China Science & Technology Forum

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Hybrid macrofiber with spider silk-like supertoughness | Zhejiang University
2019-12-04

Nature provides an infinite amount of inspiration for human beings and biomimicry is one of the most extensively used methods among scientists. Natural SSF are characterized by their superhigh tensile strength (1150 ± 200 MPa) and remarkable fracture toughness (165 ± 30 J g−1) as well as their salient breaking strain (>50%). These features are attributable to the well-organized supramolecular networks in SSF: proteins self-assemble to form rigid nano-confined crystalline β-sheets and a flexible amorphous matrix. However, SSF cannot be obtained in large quantities from spiders owing to the fact that spiders cannot be farmed due to their cannibalistic behavior. Collecting SSF from webs is also extremely time-consuming and is therefore not profitable. Another typical biomaterial that combines a rigid crystalline phase and a flexible amorphous phase is biological bone. During biomineralization, the inorganic building blocks, hydroxyapatite (HAP), orderly assemble into collagen bundles to generate hard tissues. In contrast with the tensile strength of SSF, biological bone is marked by its toughness.

Against this backdrop, Prof. TANG Ruikang and Dr. LIU Zhaoming from the Zhejiang University Department of Chemistry fabricated biomimetic mineralized organic-inorganic hybrid macrofiber by using HAP and organic polyvinyl alcohol (PVA) to simulate the rigid crystalline and flexible amorphous protein blocks of SSF, respectively. This fiber is featured by a hierarchical ordered structure, a superhigh tensile strength of 949 ± 38 MPa, a specific toughness of 296 ± 12 J g−1, and a stretch ability of 80.6%. It consists of microfibers, and its outstanding performance (e.g., extreme tolerance to temperatures ranging from −196 to 80 °C and superior ability to inhibit the transverse growth of cracks) is attributed to the hierarchical arrangement as well as the organic-inorganic integrated structure within the oriented mineralized polymer chains.

Schematic illustration of the preparation process and network microstructure of the PVA/Alg/HAP hybrid macrofiber

The biomineralization-inspired technique is of great significance due to its simplicity and efficiency, achieved by utilizing the sophisticated biomimetic mineralization tactic. The resulting fibrous material has promise for applications such as flexible ballistic fabrics owing to its excellent mechanical properties. More importantly, the composite materials PVA, Alg and HAP are inexpensive and highly available in markets. In addition, this fabrication process is simple, scalable, and cost-effective, and thus represents an alternative pathway for the development of the fiber industry.

 

[JSCh]

Chinese, US scientists identify ancient mammals with separate hearing, chewing bones
Xinhua | Updated: 2019-12-06 09:24

The fossil of a new Cretaceous mammal species found in Northeast China's Liaoning province. [Photo/cas.cn]

WASHINGTON -- Scientists in China and the United States reported a mammal living more than 120 million years ago, which provides evidence for separation of hearing and chewing modules in the evolution of therian mammals to which all extant mammals, including human beings, belong to.

The study published on Thursday in the journal Science showed that the mammal living in dinosaur's age in Northeast China did not have the bone link between the auditory bones and Meckel's cartilage.

Scientists from the Chinese Academy of Sciences and the American Museum of Natural History reconstructed 3D skeletal morphologies of the new species called Origolestes lii using high-resolution microtomography.

Skull morphologies, dentitions, jaws, and tooth wear from individuals of the same species show evidence of opening and closing movements during the biting and chewing process as well as jaw yawing and rolling. The multi-directional movements of the lower jaw during chewing are likely to be one of the selection pressures that caused the detachment of the auditory ossicles from the dental bone and the Meckel's cartilage, according to the study.

It signals a more advanced stage in the evolution of the mammalian middle ear, since the decoupled hearing and chewing modules eliminated physical constraints that interfered with each other and possibly increased the capacity of the two modules to evolve.

After the separation, the animal's hearing module may have had greater potential to develop sensitive hearing of high frequency sounds, and the chewing module may have been able to evolve diverse tooth morphologies and occlusal patterns that facilitated consuming different foods, according to the study.

 

[JSCh]

Scientists Uncover Mysteries of Chromosome Structures in Human Sperm and Embryos
By LIU Jia | Dec 05, 2019

In a study published in Nature, the research groups led by Dr. LIU Jiang’s lab from Beijing Institute of Genomics (BIG) of the Chinese Academy of Sciences and Dr. CHEN Zijiang’s lab from Shandong University uncovered the mysteries of chromosome structures in human sperm and embryos.

There are 23 pairs of chromosomes within a human cell and DNA is compressed and properly packed into a three-dimensional (3D) structure within the crowded nucleus. Human individual development starts from a fertilized egg, experiences the embryonic stage and gradually develops into a complex organism containing hundreds of distinct cell types and organs. Rich epigenetic information is coded in 3D chromatin structure in human embryos.

However, what happens to the 3D chromatin structure after the fertilization in human embryos and which key factors can affect chromosome structure dynamics remain unknown. Moreover, sperm is so special with distinct morphology and functions from other cells, it is unclear how chromosomes are compressed and folded in human sperm.

In this study, the scientists applied the optimized Hi-C method in human sperm and early embryos by using as few as 50-100 cells to map 3D chromosome structures. They revealed the key role of CTCF protein in establishing chromatin structure in human embryos.

The topologically associating domain (TAD) is the basic unit of 3D chromosome structures. Unlike mouse sperm, human sperm cells do not express the chromatin regulator protein CTCF and their chromatin does not contain TADs. After fertilization, both the TAD structures and A/B compartmentalization undergo gradual establishment during embryonic development.

In the first two days following the fertilization in human, the embryo genome almost expresses no genes until 8-cell stage at which zygotic genome activation (ZGA) occurs and embryo genome starts expressing new genes.

Remarkably, different from that in mouse or Drosophila embryos, blocking zygotic genome activation (ZGA) can inhibit TAD establishment in human embryos. Besides, the expression of CTCF has a booming increase from a limited expression level during ZGA and TAD organization is significantly reduced in CTCF knock-down embryos, suggesting that CTCF expression is required for TAD establishment during ZGA in human embryos.

The scientists uncovered that CTCF play a key role in the establishment of 3D chromatin structure during human embryogenesis. This study made a further step towards the comprehensive understanding of human embryonic development.

The dynamics of 3D chromosome structures in human sperm and embryos (Image by LIU Jiang's group)


Scientists Uncover Mysteries of Chromosome Structures in Human Sperm and Embryos----Chinese Academy of Sciences

Xuepeng Chen, Yuwen Ke, Keliang Wu, Han Zhao, Yaoyu Sun, Lei Gao, Zhenbo Liu, Jingye Zhang, Wenrong Tao, Zhenzhen Hou, Hui Liu, Jiang Liu, Zi-Jiang Chen. Key role for CTCF in establishing chromatin structure in human embryos. Nature (2019). DOI: 10.1038/s41586-019-1812-0​

 

[JSCh]

Scientists Observe Nearly Quantized Majorana Conductance Plateau in An Iron-based Superconductor----Chinese Academy of Sciences
By ZHANG Nannan | Dec 13, 2019

Recently, Prof. GAO Hongjun Gao's and Prof. DING Hong's joint research group took a step further in the research of Majorana physics using the home-upgraded ultra-low-temperature and strong-magnetic-field scanning tunneling microscope/spectroscopy (STM/STS) system.

They observed conductance plateaus as a function of tunnel coupling for the zero-energy vortex bound states (Majorana zero modes) with values close to or even reaching the 2e2/h quantum conductance by continuously tuning the tunnel-coupling between STM tip and Fe(Te,Se) single crystal.

In contrast, no plateaus were observed on neither finite energy vortex bound states nor in the continuum of electronic states outside the superconducting gap (Fig. 2). The statistical analysis of 31 Majorana zero modes show the value of Majorana plateau concentrated near the quantized conductance 2e2/h.

In 1937, Ettore Majorana, an Italian physicist, predicted an elementary particle called the Majorana Fermion, for which the particle is its own anti-particle. The Majorana Fermion in condensed matter physics is also known as Majorana zero mode. Because Majorana zero modes obey non-Abel statistics, it holds a great promise for the realization of topological quantum computing, which has caused widespread concern.

Since 2014, the study of non-trivial topological band structures in iron-based superconductors was triggered by the researchers in Institute of Physics/University of Chinese Academy of Sciences (IOP/UCAS), Chinese Academy of Sciences, from both experimental perspective and theoretical efforts.

Starting from 2017, the joint group led by Prof. GAO Hongjun and Prof. DING Hong investigated the vortices in an iron-based superconductor using STM/STS. For the first time, they reported the observation of the evidence of Majorana zero modes in an iron-based superconductor Fe(Te,Se).

These results have been then verified by independent research groups from Fudan University, the Japan Institute of Physics and Chemistry (RIKEN), and other institutions. Moreover, the joint research group further performed a detailed study of Majorana zero modes in iron-based superconductors and found that there are two distinct types of vortices on the surface of Fe(Te,Se) single crystal when applying a magnetic field. These results provide a deep understanding of vortex bound states and the topological nature of the Majorana zero mode.

Although there is already a lot of experimental evidence for the existence of Majorana zero mode in iron-based superconductors, there still needs more efforts to exclude other possibilities contributing to zero-energy conductance signals. For example, in nanowire systems, the zero-bias peaks have been observed since 2012, but many topological trivial explanations have not been excluded until Kouwenhoven's research group observed the quantized conductance plateau.

In the latest experiment, scientists also investigated how the instrumental broadening and the quasiparticle poisoning effect affect the conductance plateau value from the theoretical quantized value 2e2/h (Fig. 3).

The observation of a zero-bias conductance plateau in the two-dimensional vortex case, which approaches the quantized conductance of 2e2/h, provides spatially-resolved spectroscopic evidence for Majorana-induced resonant electron transmission into a bulk superconductor, moving one step further towards the braiding operation applicable to topological quantum computation.

This study entitled "Nearly quantized conductance plateau of vortex zero mode in an iron-based superconductor" was published on Science on December 12, 2019.

The work is supported by grants from the Ministry of Science and Technology of China, the National Natural Science Foundation of China, and the Chinese Academy of Sciences.

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Fig. 1. Zero-bias conductance plateau observed on Fe(Te,Se). (Image by IOP)

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Fig. 2. Majorana induced resonant Andreev reflection. (Image by IOP)

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Fig. 3. The conductance variation of Majorana plateau. (Image by IOP)

 

[JSCh]

Scientists Develop World-record 32.35 Tesla with An All-superconducting Magnet----Chinese Academy of Sciences
By ZHANG Nannan | Dec 09, 2019

Recently, Prof. WANG Qiuliang's group from the Institute of Electrical Engineering of the Chinese Academy of Sciences developed an all-superconducting magnet with a central magnetic field of up to 32.35 Tesla (T), which is a new record of the highest magnetic field generated by all-superconducting magnets.

The magnet was built with independently developed high-temperature interpolation magnet technology, breaking the world record of the 32.0 T superconducting magnet created by the US National High Magnetic Field Laboratory in December 2017.

The upper limit of the magnetic field strength generated by the low-temperature superconducting magnet is about 23.0T. In order to obtain a higher magnetic field, the combination of high-temperature superconducting magnets and low-temperature superconducting magnets are employed.

The high-temperature superconducting magnet is used as an inserted magnet into the bore of the low-temperature superconducting magnet, utilizing the advantages of high tensile strength and high critical currents of high-temperature superconductors under high magnetic fields.

The researchers has focused on the research of high-field high-temperature superconducting insert magnet and has developed 24.0T, 25.7T, and 27.2T all-superconducting magnets in the past years. The extremely-high magnetic field superconducting magnet, which constructed recently, produced a central magnetic field of 32.35 T in liquid helium bath, and realized the stable operation of the 32.35T all-superconducting magnet.

The high-field superconducting magnets will serve the world-class Synergetic Extreme Condition User Facility (SECUF), and will provide the most advanced high magnetic field experimental conditions for basic research and applied research in the exploration of new states of matter, new phenomena, and new laws in material science.

The excitation process of the 32.35 T all-superconducting magnet (Image by LIU Jianhua)

 

[JSCh]

Chinese scientists confirm existence of critical ice nucleus
Source: Xinhua| 2019-12-19 19:19:30|Editor: mingmei

BEIJING, Dec. 19 (Xinhua) -- Chinese scientists have provided experimental information on the existence and temperature-dependent size of critical ice nuclei for the first time.

Water freezing is ubiquitous, but the process of how water turns into ice at the micro level is unknown. Ice nucleation is the controlling step in water freezing and has, for nearly a century, been assumed to require the formation of a critical ice nucleus, according to the classical nucleation theory. But there has been no direct experimental evidence for the existence of such a nucleus, owing to its transient and nanoscale nature.

Researchers from the Institute of Chemistry, Chinese Academy of Sciences and the University of the Chinese Academy of Sciences creatively probed the existence of a critical ice nucleus and its size for ice formation with graphene oxide nanosheets.

In a paper published in the journal Nature, researchers used different-sized graphene oxide nanosheets to detect the critical size of the ice nucleus.

They inferred from the experimental data and theoretical calculations that the critical size of the graphene oxide reflects the size of the critical ice nucleus, which in the case of sufficiently large graphene oxides sits on their surface and gives rise to ice formation behavior consistent with classical nucleation theory.

"This experiment can be understood like this: using nanoparticles with a determined size as rulers to measure the critical ice nucleus and continuously reducing the temperature to make the ice nucleus size reach the required critical size. When the ice nucleus size is exactly the same as the size of the nanoparticles, it is easy to form a critical ice nucleus," Wang said.

The research has deepened the microscopic understanding of water freezing and has also provided important theoretical guidance for the application of artificial ice control. It will play a vital role in the fields of chemical industry, cryobiology and materials science.

 

[Grandy]

China Is Building an Artificial Sun

China’s nuclear fusion device. Popular Mechanics’ image
The nuclear fusion reactor will burn as hot as 360 million degrees Fahrenheit.

By Caroline Delbert
Dec 20, 2019
Xinhua/Chinese Academy of Sciences

• Fusion researchers in China will bring their artificial sun up to full speed in 2020.
• This superpowered tokamak device and the related stellarator device form the bulk of fusion technology research.
• Tokamaks are touchy and prone to destabilizing, which these scientists hope to study and ameliorate.

China has announced advancing plans for its nuclear fusion device known colloquially as an “artificial sun.” They say the device, which will reach temperatures of up to 360 million degrees Fahrenheit, is actually more like 12 artificial suns combined. The extremely high temperatures lead to the titular effect: literally, the nucleuses of two or more atoms are fused, and the process generates energy.

The experimental device, the HL-2M Tokamak, is the largest of its kind to date. A tokamak is a specific kind of fusion reactor that’s been theorized about since the 1950s, when Soviet scientists coined the term as a shortening of the Russian for “toroidal magnetic confinement.” The name is perfectly descriptive. A tokamak is a torus—the math term for a donut—in which extremely heated plasma is trapped and pressed into making chemical reactions.

There have been hundreds of small tokamaks in experimental lab settings around the world in the last 40 or more years. The plasma inside a tokamak is held there by magnetic fields, and these are prone to imperfections that can turn into disruptive flaws. Controlling them is really hard. Studying the tokamak has taken so long, and sometimes seemed so impossible to implement at large scale rather than just wildly improbable, that a second related device has threatened to overtake it in the public eye.

The stellarator, a descendent in a way and an even wilder-looking assemblage of ideas, is supposed to be more stable and less likely to spin out. It made the news in 2015 when a breakthrough with the Wendelstein 7-X stellarator led people to wonder if this new energy donut would surpass the old. But the two devices, the stellarator and the tokamak, have been developed almost in parallel by different teams since the very beginning. The 2015 stellarator breakthrough represented a milestone, but an early, experimental one.

China’s HL-2M Tokamak is known by its official name, the Experimental Advanced Superconducting Tokamak (EAST). Scientists first switched it in on 2006, but achieving milestones with EAST is hard work over many years. In 2018, it reached 180 million degrees Fahrenheit—halfway to the optimal operating temperature the team says it will reach in 2020.

In a way, EAST is proof of concept for a larger plasma fusion reactor. In a safe lab context, scientists can observe how the tokamak behaves. Because of the way they’re designed, tokamaks tend to throw the hottest, most energetic particles outside of their cores. They can instantly destabilize and fall out of the plasma-reactive zone, and most must be heated externally up to the 180 million Fahrenheit mark.

EAST is supposed to maintain that heat by itself, and its researchers have reached plasma states for tiny intervals of time during the last 13 years. Their goal now is to have a more stable, constant plasma reaction to show that such a thing can be done. After that, they hope to bring tokamaks out of research labs and into the world of commercial energy.

Source: Popular Mechanics “China Is Building an Artificial Sun”

 

[JSCh]

Shanghai team in diffusion breakthrough
Yang Meiping 22:25 UTC+8, 2019-12-19

A team from Shanghai Jiao Tong University said on Thursday that it had developed a way to make materials that can localize light waves and prevent diffusion during transmission.

Researchers said it can ensure quality of information such as images in transmission as no loss happens in the process.

The findings have been published in international science journal Nature.

Ye Fangwei, a professor at the university’s School of Physics and Astronomy and leader of the team, explained: “When I speak, everyone hears me, because the wave of the sound diffuses; when you throw a stone into a still lake, the ripple expands, because the wave of the water diffuses; when a laser is propagating in space, the laser spot becomes larger and larger with distance, because the wave of the light diffuses or diffracts. In fact, every type of wave diffuses, and diffusion is a common nature for all waves. That is why the fact that kills the diffusion and localizes waves is a fundamental, long-standing problem in science.

They used moiré lattices, which consist of two superimposed identical periodic structures with a relative rotation angle and are widely seen in life, such as the light and dark stripes seen when two combs are put together with a relative rotation angle.

The light and dark stripes seen when two combs are put together with a relative rotation angle are moiré lattices.

The team found that when it imprinted two moiré lattices in the same crystal material with some rotation angles, they can make light travel in one direction without diffusion.

It means that we might be able to transmit images or information using the moiré-lattice materials, which, in sharp contrast to the existing ones, does not need special designs.

“Our findings provide a new way to localize waves, not only light waves, but also other waves like matter waves,” Ye said.

He said the new findings had a potential application in information transportation, image processing and light manipulations, and inspire other research in several areas of science, including optics, acoustics, condensed matter and atomic physics.

The light does not diffuse when the material is imprinted with two moiré lattices with a rotation angle (right), but diffuses when the lattices are imprinted with another angle.

Source: SHINE Editor: Shen Ke

 

[JSCh]

Scientists Reveal Function of Histone Variant H2A.Z in DNA Replication Selection----Chinese Academy of Sciences
By LIU Jia | Dec 26, 2019

The research published in Nature on Dec. 25th, 2019, led by Dr. LI Guohong and Dr. ZHU Mingzhao from the Institute of Biophysics of the Chinese Academy of Sciences, has demonstrated that the histone variant H2A.Z facilitates the licensing and activation of early DNA replication origins.

DNA replication is a tightly regulated process that ensures the precise duplication of the genome during cell proliferation. Replication origins determine where replication starts on the genome and regulate the whole genome replication program. The human genome contains tens of thousands of origins; however, only about 10% of them are used in each cell cycle. So how are origins selected?

In eukaryotes, DNA wraps around histone octamers to form chromatin in the nucleus. The licensing and activation of replication origins are regulated by both the DNA sequence and chromatin features. However, chromatin-based regulatory mechanisms remain largely uncharacterized.

In this study, the scientists first found that knocking down H2AFZ genes in HeLa cells results in cell growth defects. Through mass spectrometry, many subunits of prereplication complex were enriched on H2A.Z mono-nucleosomes, indicating that H2A.Z may be involved in the licensing of DNA replication origins.

To find the mechanism of interaction between H2A.Z and the prereplication complex, the scientists then performed in vitro biochemical analysis and found that H2A.Z-containing nucleosomes bind directly to the histone lysine methyltransferase enzyme SUV420H1. This process promotes H4K20me2 deposition, which further recruits origins recognition complex 1 (ORC1) to help accomplish the licensing of DNA replication origins.

In addition, through genome-wide studies in HeLa cells, the scientists confirmed the role of H2A.Z in DNA replication. The results showed that signals from H4K20me2, ORC1 and nascent DNA strands (indicating active DNA replication origins) co-localize with H2A.Z, and the depletion of H2A.Z results in decreased H4K20me2, ORC1 and nascent-strand signals. H2A.Z-regulated replication origins have a higher firing efficiency and earlier replication timing compared with other origins.

Furthermore, the scientists generated CD4CreH2A.Zf/f mice to study the function of H2A.Z-regulated replication in a more physiological context. Using these mice, they conditionally knocked out (CKO) H2az1/H2az2 in T cells. They then found that in H2A.Z CKO mic the activated T cells have defects in cell proliferation and DNA replication.

This study describes a novel epigenetic regulation mechanism for DNA replication origin selection and offers a new way of understanding DNA replication regulation in eukaryotes. Importantly, this regulatory pathway can potentially serve as a target for cancer treatment and regulation of T cell function during immunotherapy.

Working model: Origin selection: H2A.Z nucleosomes bind Suv420H1 directly to establish H4K20me2 on chromatin, which then recruits ORC1 to bind to replication origins; Origin firing: H2A.Z-Suv420H1-H4K20me2-ORC1 axis selectively license and activate early replication origins. (Image by Dr. LI Guohong’s lab)

 

[JSCh]

Chinese scientists launch genome project for protists
Xinhua | Updated: 2020-01-03 14:37

BEIJING - Chinese scientists recently launched a program to map the genomes of about 10,000 representative species of protists and establish a large-scale database of protist genetic resources.

The program was jointly launched by the Institute of Hydrobiology of the Chinese Academy of Sciences (CAS), Tibet University, Henan Agricultural University, the Lanzhou Veterinary Research Institute of the Chinese Academy of Agricultural Sciences, the CAS Beijing Institute of Genomics and Huazhong University of Science and Technology.

A protist is a single-celled organism of the kingdom Protista, such as a protozoan or simple alga. More than 60,000 protist species have been described, and the number of unknown species is hard to estimate.

Protists are not only an important component of water ecosystems, but also an excellent source of food and nutrition for aquatic animals and humans. However, some toxic algal blooms in rivers and oceans may bring serious environmental problems, said the scientists.

At the same time, some protists are major pathogenic parasites of humans, livestock and aquatic animals, such as Plasmodium.

However, there had previously been no large-scale genome program for protists in the world. So far, genome data of only about 400 protist species have been published, said Miao Wei, deputy director of the CAS Institute of Hydrobiology.

The genome project will be based on the more than 3,000 species of eukaryotic algae and protozoa kept by the research institutes participating in the program, and more samples will be collected.

The scientists aim to complete the genome sequencing and analysis of about 10,000 protist species in three years.

The project is expected to help scientists better understand the mechanism of biodiversity, the origin and evolution of multicellular organisms and sexual reproduction, and to push forward the research on environmental protection, nutrition and disease control.

 

[JSCh]

Water lily genome expands picture of the early evolution of flowering plants
Sam Sholtis
2 January 2020

The newly reported genome sequence of a water lily sheds light on the early evolution of angiosperms, the group of all flowering plants. An international team of researchers, including scientists at Penn State, used high-throughput next-generation sequencing technology to read out the water lily’s (Nymphaea colorata) genome and transcriptome—the set of all genes expressed as RNAs.

The unusual high quality and depth of coverage of the sequence allowed the researchers to assemble the vast majority of the genome into 14 chromosomes and identify more than 31 thousand protein-coding genes. A paper describing the sequence and subsequent analysis appears December 18, 2019 in the journal Nature.

“Water lilies have been an inspiration to artists like Claude Monet because of their beauty and important to scientists because of their position near the base of the evolutionary tree of all flowering plants,” said Hong Ma, associate dean for research and innovation, Huck Distinguished Research Professor of Plant Molecular Biology, and professor of biology at Penn State, one of the leaders of the research team. “I previously contributed to the sequencing and analysis of the genome of Amborella, which represents the earliest branch to separate from other flowering plants, but Amborella lacks big showy colorful flowers and attractive floral scent, both of which serve to attract pollinators in most groups of flowering plants. We were interested in the water lily genome to help us understand how these traits evolved.”

Evolutionary comparison of the water lily genome to the genomes of Amborella, other angiosperms, and several gymnosperms—the group of seed-bearing plants that do not produce flowers—confirmed the position of Amborella, which shares some characteristics with the gymnosperms, as the earliest of currently living angiosperms to separate from other flowering plants. Water lilies were the next branch to diverge from a third branch (Austrobaileyales, which includes star anise) and a fourth very large group called the mesangiosperms, which contains over 99% of living flowering plants.

“If we make an analogy to mammalian evolution, Amborella has a similar position to that of the platypus and other egg-laying mammals,” said Ma. “The platypus is a mammal because it feeds its young with milk, but it lays eggs like birds or reptiles. Amborella, like gymnosperms, has separate male and female plants, but the water lily has male and female reproductive parts within a single flower. This makes the water lily more similar to the vast majority of other flowering plants, so having the genomes of both Amborella and water lily can help us to better analyze the evolutionary transition from gymnosperms to angiosperms.”

The researchers used molecular dating to estimate the separation of the family of water lilies (Nymphaeaceae) from other families of related aquatic plants at somewhere between 147 and 185 million years ago, when dinosaurs roamed the earth, with a whole-genome duplication (WGD)/polyploidy event at about the same time. Many of the key genes for flower development retained in this WGD.

The research team also analyzed genes in the water lily genome that are likely important for the generation of molecules for attractive floral scent and color, traits shared with most other angiosperms, but not found in Amborella. They identified a massive expansion in the number of genes involved in the biosynthesis of floral scent in water lilies; these genes seem to have evolved in parallel with the other angiosperms. They also analyzed the expression of genes involved in flower color between two species of water lily, identifying the key proteins responsible for blue petals.

“Having the water lily genome allows us to explore these important traits in flowering plants and especially among horticultural plants,” said Ma. “It’s likely that brightly colored flowers and floral scent evolved through an interaction with pollinators and such flowers are ultimately extremely important for the success of flowering plants. Identification of the key synthetic genes of blue petals has important reference value for breeding blue petal varieties.”

In addition to Ma, the research team was led by Liangsheng Zhang and Haibao Tang of the Fujian Agriculture and Forestry University in Fuzhou, China; Fei Chen and Feng Chen of Nanjing Agricultural University in Nanjing, China and the University of Tennessee, Knoxville; and Yves Van de Peer of Ghent University in Belgium, and includes 47 authors from 23 institutions.


Water lily genome expands picture of the early evolution of flowering plants | Eberly College of Science | The Pennsylvania State University

Liangsheng Zhang, Fei Chen, Xingtan Zhang, Zhen Li, Yiyong Zhao, Rolf Lohaus, Xiaojun Chang, Wei Dong, Simon Y. W. Ho, Xing Liu, Aixia Song, Junhao Chen, Wenlei Guo, Zhengjia Wang, Yingyu Zhuang, Haifeng Wang, Xuequn Chen, Juan Hu, Yanhui Liu, Yuan Qin, Kai Wang, Shanshan Dong, Yang Liu, Shouzhou Zhang, Xianxian Yu, Qian Wu, Liangsheng Wang, Xueqing Yan, Yuannian Jiao, Hongzhi Kong, Xiaofan Zhou, Cuiwei Yu, Yuchu Chen, Fan Li, Jihua Wang, Wei Chen, Xinlu Chen, Qidong Jia, Chi Zhang, Yifan Jiang, Wanbo Zhang, Guanhua Liu, Jianyu Fu, Feng Chen, Hong Ma, Yves Van de Peer, Haibao Tang. The water lily genome and the early evolution of flowering plants. Nature (2019). DOI: 10.1038/s41586-019-1852-5​

 

[JSCh]

A close look at thin ice
Marrying theoretical work with experiments and high-tech imaging techniques, atmospheric chemists Chongqin Zhu and Joseph S. Francisco of the School of Arts and Sciences and colleagues have identified a new way that ice grows in two dimensions.

On frigid days, water vapor in the air can transform directly into solid ice, depositing a thin layer on surfaces such as a windowpane or car windshield. Though commonplace, this process is one that has kept physicists and chemists busy figuring out the details for decades.

An international team of scientists, including atmospheric chemists from Penn, describe the first-ever visualization of the atomic structure of two-dimensional ice as it formed. (Image: Courtesy of Joseph Francisco)

In a new Nature paper, an international team of scientists describe the first-ever visualization of the atomic structure of two-dimensional ice as it formed. Insights from the findings, which were driven by computer simulations that inspired experimental work, may one day inform the design of materials that make ice removal a simpler and less costly process.

“One of the things that I find very exciting is that this challenges the traditional view of how ice grows,” says Joseph S. Francisco, an atmospheric chemist at the University of Pennsylvania and an author on the paper.

“Knowing the structure is very important,” adds coauthor Chongqin Zhu, a postdoctoral fellow in Francisco’s group who led much of the computational work for the study. “Low-dimensional water is ubiquitous in nature and plays a critical role in an incredibly broad spectrum of sciences, including materials science, chemistry, biology, and atmospheric science.

“It also has practical significance. For example, removing ice is critical when it comes to things like wind turbines, which cannot function when they are covered in ice. If we understand the interaction between water and surfaces, then we might be able to develop new materials to make this ice removal easier.”

In recent years, Francisco’s lab has devoted considerable attention to studying the behavior of water, and specifically ice, at the interface of solid surfaces. What they’ve learned about ice’s growth mechanisms and structures in this context helps them understand how ice behaves in more complex scenarios, like when interacting with other chemicals and water vapor in the atmosphere.

“We’re interested in the chemistry of ice at the transition with the gas phase, as that’s relevant to the reactions that are happening in our atmosphere,” Francisco explains.

To understand basic principles of ice growth, researchers have entered this area of study by investigating two-dimensional structures: layers of ice that are only several water molecules thick.

In previous studies of two-dimensional ice, using computational methods and simulations, Francisco, Zhu, and colleagues showed that ice grows differently depending on whether a surface repels or attracts water, and the structure of that surface.

In the current work, they sought real-world verification of their simulations, reaching out to a team at Peking University to see if they could obtain images of two-dimensional ice.

The Peking team employed super-powerful atomic force microscopy, which uses a mechanical probe to “feel” the material being studied, translating the feedback into nanoscale-resolution images. Atomic force microscopy is capable of capturing structural information with a minimum of disruption to the material itself, allowing the scientists to identify even unstable intermediate structures that arise during the process of ice formation.

Virtually all naturally occurring ice on Earth is known as hexagonal ice for its six-sided structure. This is why snowflakes all have six-fold symmetry. One plane of hexagonal ice has a similar structure to that of two-dimensional ice and can terminate in two types of edges—“zigzag” or “armchair.” Usually this plane of natural ice terminates with a zigzag edge.

However, when ice is grown in two dimensions, researchers find that the pattern of growth is different. The current work, for the first time, shows that the armchair edges can be stabilized and that their growth follows a novel reaction pathway.

“This is a totally different mechanism from what was known,” Zhu says.

Although the zigzag growth patterns were previously believed to only have six-membered rings of water molecules, both Zhu’s calculations and the atomic force microscopy revealed an intermediate stage where five-membered rings were present.

This result, the researchers say, may help explain the experimental observations reported in their 2017 PNAS paper, which found that ice could grow in two different ways on a surface, depending on the properties of that surface.

In addition to lending insight into future design of materials conducive to ice removal, the techniques used in the work are also applicable to probe the growth of a large family of two-dimensional materials beyond two-dimensional ices, thus opening a new avenue of visualizing the structure and dynamics of low-dimensional matter.

For chemist Jeffrey Saven, a professor in Penn Arts & Sciences who was not directly involved in the current work, the collaboration between the theorists in Francisco’s group and their colleagues in China called to mind a parable he learned from a mentor during his training.

“An experimentalist is talking with theorists about data collected in the lab. The mediocre theorist says, ‘I can’t really explain your data.’ The good theorist says, ‘I have a theory that fits your data.’ The great theorist says, ‘That’s interesting, but here is the experiment you should be doing and why.’”

To build on this successful partnership, Zhu, Francisco, and their colleagues are embarking on theoretical and experimental work to begin to fill in the gaps related to how two-dimensional ice builds into three dimensions.

“The two-dimensional work is fundamental to laying the background,” says Francisco. “And having the calculations verified by experiments is so good, because that allows us to go back to the calculations and take the next bold step toward three dimensions.”

“Looking for features of three-dimensional ice will be the next step,” Zhu says, “and should be very important in looking for applications of this work.”


A close look at thin ice | Penn Today | University of Pennsylvania

Runze Ma, Duanyun Cao, Chongqin Zhu, Ye Tian, Jinbo Peng, Jing Guo, Ji Chen, Xin-Zheng Li, Joseph S. Francisco, Xiao Cheng Zeng, Li-Mei Xu, En-Ge Wang & Ying Jiang. Atomic imaging of the edge structure and growth of a two-dimensional hexagonal ice. Nature (2020). DOI: 10.1038/s41586-019-1853-4​

 

[JSCh]

Top 10 Technology Trends in 2020 Predicted by Alibaba DAMO Academy
2020/01/02 From Alibaba DAMO Academy

Today, Alibaba DAMO Academy published The Top 10 Technology Trends in 2020. We hope that by grasping the pace of revolution of technologies, we can make better use of these “magics” and be in charge of our own future.

Trend No 1. Artificial intelligence evolves from perceptual intelligence to cognitive intelligence

Artificial intelligence has reached or surpassed humans in the areas of perceptual intelligence such as speech to text, natural language processing, video understanding etc; but in the field of cognitive intelligence that requires external knowledge, logical reasoning, or domain migration, it is still in its infancy. Cognitive intelligence will draw inspiration from cognitive psychology, brain science, and human social history, combined with techniques such as cross domain knowledge graph, causality inference, and continuous learning to establish effective mechanisms for stable acquisition and expression of knowledge. These make machines to understand and utilize knowledge, achieving key breakthroughs from perceptual intelligence to cognitive intelligence.

Trend No 2. In-Memory-Computing addresses the "memory wall" challenges in AI computing

In Von Neumann architecture, memory and processor are separate and the computation requires data to be moved back and forth. With the rapid development of data-driven AI algorithms in recent years, it has come to a point where the hardware becomes the bottleneck in the explorations of more advanced algorithms. In Processing-in-Memory (PIM) architecture, in contrast to the Von Neumann architecture, memory and processor are fused together and computations are performed where data is stored with minimal data movement. As such, computation parallelism and power efficiency can be significantly improved. We believe the innovations on PIM architecture are the tickets to next generation AI.

Trend No 3. Industrial IoT power the digital transformation

In 2020, 5G, rapid development of IoT devices, cloud computing and edge computing will accelerate the fusion of information system, communication system, and industrial control system. Through advanced Industrial IoT, manufacturing companies can achieve automation of machines, in-factory logistics, and production scheduling, as a way to realize C2B smart manufacturing. In addition, interconnected industrial system can adjust and coordinate the production capability of both upstream and downstream vendors. Ultimately it will significantly increase the manufacturers’ productivity and profitability. For manufacturers with production goods that value hundreds of trillion RMB, If the productivity increases 5-10%, it means additional trillions of RMB.

Trend No 4. Large-scale collaboration between machines become possible

Traditional single intelligence cannot meet the real-time perception and decision of large-scale intelligent devices. The development of collaborative sensing technology of Internet of things and 5G communication technology will realize the collaboration among multiple agents -- machines cooperate with each other and compete with each other to complete the target tasks. The group intelligence brought by the cooperation of multiple intelligent bodies will further amplify the value of the intelligent system: large-scale intelligent traffic light dispatching will realize dynamic and real-time adjustment, warehouse robots will cooperate to complete efficient cooperation of cargo sorting, driverless cars can cooperate to make the best tradeoff between efficiency and safety, and group uav collaboration will efficiently get through the last kilometer of distribution.

Trend No 5. Modular design makes chips easier and faster by stacking chiplets together

Traditional model of chip design cannot efficiently respond to the fast evolving, fragmented and customized needs of chip production. The open source SoC chip design based on RISC-V, high-level hardware description language, and IP-based modular chip design methods have accelerated the rapid development of agile design methods and the ecosystem of open source chips. In addition, the modular design method based on chiplets uses advanced packaging methods to package the chiplets with different functions together, which can quickly customize and deliver chips that meet specific requirements of different applications.

Trend No. 6 Large-Scale Production-Grade Blockchain Applications will Gain Mass Adoption

BaaS (Blockchain-as-a-Service) will further reduce the barriers of entry for enterprise blockchain applications. A variety of hardware chips embedded with core algorithms used in terminals, cloud and designed specifically for blockchain will also emerge, allowing assets in the physical world to be mapped to assets on blockchain, further expanding the boundaries of the Internet of Value and realizing "multi-chain interconnection". In the future, a large number of innovative blockchain application scenarios with multi-dimensional collaboration across different industries and ecosystems will emerge, and large-scale production-grade blockchain applications with more than 10 million DAI (Daily Active Items) will gain mass adoption.

Trend No. 7 A critical period before large-scale quantum computing

In 2019, the race in reaching “Quantum Supremacy” brought the focus back to quantum computing. The demonstration, using superconducting circuits, boosts the overall confidence on superconducting quantum computing for the realization of a large-scale quantum computer. In 2020, the field of quantum computing will receive increasing investment, which comes with increasing competitions. The field is also expected to experience a speed-up in industrialization and the gradual formation of an eco-system. In the coming years, the next milestones will be the realization of fault-tolerant quantum computing and the demonstration of quantum advantages in real-world problems. Either is of a great challenge given the present knowledge. Quantum computing is entering a critical period.

Trend No.8 New Materials Will Revolutionize the Semiconductor Devices

Under the pressure of both Moore's Law and the explosive demand of computing power and storage, it is difficult for classic Si based transistors to maintain sustainable development of the semiconductor industry. Until now, major semiconductor manufacturers still have no clear answer and option to chips beyond 3nm. New materials will make new logic, storage, and interconnection devices through new physical mechanisms, driving continuous innovation in the semiconductor industry. For example, topological insulators, two-dimensional superconducting materials, etc. that can achieve lossless transport of electron and spin can become the basis for new high-performance logic and interconnect devices; new magnetic materials and new resistive switching materials can realize high-performance magnetics Memory such as SOT-MRAM and resistive memory.

Trend No.9 Growing Adoption of AI Technologies that Protect Data Privacy

The compliance costs demanded by the recent data protection laws and regulations related to the processing of personal data are getting increasingly higher than ever before. In light of this, there have been growing interests in using AI technologies to protect data privacy. The essence is to enable the data consumer to compute a function over input data from different data providers while keeping those data private. Such AI technologies promise to solve the problems of data silos and lack of trust in today's data sharing practices, and will truly unleash the value of data in the foreseeable future.

Trend No.10 Cloud becomes the center of IT technology innovation

With the in-depth development of cloud computing technology, the cloud has grown far beyond the scope of IT infrastructure, and gradually evolved into the center of all IT technology innovations. The cloud has tight relationship with almost all IT technologies, including new chips, new databases, self-driving adaptive networks, big data, AI, IoT, blockchain, quantum computing and so forth. Meanwhile, it creates new technologies, such as serverless computing, cloud-native software architecture, software-hardware integrated design, intelligent automated operation. In summary, cloud computing is redefining every aspect of IT. The cloud computing is continuously turning new IT technologies into accessible services and becoming the backbone of the entire digital economy.

 

[JSCh]

NEWS RELEASE 9-JAN-2020
Preparing for the hydrogen economy
Key step taken for hydrogen fuelled future

UNIVERSITY OF SYDNEY

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Illustration highlighting the association of hydrogen (red) with dislocations in the crystal structure of steel. CREDIT: University of Sydney

In a world first, University of Sydney researchers have found evidence of how hydrogen causes embrittlement of steels. When hydrogen moves into steel, it makes the metal become brittle, leading to catastrophic failures. This has been one of the major challenges in moving towards a greener, hydrogen-fuelled future, where steel tanks and pipelines are essential components that must be able to survive in pure hydrogen environments.

Published in Science, the researchers found hydrogen accumulates at microstructures called dislocations and at the boundaries between the individual crystals that make up the steel.

This accumulation weakens the steel along these features, leading to embrittlement.

The researchers also found the first direct evidence that clusters of niobium carbide within the steel trap hydrogen in such a way that it cannot readily move to the dislocations and crystal boundaries to cause embrittlement. This effect has the potential to be used to design steels that can resist embrittlement.

Lead researcher Dr Yi-Sheng Chen from the Australian Centre for Microscopy and Microanalysis and Faculty of Engineering at the University of Sydney said these findings were an important step to finding a safe solution to produce, store and transport hydrogen.

"These findings are vital for designing embrittlement-resistant steel; the carbides offer a solution to ensuring high-strength steels are not prone to early fracture and reduced toughness in the presence of hydrogen," Dr Chen said.

Senior author Professor Julie Cairney from the Australian Centre for Microscopy and Microanalysis and Faculty of Engineering at the University of Sydney said these findings were a positive step towards implementing clean fuels.

"Hydrogen is a low carbon fuel source that could potentially replace fossil fuels. But there are challenges with the use of steel, the world's most important engineering material, to safely store and transport it. This research gives us key insights into how we might be able to improve this situation," Professor Cairney said.

Working in partnership with CITIC Metal, the researchers were able to directly observe hydrogen at microstructures in steels thanks to Microscopy Australia's state-of-the-art custom-designed cryogenic atom probe microscope.


Preparing for the hydrogen economy | EurekAlert! Science News

Yi-Sheng Chen, Hongzhou Lu, Jiangtao Liang, Alexander Rosenthal, Hongwei Liu, Glenn Sneddon, Ingrid McCarroll, Zhengzhi Zhao, Wei Li, Aimin Guo, Julie M. Cairney. Observation of hydrogen trapping at dislocations, grain boundaries, and precipitates. Science (2020). DOI: 10.1126/science.aaz0122​

 

[JSCh]

Researchers Discover Novel Formation Mechanisms of Five-fold Twinned Nanoparticles
By LI Yuan | Jan 10, 2020

Recently, two different formation mechanisms of five-fold twinning via repeated oriented attachment of ~3 nm gold, platinum, and palladium nanoparticles were clarified by in situ high-resolution transmission electron microscopy and molecular dynamics simulations. Related research findings were published online in Science on January 3.

The work was jointly done by Dr. ZHOU Gang and Dr. WANG Hao from the Institute of Metal Research (IMR) of the Chinese Academy of Sciences and international collaborators from Pacific Northwest National Laboratory and University of Michigan.

Five-fold twins have been widely employed in crystal growth, mechanical engineering, optics, and catalysis. For example, the stress of five-fold twins substantially increases the Young’s modulus of nanowires, while multi-twinned Cu nanowires exhibit excellent methane selectivity during reduction of carbon dioxide. The formation mechanism of five-fold twinned nanoparticles is a difficult issue which has puzzled material scientists for a long time.

In this study, the researchers discovered two different mechanisms to form five-fold twinned nanoparticles, both of which are driven by the accumulation and elimination of strain. Mechanism I operated via oriented attachment and atomic surface diffusion, following the nucleation and growth of zero-strain twin. And Mechanism II operated via oriented attachment and partial dislocation slipping.

The occurrence of the two mechanisms depends on the surface structure of the nanoparticles after oriented attachment. With the concave surface angle close to 90° and 150° after oriented attachment, the five-fold twinned nanoparticles are formed by Mechanism I and II, respectively.

Their findings place disparate systems into the context of well-developed theories for multiple twin formation mechanisms, hence providing a guide for interpreting and controlling twinned crystal structures and morphologies, and hopefully will result in the advances in materials design and synthesis for diverse applications.


Researchers Discover Novel Formation Mechanisms of Five-fold Twinned Nanoparticles----Chinese Academy of Sciences