the appearance of these elusive quasiparticles. Previous studies had hinted at the material's potential to exhibit a quantum spin liquid state, making it an ideal candidate for exploration. In order to enable the observation of spinons in YCu3-Br, the research team overcame numerous challenges by assembling approximately 5000 single crystals together, meeting the requirements for conducting experiments such as inelastic neutron scattering (see Fig. 1d). Using advanced techniques like inelastic neutron scattering, the team probed the material's spin excitations and observed intriguing conical spin continuum patterns, reminiscent of the characteristic Dirac cone. While directly detecting single spinon proved challenging due to experimental limitations, the team compared their findings with theoretical predictions, revealing distinct spectral features indicative of the presence of spinons in the material.   Finding spectral evidence of Dirac spinon excitations has always been a challenge. This discovery provides compelling evidence for the existence of a Dirac quantum spin liquid state, which can be akin to a clear cry cutting through the fog of spectral investigation on the quantum spin liquid state. The findings not only advance our fundamental understanding of condensed matter physics but also open doors for further exploration into the properties and applications of YCu3-Br.   Characterised by the presence of fractional spinon excitations, the quantum spin liquid state is potentially relevant to high-temperature superconductivity and quantum information. In this state, the spins are highly entangled and remain disordered even at low temperatures. Therefore, investigating the spectral signals arising from spinons obeying the Dirac equation would provide a broader understanding of the quantum spin liquid state of matter. Such understanding also serves as a guidepost toward its broader applications, including the exploration of high-temperature superconductivity and quantum information.   For a detailed explanation of the research, please visit here: https://www.scifac.hku.hk/page/detail/8595     The journal paper entitled ‘Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet’ can be accessed from here: https://www.nature.com/articles/s41567-024-02495-z   The study was supported by the Ministry of Science and Technology of China, the Chinese Academy of Sciences and grants from Hong Kong Research Grants Council. Neutron scattering measurements were performed on AMATERAS, J-PARC.   The theoretical work of the paper is carried out by Dr Chengkang Zhou, a Postdoctoral Fellow at the Department of Physics, and his supervisor, Professor Zi Yang MENG. They are supported by the Collaborative Research Fund and ANR/RGC Joint Research Scheme of the Hong Kong Research Grants Council, highlighting the forward-looking perspective and support of the Hong Kong government in the research of quantum materials. The theoretical calculations conducted in this study were performed on the High-Performance Computing Platform at the Information Technology Services, HKU, and the ‘Blackbody’ supercomputer at the Department of Physics at HKU, as well as the Beijing PARATERA Tech CO., Ltd. (https://cloud.paratera.com).   Figure 1. Left photo: (From the left) Dr Chengkang Zhou and Professor Zi Yang Meng from the Department of Physics at The University of Hong Kong. Figure 2. Right photo: (From the left) Professor Shiliang Li and Mr Zhenyuan Zeng from the Institute of Physics, Chinese Academy of Sciences.   Figure 3.  a. Schematic diagram of the conical excitations of Dirac spinons and the conical continuum spectrum formed by two spinons. b. Schematic diagram of the conical spin excitations in YCu3(OH)6Br2[Br0.33(OD)0.67]. c. Relationship between the half-width at half-maximum and energy. The solid line represents a linear fit. d. A magnified image of some co-aligned crystals, and the front view of co-aligned samples on two Cu plates.   Figure 4. (On the left): Spin excitations in YCu3(OD)6[Br0.33(OD)0.67] measured via the neutron scattering. e,f, Intensity contour plots of the INS results as a function of E and Q along the [H, 0] direction at 0.3 K (e) and 30 K (f).   Figure 5. (On the right): Linear spin wave prediction on the kagome lattice: a and b show the spin spectra without introducing disorder effects. c and d display the spectra with the same parameters but introduce disordered effects to fit the experimental results. e and f show the spectra with different kinds of disorder.

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A conceptual image illustrating the tidal disruption of a Pop III star and its subsequent feeding of a massive black hole in the early universe. Image credit: Space Telescope Science Institute/Ralf Crawford

HKU Astrophysicists Discover a Novel Method for Hunting the First Stars

A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at The University of Hong Kong (HKU) has discovered a novel method for detecting the first-generations stars, known as Population III (Pop III) stars, which have never been directly detected. The research has been widely acknowledged by the international astronomy community with a highlight from the Space Telescope Science Institute, which operates several NASA telescopes. These potential discoveries about Pop III stars hold the promise of unlocking the secrets of the universe's origin and providing a deeper understanding of the remarkable journey from the primordial cosmos to the world we inhabit today. Their findings have recently been published in The Astrophysical Journal Letters. Shortly after the Universe began with the Big Bang, the first stars, composed mainly of hydrogen and helium, began to form. The properties of these first-generation stars, Pop III, are very different from stars like our own Sun or even the ones that are forming today. They were tremendously hot, gigantic in size and mass, but very short-lived. Pop III stars are the first factories to synthesise most elements heavier than hydrogen and helium around us today. They are also very important for forming later generations of stars and galaxies. However, there have not been convincing direct detections of Pop III stars up to now, as these stars formed in the early universe are very far away and way too faint for any of our telescopes on the ground or in space. For the first time, HKU scientists discovered a novel method for detecting these first stars in the early Universe. A recent study led by the research group of Professor Jane Lixin DAI of the Department of Physics at HKU proposed that a Pop III star can be torn apart into pieces by tidal force if it wanders into the vicinity of a massive black hole. In such a tidal disruption event (TDE), the black hole feasts on the stellar debris and produces very luminous flares. The researchers investigated the complex physical process involved and demonstrated that these flares can shine across billions of light years to reach us today. Most importantly, they have found that the unique signatures of these TDE flares can be used to identify the existence of Pop III stars and gain insights into their properties. ‘As the energetic photons travel from a very faraway distance, the timescale of the flare will be stretched due to the expansion of the Universe. These TDE flares will rise and decay over a very long period of time, which sets them apart from the TDEs of solar-type stars in the nearby Universe,’ said Professor Jane Dai, principal investigator and the corresponding author of the project. ‘Interestingly, not only are the timescales of the flares are stretched, so is their wavelength. The optical and ultraviolet light emitted by the TDE will be transferred to infrared emissions when reaching the Earth.’ Dr Rudrani KAR CHOWDHURY, Postdoctoral Fellow of the Department of Physics at HKU and the first author of the paper, further added. What makes the discovery more exciting is that two NASA flagship missions, the recently launched James Webb Space Telescope (JWST) and the upcoming Nancy Grace Roman Space Telescope (Roman), have the capability to observe such infrared emissions from great distances. Professor Priya NATARAJAN of the Department of Astronomy and Physics at Yale University and a co-author of the paper mentioned, ‘Roman’s unique capabilities of simultaneously being able to observe a large area of the sky and peeking deep into early Universe makes it a promising probe for detecting these Pop III TDE flares, which would in turn serve as an indirect discovery of Pop III stars.’ Ms Janet CHANG, a PhD student at the Department of Physics at HKU and co-author of the paper, added, ‘We expect that a few dozens of these events will be detected by Roman every year if the right observation strategy is pursued.’ With these findings in mind, the next decade presents significant potential for identifying these distinct sources, leading to exciting revelations about Pop III stars and unraveling the mysteries of the universe’s inception.   Click here to view the journal paper. Click here to learn more about Professor Jane Lixin Dai and her research group.  Read the news story featured by the Space Telescope Science Institute.

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From the left: Ziqi Xu and Muhammad Hussain of the Department of Statistics and Actuarial Science, Faculty of Science; Muhammad Mubeen of the Faculty of Engineering.

Actuarial Science students Secure Victory in 2024 PRMIA Risk Management Challenge

Two Actuarial Science students, Ziqi XU and Muhammad HUSSAIN of the Department of Statistics and Actuarial Science, along with a student from the Faculty of Engineering, formed Team BossTon and achieved victory in the prestigious 2024 PRMIA Risk Management Challenge (PRMC). This year, the renowned competition focused on the banking crisis in 2023, and the team showcased their comprehensive understanding by delivering a concise analysis of the origins and progression of the crisis. Their presentation explored key factors such as interest rates, regulatory conditions, and internal risk management shortcomings. Employing a blend of conventional and innovative approaches, the team proposed various solutions to address the crisis. Their ideas included utilising algorithms to analyse social media sentiment and assess the stability of a bank's deposit franchise. They also advocated for adopting Central Bank Digital Currencies (CBDCs), immunisation strategies, and an enhanced regulatory framework for banks. Their victory holds significant importance as they surpassed master's students from leading business schools worldwide. This accomplishment not only showcases their exceptional abilities but also reflects the outstanding quality of education offered by the programme. Click here to learn more about the 2024 PRMIA Risk Management Challenge. 

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In this latest research, we have made significant advancements in the field of harnessing solar energy and biomass, resulting in the production of green chemicals and plastics.

Go 100% Green with Solar Energy and Biomass

In the global pursuit of achieving ‘Net-Zero’ chemical and material manufacturing, there are two abundant but under-used resources: solar energy and biomass, particularly in Hong Kong. In a recent publication in Angewandte Chemie International Edition, a team led by Professor Zhengxiao GUO from HKU Department of Chemistry and its collaborators, have developed a Cu(II) porphyrin framework photocatalyst that effectively harnesses solar energy to upgrade a biomass derivative, HMF (5-hydroxylmethylfurfural), into a key sustainable ingredient, FDCA (2,5-furandicarboxylic acid), e.g. to make polyethylene furanoate (PEF) as a renewable alternative to polyethylene terephthalate (PET). This breakthrough opens pathways towards the production of 100% environmentally friendly chemicals and materials, potentially revolutionising the field of bio-plastics and resins. In the past, this conversion process faced limitation due to poor selectivity and sluggish kinetics, mainly caused by the vertical coordination of HMF at relatively strong catalyst sites. To overcome this, the team purposely designed and inserted side-chain incorporated urea linkages to the ‘traditional’ Cu(II) porphyrin framework catalyst. As a result, the newly formed TBUPP-Cu MOF catalyst which alters the interaction of HMF by weakening the hydrogen bond at the urea site and promoting a flat adsorption mode via π–π stacking with the benzene moiety. The unique configuration facilitates the approach of the –CHO group of HMF to the photo-excited porphyrin ring, leading to the formation of kinetically and thermodynamically favourable intermediates and subsequent desorption. Through charge localisation and orbital energy alignment, the catalyst enables selective activation of O2 over the porphyrin, generating ·O2− and 1O2, instead of highly oxidative H2O2 and ·OH, via a ‘spin-flip’ electron transfer mechanism, which drives the ambient partial oxidation of the proximal –CHO. The effective utilisation of the redox species and the circumvented over-oxidation facilitate a FDCA selectivity over 90% and a high turnover number of 193 mole_HMF /mole_Cu. The facile production of high-purity FDCA, zero-waste recovery of intermediates and high durability feature the TBUPP-Cu MOF catalyst a promising photo-oxidation platform towards net-zero biorefining and sustainable manufacturing. Click here to view the journal paper.  

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Chang’e-6 mission is the world’s first lunar farside sample return mission.  Image credit: Dr Yuqi Qian

HKU Geologists Reveal Mysterious and Diverse Volcanism in Lunar Apollo Basin, Chang'e-6 Landing Site

The farside of the Moon is a mysterious place that is never visible from the Earth. The most remarkable feature of the Moon is its asymmetry between the lunar nearside and farside in composition, crust thickness, and mare volcanism. Scientists have not yet reached a consensus on the origin of the lunar asymmetry due to the lack of farside samples, which is one of the most significant remaining question of lunar science. Chang’e-6 mission, launched on May 3, 2024, currently heading to the Moon, is the world’s first lunar farside sample-return mission. It aims to return ~2 kg lunar soils to the Earth from the southern mare plain of the Apollo basin within the South Pole-Aitken basin, the largest impact feature in the Solar System. These samples contain enormous scientific potentials that can be used to solve the lunar dichotomy conundrum and even reshape human’s knowledge of our closest neighbour. As shown in the recent paper published in Earth and Planetary Science Letters, Dr Yuqi QIAN, Professors Joseph MICHALSKI and Guochun ZHAO from the Department of Earth Sciences at The University of Hong Kong (HKU) and their international collaborators have comprehensively studied the volcanism of the Apollo basin and its surroundings, which revealed the mysterious and diverse volcanism of the Chang’e-6 landing site with significant implications for the Chang’e-6 sample analysis and the origin of the lunar dichotomy. The study has found that the Apollo basin has extensive volcanic activities lasting from the Nectarian (~4.05 billion years ago) to the Eratosthenian Period (~1.79 billion years ago). Volcanic activity in the region was significantly influenced by crustal thickness. Dikes in intermediate-thickness crust tend to stall beneath the crater floor, spreading laterally to form a sill and floor-fractured crater. Dikes below the crust thinned by the Apollo basin event reached directly to the surface and erupted to form widespread lava flows, and dikes in thick crust stall before being able to reach the surface and form basaltic dike intrusions. ‘This fundamental finding indicates that the crustal thickness discrepancy between nearside and farside may be the primary cause of lunar asymmetrical volcanism,’ said Dr Qian, ‘which can be tested by the returned Chang’e-6 samples’. For the southern mare plain in the Apollo basin, where Chang’e-6 is going to land, there are at least two episodes of eruptions. The earlier one erupted ~3.34 billion years ago with low-Ti composition and covered the entire topographically low region between the Apollo peak ring and basin rim. The later eruption occurred ~3.07 billion years ago with high-Ti composition close to Chaffee S crater and flowed east with decreasing thickness until encountering proto-wrinkle ridges. The authors suggested the high-Ti basalts in the west have the most abundant scientific meanings. Sampling it would return high-Ti basalts, underlying low-Ti basalts and exotic nonmare materials that were transported by impact events. Professor Michalski emphasised, ‘Diverse sample sources would provide important insights into solving a series of lunar scientific questions hidden in the Apollo basin.’ ‘The result of our research is a great contribution to the Chang’e-6 lunar mission. It sets a geological framework for completely understanding the soon-returned Chang’e-6 samples and will be a key reference for the upcoming sample analysis for Chinese scientists,’ said Professor Guochun Zhao, Chair Professor of HKU Department of Earth Sciences and the co-author of the paper, ‘It moves a large step for HKU when the university seeks excellence in planetary sciences and more participation in the national space programme.’ HKU is the only university in Hong Kong that possesses lunar samples obtained by the Chang’e-5 mission from nearside. Building on the foundation of this work, the geological team from HKU will also pursue the opportunity to acquire Chang’e-6 samples as well. This initiative aims to enable HKU to possess lunar samples representing both nearside and farside, thus unlocking a new window of scientific exploration into the study of two lunar hemispheres. Click here to view the journal paper. Chang’e-6 landing site is located to the Apollo basin in the northeast of the South Pole-Aitken basin. Image credit: Dr Yuqi Qian   About Dr Yuqi Qian A planetary geologist from the Department of Earth Sciences and Laboratory for Space Research at HKU. He collaborated with colleagues from Mainland China and around the world to study alien worlds. His research focuses on the geological processes of the Moon based on the data and samples obtained by China’s Lunar Exploration Program and other nations. For more information about Dr Yuqi Qian, please visit: https://yuqiqian.com   About Professor Joseph Michalski Utilising a range of remote sensing data, including infrared, visible, magnetic, gravity, and laser data from satellites orbiting Mars and rovers on its surface, Professor Michalski and his team at HKU focus on uncovering new discoveries about the volcanology, geochemistry, tectonics, and mineralogy of Mars. He has established the Planetary Spectroscopy and Mineralogy Laboratory at HKU. This cutting-edge facility offers laboratory support for past, current, and future missions to Mars, the Moon, and asteroids in China and beyond. Professor Michalski also serves as Deputy Director of HKU's Laboratory for Space Research. For more information about Professor Joseph Michalski, please visit: https://joeplanets.com   About Professor Guochun Zhao Professor Zhao is a highly esteemed geologist with international recognition, specializing in metamorphic petrology, Precambrian geology, and supercontinents. His extensive contributions to the field include over 400 scientific papers with more than 68,000 citations, earning him prestigious accolades. He was elected as a member of Chinese Academy of Sciences in 2019, a fellow of the World Academy of Sciences for the Advancement of Science in Developing Countries in 2021, and a member of Hong Kong Academy of Sciences in 2023. In the 2024 Best Scientists Rankings, compiled by Research.com, Professor Zhao stands 8th in the world and 1st in China in Earth Sciences.  

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