Want to reduce microplastics in water? Boil it before drinking丨Tech Weekly

Compiled by Zhou Shuyi

This fish is only the size of a fingernail, but it can make a sound comparable to that of an airplane taking off

Danionella cerebrum | Source: Senckenberg/Britz

Rabindranath Tagore wrote in Stray Birds: "The fish swimming in the water are silent." However, this is not true. A study published in PNAS on February 26 showed that a small transparent fish called Danionella cerebrum, which is only 12 mm long, can make sounds as high as 140 decibels, which is as loud as hearing a jet takeoff at 100 meters.

Using a combination of high-speed photography, micro-CT scanning, RNA analysis, and finite-difference simulations, the researchers found that D. cerebrum has a unique set of sound-making structures, including drumming cartilage, specialized ribs, and fatigue-resistant muscles. This structure can pull the drumming cartilage at an acceleration of more than 2000 g, causing it to hit the swim bladder, producing rapid, loud sounds. Alternating between the cartilage on both sides of the body to hit the swim bladder can produce high-frequency sound pulses; repeated unilateral hitting produces low-frequency pulses. The combination of the two can produce a more diverse range of sounds. D. cerebrum natively inhabits the turbid waters of Myanmar. The researchers speculate that competition between males in low-visibility environments has led to this vocal communication mechanism.

Paper link:
https://www.pnas.org/doi/10.1073/pnas.2314017121

Good night! Odysseus

Intuitive Machines announced on February 29 that its Odysseus lander entered a long cold night of 14 Earth days at the lunar south pole a week after landing on the moon. If it survives the cold night, it may "wake up" in two to three weeks and reconnect with the Earth.

On February 29, the last photo sent back by Odysseus before it ran out of power (taken on the 22nd). | Source: Intuitive Machines

"Odysseus" successfully landed on the lunar surface on February 23. Initially, Intuitive Machines announced that the lander was in an upright position, but subsequent news showed that the flight preparation team did not manually unlock the safety switch before the rocket was launched, causing the lander's laser rangefinder used for navigation to fail to start normally. The staff had to use the experimental navigation system in the NASA payload to assist in the landing. This emergency measure may have caused "Odysseus" to land too fast (with a horizontal speed of about 0.89 meters per second), and the body was "tripped" and turned sideways to lean on a rock. As a result, the solar panels and antennas of "Odysseus" failed to unfold completely as planned, and the power supply and communication capabilities were limited, resulting in the mission cycle being shorter than the previously expected 7 to 10 days. (Intuitive Machines)

The moment of landing. | Source: Intuitive Machines

3D printed titanium alloy sets record for fatigue strength

3D printing, also known as additive manufacturing (AM), is a technology that manufactures physical parts by accumulating materials layer by layer based on CAD design data. Compared with traditional material removal (cutting) technology, it is a "bottom-up" material accumulation manufacturing method. However, the fatigue performance of 3D printed components under cyclic loads is generally poor, which restricts their widespread application as structural load-bearing components.

A study published in Nature on February 29 pointed out that under ideal conditions, the titanium alloy structure (called Net-AM structure) directly prepared by 3D printing technology should have excellent fatigue performance, but the measured fatigue performance is poor because defects such as pores are generated during the printing process. However, the current process of eliminating pores is often accompanied by tissue coarsening, and the treatment of fine structure will lead to the reappearance of pores and even cause new unfavorable factors such as grain boundary α phase enrichment, which can be described as a dilemma. Researchers first discovered in Ti-6Al-4V alloy that the grain boundary migration, pore growth and phase transformation process of 3D printed tissue at high temperature show asynchronous characteristics. This means that there is a heat treatment process window in between, which can not only achieve lath structure refinement, but also effectively inhibit grain boundary α phase enrichment and pore reappearance. Based on this, the new study developed a process flow for step-by-step regulation of defects and organization to prepare a nearly pore-free Net-AM Ti-6Al-4V alloy.

Tests show that the tensile-tensile fatigue strength of the new alloy has been increased from 475 MPa in the original state to 978 MPa, which is the best among titanium alloy materials, and has the highest specific fatigue strength (fatigue strength divided by density) among the material fatigue data reported so far. Researchers said that 3D printing technology is currently widely used in the aerospace field. The fatigue life of devices prepared with the new technology can be increased by ten to a hundred times under the same load; under the same expected life span, the load bearing capacity can be increased by 10% to 15%.

Paper link:
https://www.nature.com/articles/s41586-024-07048-1

Want to reduce microplastics in your water? Boil it before drinking

Microplastics and nanoplastics (NMP) have come with the tide of industrialization, sweeping every corner of modern life. If you are worried about the ubiquitous NMP in drinking water, you may want to try this simple and easy method - boil it before drinking. According to a study published in Environmental Science & Technology Letters on February 28, boiling hard tap water can remove more than 80% of three common nanoplastics (polystyrene, polyethylene and polypropylene).

Boiling tap water can encapsulate microplastics in scale particles, making them easier to filter and remove. | Source: Eddy Zeng

Mineral-rich hard water naturally forms scale (mainly calcium carbonate) after boiling. Calcium carbonate crusts form a crystalline structure that can wrap plastic particles. These substances gradually accumulate and precipitate into scale, thereby removing free NMP from the water. Researchers collected hard tap water samples from Guangzhou, China, added different amounts of nanoplastics (NPs) to them; after boiling the samples for five minutes and cooling them, the content of free plastic particles in them was measured. The results showed that as the water temperature increased (25℃~90℃), the NP removal rate in the samples gradually increased from 2% to 28%, and the removal rate increased sharply to 84% at 100℃. The harder the water quality (the higher the mineral content), the more obvious the removal effect: the nanoplastic removal rate of hard water (calcium carbonate content 300mg/L) after boiling reached 90%; even soft water (calcium carbonate content less than 60 mg/L) can still remove more than 25% of nanoplastics by boiling. Researchers suggest that filters can be used to remove suspended scale particles in drinking water to reduce the intake of microplastics.

Paper link:
http://dx.doi.org/10.1021/acs.estlett.4c00081

Lasso discovers first super cosmic ray acceleration source

The High Altitude Cosmic Ray Observatory (LHAASO) discovered a giant ultra-high-energy gamma-ray bubble structure in the star-forming region of Cygnus, finding for the first time in history the source of cosmic rays with energies higher than 100 million electron volts. The relevant results were published in Science Bulletin on February 26.

Cosmic rays are charged particles (mainly protons) that move at nearly the speed of light in interstellar space. They interact with the interstellar medium during propagation, producing secondary particles such as gamma-ray photons and neutrinos. Measurements have found that the cosmic ray energy spectrum (i.e., the distribution of cosmic ray numbers in terms of particle energy) has a kink structure around 1 quadrillion electron volts, shaped like a knee joint, and is called the "knee" of the cosmic ray energy spectrum. Previous studies have suggested that celestial bodies in the Milky Way can accelerate cosmic rays to about 1 quadrillion electron volts at most.

Cosmic ray energy spectrum and its "knee" structure. | Source: Institute of High Energy Physics, Chinese Academy of Sciences

The giant ultra-high-energy gamma-ray bubble structure discovered by Lasso has a diameter of about 1,000 light-years and a center about 5,000 light-years from the Earth. The energy of the photons observed in it can reach up to 2 quadrillion electron volts. To produce gamma photons with an energy of 2 quadrillion electron volts, cosmic ray particles with an energy of more than 10 times are generally required. This indicates that there is a cosmic ray acceleration source inside the bubble structure, which continuously produces high-energy cosmic ray particles with an energy of up to 200 quadrillion electron volts. The massive star cluster (Cygnus OB2 association) located near the center of the bubble is the most likely corresponding celestial body to the cosmic ray acceleration source. The radiation intensity of these stars is hundreds to millions of times that of the sun. The huge radiation pressure blows out the surface material of the stars, forming a stellar wind of thousands of kilometers per second, colliding with the surrounding medium, forming an extreme environment of strong shock waves and strong turbulence, becoming a powerful particle accelerator. This is the first super cosmic ray acceleration source that people have been able to certify so far. Researchers said that as the observation time increases, "Lasso" may detect more similar super cosmic ray acceleration sources, which is expected to solve the mystery of the origin of cosmic rays in the Milky Way.

Paper link:
https://doi.org/10.1016%2Fj.scib.2023.12.040

New breakthrough in lithium batteries, can be "charged and discharged freely" in an environment of -70℃ to 60℃

Lithium-ion soft-pack batteries under research. | Source: Zhejiang University

Researchers from Zhejiang University published a paper in Nature on February 29, researching and designing a new electrolyte that can support reversible charging and discharging of high-energy lithium-ion batteries in an ultra-wide temperature range of -70°C to 60°C, and rapid charging and discharging at room temperature. The new research has developed and verified a set of new extreme electrolyte design principles, breaking the traditional lithium-ion transmission mode. Test data show that the ionic conductivity of the new electrolyte is 4 times that of commercial electrolytes at room temperature of 25°C, and is 3 orders of magnitude higher than commercial electrolytes at -70°C. According to reports, the new electrolyte is currently expensive and can be first used in extreme temperature conditions such as polar scientific research, space exploration, and seabed exploration.

Paper link:
https://www.nature.com/articles/s41586-024-07045-4

Why did humans lose their tails?

From the Old World monkeys tens of millions of years ago to today's humans, an important morphological change is the degeneration and disappearance of the tail. Not only humans, but also chimpanzees, gorillas, orangutans and gibbons have no tails. These animals belong to the same superfamily as humans, Hominoidea. It is speculated that the ancestors of the Hominoidea parted ways with the Old World monkeys about 25 million years ago, and their tails began to degenerate. This phenotypic change gave apes the advantage of walking upright, while losing the ability to use the tail to maintain balance when climbing, which may have contributed to the human ancestors moving from the tree canopy to the ground. But the genetic basis of the disappearance of the tail has always been an unsolved mystery.

The ancestors of the hominids diverged from the Old World monkeys about 25 million years ago. | Source: Itai Yanai et al.

A study published in Nature on February 28 showed that the insertion of a repetitive sequence into a specific gene changed the configuration of the resulting protein, which may have led to the disappearance of the tail in the hominid superfamily. The researchers screened 140 genes related to the development of the tail of vertebrates, and identified Alu elements in the introns of the TBXT gene of the hominid superfamily that were not found in other monkeys. Alu elements are a type of repetitive sequence that is widely present in the genomes of mammals, especially humans. The research team found that although the process of Alu insertion into the intron of the TBXT gene did not change the coding region, it led to alternative splicing - producing different mRNA splicing isomers, changing the structure of the protein product, and thus leading to differences in the tail phenotype.

To verify this speculation, the research team constructed a special heterozygous mouse to simulate the expression pattern of TBXT in the hominid superfamily. This mouse expresses two different forms of the Tbxt gene, a normal full-length form and an exon skipping form mediated by the insertion of the Alu element. The results showed that the tails of mice that can produce two protein isoforms were shortened or disappeared, depending on the relative abundance of expression in the embryonic tail bud. This indicates that exon skipping caused by Alu insertion is sufficient to induce the loss of the tail.

In addition, the authors found that mice with Alu element insertion may develop neural tube defects, suggesting that the evolutionary process of tail loss may increase the risk of neural tube defects in humans. The incidence of this defect in human newborns is about 1/1000, and the child's brain, spine or spinal cord shows some kind of birth defect, which may cause neurological damage. (WuXi AppTec)

Paper link:
https://www.nature.com/articles/s41586-024-07095-8

This article is supported by the Science Popularization China Starry Sky Project

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.

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