China Science & Technology Forum

[onebyone]

Improved ion thruster

Researchers from the Harbin Institute of Technology in China have created a new inlet design for Cylindrical shaped Hall thrusters (CHTs) that may significantly increase the thrust and allows spaceships to travel greater distances.

Xenon is often used as a propellant for Hall Thrusters. This is accelerated by an electric field which strips electrons from neutral xenon atoms, creating a plasma. Plasma ejected from the exhaust end of the thruster can deliver great speeds, typically around 70,000 mph.

CHTs are designed for low-power operations while low propellant flow density can cause inadequate ionization—a crucial step in the creation of the plasma and the generation of thrust. A thruster’s performance improves by increasing the gas density in the discharge channel, while lowering its axial velocity—the speed perpendicular to the thrust direction.

Physics of Plasmas – Effect of vortex inlet mode on low-power cylindrical Hall thruster

a new propellant inlet mode for a low-power cylindrical Hall thruster called the vortex inlet mode. This new mode makes propellant gas diffuse in the form of a circumferential vortex in the discharge channel of the thruster. Simulation and experimental results show that the neutral gas density in the discharge channel increases upon the application of the vortex inlet mode, effectively extending the dwell time of the propellant gas in the channel. According to the experimental results, the vortex inlet increases the propellant utilization of the thruster by 3.12%–8.81%, thrust by 1.1%–53.5%, specific impulse by 1.1%–53.5%, thrust-to-power ratio by 10%–63%, and anode efficiency by 1.6%–7.3%, greatly improving the thruster performance.

Low-power Hall thrusters (HTs) have recently received increased attention as one of the most promising electric propulsion systems for space applications, particularly in conjunction with advanced space missions such as formation flying and micro-spacecraft constellation. Hall thrusters (HTs) have been developed to have a relatively high efficiency of 45%–55% in the power range of 0.5 to 5 kW.2 However, scaling down the HT to a low power range has several challenges owing to its large surface-to-volume ratio and difficulty in miniaturizing the inner magnetic pole, which would aggravate the channel erosion and decrease the thruster lifetime. A cylindrical Hall thruster (CHT) is a type of Hall thruster designed for low power operations. Unlike conventional annular Hall thrusters, the CHT has a smaller surface-to-volume ratio that makes it more convenient for miniaturization and ensures reduced plasma-wall interactions, leading to erosion of the thruster channel. Its performance is comparable with that of a conventional coaxial Hall thruster of the same size.

Neutral flow dynamics is a basic physical process that has a very important effect on the ionization and plasma motion of a Hall thruster. Neutral flow dynamics can be described by distributions of neutral density and velocity, where the density and velocity of the neutral gas directly affect the plasma density in the discharge channel and the residence time of the neutral gas in the discharge channel. Generally, higher neutral gas density in the discharge channel and lower axial velocity will improve the ionization rate of the thruster and thus improve the overall performance of the thruster.

The most practical way to alter the neutral flow dynamics in the discharge channel is by changing the gas injection method or the geometrical morphology of the discharge channel. Vial et al. and Kim et al. tested a variety of anode geometries and concluded that the divergence of the plume was decreased due to geometry changes that increased the neutral residence time and caused ionization improvements. They pointed out that an optimal injection method must maintain an azimuthally and radially uniform neutral flow, which will maximize the neutral residence time. The neutral velocity can be controlled by changing the anode injection method or by directly cooling the anode to reduce the neutral thermal velocity. They cooled the propellant to reduce the velocity of the flow, leading to lower discharge oscillations and hence increased thruster stability. Another method to study neutral flow dynamics is changing the profile of the discharge channel. Raitses et al. diminished the discharge channel cross-section at the ionization zone. The ionization efficiency was increased by increasing the neutral density in this region.

In general, reducing the axial velocity of the neutral gas in the discharge channel is an effective means of increasing the ionization rate of the thruster.

They recently proposed a magnetically insulated anode structure for the low-power CHT, which effectively improves the life and performance of the thruster by changing the distribution of the magnetic field lines in the discharge channel. In this paper, a circumferential vortex inlet mode is proposed on the basis of the low-power CHT with magnetic induction. The influence of the vortex inlet mode on the low-power CHT performance is studied via computer simulations as well as experimentally.

“The work we report here only verified the practicability of this gas inlet design,” Wei said. “We still need to study the effect of nozzle angle, diameter, the ratio of depth to diameter and the length of the discharge channel.”

According to Wei, the vortex design will be tested in flight-type HTs in the near future and could potentially be used in spaceflights.

https://www.nextbigfuture.com/2017/08/improved-ion-thruster.html

 

[JSCh]

The world’s next fastest supercomputer will help boost China’s growing sea power
Ambitious plan for device capable of a billion billion calculations per second will be built as part of project to expand country’s influence across the seas

PUBLISHED : Wednesday, 23 August, 2017, 11:31am
UPDATED : Wednesday, 23 August, 2017, 2:29pm

Stephen Chen

China is planning to boost its computing power tenfold within a couple of years by building a new generation supercomputer.

The machine will be based on the coast of Shandong province to process the data collected from the world’s oceans, according to scientists briefed on the project.

An Hong, professor of computer science with the University of Science and Technology of China in Hefei and a member of a committee advising the central government on high performance computer development, said the world’s first exascale computer would have a dedicated mission of helping China’s maritime expansion.

An exascale computer is defined as one that can carry out one billion billion calculations per second. It is not only 10 times faster than Sunway Taihulight – at present the world’s fastest computer which operates from Wuxi, Jiangsu – but equal to the calculation power of all the world’s top 500 super computers combined.

An said the machine could be finished as soon as 2019. Three independent supercomputer manufacturers on the mainland are competing for the contract. They include Sugon, or the Dawning Information Industry, which is owned by the Chinese Academy of Sciences; the National University of Defence Technology, which built the Tianhe series supercomputers, and the Sunway team. They have produced blueprints featuring vastly different architectures, according to An.

The authorities are looking to pick a design that not only offers a high performance but will be ready for immediate use once built. The budget for the project is expected to be between one and two billion yuan (US$150 million-US$300 million).

“The most important question to us is not whether China can build an exascale computer, or how fast, but why,” An said.

“There is indeed a race among nations on supercomputers, but this is not our concern. Our concern is the ocean,” she added.

When elected leader of the Chinese Communist Party in 2012, President Xi Jinping promised to turn China into a “hai shang qiang guo”, or maritime superpower, with an expansionist policy that would, according to the state media, be comparable with the fleet of Zheng He established during Ming dynasty six centuries ago to spread China’s influence over the world.

Within the space of a few years, China has effectively tightened its grip on the South China Sea, dismissed numerous neighbours’ claims over disputed waters, acquired military ports in South Asia and the African east coast, developed some of the world’s most advanced nuclear submarines with electromagnetic drive, explored vast areas of the sea bed for energy and mineral deposits, and launched the Belt and Road Initiative to strengthen economic ties with other countries, the “belt” roughly following Zheng He’s ports of call.

Chinese vessels, naval outposts and unmanned monitoring facilities – including a global network of buoys, satellites, sea floor sensors and underwater gliders – are generating countless steams of data every second.

According to marine researchers, these data contain a rich variety of information such as sea current readings, trace chemicals, regional weather and anomalies in water density that could be used for anything from helping submarines avoid turbulence to negotiating cuts to green house gas emissions.

Feng Liqiang, operational director of the Marine Science Data Centre in Qingdao, Shandong said the exascale computer would be able to pull all marine-related data sets together to perform the most comprehensive analysis ever.

“It will help, for instance, the simulation of the oceans on our planet with unprecedented resolution. “The higher the resolution, the more reliable the forecast on important issues such as El Nino and climate change,” he said.

“It will give China a bigger say over international affairs,” Feng added.

In June, the US government commissioned six companies including IBM, Intel and Hewlett Packard Enterprise to come up with countermeasures against China’s lead on high performance computing.

China not only hosts Sunway and Tianhe, which currently rank first and second on international performance charts with speeds that far exceed those of their foreign competitors, but also overtook the US last year in terms of installed supercomputing capacity, an event described as an “inflection point” by Horst Simon, deputy director of the Lawrence Berkeley National Laboratory in California.

The White House currently hopes that American companies will be able to come up with a design to have an exascale computer up and running by 2021.

A major challenge for exascale computing is cooling. Researchers have struggled to find a way to reduce the tremendous heat generated by a large number of chips. The problem not only prevents the computer from reaching peak performance but also leads to large electricity bills.

Though the exact location of the Chinese exascale computer has not yet been determined by the authorities, Zhang Haichun, professor at the computer science and technology department, the Ocean University of China in Qingdao, said the city, the largest port in Shandong, had numerous advantages as a home for the exascale computer.

Qingdao has more ocean-related research institutes than any other city along China’s coastline. The world’s largest marine data centre is under construction, and it is directly linked to the nation’s major monitoring networks above and under the ocean, he said.

“Putting the machine in Qingdao will save the trouble of transmitting a large amount of data over long distance through optic fibres. An expensive data plan can break the project’s bank account,” Zhang said.

But marine scientists said that a single computer would not bridge the maritime power gap between China and the US overnight.

“Our data is increasing at a fast pace but it is still dwarfed by the amount gathered by the US through decades of patient, continuous effort,” said Feng.

“We also lack the powerful software with sophisticated algorithms to handle the data at full exascale speed,” he added.

Lu Xianqing, professor at the Key Laboratory of Physical Oceanography under the Ministry of Education in Qingdao, said he had “serious doubts” whether the project would fulfil its mission due to the difficulty of accessing marine-related data in China.

Unlike in the US, where most ocean data gathered from public-funded research is open to access after a limited protection period, there is no official information sharing mechanism on the mainland.

“The State Ocean Administration runs and hoards its own data sets, as do the PLA Navy, the Chinese Academy of Sciences and many universities. Every institute is treating data as private asset for the interests of their own research” he said.

There are also fears that the exchange of data might lead to leaks and threaten national security. Foreign submarines, for instance, need detailed information on China’s offshore areas. These security concerns have prompted government officials to classify most data collected from the sea as confidential.

“Getting data for the computer may turn out to be more difficult than building it,” Lu said.

An said the Chinese government might approve the construction of another exascale computer, but its purpose and location was still uncertain uncertainty.

Besides US and China, the European Union and Japan are also trying to build an exascale computer by around 2020.



The world’s next fastest supercomputer will help boost China’s growing sea power | South China Morning Post

 

[JSCh]

22 August 2017
When mammals picked up the evolutionary pace
Study suggests diversification was underway before demise of the dinosaurs.

Whether the rise of placental mammals occurred before or after the mass-extinction event that eliminated the dinosaurs 66 million years ago is hotly debated. Fossils found so far suggest that it happened afterwards, but ‘molecular clock’ calculations — based on the rate of genetic mutations estimated from the DNA of modern animals — indicate an earlier start time.

Shaoyuan Wu and Scott Edwards at Jiangsu Normal University in Xuzhou, China, and their colleagues ran multiple molecular analyses using genome data from 82 mammalian species. Different molecular-clock models gave highly variable timing estimates for when the placental-mammal diversification spurt started.

But combining data from different analyses strongly suggests that the radiation started while dinosaurs were still alive, and continued steadily during and after their extinction. The radiation probably began in response to the earlier diversification of flowering plants, rather than the removal of dinosaurs, the authors say.

• Proc. Natl Acad. Sci. USA (2017)

When mammals picked up the evolutionary pace : Nature.com > Research Highlights

 

[Martian2]

China to launch new 400 km/hr trains | Traveller

China owns the world record for the world's fastest high-speed trains. Previously, China's high-speed trains traveled at an average of 350 km/hr. Next month, a new generation of Chinese high-speed trains will traverse the Beijing-Shanghai route at a top speed of 400 km/hr.

You may wonder: Doesn't France's TGV own the world high-speed train record? The answer is clearly no. The French TGV speed stunt was accomplished by stripping out all commercial seats, using custom-designed wheels and suspension system for a one-run stunt, and reducing the number of train cars from 10 to 4. Also, I think the French might have installed a second engine to help provide more power.

China's high-speed train record is accomplished through legitimate commercial service, without any ridiculous tricks like the French TGV. The French also cheated by modifying the train tracks for the special speed run. Finally, the French TGV record was a silly speed stunt that occurred only on a tiny straight portion of the train tracks.
----------

World's fastest trains: China to launch new, 400 km/h trains on Beijing to Shanghai route | Traveller

"New generation trains will service the route starting next month, making the 1250-kilometre journey from the capital to Shanghai in just 4 hours, 30 minutes.

The latest trains were unveiled in June and have a top speed of 400 kilometres per hour, according to the official Xinhua News Agency."

 

[cirr]

Chinese scientists give big boost to cancer-killing virus

2017-08-24 09:43

Xinhua Editor: Gu Liping

Chinese scientists have found a compound that helped a tumor-targeting virus kill liver cancer more effectively while sparing healthy cells, offering new hope for treating the world's second most common cancer killer, according to a study published Wednesday.

A therapy using viruses that selectively kill cancer cells, dubbed oncolytic viruses, is rapidly progressing through clinical evaluation, but the therapeutic efficacy in humans has been less than expected from preclinical studies, according to the study published in the U.S. journal Science Translational Medicine.

Oncolytic virotherapy involving M1 virus, a mosquito-borne pathogen that predominantly causes mild illness in horses, is believed to be a potentially attractive strategy for the treatment of hepatocellular carcinoma (HCC), the most common type of liver cancer.

In order to boost the virus's antitumor effects, Professor Guangmei Yan of Sun Yat-sen University in China and colleagues screened 350 small molecules to identify compounds that can enhance viral killing of cultured HCC cells.

The researchers found that Eeyarestatin I, an inhibitor of the protein VCP, which has been linked to causing malignancy, as the strongest sensitizer for M1 virus, as it increased the potency of the virus by as much as 3,600-fold against the HCC cells.

The dual regimen had no effect on non-cancerous cells, they said.

In multiple mouse models of HCC, M1 together with Eeyarestatin I were found to shrink tumors and significantly prolong survival.

The researchers further demonstrated that the duo was safe and well-tolerated in monkeys.

"We can describe the M1 oncolytic virus as a guided missile that automatically targets tumor cells, and the addition of the VCP inhibitor is just like binding the missile to powerful explosives with the ability of auto-selection," Yan explained to Xinhua.

"The outcome is self-evident with such a strong combination," he said.

Yan said they plan to submit a clinical trial application for the combination therapy strategy in 2018.

"Hepatocellular carcinoma is the second leading cause of cancer-related death in men and claims more than 700,000 lives per year worldwide," their paper wrote. "Our study identifies combined VCP inhibition and oncolytic virus as a potential treatment for HCC and demonstrates promising therapeutic potential."

http://www.ecns.cn/2017/08-24/270557.shtml

 

[JSCh]

Laser to uncover secrets of universe
By Zhang Zhihao | China Daily | Updated: 2017-08-24 07:27

Scientists adjust the facility that can generate 140 trillion photons per laser pulse in one picosecond in Dalian, Northeast China's Liaoning province, Jan 13, 2016. (PHOTO / XINHUA)

China is building a laser 20 times stronger than the most powerful one now in use to probe the secrets of the universe and create new materials for a wide array of products.

Last year, the Shanghai Institute of Optics and Fine Mechanics created the world's highest peak power pulsed lasers - intense lasers that generate beams in extremely short bursts - clocking in at 5.3 quadrillion watts (a quadrillion is 1 followed by 15 zeros) in less than 30 quadrillionths of a second.

Now, it is building an even stronger one, which can produce 100 quadrillion watts - about 50,000 times the planet's total power consumption - in an extremely short time, said Li Ruxin, project leader and director of the institute, which is part of the Chinese Academy of Sciences.

The laser is part of a new laboratory called Station of Extreme Light at the Shanghai Coherent Light Facility, one of China's key science facilities that include other major projects like the Five-hundred-meter Aperture Spherical radio Telescope, better known as FAST, the world's largest radio telescope.

The station also will house a new hard X-ray free-electron laser, one of the world's most powerful X-ray lasers used for imaging extremely small phenomena-like protein structures and chemical reactions.

Scientists around the world, from the United States to Japan, have conducted a feasibility study and endorsed the station's planning and design in July. The facility will be completed within a decade and its applications "will go far beyond other existing or planned facilities", according to the review committee.

The new laser is so powerful that it can simulate extreme conditions that are akin to the core of a massive star or even a black hole, Li said. This can lead to new discoveries that can help scientists tackle many unsolved mysteries of the universe, from its origin to quantum mechanics.

One of the main objectives is using the laser to unravel the "weird quantum property of empty space, which has puzzled scientists for more than 80 years", Li said. "Normally, a vacuum is thought of as completely empty, but in quantum electrodynamics, it is actually full of virtual particles that appear and vanish all the time," he said.

"However an extremely strong electric and magnetic field can affect this space and the light passing through it. So vacuum can actually behave as a prism, or 3-D movie glasses."

Scientist only got a glimpse of this strange phenomenon recently by observing neutron stars, which are the dense remnant cores of massive stars that have at least 10 times more mass and billions of times stronger magnetic fields than the sun.

But these stars are often light years away, making them extremely hard to study accurately. "Now for the first time, we can directly create and then measure the quantum properties of vacuum on earth using the laser," Li said.

Apart from cutting-edge scientific research, the laser will have plenty of practical applications. "By simulating extreme conditions via lasers, scientists can test and create stronger and more durable materials for industrial and social needs," he said.

This includes stronger wheels for high-speed trains, safer nuclear reactors, faster processing of nuclear waste and new medical tools for cancer diagnosis and treatment, Li said.

"High-power lasers are one of the greatest tools in modern science," Li said, adding that there are about a dozen labs worldwide dedicated to using these "big guns of science".

While these lasers have immense power output, the energy they deliver is actually low, Li said. "It will only take around 1,500 joules of energy to run the new 100 quadrillion-watt laser," he said. This is around 360 calories, or two cans of soda.

In physics, the equation for power is energy divided by time. By reducing the time to a quadrillionth of a second, scientists can create immense power output with little energy.

In 2015, Japanese scientists built what was then the most powerful laser in Osaka, which produced a 2 quadrillion-watt pulse in less than a trillionth of a second. The US, United Kingdom, France, Germany and Canada also have their own intense laser facilities.

"The Station of Extreme Light will become a unique and valuable platform for scientists around world, from physics to medicine, to cooperate and study," Li said.

 

[Martian2]

Will China opt for breakthrough four-mirror 12 meter-aperture telescope?

Currently, the largest general-purpose telescope in China has a 2 meter aperture.

The Chinese government has provided funding for a new 12 meter-aperture telescope.

The question in China is whether the new telescope (at a cost of $300 million) will be based on a proven 3-mirror design or will China attempt to build an untested Chinese four-mirror system?

The Chinese Nanjing Institute of Astronomical Optics and Technology (NIAOT) four-mirror design will provide higher-quality images, but no one in the world has built a four-mirror telescope. The technological challenges can be overcome, but the cost in time and money are unknown. The other drawback is a more limited field-of-view with a four-mirror design. The field-of-view can be fixed by simply pointing the telescope more often at a different spot in the sky.

Will China jump into the technological unknown and choose the Chinese four-mirror telescope design? Stay tuned and find out how this story ends.
----------

Row threatens Chinese telescope | Physics World

 

[JSCh]

Chinese scientists make breakthrough in super steel
Source: Xinhua| 2017-08-25 04:38:49|Editor: Mu Xuequan



WASHINGTON, Aug. 24 (Xinhua) -- Chinese scientists said Thursday they have developed a super steel that has a high level of both strength and ductility, a breakthrough that may have a wide variety of industrial applications.

Furthermore, its material cost is just one-fifth of that of the steel used in the current aerospace and defence applications, they reported in the U.S. journal Science.

Strength and ductility are desirable properties of metallic materials for wide-ranging applications, but increasing strength often leads to the decrease in ductility, which is known as the strength-ductility trade-off.

A Hong Kong-Beijing-Taiwan mechanical engineering team led by Huang Mingxin from the University of Hong Kong adopted a new manufacturing technique called deformed and partitioned (D&P) to addressed the problem.

"Steels have been the most widely used metallic materials in the history of mankind and can be produced with much higher efficiency than any other metallic materials," the team said in a statement.

"Therefore developing a strong and ductile breakthrough steel has been a long quest since the beginning of Iron Age in mankind history."

The team explained that it is very difficult to further improve the ductility of metallic materials when their yield strength is beyond two Gigapascal (GPa).

Now, they made "a successful attempt in realizing the above dream" as the newly developed method yields a "breakthrough steel" that has the "unprecedented" yield strength of 2.2 GPa and uniform elongation of 16 percent.

"The developed D&P steel demonstrated the best combination of yield strength and uniform elongation among all existing high-strength metallic materials," the researchers said.

"In particular, the uniform elongation of the developed D&P steel is much higher than that of metallic materials with yield strength beyond 2.0 GPa."

According to the team, the "breakthrough steel" belongs to the system of so-called medium manganese steel that contains 10 percent manganese, 0.47 percent carbon, 2.0 percent aluminium and 0.7 percent vanadium.

"No expensive alloying elements have been used exhaustively but just some common alloying compositions that can be widely seen in the commercialized steels," they said.

Another advantage is that this steel can be developed using conventional industrial processing routes, including warm rolling, cold rolling and annealing.

"This is different from the development of other metallic materials where the fabrication processes involve complex routes and special equipment, which are difficult to scale-up," said the team.

"Therefore, it is expected that the present breakthrough steel has a great potential for industrial mass production."

The research outcome was a collective contribution from scientists at the University of Hong Kong, University of Science and Technology Beijing, City University of Hong Kong, and a university in Taiwan.

B. B. He, B. Hu, H. W. Yen, G. J. Cheng, Z. K. Wang, H. W. Luo, M. X. Huang. High dislocation density–induced large ductility in deformed and partitioned steels. Science (2017). DOI: 10.1126/science.aan0177​

 

[JSCh]

More Solar Power Thanks to Titanium: Modification of a hematite photoanode by a conformal titanium dioxide interlayer for effective charge collection
Thursday, August 24, 2017 11:05 am EDT

Earth-abundant, cheap metals are promising photocatalytic electrode materials in artificial photosynthesis. A team of Chinese scientists now reports that a thin layer of titania beneath hematite nanorods can boost the performance of the photoanode. As outlined in their report in the journal Angewandte Chemie, the nanostructured electrode benefits from two separate effects. This design combining nanostructure with chemical doping may be exemplary for improved "green" photocatalytic systems.

With the help of a catalyst, sunlight can drive the oxidation of water to oxygen and the release of electrons for current generation, a process also called artificial photosynthesis. Iron oxide in the form of hematite is a convenient and cheap catalyst candidate, but the electrons set free by the chemical reaction tend to be trapped again and get lost; the electricity flow is inefficient. As a solution, Jinlong Gong from Tianjin University, China, introduced a nanometer-thin passivation layer of titania. Not only does this prevent charge recombination between the hematite electrode structure and the substrate, but it also provides the iron oxide with a considerable doping source to increase its charge-carrier density, a highly promising effect for photoelectric applications.

Hematite may be an abundant material (iron ore), but despite its photocatalytic advantages like photostability and good energetic preconditions, scientists still struggle with its sluggish kinetics and poor electrical conductivity. Nanostructured hematite may be one solution. The hematite photocatalysts are grown on conductive glass substrates in nanorod arrays, which are further furnished with branchlets to obtain a bushy, dendritic shape. This branched nanorod structure greatly enlarges the surface to promote the water-oxidation reaction, but the problem of charge recombination, especially at the hematite-substrate interface, is not solved.

Therefore, Gong and his colleagues grew dendritic hematite nanorods on an interlayer of titanium dioxide, which by itself is a photoactive material. If sufficiently thin, the coated structure can both prevent charge recombination and provide conductivity, but this was not the only intention the scientists had. "The titanium dioxide interlayer was considered to act as a titanium cation source to dope hematite," they argued. Doping here means to increase the charge-carrier density in the photocatalyst by bringing in more positive centers and boost the electrical conductivity.

Both effects, passivation and doping, indeed produced a more than four times higher photocurrent under standardized conditions. The addition of an iron hydroxide co-catalyst pushed the photocurrent density even further to a value more than five times above that of the undoped system. This design combining cheap materials, few preparation steps, and enhanced electrical performance may be exemplary for improved systems in green artificial photosynthesis.

(3112 characters)

Cite and link: Jinlong Gong et al., Angewandte Chemie International Edition, 10.1002/anie.201705772. doi.org/10.1002/anie.201705772



More Solar Power Thanks to Titanium: Modification of a hematite photoanode by a conformal titanium dioxide interlayer for effective charge collection | Wiley News Room – Press Releases, News, Events & Media

 

[JSCh]

Structures of A Plant Photosynthetic Machine Provide High-resolution Insights into Light Harvesting Process Under Low Light
Aug 25, 2017

Photosynthesis is a biological process mediating the conversion of solar energy into chemical energy. The so-called oxygenic photosynthesis, performed by plants, algae and cyanobacteria, is one of the most amazing chemical reactions on the planet. It provides food and energy for nearly all living organisms, and also contributes to the formation of the atmosphere and maintenance of the carbon-oxygen balance on the earth.

In plants, the primary light reaction of photosynthesis initiates at photosystem II (PSII), a membrane-embedded supramolecular machine responsible for catalyzing the water-splitting reaction. Surrounding the PSII, a number of peripheral antenna complexes dynamically associate with it to form the PSII–LHCII supercomplexes of variable sizes in response to different light conditions.

The C2S2M2-type supercomplex is known as the largest stable form of PSII-LHCII supercomplex isolated from Arabidopsis and pea so far, and crucial for plants to achieve optimal light-harvesting efficiency when they grow under low light conditions. Structural analysis of the C2S2M2 supercomplex is a pivotal step toward our understanding of the molecular mechanisms underlying the processes of light harvesting, energy transfer and PSII functional regulation in plants.

CHANG Wenrui-LI Mei’s group, ZHANG Xinzheng’s group and LIU Zhenfeng’s group from the Institute of Biophysics (IBP) at CAS collaborate and solved two cryo-electron microscopy (cryo-EM) structures of C2S2M2-type PSII-LHCII supercomplex from pea at 2.7 and 3.2 Å resolution, respectively.

The 2.7 Å resolution structure of C2S2M2 supercomplex represents the highest resolution structure of membrane protein complexes solved through single-particle cryo-EM method so far. The supercomplex has a total molecular mass of 1.4 megadalton and forms a homodimer. Each monomeric PSII-LHCII contains 28 or 27 protein subunits, and binds 159 chlorophylls, 44 carotenoids and numerous other cofactors.

The overall structural features and the arrangement of each individual subunits, as well as the sophisticated pigment network and the complete energy transfer pathways within the supercomplex have been revealed in great details through this study.

In addition, comparison of the two C2S2M2 structures solved at different states suggested the potential mechanism of functional regulation on the light-harvesting process and the oxygen-evolving activity of plant PSII.

The research work, entitled “Structure and assembly mechanism of plant C2S2M2-type PSII-LHCII supercomplex”, was published in Science on Aug. 25, 2017. The breakthrough is achieved through continuous and persistent efforts by the team from IBP after their previous work on the cryo-EM structure of spinach C2S2-type PSII-LHCII supercomplex was published on Nature last year.

The project was supported by grants from the Chinese Academy of Sciences, the Ministry of Science and Technology of China, the National Natural Science Foundation of China and “National Thousand (Young) Talents Program” from the Office of Global Experts Recruitment in China.

​

The overall structure of C2S2M2-type PSII-LHCII supercomplex with backgroud of pea leaves (up: top-view; down: side-view). Subunits are colored differently: the main transmembrane core subunit, magenta; small intrinsic core subunit, white; oxygen evolving complex subunit PsbO (blue), PsbP (light orange) and PsbQ (lime); peripheral light harvesting complexes S-LHCII (green), M-LHCII (cyan), CP29 (orange), CP26 (purple) and CP24 (yellow). (Image by IBP)



Structures of A Plant Photosynthetic Machine Provide High-resolution Insights into Light Harvesting Process Under Low Light---Chinese Academy of Sciences

Xiaodong Su, Jun Ma, Xuepeng Wei, Peng Cao, Dongjie Zhu, Wenrui Chang, Zhenfeng Liu, Xinzheng Zhang, Mei Li. Structure and assembly mechanism of plant C2S2M2-type PSII-LHCII supercomplex. Science (2017). DOI: 10.1126/science.aan0327​

 

[JSCh]

Chinese scientists make breakthrough in super steel
Source: Xinhua| 2017-08-25 04:38:49|Editor: Mu Xuequan



WASHINGTON, Aug. 24 (Xinhua) -- Chinese scientists said Thursday they have developed a super steel that has a high level of both strength and ductility, a breakthrough that may have a wide variety of industrial applications.

Furthermore, its material cost is just one-fifth of that of the steel used in the current aerospace and defence applications, they reported in the U.S. journal Science.

Strength and ductility are desirable properties of metallic materials for wide-ranging applications, but increasing strength often leads to the decrease in ductility, which is known as the strength-ductility trade-off.

A Hong Kong-Beijing-Taiwan mechanical engineering team led by Huang Mingxin from the University of Hong Kong adopted a new manufacturing technique called deformed and partitioned (D&P) to addressed the problem.

"Steels have been the most widely used metallic materials in the history of mankind and can be produced with much higher efficiency than any other metallic materials," the team said in a statement.

"Therefore developing a strong and ductile breakthrough steel has been a long quest since the beginning of Iron Age in mankind history."

The team explained that it is very difficult to further improve the ductility of metallic materials when their yield strength is beyond two Gigapascal (GPa).

Now, they made "a successful attempt in realizing the above dream" as the newly developed method yields a "breakthrough steel" that has the "unprecedented" yield strength of 2.2 GPa and uniform elongation of 16 percent.

"The developed D&P steel demonstrated the best combination of yield strength and uniform elongation among all existing high-strength metallic materials," the researchers said.

"In particular, the uniform elongation of the developed D&P steel is much higher than that of metallic materials with yield strength beyond 2.0 GPa."

According to the team, the "breakthrough steel" belongs to the system of so-called medium manganese steel that contains 10 percent manganese, 0.47 percent carbon, 2.0 percent aluminium and 0.7 percent vanadium.

"No expensive alloying elements have been used exhaustively but just some common alloying compositions that can be widely seen in the commercialized steels," they said.

Another advantage is that this steel can be developed using conventional industrial processing routes, including warm rolling, cold rolling and annealing.

"This is different from the development of other metallic materials where the fabrication processes involve complex routes and special equipment, which are difficult to scale-up," said the team.

"Therefore, it is expected that the present breakthrough steel has a great potential for industrial mass production."

The research outcome was a collective contribution from scientists at the University of Hong Kong, University of Science and Technology Beijing, City University of Hong Kong, and a university in Taiwan.

B. B. He, B. Hu, H. W. Yen, G. J. Cheng, Z. K. Wang, H. W. Luo, M. X. Huang. High dislocation density–induced large ductility in deformed and partitioned steels. Science (2017). DOI: 10.1126/science.aan0177​

New way to make steel that is both stronger and more ductile
August 25, 2017 by Bob Yirka

(a) Electron backscatter diffraction (EBSD) phase image showing the lamella microstructure of layered austenite grains embedded in tempered martensite matrix.(b) The dislocation structures in martensite as enlarged in transmission electron microscopy (TEM) image.(c) TEM image showing the elongation of dislocation cell structure after the 8% tensile strain.(d) TEM image confirming the transformation of metastable austenite to martensite after 16% tensile strain. Credit: The University of Hong Kong

(Phys.org)—A team of researchers from several institutions in China and Taiwan has developed a new way to make steel that offers more strength and ductility. In their paper published in the journal Science, the team describes part of the process and the ingredients that went into making the new type of steel and suggest possible applications.

As the researchers note, there are many industrial applications based on steel that require a high degree of strength and ductility (the ability to be pulled or deformed without breaking)—the higher degree of both, the better. But traditional steel-making techniques generally require a tradeoff: More strength means less ductility, or vice-versa. In this new effort, the researchers report that they have found a way around this problem.

To make the new steel, the researchers developed a new technique they call deformed and partitioned (D&P)—they cannot give all the details, of course, because that would prevent them from capitalizing on what they have created. But they do divulge that it belongs to a class of metal that the industry has defined as "breakthrough steels," which are medium manganese steels that are made with 0.47 percent carbon, 10 percent manganese, 0.7 percent vanadium and 2.0 percent aluminum.

They report also that the process involves cold rolling, which is followed up by tempering in a low temperature environment, and that metastable austenite grains are embedded somewhere in the process—this, they note, helps retain ductility while allowing for controlled defects that give the metal its strength. The group claims that the result is a steel with a yield strength of 2.2 GPa and 16 percent uniform elongation, which would make it the best in its class. They suggest the desired properties are due to the type of matrix formed during the rolling and tempering process.

​

Tensile properties of the he present breakthrough D&P steel compared with other high-strength steels, including maraging steel, nanotwinned (NT) steel, quenching and partitioning (Q&P980) steel and dual-phase (DP780) steel. Credit: The University of Hong Kong

In addition to offering both more strength and ductility, the steel is also cheaper to make than other steels that are used in critical applications such as airplanes and rockets—the team claims that it can be made for just a fifth the cost of other more traditional methods. They also note that the process they developed offers the same desirable characteristics of other alloys.


https://phys.org/news/2017-08-steel-stronger-ductile.html

 

[JSCh]

Public Release: 24-Aug-2017
ILCregs play an important role in regulation of intestinal inflammation
Chinese Academy of Sciences Headquarters
https://www.eurekalert.org/multimedia/pub/148907.php

​

Fig.1 ILCregs contribute to the resolution of innate intestinal inflammation by inhibition of ILC1s and ILC3s.
Credit: Image by IBP

The intestine contains an extensive and diverse microbial flora, including potential pathogens and dietary antigens that needs to be tolerated. Dysregulation of mucosal responses may cause a loss of tolerance, leading to harmful intestinal inflammation such as human inflammatory bowel disease (IBD).

Innate lymphoid cells (ILCs) are located in mucosal surfaces to potentiate immune responses, sustain mucosal integrity and promote lymphoid organogenesis. Three subsets of ILCs have been defined to date and produce substantial effector cytokines upon harmful stress. These ILCs play critical roles in the regulation of type 1, type 2, and type 3 (or Th17 cell) responses, controlling host protective immunity and intestinal homeostasis.

Researchers from FAN Zusen's group at the Institute of Biophysics (IBP) of the Chinese Academy of Sciences have identified a regulatory subpopulation of ILCs (called ILCregs) that exist in the gut and harbor a unique genetic identity distinct from ILCs or regulatory T cells (Tregs).

During inflammatory stimulation, ILCregs can be induced in the intestine and suppress the activation of ILC1s and ILC3s via secretion of IL-10, leading to protection against innate intestinal inflammation.

In addition, TGF-ß1 is consequently secreted by ILCregs upon intestinal inflammation, and autocrine TGF-ß1 sustains the maintenance and increase of ILCregs. Therefore, ILCregs exert an inhibitory role in the innate immune response, favoring the resolution of intestinal inflammation.

Researchers found that ILCregs may be used to develop potential therapies to restore immune tolerance in chronic inflammatory and autoimmune diseases.

###​

This research, entitled "Regulatory Innate Lymphoid Cells Control Innate Intestinal Inflammation," which was published in Cell on August 24, involved cooperation with the Institute of Biophysics (IBP), the Institute of Genetics and Developmental Biology, Sichuan University and Jinan University. Profs. FAN Zusen and WANG Shuo (IBP) are the corresponding authors. Drs. WANG Shuo and XIA Pengyan (IBP) are the co-first authors of this paper.

This work was supported by the National Natural Science Foundation of China, the Strategic Priority Research Programs of the Chinese Academy of Sciences, the Youth Innovation Promotion Association of CAS, and the China Postdoctoral Science Foundation.


ILCregs play an important role in regulation of intestinal inflammation | EurekAlert! Science News

Shuo Wang, Pengyan Xia, Yi Chen, Yuan Qu, Zhen Xiong, Buqing Ye, Ying Du, Yong Tian, Zhinan Yin, Zhiheng Xu, Zusen Fan. Regulatory Innate Lymphoid Cells Control Innate Intestinal Inflammation. Cell (2017). DOI: http://dx.doi.org/10.1016/j.cell.2017.07.027​

 

[JSCh]

Researchers create single-crystal perovskite solar cells
August 29, 2017

​

Single crystalline CH3NH3PbI3 self-grown on FTO/TiO2 substrate. (a) Schematic self-growth via temperature gradient and capillary effect; (b) cross-sectional SEM image of CH3NH3PbI3 on FTO/TiO2; (c) high resolution TEM image of single crystalline CH3NH3PbI3. Credit: Science China Press

Photovoltaic conversion is regarded as the ultimate solution to the growing demand for energy, yet traditional silicon-based solar cells are expensive to produce, and production itself involves intensive energy consumption. Emerging hybrid organic-inorganic solar cells based on perovskite CH3NH3PbI3, on the other hand, are not only inexpensive to process but also flexible, and thus are widely pursued as one of the most promising next-generation photovoltaic conversion technologies.

Since first reported in 2009, the photovoltaic conversion efficiency of perovskite solar cells has increased spectacularly from 3.81 percent to 22.1 percent in just seven years, and this unprecedented rise has fueled worldwide pursuit for new efficiency records. Nevertheless, in the last two years, the pace of perovskite solar cell efficiency gains has slowed considerably despite the distance from the projected theoretical limit of 31 percent. Therefore, researchers are exploring new strategies to further enhance perovskite solar cell performance.

The current perovskite solar cells are based on polycrystalline CH3NH3PbI3 films, and thus inevitably have many defects in grains and grain boundaries that affect the device performance. Researchers have made efforts to produce bulk CH3NH3PbI3 crystals that exhibit exceptional photovoltaic properties such as long diffusion length and lifetime of photogenerated charge carriers, though the integration of bulk crystal into the perovskite solar cell architecture has proved challenging.

Now, a team of Chinese and U.S. scientists led by Profs. Jiangyu Li and Jinjin Zhao has successfully grown single-crystalline CH3NH3PbI3 film directly on electron-collecting FTO/TiO2 substrate, as shown in Fig. 1. They took advantage of temperature gradient and the capillary effect during the growth process, enabling them to produce high-quality single crystalline film tightly integrated on FTO/TiO2. This proves critical, as FTO/TiO2 is the most widely used electron-collecting substrate for perovskite solar cells, making subsequent device fabrication straightforward.

Indeed, the single crystalline CH3NH3PbI3 film shows excellent photovoltaic properties. Measured directly on an FTO glass substrate with poor electron extraction, the time-resolved photoluminescence has much longer carrier lifetime in single crystalline CH3NH3PbI3 film compared to polycrystalline film, as seen in Fig. 2(a). When a TiO2 electron-collecting layer is added to the FTO glass, then the charge carrier lifetime drops substantially, thanks to efficient electron extraction at the TiO2/perovskite interface. As a result, the device exhibits photovoltaic conversion efficiency of 8.78 percent, the highest reported to date for a single crystalline perovskite solar cells. The team says that the system has much room for improvement, and with continuous optimization of materials and devices, they believe that the single crystalline perovskite solar cells will rival their polycrystalline counterparts in the foreseeable future.

​

Photo-carrier properties and photovoltaic performance of single crystalline and polycrystalline CH3NH3PbI3. (a) time-resolved photoluminescence shows longer charge lifetime in single crystalline film and efficient charge collection at the interface with FTO/TiO2 substrate; and (b) current density-voltage curve shows a photovoltaic efficiency of 8.78 percent. Credit: Science China Press



https://phys.org/news/2017-08-single-crystal-perovskite-solar-cells.html

Jinjin Zhao, Guoli Kong, Shulin Chen, Qian Li Boyuan Huang, Zhenghao Liu, Xingyuan San, Yujia Wang, Chen Wang, Yunce Zhen, Haidan Wen, Peng Gao, Jiangyu Li. Single crystalline CH3NH3PbI3 self-grown on FTO/TiO 2 substrate for high efficiency perovskite solar cells, Science Bulletin (2017). DOI: 10.1016/j.scib.2017.08.022​

 

[JSCh]

Chinese company plans hyperloop traveling at 1,000 km/h
By Zhao Lei | chinadaily.com.cn | Updated: 2017-08-30 11:14

​

China Aerospace Science and Industry Corp, one of the nation's major space contractors, announced that it has launched research and development of a futuristic ultrafast transport system popularly known as hyperloop, in Wuhan, capital of Hubei province, on Wednesday.

The CASIC hyperloop will be a maglev line on which a pod will travel on partly elevated tubes or tunnels at superfast speed reaching 1,000 km per hour.

CASIC is the first Chinese enterprise and the world's third, following the United States' Hyperloop Transportation Technologies and Hyperloop One, that has started developing hyperloop system. The project will benefit from the company's rich experience and expertise in systems engineering and supersonic vehicles, said CASIC.

 

[JSCh]

China focus: China aims high in nanotechnology
Source: Xinhua| 2017-08-30 14:57:42|Editor: Yang Yi



BEIJING, Aug. 29 (Xinhua) -- China has become a nanotechnology powerhouse, according to a report released at the 7th International Conference on Nanoscience and Technology (ChinaNANO 2017) in Beijing on Tuesday.

China's applied nanoscience research and the industrialization of nanotechnology have been developing steadily, with the number of nano-related patent applications ranking among the top in the world, said the report.

The report was co-produced by Springer Nature, National Center for Nanoscience and Technology (NCNST), and the National Science Library of the Chinese Academy of Sciences (CAS).

According to Bai Chunli, president of CAS, China faces new opportunities for nanoscience research and development as it builds the NCNST and globally influential national science centers.

"We will strengthen the strategic landscape and top-down design for developing nanoscience, which will contribute greatly to the country's economy and society," said Bai.

Nanoscience is the study of the interaction, composition, properties and manufacturing methods of materials at the nanometer scale.

The science encourages integration of many disciplines and has a direct impact on daily work and life because it leads to the discovery of advanced technology.

In 1997, around 13,000 nanoscience-related papers were published worldwide. By 2016, the number had risen to more than 154,000, the report said.

Over the same period, the number of papers related to nanoscience from China grew from 820 in 1997 to over 52,000 in 2016.

Since 2007, the average compound annual growth rate of China's most cited nanoscience papers was 22 percent -- three times the global rate, the report stated.

In terms of the number of nano-related patent applications, China has reached 209,344 over the past 20 years, accounting for 45 percent of the world's total.

In 2003, CAS and the Ministry of Education co-established the NCNST. Key to the NCNST's success has been the involvement of three of China's top research institutions -- Tsinghua University, Peking University and CAS, said Liu Minghua, director of the NCNST.

Liu said that thanks to robust funding, a growing number of Chinese scientists have been attracted to research of nanomaterials. Additionally, more foreign-trained Chinese researchers have returned to China under favorable policies.

Energy nanotechnology and catalytic nanomaterials are the top two fields in which China has made remarkable achievements.

Faced with mounting public pressure to tackle deteriorating environmental problems, China is putting great effort into the research and development of new energy, as well as efficient energy and environmental protection technology.

This has made energy nanotechnology a promising area, leading Chinese researchers to research batteries and energy storage and conversion, Liu said.

Catalytic nanomaterials research is considered China's most promising area of nanoscience. Nanostructure-based catalysts can speed up chemical reactions and could be useful in chemical industries and oil refining, experts said.

Bai said both challenges and opportunities await China. More breakthroughs in basic nanoscience research need to be made, and the gap between basic research and application should be closed.

CAS will foster more young scientists who can innovate, accelerate the building of value chains, and foster broad and efficient international collaboration, Bai said.

"Through our joint efforts, we expect to apply nanotechnology to various sectors that will benefit the people and help China to be a global leader in science and technology," Bai said.