China Science & Technology Forum

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IMECAS Developed High Performance Negative Capacitance FinFETs Featuring with both Ultra-Steep Subthreshold Swing and Enhanced Driving Current
Author： CUI Dongmeng
Update time： 2019-05-17

　　With the aggressive downscaling of Complementary Metal-Oxide-Semiconductor (CMOS) technology into sub-5 nm nodes, Si-based Field Effect Transistor, the key block of modern Integrated Circuit (IC), is confronted with a serious challenge i.e. tremendously increasing power consumption in a chip consisting of billons of transistors. Transistors of novel architectures, such as multi-gate (e.g. FinFET) or gate-all-around (GAA) devices with high-k/metal gate (HKMG), are able to work properly at small supply voltage with lowered power consumption. Nevertheless, a physical limit of Boltzmann tyranny originating from basic thermodynamics theory renders the subthreshold swing (SS) of a Si-based transistor no less than 60 mV/dec at room temperature, which unfortunately leads to the reluctant reduction of power consumption in state-of-the-art transistors.

　　By integrating hafnium based ferroelectric materials in the HKMG process, so-called differential negative capacitances (NC) can be realized under certain conditions to amplify the surface potential of the channel, thus breaking through the traditional Boltzmann tyranny and obtaining a steeper SS for significantly improved switching behavior. Consequently, a smaller supply voltage can be employed for the operation of IC. It is worth noting that even some progress has been made in recent years, the exploration of novel ferroelectric materials in mainstream FinFETs is, however, still in the inception phase and as-fabricated devices generally show poor performance due to numerous challenges of materials and integration process.

　　In order to cope with these challenges and accomplish the goal of reduced power consumption and improved device performance simultaneously, researchers from Integrated Circuit Advanced Process Center (ICAC) of Institute of Microelectronics, Chinese Academy of Sciences (IMECAS) have developed new processes for the growth of ferroelectric Hafnium Zirconium Oxide (HZO) and integration in FinFETs etc. High performance NC p-FinFETs of different gate lengths featuring with an ultra-thin 3-nm-thick ferroelectric HZO are demonstrated.

　　In detail, in order to realize a low interface defect density of HZO/SiO2/Si, both the atomic-layer deposition (ALD) process and post-annealing process have been carefully modulated during the growth of ultra-thin HZO. Thanks to the fully depleted Fin channels under strong 3D gate control, low interface defect density of HZO/SiO2/Si and appropriate engineering of capacitance matching, as-fabricated FinFETs show greatly improved subthreshold swing (SS) values i.e. 34.5 mV/dec with 500 nm gate length (LG) and 53 mV/dec with 20 nm LG, and small hysteresis voltages i.e. ~9 mV with 500 nm LG and ~40 mV with 20 nm LG. The SS is much smaller than Boltzmann tyranny of 60 mV/dec and the hysteresis voltage is well controlled to an acceptable level. In addition, compared to that of conventional FinFETs with general HfO2, a prominent enhancement of driving current by 260% is also obtained for as-fabricated NC FinFETs. The ratio between Ion and Ioff is as high as 1.23×106. Taking ultra-steep SS, enhanced driving current and small hysteresis into account, as-fabricated NC FinFETs in this work pave a way for developing core transistors with almost identical performance while remarkably lowered power consumption in the future. The latest results have been published in a prestigious journal “IEEE Electron Device Letters” (DOI: 10.1109/LED.2019.2891364).

　　This work was financially supported by the National Science and Technology Major Project 02 and the National Key Research and Development Program.

Fig. 1 (a) 3D schematic of NC FinFETs; (b-c) TEM images of NC p-FinFETs across AA’ directions; (d) Measured IDS-VGS curves of NC p-FinFET, where steep average SSfor and SSrev of 43.2 and 34.5 mV/decade are achieved,(e) extracted SS as a function of the IDS of the device in (d); (f) comparison between our work and reported NC FETs from other groups.

 

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China develops underground experimental facility with world’s most intense beam
By Sun Haoran Source:Global Times Published: 2019/5/28 21:37:19

Photo of a high-current high-voltage accelerator - an underground experimental facility with the world's highest beam intensity, that was developed by the China Institute of Atomic Energy under the China National Nuclear Corporation (CNNC). Photo: WeChat account of the CNNC

China has developed a high-current high-voltage accelerator - an underground experimental facility with the world's highest beam intensity.

The accelerator was developed by the China Institute of Atomic Energy (CIAE) under the China National Nuclear Corporation (CNNC), according to the CNNC website on Tuesday.

It reached an advanced level among similar devices in the world, indicating that China has mastered the manufacturing technology of high-current, high-voltage accelerators, the statement said.

"This device can enhance the anti-radiation reinforcement of chips that would help promote development in aeronautics, space and satellites," a CIAE research fellow told the Global Times on Tuesday.

"It can also be used in the military, including research on nuclear physics and the establishment of nuclear data, or archaeological studies, such as measuring the age of ancient artifacts," the research fellow said.

The accelerator will be installed at the China Jinping Underground Laboratory, according to the CNNC website.

Proton and helium ion beams it produced have already been used in nuclear astrophysics experiments in Jinping for 400 hours, CNNC said.

The Jinping lab, which is 2,400 meters under a mountain in Southwest China's Sichuan Province, is now the deepest underground laboratory in the world.

It provides a unique and good environment for studies in many major fundamental frontier topics, such as dark matter detection, nuclear astrophysics and neutrino experiments, according to CNNC.

It is expected to gradually develop into a national basic research platform that will open up to the whole world, the CNNC added.

 

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Atomically thin material could cut need for transistors in half
It can do AND or OR logic in a single transistor, switch states using light.

JOHN TIMMER - 5/29/2019, 3:20 AM

With the development of carbon nanotubes and graphene, scientists were given an entirely new collection of materials to work with: sheets and tubes that could be consistently made with thicknesses roughly those of individual atoms. These materials hold the promise of building electronic devices with dimensions smaller than is currently possible through any other process and with properties that can be tuned by using different starting materials.

So far, most of the attention has gone to re-creating new versions of familiar devices. But a new paper by a group of researchers in Shanghai looks into what can be done if you're not constrained by the sorts of devices we currently make in silicon. The result is a device that can perform basic logic in half the transistors silicon needs, can be switched between different logical operations using light, and can store the output of the operation in the device itself.

OR or AND?
Computer instructions can be distilled down to a series of simple logical operations. Of these, the simplest are AND and OR. AND produces a value of 1 only if both of its two inputs are also 1; OR does so if either of the two inputs are 1.

But there's a mismatch between these logical operations and what we can do with silicon: a silicon transistor can only take input from a single source instead of the two required here. As a result, these operations require two transistors on a processor.

Transistors made of an atomically thin material can have fundamentally different structures, though. To test some of these, the researchers used molybdenum disulfide (MoS2), which forms graphene-like sheets slightly thicker than its component atoms. Like silicon, MoS2 is a semiconductor; unlike silicon, putting input gates both above and below a single layer of the material is relatively easy to do. This allows for the layer to take input from two different sources, making it a direct match for the logical operation's input.

Better yet, the researchers found they could make extremely similar devices that performed different logical operations. MoS2's individual layers may be atomically thin, but it's possible to stack multiple layers on top of each other. Initially, with just a few sheets stacked, the MoS2 formed a single semiconducting layer that would switch to conducting only if the gates both above and below it were in the "on" state. This makes for a perfect match to the AND function.

But keep adding layers, and the thickness would eventually reach a point where the upper and lower gates could independently control the conduction of the sheets of MoS2 nearest them. The authors compared it to having two "channels" on the same device. If either of those channels was set to "on," then some current would flow through the device, making its global state "on." This was a perfect match to the logical OR function.

The critical thickness turned out to be four nanometers, or less than half the size of existing features in cutting-edge chips. If the MoS2 sheets were stacked into a layer above 4nm, then the transistor would behave as an OR gate. Below that thickness, and it would perform AND operations.

Light and memory
At this point, the paper switched into something like "but wait, there's more!" One demonstration was that it's possible to switch an AND device into something that performs OR operations using the right wavelength of light. The gist of this is that the input gates work by exciting electrons within MoS2 into a state where they contribute to carrying current. In a thin layer of MoS2, both inputs have to be pushing electrons into the conduction band to get any current flowing. This gives us an AND function.

But light of the appropriate wavelength can also push electrons into the conduction band. As a result, light lowers the requirement for having conducting electrons induced by the input. As a result, you only need one of the two input gates to be in the "on" state for the transistor to conduct. Thus, shining light on a thin sheet of MoS2 is enough to convert an AND device into an OR device.

The researchers didn't stop there, either. For their final demonstration, they slipped in a layer of graphene next to the MoS2. Graphene is capable of capturing some of the conducting electrons and storing them. If the transistor ends up in the "on" state, enough of these electrons will spill over into the graphene that it will have sufficient charge to keep it in the "on" state. And that's where the transistor will stay until the electrons are specifically drained from the graphene. In this way, the graphene can act as a one-bit memory, storing the results of one past operation until the device is reset.

How many transistors do we really need?
Overall, the work serves as a good reminder that atomically thin materials have distinctive properties compared to the things we're currently working with, and it's worthwhile to think about how to leverage those properties effectively. Cutting the number of transistors needed for basic logic operations in half seems like a good way to significantly reduce the complexity of chips.

To an extent, the light-based switching demonstrated here runs counter to that since access to the transistor has to be maintained for light to pump into it. Still, there are probably some cases where optical circuitry is integrated with a chip when this might be useful. Having a situation where results of operations can be stored in the transistor that performed the operation could potentially be useful, but it would require a radically different programming model to do anything with it.

Because of these complications, it's not clear if anything much will come of these specific demonstrations. But should MoS2 find its way into chips for any reason, you can expect people will be looking for ways to fully take advantage of its abilities.


Atomically thin material could cut need for transistors in half | Ars Technica

Chunsen Liu, Huawei Chen, Xiang Hou, Heng Zhang, Jun Han, Yu-Gang Jiang, Xiaoyang Zeng, David Wei Zhang, Peng Zhou. Small footprint transistor architecture for photoswitching logic and in situ memory. Nature Nanotechnology (2019). DOI: 10.1038/s41565-019-0462-6​

 

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NEWS RELEASE 31-MAY-2019
Breaking the symmetry in the quantum realm
UNIVERSITY OF SCIENCE AND TECHNOLOGY OF CHINA

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The figure describes the dynamics of two spins as a harmonious couple-dance. Different from a solo-dance of a single spin, the couple-dance would present more unique and charming features, such as parity-time symmetry breaking demonstrated in the work. CREDIT: images created by Guoyan Wang & Lei Chen

For the first time, researchers have observed a break in a single quantum system. The observation--and how they made the observation--has potential implications for physics beyond the standard understanding of how quantum particles interact to produce matter and allow the world to function as we know it.

The researchers published their results on May 31st, in the journal Science.

Called Parity-Time (PT) Symmetry, the mathematical term describes the properties of a quantum system--the evolution of time for a quantum particle, as well as if the particle is even or odd. Whether the particle moves forward or backward in time, the state of oddness or evenness remains the same in the balanced system. When the parity changes, the balance of system -- the symmetry of the system -- breaks.

In order to better understand quantum interactions and develop next-generation devices, researchers must be able to control the symmetry of systems. If they can break the symmetry, they could manipulate the spin state of the quantum particles as they interact, resulting in controlled and predicted outcomes.

"Our work is about that quantum control," said Yang Wu, an author on the paper and a PhD student in the Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics at the University of Science and Technology of China. Wu is also a member of the Chinese Academy of Sciences Key Laboratory of Microscale Magnetic Resonance.

Wu, his PhD supervisor Rong and colleagues used a nitrogen-vacancy center in a diamond as their platform. The nitrogen atom with an extra electron, surrounded by carbon atoms, creates the perfect capsule to further investigate the PT symmetry of the electron. The electron is a single-spin system, meaning the researchers can manipulate the entire system just by changing the evolution of the electron spin state.

Through what Wu and Rong call a dilation method, the researchers applied a magnetic field to the axis of the nitrogen-vacancy center, pulling the electron into a state of excitability. They then applied oscillating microwave pulses, changing the parity and time direction of the system and causing it to break and decay with time.

"Due to the universality of our dilation method and the highly controllability of our platform, this work paves the way to study experimentally some new physical phenomena related to PT symmetry," Wu said.

Corresponding authors Jiangfeng Du and Xing Rong, professors with the Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics at the University of Science and Technology of China, were in agreement.

"The information extracted from such dynamics extends and deepens the understanding of quantum physics," said Du, who is also an academician of the Chinese Academy of Sciences. "The work opens the door to the study of exotic physics with non-classical quantum systems."

The other authors include Wenquan Liu, Jianpei Geng, Xingrui Song, Xiangyu Ye, Chang-Kui Duan and Xing Rong. All of the authors are affiliated with the Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics at the University of Science and Technology of China. Liu, Ye, Duan, Rong and Du are also affiliated with both the University's CAS Key Laboratory of Microscale Magnetic Resonance, and the University's Synergetic Innovation Center of Quantum Information and Quantum Physics.


Breaking the symmetry in the quantum realm | EurekAlert! Science News

Yang Wu, Wenquan Liu, Jianpei Geng, Xingrui Song, Xiangyu Ye, Chang-Kui Duan, Xing Rong, Jiangfeng Du. Observation of parity-time symmetry breaking in a single-spin system. Science (2019); DOI: 10.1126/science.aaw8205​

 

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Cameras can watch for people who need help, but a system of microphones and speakers uses sound to do the same task. Credit: Artyom Geodakyan/TASS/Getty

APPLIED PHYSICS * 31 MAY 2019
Deep learning monitors human activity based on sound alone
Reflected sound waves can distinguish a sitting person from a walking person.

A combination of microphones and artificial-intelligence algorithms can identify whether a person in a room is sitting, standing, walking or falling.

The use of deep-learning algorithms for identifying human activity from video feeds has promising applications, such as alerting caregivers of a medical emergency. But continuous video surveillance raises the possibility of leaks, hacks and loss of privacy.

As an alternative to video, a team led by Xinhua Guo at the Wuhan University of Technology in China and Kentaro Nakamura of the Tokyo Institute of Technology turned to high-frequency sound waves. The researchers designed an acoustical array with four speakers that emit a signal of 40 kHz — above the range of human hearing — into a room. Surrounding the speakers are 256 small microphones that pick up the high-pitched tones reflected back by the environment.

The team used the array to track volunteers as they sat, stood, walked or fell. After deep-learning algorithms were trained on the reflected high-frequency sounds, the programs could identify an individual’s activity with up to 97.5% accuracy.

Monitoring devices like these, which rely on high-frequency sounds, could assuage privacy concerns, the authors write.

App. Phys. Lett. (2019)​

Deep learning monitors human activity based on sound alone : Research Highlights | Nature

 

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Chinese scientists make breakthrough in injectable cartilage
2019-06-04 15:49:53

(Photo/Video screenshot on CNSTV)​

(ECNS) -- The Chinese team that constructed the world’s first ear in a lab and grafted it onto a patient last year has made new progress by developing injectable cartilage that can be used in human tissue repair and plastic surgery.

The regeneration technique involves taking a small part of cartilage tissue from behind the ear of a patient, culturing seed cells in the lab and reproducing cells in a sufficient amount to fill a biodegradable mould made by 3D-printing.

Professor Cao Yilin, director of National Tissue Engineering Research Center, said it marks a breakthrough from previous technology as the cultured cells can be injected into a patient’s body parts like the nose and chin where they continue to develop into normal tissue, a minimally invasive treatment similar to natural growth.

The technology can effectively avoid many side-effects caused by hyaluronic acid and is now used in clinical applications. It’s expected to be applied in surgeries and organ reconstruction.

Shi Junli, an instructor in cartilage regeneration, said the technology’s advantage lies in the use of a patient’s own cells so it’s safe and has little chance of rejection.

 

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Chinese scientists find 5 million tons of lithium deposits in Yunnan
Source:Global Times Published: 2019/6/4 22:08:40

A plant worker in Changxing county, East China's Zhejiang Province, checks lithium-ion batteries automatically produced for electronic vehicles (EVs) on Tuesday. Changxing is the province's first EV industry development base, with EV-related company output reaching 30.55 billion yuan ($4.49 billion) in 2017. Photo: VCG

Chinese scientists have found a major lithium deposit in Southwest China's Yunnan Province, estimated to contain more than 5 million tons.

There are approximately 40 million tons of proven lithium reserves in the world, the Xinhua News Agency's Globe magazine reported.

A team led by research fellow Wen Hanjie from the Institute of Geochemistry under the Chinese Academy of Sciences found 340,000 tons of lithium oxide in a test site in central Yunnan.

They estimated the total amount of lithium to be in excess of 5 million tons. The lithium discovered is a new type in carbonate formation, the institute said on its website on Monday.

Lithium, a chemical element mainly contained in brines, pegmatite and clay, is viewed by some analysts as one of the most valuable metals in the first half of the 21st century.

The increasing reliance of the high-tech industry on lithium makes it an essential strategic resource for industrialized countries, analysts said.

The prices of lithium carbonate increased from less than 50,000 yuan ($7,236) per ton in October 2015 to 80,000 yuan per ton by the end of 2018. The value of the global lithium market is expected to rise from $60 trillion in 2017 to $100 trillion in 2025, the Globe magazine reported.

About 80 percent of lithium used in China from 2011 to 2015 was imported, Xinhua reported. The Institute of Geochemistry said on its website that it is urgently necessary for China to find new sources of lithium, as the country has abundant carbonate clay resources.

The discovery was the result of a national project to search for mineral resource bases, experts said.

 

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Dancing on Pine Needle Tip: Significant Evolution of Catalyst Structure for Hydrogen Generation by Water Electrolysis
Jun 06, 2019

In a study published in Nature Energy on June 3, Prof. SONG Li and Prof. JIANG Jun from University of Science and Technology of China (USTC) of the Chinese Academy of Sciences reported their ingenious design of a pin-point catalyst with pine-ball structure using platinum metal. Compared with commercial platinum-carbon catalysts, the amount of platinum metal was reduced by nearly 75 times and the cost of the catalyst was greatly reduced while the catalytic hydrogen production remained almost unchanged.

In the story of Hongloumeng (The Story of the Stone), a few people are busy in Jiafu while most people have nothing to do. Similar problem exists in traditional catalysts for hydrogen generation. Catalytic processes generally occur on the surface of catalysts and involve a single or several neighboring atoms. The platinum atoms on the surface manufactured in the traditional way are very busy, while the platinum atoms inside contribute little. To make these platinum atoms in catalysts move without eating from the same pot, Prof. SONG's team came up with a idea to maximize the platinum atoms on the surface of catalysts.

They first chose the sphere with the largest surface per unit mass, and made the flat catalysts into "spheres" one by one, transforming the previously confined two-dimensional reactions into three-dimensional. Once a small bungalow was transformed into a spherical high-rise, and the number of people that could be accommodated-that is, the site where reactions could take place-increased greatly. At the same time, each platinum atom is located on the spherical surface, which ensures that they are on the "production line". In this way, the catalyst forms a "ball" full of needle tips, each of which is a single atom of platinum, and no "human" can "hide" behind.

"This design also brings a surprising additional effect. Theoretical simulation shows that the curved sphere will form a very strong local electric field at the tip of the platinum atom, which is equivalent to adding an accelerating track to the foot of platinum atom, resulting in further enhancement of the catalytic efficiency." Prof. JIANG said.

The rate of hydrogen formation increases greatly when the reactants in the electrolytic solution pass through the "loose balls" of needle tips on one surface after another. "With the same hydrogen production, the catalyst we designed only needs one platinum, while the traditional commercial platinum-carbon catalyst needs seventy or eighty platinum, which greatly reduces the cost of the catalyst." Prof. SONG said.

Platinum metal plays an important role in hydrogen generation by water electrolysis reaction. This study minimizes the amount of platinum without affecting the catalytic effect of hydrogen evolution reaction, and points out the direction for further optimizing the performance of catalyst.

Hydrogen energy is an efficient and clean energy. Hydrogen generation by water electrolysis has attracted great attention because of its advantages of zero emission and zero pollution.

The design of the structure of platinum atom catalyst, which greatly improves the hydrogen generation efficiency of electrolytic solution when it passed through pinpoint catalyst "pine ball". (Image by LI Jin)



Dancing on Pine Needle Tip: Significant Evolution of Catalyst Structure for Hydrogen Generation by Water Electrolysis---Chinese Academy of Sciences

Daobin Liu, Xiyu Li, Shuangming Chen, Huan Yan, Changda Wang, Chuanqiang Wu, Yasir A. Haleem, Sai Duan, Junling Lu, Binghui Ge, Pulickel M. Ajayan, Yi Luo, Jun Jiang, Li Song. Atomically dispersed platinum supported on curved carbon supports for efficient electrocatalytic hydrogen evolution. Nature Energy (2019). DOI: 10.1038/s41560-019-0402-6​

 

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NEWS AND VIEWS * 05 JUNE 2019
How to make the thinnest possible free-standing sheets of perovskite materials
2D crystalline membranes are easily made from some materials, but not from those with strong 3D lattices, such as technologically useful perovskite oxides. Free-standing perovskite monolayers have finally been made.

Yorick A. Birkhölzer & Gertjan Koster

Science often benefits from the discovery of extremes. Once we have proved the existence of an extreme, it can help us to build models that explain scientific phenomena. In the field of materials science, an outstanding experimental goal has been to prepare sheets of technologically useful transition-metal oxides, such as perovskites, at their fundamental minimum thickness. In a paper in Nature, Ji et al.1 report the preparation of the first such sheets for the perovskite oxides strontium titanate (SrTiO3) and bismuth ferrite (BiFeO3), and provide a glimpse of their properties.

Many technologically beneficial materials are crystalline, including transition-metal oxides. The atomic or molecular order in a crystal is defined by the unit cell, which is the smallest repeating unit of the crystal structure. In the case of strontium titanate, for example, the unit cell is a cube that has edges about 0.4 nanometres long2. This represents the smallest possible length or thickness of the objects (2D sheets, 1D rods or 0D ‘dots’) that can be made from this material — and is therefore of interest to nanotechnologists, who try to reduce the size of materials in search of previously unseen properties and functions.


...

How to make the thinnest possible free-standing sheets of perovskite materials | Nature

Dianxiang Ji, Songhua Cai, Tula R. Paudel, Haoying Sun, Chunchen Zhang, Lu Han, Yifan Wei, Yipeng Zang, Min Gu, Yi Zhang, Wenpei Gao, Huaixun Huyan, Wei Guo, Di Wu, Zhengbin Gu, Evgeny Y. Tsymbal, Peng Wang, Yuefeng Nie & Xiaoqing Pan. Freestanding crystalline oxide perovskites down to the monolayer limit. Nature (2019). DOI: 10.1038/s41586-019-1255-7​

 

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Science
China’s ‘artificial sun’ project just got a whole lot hotter, scientists say

• New facility in Sichuan province will enable researchers to recreate the ‘extreme environments’ necessary to harness nuclear fusion
• Plasma-generating machine capable of producing temperatures 13 times as hot as the sun

Stephen Chen
Published: 11:15pm, 6 Jun, 2019

Chinese scientists hope a new research facility will help them take another step forward in harnessing the power of the sun. Photo: EPA

A new research facility that will enable Chinese scientists to carry out vital experiments in the development of a nuclear fusion reactor – or so-called artificial sun – is set to open later this year, according to the company behind the project.

The new centre, in Chengdu, capital of southwest China’s Sichuan province, will have at its heart an “HL-2M machine”, which is capable of generating plasma – another name for hot gas – at temperatures of up to 200 million degrees Celsius, China National Nuclear Corporation (CNNC) said in a statement on its website on Thursday.

The ability to generate such intense heat is essential to the fusion process, which is how the sun produces energy, though it operates at a temperature of a mere 15 million degrees.

The International Thermonuclear Experimental Reactor (ITER), currently under construction in southern France, is designed to operate at up to 150 million degrees.

The HL-2M machine will be able to generate plasma as hot as 200 million degrees Celsius, says China National Nuclear Corporation. Photo: Weibo

The development of the Sichuan facility is another step forward in the nation’s push to build the China Fusion Engineering Test Reactor by 2021, CNNC said.

“This device [the HL-2M] is a critical platform,” the company said.

China is among the world’s leading players in the development of fusion technology – which has the potential to generate an endless supply of clean energy – and plans to build an experimental reactor as early as 2021, finish an industrial prototype by 2035 and go into large-scale commercial use by 2050.

The principle challenge for scientists is how to control the energy they produce. In Sichuan, researchers will be able to carry out “unprecedented experiments in extreme environments”, CNNC said.

The HL-2M uses a doughnut-shaped chamber known as tokamak to study how to produce and contain the fusion power.

Electric currents of up to 3 million amps will flow through a 90-tonne copper coil to generate a powerful magnetic field that in turn “contains” the plasma produced by the fusion process and prevents it from causing the facility to go into meltdown.

The coil developed for the HL-2M is among the facility’s key achievements as it has shown immense ability to withstand shocks, the CNNC said.

Scientists hope nuclear fusion might one day provide the answer to the world’s energy needs. Photo: Alamy

Gao Zhe, a physics professor at Tsinghua University in Beijing, said that scientists around the world still had many problems to overcome in the field of nuclear fusion, not least the issue of containing plasma.

Man-made fusion is far less stable than the natural process inside the sun and the hot gas sometimes produces random flares that can break through the magnetic cage and damage the inner wall of the reaction chamber.

New facilities, like the HL-2M, would give researchers more scope to study and find solutions to such issues, Gao said.

“There is no guarantee that all these problems will be solved. But if we don’t do it, the problems will definitely not be solved,” he said.
https://www.scmp.com/business/compa...l-china-use-nuclear-option-banning-rare-earth
Gao said scientists were likely to use the new machine in conjunction with other facilities already in operation, such as the EAST superconducting tokamak in Hefei, capital of the southeast China province of Anhui.

The CNNC said the new facility in Sichuan will also support the development of the ITER project, of which China is a member nation, along with the United States, India, Japan, Russia and South Korea.

The ITER is the world’s largest and costliest international scientific collaboration project, with a price tag of about €20 billion (US$22.5 billion). The construction phase is expected to be completed in 2025.

This article appeared in the South China Morning Post print edition as: Ray of hope over ‘artificial sun’ research facility

 

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10:03, 09-Jun-2019
E China's Zhejiang University makes key advances in graphene sector
Peng Xiaoyun

Graphene, a one-atom-thick layer of carbon atoms, is a kind of material that will boost 5G's potential. And Zhejiang University in east China has made breakthroughs in the field of graphene, with two graphene products granted international patents.

Graphene manufacturers are clustered in the UK, China, and the United States. China boasts the most manufacturers with over 4,000. According to China Daily's report, half of the world's graphene-related patents have been filed in China.

Graphene's flexible properties can be used to develop a number of high-tech products. The thinnest material is one that has a research focus in China. A graphene research team from Zhejiang University has been developing the emerging sector for several years.

The team has introduced a number of graphene products to the market. Two of those, single-layer graphene oxide and graphene composite fiber, have been granted international patents.

​

Professor Gao Chao from the team said that the annual output of graphene products is expected to reach 10 tons. "We have made great progress in the sector. The graphene industry has entered a new era. China is now leading the international graphene technology," Gao noted.

The graphene sector's production value reached 18 million U.S. dollars in 2017, jumping nearly 70 percent from the previous year, accounting for a little more than one-fifth of the global market. And the global graphene industry is expected to grow at an annualized rate of 40 percent from 2018 to 2026.

In 2017, the demand for graphene for lithium batteries constituted more than 50 percent of the total. But that proportion will decrease in the future as graphene is increasingly used in new energy, composite materials, wearables, thermal management, energy conservation and environmental protection.

 

[JSCh]

DNA Base Editing Induces Substantial Off-target RNA Mutations and Their Elimination by Mutagenesis
Jun 11, 2019

In a study published in Nature on June 10, researchers from Dr. YANG Hui’s Lab at the Institute of Neuroscience of the Chinese Academy of Sciences (CAS), and collaborators from the CAS-MPG Partner Institute for Computational Biology of CAS and Sichuan University demonstrated that DNA base editors generated tens of thousands of off-target RNA single nucleotide variants (SNVs) and these off-target SNVs could be eliminated by introducing point mutations to the deaminases.

This study revealed a previously overlooked aspect of the risk of DNA base editors and further provided a solution to the problem by engineering deaminases.

DNA base-editing methods have enabled direct point mutation correction in genomic DNA without generating any double-strand breaks (DSBs), but the potential off-target effects have limited the application of these methods. Adeno-associated viruses (AAV) are the most common delivery system for DNA editing gene therapies. Since these viruses can sustain long-term gene expression in vivo, the extent of potential RNA off-target effects induced by DNA base editors is of great concern for their clinical application.

Several previous studies have evaluated off-target mutations in genomic DNA by DNA base editors. Meanwhile, the deaminases integral to commonly used DNA base editors often exhibit RNA binding activities. For example, the cytosine deaminase APOBEC1 used in cytosine base editors (CBEs) was found to target both DNA and RNA, and the adenine deaminase TadA used in adenine base editors (ABEs) was found to induce site-specific inosine formation on RNA. However, any potential RNA mutations caused by DNA base editors had not been evaluated.

In order to evaluate the off-target effect of DNA base editors at the level of RNA, the researchers counted the off-target RNA SNVs in each replicate of CBE- or ABE-treated cells, and then explored the possibility of eliminating the off-target RNA SNVs by engineering deaminases of DNA base editors.

They transfected one type of CBE, BE3 (APOBEC1-nCas9-UGI), or ABE, ABE7.10 (TadA-TadA*-nCas9), together with GFP and with or without single-guide RNA (sgRNA), into HEK293T-cultured cells. After validating the high on-target efficiency of DNA editing by both BE3 and ABE7.10 in these HEK293T cells, they performed RNA-seq at an average depth of 125X on these samples and quantitively evaluated the RNA SNVs in each replicate.

The on-target editing efficiency was evaluated in each replicate of the CBE- or ABE-treated cells to guarantee efficient editing. Then the number of off-target RNA SNVs in CBE- and ABE-treated groups was compared with the GFP-only control group. They found strikingly higher numbers of RNA SNVs in DNA base editor-treated cells.

Furthermore, the researchers found that the mutation bias in BE3- or ABE7.10-treated cells was the same as that of APOBEC1 or TadA, respectively, indicating the off-target effects were caused by the overexpression of DNA base editors. They also identified CBE- and ABE-specific motifs and genetic regions of these off-target RNA SNVs.

To eliminate the RNA off-target activity of base editors, they examined the effect of introducing point mutations on APOBEC1 or TadA. Three high-fidelity variants, BE3W90Y+R126E, BE3 (hA3AR128A) and BE3 (hA3AY130F), reduced RNA off-target SNVs to the base level. Similarly, an ABE variant ABE7.10F148A also showed complete elimination of off-target effects.

This study obtained both high-fidelity variants for both CBEs and ABEs by introducing point mutations to the deaminases and provided a proposed method using rational engineering to increase the specificity of base editors.



DNA Base Editing Induces Substantial Off-target RNA Mutations and Their Elimination by Mutagenesis---Chinese Academy of Sciences

Changyang Zhou, Yidi Sun, Rui Yan, Yajing Liu, Erwei Zuo, Chan Gu, Linxiao Han, Yu Wei, Xinde Hu, Rong Zeng, Yixue Li, Haibo Zhou, Fan Guo & Hui Yang. Off-target RNA mutation induced by DNA base editing and its elimination by mutagenesis. Nature (2019). DOI: 10.1038/s41586-019-1314-0​

 

[JSCh]

NEWS RELEASE 10-JUN-2019
Light energy and biomass can be converted to diesel fuel and hydrogen
CHINESE ACADEMY OF SCIENCES HEADQUARTERS

Scientists recently developed a method to produce diesel fuel and hydrogen by exploiting light energy (solar energy or artificial light energy) and biomass-derived feedstocks. Their findings were published in Nature Energy.

Biomass, including agricultural straw and forest waste, is the largest source of sustainable carbon resources in nature and is able to replace petrochemical resources to provide abundant derivative products. As an alternative to photocatalytic water splitting to provide hydrogen, splitting of biomass or its derivatives usually yields higher light transformation efficiencies and higher rates of hydrogen production.

Nevertheless, oxidative products derived from biomass are mostly useless, causing waste of sustainable biomass resources and environmental pollution. Therefore, developing technologies that merge hydrogen production and biomass conversion into value-added chemicals or fuels is expected to bring about a "double guarantee" of materials and energy for industrial manufacture and daily life.

Prof. WANG Feng and his group at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences developed a process for using light energy to drive the valorization of downstream biomass products, namely methyl furan compounds, to produce hydrogen and diesel fuel precursors simultaneously.

The reactions were carried out at room temperature and pressure, and produced hydrogen and diesel fuel precursors that are constituted by isomeric oxygenates with variety of carbon numbers typical of diesel fuel. Removal of the oxygen contents from the diesel fuel precursors produced sustainable diesel fuels with components close to current petroleum diesel; hydrogen could be used to remove the oxygen from the diesel fuel precursors or be used alone.

This process realizes the directional transformation of light energy and biomass to hydrogen energy and diesel fuels, and provides a way to produce clean energy using solar energy and sustainable carbon sources present on the earth's surface.


Light energy and biomass can be converted to diesel fuel and hydrogen | EurekAlert! Science News

Nengchao Luo, Tiziano Montini, Jian Zhang, Paolo Fornasiero, Emiliano Fonda, Tingting Hou, Wei Nie, Jianmin Lu, Junxue Liu, Marc Heggen, Long Lin, Changtong Ma, Min Wang, Fengtao Fan, Shengye Jin & Feng Wang. Visible-light-driven coproduction of diesel precursors and hydrogen from lignocellulose-derived methylfurans. Nature Energy (2019). DOI: 10.1038/s41560-019-0403-5​

 

[JSCh]

Oldest evidence of marijuana use discovered in 2500-year-old cemetery in peaks of western China | Science | AAAS
By Andrew Lawler
Jun. 12, 2019 , 2:00 PM

Today, more than 150 million people regularly smoke cannabis, making it one of the world's most popular recreational drugs. But when and where humans began to appreciate the psychoactive properties of weed has been more a matter of speculation than science. Now, a team led by archaeologists Yang Yimin and Ren Meng of the Chinese Academy of Sciences in Beijing reports clear physical evidence that mourners burned cannabis for its intoxicating fumes on a remote mountain plateau in Central Asia some 2500 years ago.

The study, published today in Science Advances, relies on new techniques that enable researchers to identify the chemical signature of the plant and even evaluate its potency. "We are in the midst of a really exciting period," says team member Nicole Boivin of the Max Planck Institute for the Science of Human History (MPI-SHH) in Jena, Germany. The paper is part of a wider effort to track how the drug spread along the nascent Silk Road, on its way to becoming the global intoxicant it is today.

Cannabis, also known as hemp or marijuana, evolved about 28 million years ago on the eastern Tibetan Plateau, according to a pollen study published in May. A close relative of the common hop found in beer, the plant still grows wild across Central Asia. More than 4000 years ago, Chinese farmers began to grow it for oil and for fiber to make rope, clothing, and paper.

Pinpointing when people began to take advantage of hemp's psychoactive properties has proved tricky. Archaeologists had made claims of ritual cannabis burning in Central Asian sites as far back as 5000 years ago. But new analyses of those plant remains by other teams suggest that early cannabis strains had low levels of tetrahydrocannabinol (THC), the plant's most powerful psychoactive component, and so lacked mind-altering properties. One academic who works in Central Asia said he and colleagues tried to smoke and eat wild varieties—but got no buzz.

Ancient people put cannabis leaves and hot stones in this brazier, and likely inhaled the resulting smoke.

XINHUA WU
The cannabis burned 2500 years ago at the Jirzankal cemetery, 3000 meters high in the Pamir Mountains in far western China, was different. Excavations there have uncovered skeletons and wooden plates, bowls, and Chinese harps, as well as wooden braziers that held burning material. All are typical of the Sogdians, a people of western China and Tajikistan who generally followed the Persian faith of Zoroastrianism, which later celebrated the mind-expanding properties of cannabis in sacred texts. At Jirzankal, glass beads typical of Western Asia and silk from China confirm the long-distance trade for which the Sogdians became famous, and isotopic analysis of 34 skeletons showed that nearly a third were migrants. Radiocarbon analysis put the burials at about 500 B.C.E.

The wooden braziers were concentrated in the more elite tombs. Yang's and Ren's team ground bits of brazier into powder and applied gas chromatography and mass spectrometry to identify chemical compounds left behind. They found unusually high levels of THC compared with typical wild cannabis, although much less than in today's highly bred plants. The cannabis was apparently burned in an enclosed space, so mourners almost certainly inhaled THC-laced fumes, the authors say, making this the earliest solid evidence of cannabis use for psychoactive purposes.

Archaeologists have spotted signs of ancient cannabis use from western China to the Caucasus.

0250KmCHINAPamir MountainsJirzankal cemeteryTAJIKISTANCaucasusMountainsIRANCaspian Sea
N. DESAI/SCIENCE
The region's high altitude could have stressed the cannabis, creating plants naturally high in THC, says co-author Robert Spengler, also of MPI-SHH. "It is quite likely that people came across cannabis plants at higher elevations that were naturally producing higher THC levels," he says. But humans may also have intervened to breed a more wicked weed, he adds.

"The methods are convincing, and the data are unambiguous regarding early use of cannabis as a psychoactive substance," says Tengwen Long, an environmental scientist at the University of Nottingham in the United Kingdom who has researched cannabis origins. But Megan Cifarelli, an art historian at Manhattanville College in Purchase, New York, who has studied ancient drug use, notes the aromatic fumes might also have had another purpose: to mask the smell of a putrefying corpse.

Yang's and Ren's team thinks cannabis use was restricted to elites until potent pot began to spread across Central Asia through the Silk Road linking China with Iran. In 440 B.C.E., the Greek historian Herodotus wrote that the nomadic Scythians, who controlled vast areas from Siberia to Eastern Europe, made tents and heated rocks in order to inhale hemp vapors that made them "shout for joy." And Andrei Belinski, an archaeologist based at the heritage museum in Stavropol, Russia, in 2013 began to excavate a nearby 2400-year-old Scythian tomb that held gold vessels bearing residues of both opium and cannabis, supporting the idea that elites used the drug first.

Ancient artwork and textual references from Syria to China hint at even earlier cannabis drug use, and the new analytical methods could soon provide concrete evidence of this, says Michael Frachetti, an archaeologist at Washington University in St. Louis, Missouri. But it's already clear that the ancient Silk Road trafficked in more than spices, grains, and ideas. "Crops weren't just about food," he says. "They were also about making contact with another world."

Posted in:

• Archaeology
• Asia

doi:10.1126/science.aay3693

 

[JSCh]

NEWS RELEASE 12-JUN-2019
Scientists develop a primate model for autism by genome-editing
CHINESE ACADEMY OF SCIENCES HEADQUARTERS

A China-U.S. joint research team reported the generation of germline-transmittable cynomolgus macaques with Shank3 mutations, known to cause a form of autism.

The study, published in Nature, was conducted by scientists from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences (CAS), Massachusetts Institute of Technology, Sun Yat-Sen University and South China Agricultural University.

Through the genome-editing system CRISPR, they engineered macaque monkeys to express a gene mutation linked to autism and other neurodevelopmental disorders in humans. These monkeys showed some behavioral traits and brain connectivity patterns similar to those in humans with these conditions.

Autism Spectrum Disorders (ASD) is complex developmental disorders with a strong genetic basis. Scientists have identified hundreds of genetic variants associated with ASD, many of which individually confer only a small degree of risk. In this study, the researchers focused on one gene with a strong association, known as Shank3.

"The new type of model, however, could help scientists to develop better treatment options for some neurodevelopmental disorders," said FENG Guoping, who is the James W. and Patricia Poitras Professor of Neuroscience, a member of MIT's McGovern Institute for Brain Research, and one of the senior authors of the study.

Mouse models of ASD, due to their neural and behavioral differences from primates, haven't worked out very well. The reported behavioral and neural traits of Shank3 mutant primates provide new insights into the circuit-based pathophysiological model of ASD.

The primate model is close to humans in evolution and has many similarities to humans in brain structure. For example, the prefrontal cortex in nonhuman primates is well developed, which plays important roles in decision-making, attention and social interactions. Deficits in these cognitive functions have been associated with brain disorders including autism. Therefore, "nonhuman primates are hopeful to become an ideal animal model for simulating some human brain diseases," said Prof. ZHOU Huihui from SIAT.

The Association for Assessment and Accreditation of Laboratory Animal Care (AAALAC) is a private, nonprofit organization that promotes the humane treatment of animals in science through voluntary accreditation and assessment programs. SIAT received AAALAC accreditation in 2018 for its primate experiment platform, which laid a foundation for collaboration with international pharmaceutical companies to pursue new treatments of brain disorders in the future.

"We urgently need new treatment options for autism spectrum disorder, and treatments developed in mice have so far been disappointing. While the mouse research remains very important, we believe that primate genetic models will help us to develop better medicines and possibly even gene therapies for some severe forms of autism," says Robert Desimone, the director of MIT's McGovern Institute for Brain Research, the Doris and Don Berkey Professor of Neuroscience, and an author of the paper.


Scientists develop a primate model for autism by genome-editing | EurekAlert! Science News

Yang Zhou, Jitendra Sharma, Qiong Ke, Rogier Landman, Jingli Yuan, Hong Chen, David S. Hayden, John W. Fisher, Minqing Jiang, William Menegas, Tomomi Aida, Ting Yan, Ying Zou, Dongdong Xu, Shivangi Parmar, Julia B. Hyman, Adrian Fanucci-Kiss, Olivia Meisner, Dongqing Wang, Yan Huang, Yaqing Li, Yanyang Bai, Wenjing Ji, Xinqiang Lai, Weiqiang Li, Lihua Huang, Zhonghua Lu, Liping Wang, Sheeba A. Anteraper, Mriganka Sur, Huihui Zhou, Andy Peng Xiang, Robert Desimone, Guoping Feng, Shihua Yang. Atypical behaviour and connectivity in SHANK3 -mutant macaques. Nature (2019). DOI: 10.1038/s41586-019-1278-0​