China Science & Technology Forum

[JSCh]

Microscale superlubricity could pave way for future improved electromechanical devices

Date: August 1, 2018
Source: American Friends of Tel Aviv University

Lubricity measures the reduction in mechanical friction and wear by a lubricant. These are the main causes of component failure and energy loss in mechanical and electromechanical systems. For example, one-third of the fuel-based energy in vehicles is expended in overcoming friction. So superlubricity -- the state of ultra-low friction and wear -- holds great promise for the reduction of frictional wear in mechanical and automatic devices.

A new joint Tel Aviv University/Tsinghua University study finds that robust structural superlubricity can be achieved between dissimilar, microscale-layered materials under high external loads and ambient conditions. The researchers found that microscale interfaces between graphite and hexagonal boron nitride exhibit ultra-low friction and wear. This is an important milestone for future technological applications in space, automotive, electronics and medical industries.

The research is the product of a collaboration between Prof. Oded Hod and Prof. Michael Urbakh of TAU's School of Chemistry; and Prof. Ming Ma and Prof. Quanshui Zheng of Tsinghua University's Department of Mechanical Engineering and their colleagues. It was conducted under the auspices of the joint TAU-Tsinghua collaborative XIN Center and was published in Nature Materials on July 30.

Enormous implications for computer and other devices

The new interface is six orders of magnitude larger in surface area than earlier nanoscale measurements and exhibits robust superlubricity in all interfacial orientations and under ambient conditions.

"Superlubricity is a highly intriguing physical phenomenon, a state of practically zero or ultra-low friction between two contacting surfaces," says Prof. Hod. "The practical implications of achieving robust superlubricity in macroscopic dimensions are enormous. The expected energy savings and wear prevention are huge."

"This discovery may lead to a new generation of computer hard discs with a higher density of stored information and enhanced speed of information transfer, for example," adds Prof. Urbakh. "This can be also used in a new generation of ball bearing to reduce rotational friction and support radial and axial loads. Their energy losses and wear will be significantly lower than in existing devices."

The experimental part of the research was performed using atomic force microscopes at Tsinghua and the fully atomistic computer simulations were completed at TAU. The researchers also characterized the degree of crystallinity of the graphitic surfaces by conducting spectroscopy measurements.

Close collaboration

The study arose from an earlier prediction by theoretical and computational groups at TAU that robust structural superlubricity could be achieved by forming interfaces between the materials graphene and hexagonal boron nitride. "These two materials are currently in the news following the 2010 Nobel Prize in Physics, which was awarded for groundbreaking experiments with the two-dimensional material graphene. Superlubricity is one of their most promising practical applications," says Prof. Hod.

"Our study is a tight collaboration between TAU theoretical and computational groups and Tsinghua's experimental group," says Prof. Urbakh. "There is a synergic cooperation between the groups. Theory and computation feed laboratory experiments that, in turn, provide important realizations and valuable results that can be rationalized via the computational studies to refine the theory."

The research groups are continuing to collaborate in this field studying the fundamentals of superlubricity, its extensive applications and its effect in ever larger interfaces.

Journal Reference:

1. Yiming Song, Davide Mandelli, Oded Hod, Michael Urbakh, Ming Ma, Quanshui Zheng. Robust microscale superlubricity in graphite/hexagonal boron nitride layered heterojunctions. Nature Materials, 2018; DOI: 10.1038/s41563-018-0144-z

Microscale superlubricity could pave way for future improved electromechanical devices -- ScienceDaily

 

[JSCh]

NEWS AND VIEWS | 01 AUGUST 2018
Reflection forbidden and refraction reversed in an artificial crystal
At the interface between two facets of an artificial crystal, sound waves can be transmitted in the opposite direction to that expected, and undergo no reflection. Such wave behaviour could have many applications.

Baile Zhang

Waves change direction when they pass from one medium to another — a phenomenon called refraction. This effect underlies most optical lenses and instruments, and is widely found in acoustics when an acoustic beam behaves like an optical beam. In general, some of the waves are reflected during the refraction process. In a paper in Nature, He et al.1 report an impressive demonstration of a previously unobserved refraction phenomenon. They show that, in a certain artificially engineered material, an acoustic beam can be refracted in the opposite direction to that seen in ordinary materials, without reflection. The authors’ findings could lead to improved control of waves in electronic and photonic systems.

When an acoustic or optical ray strikes the interface between two different media, part of its energy passes through the interface to form a refracted ray (Fig. 1a). The remaining energy reflects from the interface to produce a reflected ray. In nature, the incident and refracted rays are always on opposite sides of the normal — an imaginary line perpendicular to the interface. But, in theory, this need not be the case.

Figure 1 | Comparison of refraction phenomena. a, In conventional refraction, when an acoustic or optical ray (red) hits the interface between two different media, a reflected ray (dark blue) and a refracted ray (light blue) are produced. The incident and refracted rays exist on opposite sides of the normal — an imaginary line perpendicular to the interface. b, In negative refraction, the refracted ray emerges on the same side of the normal as the incident ray. c, He et al.1 report a previously unobserved type of refraction for acoustic rays, in which not only are the incident and refracted rays on the same side of the normal, but also there is no reflected ray. (Figure adapted from ref. 1.)

In 1968, the Russian physicist Victor Veselago considered a hypothetical material that has a negative refractive index2. A refractive index describes how waves propagate in a medium, and is positive in all conventional materials. Veselago showed that the way in which refraction usually occurs could be reversed in a negative-index material: the refracted ray could emerge on the same side of the normal as the incident ray (Fig. 1b).

Although intriguing, negative refraction did not trigger much attention, and was considered impossible for more than 30 years because it was thought that negative-index materials could not exist. The situation changed in 2000, when the British physicist John Pendry made a shocking prediction3: that negative refraction could be used to make a lens that could focus light more tightly than is normally possible. He also identified a practical way to construct negative-index materials in the lab using artificial structures. Such materials, now generally referred to as metamaterials, stimulated research into concepts such as invisibility cloaking4 that had previously existed only in science fiction.

​

Read the paper: Topological negative refraction of surface acoustic waves in a Weyl phononic crystal

In the years since Pendry’s work, the pursuit of negative refraction has led to developments in optics, acoustics, plasmonics (the study of how light interacts with electrons in metals) and even graphene-based electronics5. Versions of negative refraction have been realized in each of these areas. However, the phenomenon is generally accompanied by reflection, which is often undesirable. In many cases, such as in experiments involving the refraction of electrons through an interface5, reflection can even dominate negative refraction.

The property of reflection immunity is not found in natural optical materials for light. However, it does occur in exotic phases of matter known as topological quantum matter, for quantum-mechanical electronic waves. A well-studied example is the topological insulator, which is an electrical insulator in its interior, but conducts electricity on its surface through electronic waves called topological surface states. Such states are able to propagate unidirectionally — they bypass obstacles and defects, rather than being reflected.

He and colleagues’ demonstration was directly inspired by another emerging topological quantum matter: the Weyl semimetal6. The topological surface states in this material cannot propagate in all directions; propagation is confined to a certain range of directions, which connect to form what are known as Fermi arcs6. Because the limited range of propagation directions does not include the direction in which reflection would normally occur, reflection is forbidden (Fig. 1c).

In their experiment, He et al. used an artificial crystal that is an acoustic analogue of the Weyl semimetal. They found that, at the interface between two adjacent facets of the crystal, airborne acoustic waves could undergo negative refraction without reflection. The authors’ results represent the first realization of negative refraction for topological surface states.

There are a few limitations of the work. For instance, the refraction does not occur in a flat plane, contrary to the common impression of refraction. Moreover, the interface scatters some of the acoustic waves into the crystal’s interior, resulting in energy loss. Nevertheless, the demonstration opens the door to many exciting opportunities for further research.

The immediate question is whether He and colleagues’ refraction phenomenon could be realized in optical systems for light and condensed-matter systems for electrons. Another question, which will be of interest to both optical and condensed-matter physicists, is how to engineer the range of propagation directions — and, in turn, the Fermi arcs — to achieve greater control of negative refraction. In this sense, the authors’ work provides the first practical use of Fermi arcs, which are currently being enthusiastically explored in condensed-matter systems7,8 and in optical structures called photonic crystals9.

The refraction phenomenon could also find widespread use in acoustics. For example, the combination of negative refraction and zero reflection could lead to improved resolution in ultrasonic imaging and testing. Moreover, acoustic waves are used in biomedical microfluidic devices to trap, sort and deliver cells and drug particles. Reflection-free acoustic waves are strongly desirable in such applications, because reflections at the interfaces and sharp corners of microfluidic channels are currently a huge limitation to device efficiency. Topological acoustics is therefore a promising research field that not only can produce phenomena that are difficult to realize in other physical systems, but could also bring about transformative technologies.

Nature 560, 37-38 (2018)

doi: 10.1038/d41586-018-05806-6



Reflection forbidden and refraction reversed in an artificial crystal | Nature.com

Hailong He, Chunyin Qiu, Liping Ye, Xiangxi Cai, Xiying Fan, Manzhu Ke, Fan Zhang & Zhengyou Liu. Topological negative refraction of surface acoustic waves in a Weyl phononic crystal. Nature (2018); DOI: https://doi.org/10.1038/s41586-018-0367-9​

 

[JSCh]

NEWS | 01 AUGUST 2018
Entire yeast genome squeezed into one lone chromosome
In a dramatic restructuring, two teams have created versions of baker’s yeast with vastly reduced chromosome counts.

Ewen Callaway

Brewer’s yeast is a single-celled organism that usually has 16 chromosomes.Credit: Thomas Deerinck, NCMIR/Getty

For millions of years, brewer’s yeast and its close relatives have packed their DNA into 16 distinct chromosomes. Now, two teams have used CRISPR gene-editing to stuff all of yeast’s genetic material — save a few non-essential pieces — into just one or two chromosomes. The feat represents the most dramatic restructuring yet of a complex genome and could help scientists understand why organisms split their DNA over chromosomes. And, to the researchers’ surprise, the changes had little effect on most functions of the yeast (Saccharomyces cerevisiae).

“That was the biggest shocker — that you can just get away with this and yeast seem to shrug its shoulders,” says Jef Boeke, a geneticist at New York University whose team jammed the yeast genome onto a pair of chromosomes1. A China-based group used a different technique to make yeast with one ‘super-chromosome’2. Both teams report their findings in Nature on 1 August.

Genetics 101
Yeast belongs to the eukaryotes, the branch of life that includes humans, plants and animals and whose cells store genetic material in a membrane-bound nucleus. But the number of chromosomes that eukaryotes have varies wildly and seems to have no correlation with the amount of genetic information they possess. In humans, genetic material is spread over 46 chromosomes, whereas male jack jumper ants (Myrmecia pilosula) have just 1. Single-celled brewer’s yeast — whose genome, at 12 million DNA letters long, is hundreds of times shorter than that of humans — boasts 16 chromosomes.

“We don’t know why they have such different numbers,” says Zhongjun Qin, a molecular biologist at the Chinese Academy of Sciences’ Shanghai Institute of Plant Physiology and Ecology, whose team created the lone-chromosome yeast strain. “I thought it was probably random.”

Qin and his colleagues reasoned that if an organism’s chromosome count were down to chance rather than an underlying rule of nature, there should be no reason that a yeast cell shouldn’t be viable with 1 chromosome instead of 16. Researchers in the past had fused two3 — even four4 — yeast chromosomes together, and another team split the 16 chromosomes into 33. All products had viable cells5. But no one had ever performed such extreme genetic surgery as Qin and his colleagues set out to do several years ago.

Their initial attempts ended in failure — until they turned to the genome-editing tool CRISPR–Cas9, which is adept at excising specific DNA sequences. Qin and his colleagues used CRISPR to remove DNA at telomeres, the ends of chromosomes that protect them from degrading. They also snipped out centromeres, sequences in the middle that are important to DNA replication.

These changes paved the way for a fit of tidying that would make home-organization guru Marie Kondo proud. The researchers first fused two chromosomes, then joined this product to another one, and in successive rounds, to another and another — until they were left with a lone-chromosome yeast strain (see ‘Minimal yeast’).

Source: Refs 1, 2

Boeke’s team also used CRISPR to remove superfluous telomeres and centromeres to create strains with progressively fewer chromosomes. They ended up with a yeast strain that had two extra-long chromosomes, but they could not get the pair to fuse into one. (Boeke is also leading a separate, international effort to synthesize an entire yeast genome from scratch.)

One explanation for the difference is that Qin’s team also jettisoned 19 repetitive stretches of DNA. These sequences might have interfered with the mechanism that cells use to stitch two chromosomes into one, suggests Qin. Or, Boeke says, it could be down to chance: there are about 10–19 different ways to arrange yeast’s 16 chromosomes into 1, and the Chinese team might simply have hit a winning combination.

Growing pains
Both strains of ‘minimal’ yeast looked normal under a microscope, and the changes to chromosome number had little impact on their gene activity. But while Boeke’s strain underwent normal asexual reproduction and grew as efficiently as 16-chromosome strains, the lone-chromosome yeast divided more slowly.

The only major defect — in both strains — was in sexual reproduction, in which yeast cells with two genome copies produce ‘spores’ that have only one. The Chinese team’s single-chromosome strain grew even more slowly compared with normal yeast when its genome was doubled through mating, and it produced fewer spores.

Boeke and his colleagues observed defects when they tried to coax yeast strains with differing numbers of chromosomes to produce spores. This genetic incompatability could be used to prevent synthetic yeast, released into the environment from mating with wild strains, Boeke says. He also notes that the two-chromosome yeast might qualify as a distinct species because it can’t breed with normal yeast, despite having near-identical DNA.

Scientists tend to focus on the role of DNA-sequence changes in creating new species, but these studies suggest that natural chromosome fusions could also play a part, says Gianni Liti, a geneticist at the University of Cote d’Azur in Nice, France, who reviewed the papers and wrote an accompanying essay6.

William Noble, a computational biologist at the University of Washington in Seattle, says that studying such strains could help to explain why nearly all eukaryotes apportion their DNA into multiple chromosomes. “Why bother?” he says. “If you only needed one, it would be the ‘Occam’s razor’ solution.



Entire yeast genome squeezed into one lone chromosome | Nature.com

Yangyang Shao, Ning Lu, Zhenfang Wu, Chen Cai, Shanshan Wang, Ling-Li Zhang, Fan Zhou, Shijun Xiao, Lin Liu, Xiaofei Zeng, Huajun Zheng, Chen Yang, Zhihu Zhao, Guoping Zhao, Jin-Qiu Zhou, Xiaoli Xue & Zhongjun Qin. Creating a functional single-chromosome yeast. Nature (2018). DOI: https://doi.org/10.1038/s41586-018-0382-x​

​

China "creates" world's first single-chromosome eukaryote
New China TV
Published on Aug 2, 2018

Could humans create life that doesn't exist on Earth? Researchers in China's Shanghai have fused chromosomes to create a new yeast strain.

 

[JSCh]

Chinese students set record in RoboSub win
2018-08-06 16:31:43Ecns.cnEditor : Mo Hong'e
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A student from Harbin Engineering University operates on the computer during the 21st International RoboSub Competition held in San Diego, the United States. (Photo provided to China News Service)

(ECNS) - A student team from Harbin Engineering University has won first place in the 21st International RoboSub Competition held in San Diego, the United States, setting a record among Chinese universities.

An EV team from the university is attending the contest for the 8th time since 2011. EV teams won 4th place, 5th place, 6th place and 4th place in 2012, 2013, 2016 and 2017 respectively.

RoboSub, an underwater robotics program, allows high school and college students from around the world to design and build an autonomous underwater vehicle (AUV) that navigates a series of tasks, mimicking ongoing research.

Since the competition started in 1998, all previous first-place winners were students from the United States or Canada.

The 2018 International RoboSub Competition ran from July 30 to Aug. 5 and was held at the U.S. Navy Space and Naval Warfare Systems Center Pacific's TRANSDEC facility in San Diego. It is organized by RoboNation with funding from the U.S. Office of Naval Research and hosted by the U.S. Navy’s SSC Pacific.

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From slayerhuahua of cjdby.net

 

[JSCh]

Dirac-source field-effect transistors as energy-efficient, high-performance electronic switches

1. Chenguang Qiu1,
2. Fei Liu2,
3. Lin Xu1,
4. Bing Deng3,
5. Mengmeng Xiao1,
6. Jia Si1,
7. Li Lin3,
8. Zhiyong Zhang1,*,
9. Jian Wang2,
10. Hong Guo4,
11. Hailin Peng3,
12. Lian-Mao Peng1,*

1. ↵*Corresponding author. Email: zyzhang@pku.edu.cn (Z.Z.); lmpeng@pku.edu.cn (L.-M.P.)

Hide authors and affiliations

Science 27 Jul 2018:
Vol. 361, Issue 6400, pp. 387-392
DOI: 10.1126/science.aap9195

Cooler electrons for transistors
The operating power of field-effect transistors is constrained in part by the minimum change in voltage needed to change the current output. This subthreshold swing (SS) limit is caused by hotter electrons from a thermal electron source leaking over the potential of the gate electrode. Qiu et al. show that graphene can act as a Dirac source that creates a narrower distribution of electron energies. When coupled to a carbon nanotube channel, the decrease in SS would allow the supply voltage to be decreased from 0.7 to 0.5 volts.

Science, this issue p. 387

Abstract
An efficient way to reduce the power consumption of electronic devices is to lower the supply voltage, but this voltage is restricted by the thermionic limit of subthreshold swing (SS), 60 millivolts per decade, in field-effect transistors (FETs). We show that a graphene Dirac source (DS) with a much narrower electron density distribution around the Fermi level than that of conventional FETs can lower SS. A DS-FET with a carbon nanotube channel provided an average SS of 40 millivolts per decade over four decades of current at room temperature and high device current I60 of up to 40 microamperes per micrometer at 60 millivolts per decade. When compared with state-of-the-art silicon 14-nanometer node FETs, a similar on-state current Ion is realized but at a much lower supply voltage of 0.5 volts (versus 0.7 volts for silicon) and a much steeper SS below 35 millivolts per decade in the off-state.


Dirac-source field-effect transistors as energy-efficient, high-performance electronic switches | Science

 

[JSCh]

China Focus: Chinese scientists make nano "Trojan horse" to strangle tumors
Source: Xinhua| 2018-08-09 12:28:31|Editor: mym


BEIJING, Aug. 9 (Xinhua) -- Chinese scientists have folded DNA molecules in an origami-like process to make a nano "Trojan horse", which is thinner than 1/4000 of a hair and can release "killers" to fight cancer tumors.

Cancer cells need a lot of nutrition to multiply, but they don't produce nutrient substances, said lead researcher Nie Guangjun, of China's National Center for Nanoscience and Technology (NCNST).

All the blood, oxygen and energy are conveyed to cancer cells through blood vessels, so many scientists are trying to create blocks on the blood vessels feeding tumors.

Through precision control, researcher Ding Baoquan folded a single-strand DNA of a phage (a type of virus) into a rectangular sheet. Then he put four "killers" -- molecules of thrombin (a clotting enzyme in blood plasma) -- on the sheet and rolled them up.

At the interface, "locks" made by fragments of nucleolin protein DNA were installed, forming a tube-shaped nano "Trojan horse" or nanorobot, which is 90 nanometers long and has a diameter of 19 nanometers.

After injection, the "Trojan horse" travels in blood vessels and only tumors have the "key" to open the "locks." Once unlocked, the killer thrombin molecules are released, attracting platelets and fibrinogen protein to form a large thrombus, or clot, in the blood vessel within hours to cut off the blood supply and "starve" the tumor to death, Nie said.

The nanorobot can be cleared out of the body after it has finished its task.

Researchers have conducted controlled experiments on more than 200 mice with melanoma, breast cancer, ovarian cancer and primary lung cancer, and found the nanorobots are effective in strangling the tumors, Nie said.

In one experiment on eight mice with melanoma, the tumors in three mice totally disappeared. The average survival life of the mice was prolonged from 20.5 days to 45 days. No metastasis was found, according to Nie.

The incidence of malignant tumors has been rising in China in recent years, becoming a major health threat. Interventional embolization therapy has become the first therapeutic choice for patients with advanced liver cancer. About 600,000 to 800,000 Chinese with liver cancer receive interventional therapy every year.

However, patients face anesthetic risks in this therapy and doctors face exposure to X-ray radiation, so a safer, more effective and convenient treatment is a priority, and nanotechnology has opened new opportunities, Nie said.

The research began five years ago, when NCNST researchers first looked at cutting off the tumor blood supply by using DNA-based nano carriers.

Shi Quanwei, another member of the research team, said laboratory verification of the nanorobot idea has been completed, but industrial production and application of the nanorobot is still a long way off.

"We hope to attract investment to improve the production technique and enlarge the manufacturing scale of the nanorobot, and conduct further research on its effect and safety before application for clinical trials," Shi said.

"We need to make breakthroughs on technical bottlenecks, and hope to transform the basic research into practical therapy to benefit patients with tumors."

The research was recently selected as one of 30 winning projects at a contest of innovative future technologies in Shenzhen, south China's Guangdong Province. The contest encouraged young Chinese scientists to conceive groundbreaking technologies and trigger innovation.

 

[JSCh]

SILKY SMOOTH —
Researchers insert a spider web gene into the silkworm
35 percent of the silkworm's cocoon is made of spider silk protein.

JOHN TIMMER - 8/8/2018, 11:18 PM

Missouri Department of Conservation

Spider silk is a bit of a dream material, stronger than steel by some measures yet incredibly light and flexible. Obtaining spider silk, however, is a bit of a nightmare, as most spider species are both extremely territorial and prone to cannibalism. While we have managed to identify the genes that are needed to produce silk, inserting those into other species hasn't worked out especially well, since silk formation depends on fairly precise mixtures of several proteins, as well as how the spider extrudes the fiber.

A Chinese group is now reporting some progress in overcoming at least some of these challenges. Their trick was to insert the genes into a domesticated species that already makes something like spider silk—specifically, the species that gave us the term silk. The new bit of genetic engineering has resulted in a silkworm that produces a hybrid silkworm/spider material that's not as tough but is a bit stretchier than native spider silk.

More than meets the eye
If you've ever watched a spider spinning a web, silk production seems remarkably simple. But there's enough going on there to make a materials scientist dizzy. Most spiders make more than one kind of silk, as the properties that might make a good web might not be the same as the ones that would effectively arrest a fall after a spider has leapt off a tree branch. The differences come in part because silk is composed of multiple proteins, and some spiders have genes for different versions of these proteins. If they have some control over which starting materials go into their silk, a spider species can adjust its properties.

But starting materials aren't the only means to alter silk. The rate at which it's extruded by the spider controls factors like the thickness of the silk, its water content, and how quickly it undergoes any reactions with oxygen. All of these can also influence the properties of the silk.

So making useful silk isn't simply a matter of getting a single gene from a spider and sticking it in bacteria. The Chinese researchers decided to focus on finding a way to produce the silk in a spider-like environment, while avoiding the cannibalism issue. That led them to an insect we domesticated many centuries ago that also produces silk: the silkworm itself. While the original silk clearly has some different material properties than spider silk, there is some overlap, including a set of proteins with functional similarities.

They weren't the first ones to try this; earlier attempts had been made to put spider genes in the silkworm. But these were based on a simple insertion of the gene from spiders, which turned out not to make much protein. The little that was made (typically five percent of the total silk or less) was also mixed in with the equivalent protein from the silkworm.

Editing in some spider
To get around these issues, the researchers decided to use gene editing. They designed proteins that would cut the silkworm's chromosomes on either side of a gene that encodes a major silk protein. RNA encoding those proteins was injected into silkworm eggs, along with a DNA template that would allow the egg to repair the chromosome by inserting a spider silk gene instead. This put the spider gene under the control of the factors the silkworm normally uses to create silk proteins, which worked much better, as about 35 percent of the resulting silk was composed of the spider protein.

That's not as good as the gene it replaced, which is normally about double that percentage of the silk fibers. But the spider gene is much smaller, so this wasn't a direct one-to-one replacement of the gene. In fact, the researchers suspect that the silkworm had some trouble due to the differences between the spider protein and the one that it used to make, as the silk-producing glands had some defects in the engineered animals.

The silk itself was also slightly different, shrinking in diameter by about 16 percent. Its ability to withstand stress without breaking was down by a similar percentage. But there were some good features; the spider-silkworm hybrid silk could be stretched to about 1.5 times the length that normal silk could without breaking.

Overall, this appears to be a good first step. There are clear problems due to the mismatch between the spider protein and the silkworm version it replaces. It may be possible to engineer the spider protein to increase its size; a lot of its structure is composed of repeated variations of a string of amino acids, and it's possible that the number of repeats could be expanded without causing problems. Alternatively, we can engineer more of the spider proteins into their silkworm equivalents, gradually transitioning the whole silk into something more spider-like. Whether that would allow silkworms to form cocoons (the normal purpose of the silk) isn't clear, but that may not matter for the production of large amounts of spider silk.

PNAS, 2017. DOI: 10.1073/pnas.1806805115 (About DOIs).



Researchers insert a spider web gene into the silkworm | Ars Technica

 

[JSCh]

Medical researcher endured pain to help others
By Zhou Wenting in Shanghai | chinadaily.com.cn | Updated: 2018-08-08 17:37

Wang Yiping. [Photo provided to chinadaily.com.cn]​

This spring, Wang Yiping, a Shanghai-based researcher who focused on new drug discoveries for 30 years, planned to fly to the United States in May to attend his daughter's university graduation.

The scientist, who in 2005 developed a new drug that has benefited 15 million coronary heart disease and angina patients in China and aspired to "invent drugs that are the first choice for doctors around the world", was found dead on April 11 in his office, near his lab, at the Shanghai Institute of Materia Medica, Chinese Academy of Sciences.

Wang, who had been running non-stop against time in his dedication to benefiting millions of patients and had fought against tremendous pains and deteriorating health, died suddenly at 55.

Near him was a syringe for a pain killer that he often used, which he kept secret from most coworkers.

Wang was diagnosed with Crohn's disease, an incurable chronic bowel disease, at 30 and underwent a surgical operation to remove a 1-meter length of his small intestine. He constantly endured severe abdominal pain, bloody stools, and fainting. Water sometimes triggered diarrhea, so he drank as little as possible, which caused kidney stones.

Wang's wife, Fang Jie, said during the past four years, parents of most of their daughter's classmates had visited their children in the US multiple times, but they never made a trip because Wang devoted almost all of his time to the lab, even on weekends and holidays.

"He said he was just at the prime age for a scientist to churn out research results. He had heard the sound of the hourglass and said he aimed to produce two other new drugs within a decade. That was what he said one week before he passed away," Fang said.

Xuan Lijiang, Wang's research partner, said Wang's ambition was for his heart drug to benefit patients worldwide suffering from cardiovascular disease, one of the top causes of death in the world.

"We have plans to promote the drug overseas and its registration in Europe has started," Xuan said, adding that the drug is an injection based on traditional Chinese medicine techniques and is the first and sole new drug accredited by the China Food and Drug Administration as "a paragon of adapting TCM to modern medicine".

The drug, depside salts, derived from the roots of salvia miltiorrhiza (danshen, a popular TCM herb) received a warm response after its market debut. Li Shuijun, a doctor at Shanghai Xuhui District Central Hospital, said the supply of the drug in its initial years often could not be guaranteed due to high demand.

Xuan said Wang had been attempting for years to change the current formulation of the injection into an oral form so that patients could easily use the medication themselves at home.

The phase II clinical trial of another new drug developed by Wang to fight against arrhythmia, or irregular heartbeat, has been completed in China and is being carried out in the United States.

Li Jun, deputy Party director of the institute, recalled Wang said in March that he suffered from pain more frequently and hormone drugs used to treat him no longer seemed to work. He suggested Wang try biologics immediately as the only remaining treatment.

"He said it was the last thing he'd like to do. It was most likely that his body gained resistance to biologics, which meant there was no other solution for him to control the disease. So he would rather double the amount of hormone drugs to gain more time to develop the two ongoing new drugs in his lab," he said.

 

[JSCh]

China plans large quake research facility in Tianjin University
Source: Xinhua| 2018-08-09 18:14:52|Editor: Yurou


TIANJIN, Aug. 9 (Xinhua) -- Tianjin University has received approval from the National Development and Reform Commission to build a large-scale earthquake simulation engineering research facility.

The facility will be used to study the impact of earthquakes on large engineering projects on land and in the sea and explore solutions to improve their abilities to withstand the impacts, said Zhong Denghua, university president and lead scientist of the project.

The project covers 77,000 square meters with an estimated investment of 1.5 billion yuan (about 220 million U.S. dollars) and will take five years to build at the university's Beiyangyuan Campus.

The planned facility is bigger than existing ones, said Zhong.

There are a growing number of high-rise buildings, cross-sea bridges, large hydropower stations, super-long tunnels, offshore wind power plants and large nuclear power stations in China, all which have a high demand for anti-seismic research, said Xie Lili, an academician of the Chinese Academy of Engineering.

Collapsing buildings have high casualty and asset losses during major quakes, so it is important to identify vulnerable parts of engineering structures and improve their ability to withstand the impacts of earthquakes, he said.

 

[JSCh]

New efficiency record for organic photovoltaic cells
August 10, 2018 by Bob Yirka, Tech Xplore

Credit: CC0 Public Domain​

A team of researchers affiliated with several institutions in China has established a new efficiency record for organic photovoltaic cells. In their paper published in the journal Science, the group describes their approach and the efficiency they achieved.

Over the past several years, scientists have been trying to find a way to improve the efficiency of organic photovoltaic cells, but have been stymied by the charge characteristics of organic materials. Organic materials are not only cleaner, but offer other potential benefits such as allowing for lighter-weight cells—they would also be bendable, making them useful for more applications. But they have proven to be inefficient compared to non-organic cells—some have even suggested they may never improve beyond 15 percent. Those based on silicon, by comparison, are in the 18 to 22 percent range. In this new effort, the researchers in China claim to have found a way to build an organic photovoltaic cell that tested at 17.3 percent efficiency.

The researchers report that the key to their success was the use of models they developed to predict which materials would allow for multilayer use. Organic photovoltaic cells rely on the use of pairs of organic molecules—one to absorb light and release an electron and another to grab the released electron. Because of this arrangement, organic cells are made using tandem cells made with layers of different materials. The researchers suggest that past efforts to improve efficiency have not yielded desired results because of the poor choices of materials that were available for use. They suggest the way to improve efficiency is to seek out new materials that when layered allow for improved efficiency. And that is where their model comes into play.

The researchers report that their model is theory-based and works by including the characteristics of two materials—it looks at how well the two materials would work together in converting sunlight to electrical energy and produces a rating. They report also that they believe their approach will one day lead to the discovery of materials that will allow solar cells to reach 25 percent efficiency. One downside, however, is durability—the test cells used by the team began degrading after just 166 days of continuous use.

Explore further: Printable solar cells a step closer with new design principles

More information: Lingxian Meng et al. Organic and solution-processed tandem solar cells with 17.3% efficiency, Science (2018). DOI: 10.1126/science.aat2612


New efficiency record for organic photovoltaic cells | Tech Xplore

 

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SHU-HONG YU​

This synthetic wood is as strong as the real thing—and won’t catch fire
By Robert F. Service
Aug. 10, 2018 , 2:00 PM

Plastic-wood composites have long been a favorite of homeowners looking to build decks and fences that don’t require sanding, staining, and painting. But these engineered woods typically aren’t as strong as natural wood and can be even more prone to catching fire. Now, researchers report they’ve created a synthetic wood (pictured) that matches natural wood’s strength and is flame resistant to boot.

One key to wood’s strength is a component called lignin, a natural polymer with a weblike structure that binds tiny crystallites of another component called cellulose together. The new composites replace lignin with a synthetic polymer version called resol, which has a similar weblike structure. Researchers used resol to bind a variety of different synthetic crystallites together into a family of different synthetic woods in which the color and other properties could be tailored by the crystallites added.

As the composites cure, they adopt a cell-like structure that looks like natural wood’s cellular structure. This helps the materials resist compression, lending them high strength. And because resol is fire retardant, the final composites don’t catch fire even when exposed to an open flame, the researchers report today in Science Advances.



This synthetic wood is as strong as the real thing—and won’t catch fire | Science | AAAS

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Chinese researchers develop new way to make high-quality artificial wood
Source: Xinhua| 2018-08-11 02:26:49|Editor: Mu Xuequan


WASHINGTON, Aug. 10 (Xinhua) -- Chinese scientists developed a new strategy for large-scale fabrication of bio-inspired artificial wood that manifested lightweight and high-strength properties with the mechanical strength comparable to that of natural wood.

A study published on Friday in the journal Science Advances described the high-performance polymeric materials with wood-like cellular microstructures.

A research team led by Yu Shuhong from the University of Science and Technology of China (USTC) transformed traditional phenolic resin and melamine resin into the artificial wood-like materials by self-assembly and the thermocuring process.

Their strategy provided a new route to fabricate and engineer a wide range of high-performance biomimetic engineering composite materials with desirable multiple functions and advantages over the traditional counterparts, having broad potential applications in many technical fields.

The liquid thermoset resins were firstly "unidirectionally" frozen to prepare a "green body" with the cellular structure, followed by the subsequent thermocuring to get the artificial polymeric woods. They are highly controllable in the pore size and wall thickness.

Starting from aqueous solution, the strategy also represented a green approach to prepare multifunctional artificial woods by compositing various nanomaterials, such as cellulose nanofibers and graphene oxide, according to the study.

Compared with natural woods, the artificial woods have better corrosion resistance to water and acid with no decrease in mechanical properties. They also have better thermal insulation and fire retardancy.

The artificial polymeric woods stand out from other engineering materials such as cellular ceramic materials and aerogels in terms of specific strength and thermal insulation properties.

As a kind of biomimetic engineering materials, this new family of bio-inspired polymeric woods is supposed to replace the natural wood when used in harsh environments, Yu told Xinhua.

 

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Nanoparticles Take Solar Desalination to New Heights
Tellurium nanoparticles could help absorb solar radiation or be integrated into sensors and tiny antennas
By Dexter Johnson

Image: Science Advances​

For at least the last decade, “solar thermal” technologies, in which sunlight is used to convert water into steam that runs electric turbines or performs desalination, has been a kind of darling of the investment community. About six years ago, nanoparticles started to get into this solar-thermal game when Rice University researchers added some nanoparticles to cold water and were able to make steam when they exposed the combination to sunlight.

Since then, a lot of work in what is now termed photothermal conversion has turned to the field of plasmonics, which exploits the wave of electrons that is produced when photons strike a metallic surface. However, producing plasmonic nanostructures is certainly not as straightforward as just adding some nanoparticles to water.

Now, researchers in China have combined the ease of adding nanoparticles to water with plasmonics to create a photothermal conversion process that exceeds all plasmonic or all-dielectric nanoparticles previously reported.

Researchers at Sun Yat-sen University in China demonstrated in the journal Science Advances what they claim is the first material that simultaneously has both plasmonic-like and all-dielectric properties when exposed to sunlight.

The key to achieving this combination is the use of tellurium (Te) nanoparticles, which have unique optical duality, according to G. W. Yang, professor at Sun Yat-sen University and coauthor of the research.

By dispersing these nanoparticles into water, the water evaporation rate is improved by a factor of three under solar radiation. This makes it possible to increase the water temperature from 29 degrees to 85 degrees Celsius within 100 seconds.

Image: Science Advances​

Thermal images show the difference in solar radiation absorbed by a bare silicon wafer (left) and a Te nanoparticle (right).

“The Te nanoparticles perform like a plasmonic nanoparticle when it is smaller than 120 nanometers (nm) and then as a high-index all-dielectric nanoparticle when those nanoparticles are larger than 120 nm,” said Yang.

The Te nanoparticles are able to achieve this duality because they have a wide size distribution (from 10 to 300 nm). This enhanced absorption can cover the whole solar radiation spectrum.

Another property of the Te nanoparticle is that when it is excited by sunlight, the excitation energy is transferred entirely to the carriers (electrons and holes). This pushes the carriers out of equilibrium and into special states of momentum with higher temperatures.

Yang explains that as the system evolves toward equilibrium, these carriers relax. As the carriers scatter, it leads to a phenomenon known as Coulomb thermalization, which forms a hot gas of thermalized carriers that couple with phonons and transfer their excess energy to the lattice. This results in the efficient heating of the Te nanoparticles.

For this approach to work for commercial desalination, Yang acknowledges that the current method of producing the Te nanoparticles with nanosecond laser ablation in liquid is limited. “Now, we are trying to prepare the Te nanoparticles by other methods,” he added.

But because the Te nanoparticles have a unique optical duality, Yang envisions other applications for the technology. “We want to apply them in sensors or nanoantennas,” he said.


Nanoparticles Take Solar Desalination to New Heights - IEEE Spectrum

 

[JSCh]

NEWS | 15 AUGUST 2018
‘Green revolution’ crops bred to slash fertilizer use
Researchers have identified a molecule that increases plant growth while reducing the need for nitrogen.

Jeremy Rehm

The green revolution created hardier rice that needs more fertilizer than older varieties.Credit: Anuwar Hazarika/Reuters​

A gene that enhances plants’ ability to absorb nitrogen could be used to breed high-yield varieties of rice, wheat and other staple crops that would need less fertilizer, researchers report on 15 August in Nature1. That could slash costs for farmers worldwide, and help to limit the environmental damage that occurs when nitrogen-rich water and soil wash from farm fields into rivers and oceans.

The research focused on crops bred during the ‘green revolution’ of the 1960s, a period when agricultural scientists boosted yields by breeding smaller, hardier versions of common crops. Farmers used these alongside improved irrigation methods, strong pesticides and efficient fertilizers. That sent the global harvest of cereal crops soaring from 741 million tonnes in 1961 to 1.62 billion in 1985.

But the latest study shows that there is still room for improvement, says Kathryn Barton, a plant scientist at the Carnegie Institution for Science in Stanford, California. “If you thought that these green-revolution varieties were it — that they’re the end of the line — you’re wrong, because there is more we can do,” she says.

That’s because modern crops have a weakness: they can’t absorb nitrogen as well as traditional crops can, so they need a lot of fertilizer to grow. In 2015 alone, the world’s farmers used roughly 104 million tonnes of nitrogen-rich fertilizer.

That practice is costly for farmers and harmful to the environment, says study co-author Xiangdong Fu, a plant geneticist at the Chinese Academy of Sciences Institute of Genetics and Developmental Biology in Beijing. When nitrogen-rich runoff from farm fields reaches rivers, lakes and oceans, it can feed massive algal blooms that consume oxygen and suffocate aquatic organisms. “That’s why we need to look for new varieties — ones that can produce high yields but with less fertilizer,” Fu says.

To do that, he and his colleagues examined the role of molecules called DELLA proteins that had been identified as the cause of green-revolution plants’ poor nitrogen absorption and short stature. In conventional crops, these proteins are destroyed by hormones that stimulate plant growth. But DELLA proteins flourish in green-revolution crops because the plants are immune to the hormones’ influence, or produce less of them.

Protein vs protein
Fu and his colleagues wanted to find a way to combat the accumulation of DELLA proteins. They began their search by comparing the DNA of 36 varieties of dwarf rice, and looking at the varieties’ ability to absorb nitrogen. The scientists identified two genes that control nitrogen consumption: one that codes for DELLA proteins, and another that codes for a protein called growth-regulating factor 4 (GRF4), which had been thought to increase only grain size and yield. Fu’s team found that GRF4 counteracts the effects of DELLA proteins by encouraging plants to absorb and metabolize nitrogen and carbon to support growth.

Then the researchers bred rice plants to produce a higher concentration of the GRF4 protein. The result was short plants with high yields that required less nitrogen than conventional green-revolution varieties.

The strategy is promising, says Jennifer Volk, an environmental-quality specialist at the University of Delaware in Dover. Farmers use several methods to lessen the environmental harms caused by excess nitrogen and other plant nutrients, such as constructing wetlands whose aquatic plants filter excess nitrogen and phosphorus from water before it drains to streams and rivers, she says. “Going this next step — making the crop more effective and efficient at taking those nutrients up — would tighten that system up even more,” Volk says.

But Anna Michalak, an environmental engineer at the Carnegie Institution who has studied the link between climate change and nutrient runoff in water systems, is more cautious about the implications of the study’s findings. “Whenever something seems like a win–win situation, I immediately think there’s something we haven’t thought of,” she says. “We’re never quite smart enough to anticipate what will happen.”

Nevertheless, Fu and his colleagues are in the middle of preparing a patent, and have already begun plant-breeding programmes in China. Fu anticipates that other parts of the world might see these new breeds of crop in five years.

doi: 10.1038/d41586-018-05980-7



‘Green revolution’ crops bred to slash fertilizer use | Nature.com

Shan Li, Yonghang Tian, Kun Wu, Yafeng Ye, Jianping Yu, Jianqing Zhang, Qian Liu, Mengyun Hu, Hui Li, Yiping Tong, Nicholas P. Harberd & Xiangdong Fu. Modulating plant growth–metabolism coordination for sustainable agriculture. Nature (2018). DOI: 10.1038/s41586-018-0415-5​

 

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NEWS AND VIEWS | 15 AUGUST 2018
An immune response with a sweet tooth
A previously unknown pathway that enables mammalian cells to recognize infection and trigger an immune response requires a kinase enzyme in the host cell to bind a sugar molecule produced by infecting bacteria.

John-Demian Sauer

Bacterial infections are a major cause of disease and death worldwide. The innate branch of the mammalian immune system, which recognizes and reacts to general characteristics of pathogenic organisms, has a key protective role. Writing in Nature, Zhou et al.1 describe a mechanism by which the innate immune system is activated in response to bacterial sugar molecules. This finding broadens our understanding of the types of molecule that can be recognized as hallmarks of bacterial infection and the host proteins that can recognize such molecules.


---> An immune response with a sweet tooth | Nature.com

Ping Zhou, Yang She, Na Dong, Peng Li, Huabin He, Alessio Borio, Qingcui Wu, Shan Lu, Xiaojun Ding, Yong Cao, Yue Xu, Wenqing Gao, Mengqiu Dong, Jingjin Ding, Da-Cheng Wang, Alla Zamyatina & Feng Shao. Alpha-kinase 1 is a cytosolic innate immune receptor for bacterial ADP-heptose. Nature (2018). DOI: 10.1038/s41586-018-0433-3​

 

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Chinese researchers develop world's first-ever 4D printing for ceramics
Source: Xinhua| 2018-08-18 02:22:19|Editor: yan


WASHINGTON, Aug. 17 (Xinhua) -- Chinese researchers have developed the world's first-ever 4D printing for ceramics that are mechanically robust and can have complex shapes, offering broad potential applications in telecommunications, electronics and even space exploration.

Researchers at City University of Hong Kong reported in a study published on Friday in the journal Science Advances a novel "ceramic ink," a mixture of polymers and ceramic nanoparticles.

The 3D-printed ceramic precursors printed with this novel ink are soft and can be stretched three times beyond their initial length, according to the study.

These flexible and stretchable ceramic precursors allow complex shapes, such as origami folding. With proper heat treatment, ceramics with complex shapes can be made, making them the 4D ceramics.

4D printing is conventional 3D printing combined with the additional element of time as the fourth dimension, where the printed objects can re-shape or self-assemble themselves over time with external stimuli, such as mechanical force, temperature, or a magnetic field.

The existing 3D-printed ceramic precursors, which are usually difficult to deform, also hinder the 4D printing of ceramics with complex shapes.

The researchers led by Lv Jian, chair professor of mechanical engineering, made use of the elastic energy stored in the stretched precursors for shape morphing.

When the stretched ceramic precursors are released, they undergo self-reshaping and after heat treatment, the precursors turn into ceramics.

The resultant elastomer-derived ceramics are mechanically robust. They can have a high compressive strength-to-density ratio and can come in large sizes with high strength compared to other printed ceramics.

"With the versatile shape-morphing capability of the printed ceramic precursors, its application can be huge," said Lv.

One promising application will be for electronic devices because ceramic materials have much better performance in transmitting electromagnetic signals than metallic materials. With the arrival of 5G networks, ceramic products will play a more important role in the manufacture of electronic products.

Also, the artistic nature of ceramics and their capability to form complex shapes also provide the potential for consumers to tailor-make uniquely designed ceramic mobile phone back plates.

Furthermore, this innovation can be applied in aero industry and space exploration. "Since ceramic is a mechanically robust material that can tolerate high temperatures, the 4D-printed ceramic has high potential to be used as a propulsion component in the aerospace field," said Lv.